Being Silenced: The Impact of Negative Social Reactions on the Disclosure of Rape

Rape survivors who speak out about their assault experiences are often punished for doing so when they are subjected to negative reactions from support providers. These negative reactions may thereby serve a silencing function, leading some rape survivors to stop talking about their experiences to anyone at all. The current study sought to examine this worst case scenario. Focusing on the qualitative narratives of eight rape survivors who initially disclosed the assault but then stopped disclosing for a significant period of time, this study sought to provide an in-depth description of how negative reactions silenced these survivors. Three routes to silence were identified: 1) negative reactions from professionals led survivors to question whether future disclosures would be effective; 2) negative reactions from friends and family reinforced feelings of self-blame; and 3) negative reactions from either source reinforced uncertainty about whether their experiences qualified as rape. Implications for future research and practice are discussed.
Feminist activists and scholars have long been interested in the dynamics that keep women from speaking about their experiences. These analyses emphasize the sociopolitical nature of voice and silence. In this tradition, feminist sociologist Shulamit Reinharz describes voice as “having the ability, the means, and the right to express oneself, one's mind, and one's will. If an individual does not have these abilities, means, or rights, he or she is silent” (Reinharz, 1994, p. 180). This conceptualization highlights social power structures that privilege some voices while excluding others. As metaphors for privilege and oppression, to speak and be heard is to have power over one's life. To be silenced is to have that power denied.
Silence is thus emblematic of powerlessness in our society. It is therefore not surprising that rape survivors often remain silent about their experiences (George, Winfeld, & Blazer, 1992; Koss, 1985; McAuslan, 1998). Feminist scholars have long argued that rape serves an active function of reinforcing women's powerlessness and “keeping women in their place” (e.g., Brownmiller, 1975; MacKinnon, 1987). How, then, can we expect women to break the silence about the very experience used to reinforce powerlessness?
Amazingly enough, many women do find the strength to break this silence and speak out. Nearly two-thirds of all rape survivors disclose the assault to at least one person (Golding, Siegel, Sorenson, Burnam, & Stein, 1989; Fisher, Daigle, Cullen, & Turner, 2003; Ullman & Felipas, 2001; Ullman, 1996a, 1996b, 1996c). But, the consequences of speaking out are not always positive. Numerous studies have documented negative social reactions from significant others and community systems. Negative social reactions from informal support providers encompass both overtly negative reactions such as blaming or doubting victims (Davis, Brickman, & Baker, 1991; Golding et al., 1989; Ullman, 2000) as well as well-intentioned support efforts that are nonetheless experienced as negative (e.g., encouraging secrecy, patronizing behavior)(Herbert & Dunkel-Schetter, 1992; Sudderth, 1998). Anywhere from one-quarter to three-quarters of survivors receive negative social reactions from at least one member of their informal support network (Campbell, Ahrens, Wasco, Sefl, & Barnes, 2001; Golding et al., 1989; McAuslan, 1998; Filipas & Ullman, 2001).
Survivors are also likely to receive negative reactions from formal support providers. Negative reactions from professional sources may be particularly harmful for survivors. When “experts” doubt survivors, hold them responsible for the assault, or refuse to provide assistance, survivors may question both the effectiveness of such services and the usefulness of reaching out for help to anyone at all. Unfortunately, negative reactions from community system personnel appear to be all too common. Rape victims frequently report receiving negative or unhelpful reactions from legal and medical personnel (Campbell, Sefl, Barnes, Ahrens, Wasco, & Zaragoza-Diesfeld, 1999; Campbell, Wasco, Ahrens, Sefl, & Barnes, 2001; Golding et al., 1989; Filipas & Ullman, 2001).
When rape survivors are exposed to victim-blaming behaviors or attitudes, the experience may feel like a “second assault” or a “second rape”, a phenomenon known as “secondary victimization” (Campbell, 1998; Madigan & Gamble, 1991; Martin & Powell, 1994; Williams, 1984). In many instances, these behaviors are overt as system personnel explicitly hold survivors responsible for the assault, doubt the veracity of survivors’ stories, or minimize the seriousness of the crime (Madigan & Gamble, 1991). In other instances, this revictimization occurs when rape survivors are denied needed or desired services (Campbell & Bybee, 1997; Campbell et al., 2001; National Victim Center, 1992).
Speaking out about the assault may therefore have detrimental consequences for rape survivors as they are subjected to further trauma at the hands of the very people they turn to for help. Negative reactions can thereby serve a silencing function. Women who initially break the silence and speak out about the assault may quickly reconsider this decision and opt to stop speaking. Negative reactions such as being blamed, being denied help, or being told to stop talking about the assault may effectively quash rape survivors’ voices, rendering them silent and powerless.
The experiences of survivors who have been silenced by such reactions, however, has remained largely unexamined. As an initial examination of this unstudied area, the current study identified a select sample of rape survivors who had been so traumatized by negative social reactions that they stopped speaking about the assault altogether. This sample was selected from a larger project on the impact of community services on rape survivors’ well-being (Campbell et al., 1999). The author of the current study was the Interview Coordinator for this larger project. While conducting interviews, she became interested in survivors who ceased talking to anyone about the assault for significant periods of time. This interest led to the current project which sought to obtain an in-depth understanding of how the negative reactions rape survivors received led to their decision to stop speaking about the assault. Qualitative analysis is particularly suited to this type of inquiry. Engaging in an in-depth, context-laden analysis of a smaller number of cases enables us to gain a fuller understanding of how the phenomenon in question is experienced by our participants (Guba & Lincoln, 1994). Creating such a thick description (Geertz, 1973) of how negative reactions can silence some rape survivors is the goal of the current study.
Method
Recruitment procedures
Recruitment procedures for the larger study were modeled after techniques of adaptive sampling (Thompson & Seber, 1996) whereby researchers systematically sample from locations that are frequented by the population of interest (see also Campbell et al., 1999 for a detailed review of this recruitment strategy). We sought to ensure both breadth of coverage by systematically recruiting from the 69 zip codes in Chicago and depth of coverage by targeting locations frequented by women during their daily lives (e.g., laundromats, bookstores, churches). Posters, fliers, and in-person presentations inviting rape survivors to call for more information were distributed in these locations. These recruitment efforts were systematically plotted and tracked to ensure breadth of coverage with intensive efforts in zip codes with high concentrations of traditionally overlooked populations (e.g., women of color, lower socioeconomic neighborhoods). In-person interviews were then scheduled with women who were at least 18 years old and had been raped when they were 16 years old or older.
Recruitment was conducted between September 1997 and April 1998 and resulted in 102 interviews with adult rape survivors. A smaller subset of survivors who had been silenced by negative reactions was then selected for the current study. Specifically, survivors who initially disclosed the assault within 3 days, received at least one negative reaction during those initial disclosures, and then ceased disclosing altogether for 9 months or more were included in this sample. These inclusion criteria were purposefully stringent. As the first exploratory study of this phenomenon, an extreme sample was purposefully selected to begin to shed light on the relationship between negative social reactions and silence. The final sample of eight rape survivors was thus intentionally small in order to highlight the worst case scenario. The use of such small samples in critical case and narrative analyses has been deemed more than adequate in the qualitative literature (Sandelowski, 1995) and thus was deemed sufficient for the purposes of the current study. More subtle manifestations of the relationship between negative social reactions and silence can be examined in future studies.
Participant characteristics
Five of the eight survivors were African American while the remaining three were White. None of these survivors were currently married and five did have children. Five of these survivors had at least a high school degree. Five survivors were also currently employed. Half of the women were raped by someone known to them. Their average age at the time of the assault was 23.88 (SD=7.32). Half of these assaults involved a weapon, five resulted in injuries, and two involved alcohol. The only significant difference between this smaller subset of survivors and the larger pool of 102 survivors was time since the assault. The average time since the assault was greater for the survivors in this smaller sample (M=16.10, SD=11.59).
Measures
Qualitative data was obtained from an in-person interview developed for the larger study. The interviews for the current sample lasted an average of 2.20 hr (SD=55.29 min) and were conducted by one of 13 ethnically diverse graduate and undergraduate interviewers who had received extensive training on sexual assault and interviewing skills. Great care was taken to provide a safe and sensitive interview environment, resulting in positive feedback from participants at the end of the interview (see Campbell et al., 2004 for a lengthier description of steps taken to ensure participant well-being).
The semi-structured interview was designed to obtain a comprehensive picture of rape survivors’ post-assault experiences. This interview consisted of 20 main content areas that covered the assault itself, initial disclosures, interactions with five key community systems (e.g., legal, medical, mental health, rape crisis centers, and religious community), reasons for non-disclosure, social reactions, the impact on survivors’ social and sexual activities, psychological and physical health symptoms, and changes in survivors’ worldviews. Survivors received $30 and a community referral booklet for their participation.
Although information about survivors’ assault and disclosure experiences emerged throughout this interview, several questions were more useful in generating data related to the aims of the current study. Each of these questions is described below.
The assault. Survivors were asked to describe the assault in their own words: “Could you tell me about the assault? What happened? Would you tell me your story?”
First disclosures. Five questions were used to elicit information on survivors’ first disclosures: 1) “Who was the first person you told about the assault?”; 2) “Why was __ the first person you told about the assault?”; 3) “How did __ react?”; 4) “How did __ reaction affect you?”; and 5) “Looking back over it now, how do you feel about telling __? Was this a good choice? a bad choice? Why?”
Disclosure to formal support providers. Separate sections focused on survivors’ interactions with legal, medical, mental health, rape crisis, and religious communities. In each section, survivors were asked: 1) “How did you decide to contact the [community system] about the assault?”; 2) “What was it like for you [receiving each service]?”; and 3) “How did [community system] treat you [while receiving each service]?” Participants were also read a list of negative reactions (e.g., blamed, doubted, denied services) and were asked to indicate which of these reactions they experienced.
Disclosure to informal support providers. Descriptions of survivors’ interactions with family and friends emerged primarily during their responses to Ullman's (2000) Social Reactions Questionnaire. Survivors were read a list of positive and negative social reactions and were asked: 1) whether they received that reaction; 2) who reacted that way; and 3) how that reaction made them feel. While the SRQ is traditionally administered in written form, the oral presentation of these items allowed survivors to explain these interactions more fully.
Reasons for non-disclosure. Several questions assessed rape survivors’ reasons for not telling other people about the assault. These questions allowed rape survivors to explain their reasons for non-disclosure in their own words. A series of four questions explicitly asked survivors about their reasons for not disclosing to specific community systems. These questions focused on survivors’ reasons for not seeking out disclosure opportunities: 1) “So, you did not have any contact with the [specific community system], why was that?”; 2) “Were there things that prevented you from seeking assistance from [specific community system]? If so, what were they?”; 3) “Is there anything that could have been done to make it more likely that you would have turned to [specific community system] for help?”; and 4) “Looking back over it now, do you think it was a good choice, or bad choice, to not seek help from [specific community system]? Why is that?”
Information about survivors’ reasons for not telling friends and family about the assault emerged in three specific sections of the interview. Survivors discussed their reasons for not telling additional friends and family when discussing their first disclosure experiences (described above), their interactions with family and friends (described above), and when asked “how did this experience change your understanding of … a) your family; and b) your friends?” In these sections, survivors discussed reasons for not telling specific friends and family as well as reasons for not wanting to tell informal support providers in general.
Analysis procedures
This project used a qualitative approach to data analysis. In particular, narrative analysis, based on the recommendations of Miles and Huberman (1994), was used to help identify themes in survivors’ narratives. The first step of this process was to reduce and organize transcribed data. The lead investigator first identified transcript segments that pertained to assault and disclosure experiences and noted key concepts in both the margins and on separate index cards. This process resulted in hundreds of index cards referring to dozens of concepts (similar to the labeling stage of open-coding advocated by Strauss & Corbin, 1990). Undergraduate research assistants who had been recruited from the lead investigator's research methods class were then trained to conceptually group these concepts into larger categories (similar to the discovering categories stage of open-coding advocated by Strauss & Corbin, 1990) by sorting the index cards into conceptually similar and dissimilar piles. A consensus model was used throughout this process whereby disagreements were discussed until agreement on the proper placement of the cards was reached. Each pile was then reviewed one more time and a consensus approach was used to create a name and definition for each concept being described. The resulting names and definitions were then used to create a codebook.
This codebook was then used to code the transcripts. To train the research assistants, the first transcript was coded together as a group. Each research assistant was then given her own transcript which she coded independently while the lead investigator simultaneously coded all eight transcripts. Appropriate code(s) were written in the margin next to the corresponding text segment. Codes were then compared, interrater reliability was computed, and final decisions about appropriate codes were made using a consensus approach. Two types of discrepancies were noted: disagreements and omissions. Disagreements occurred when a research assistant assigned one code while the author assigned a different code. Overall, there were few outright disagreements. The kappa coefficient for coding disagreements was .94 indicating excellent interrater reliability (Fleiss, 1971 as cited in Pett, 1997). More commonly, coding discrepancies involved omissions where either the research assistant or the author applied a code that the other coder overlooked. This occurred exclusively in cases where multiple codes were warranted. When omissions were included in the calculation of interrater reliability, the kappa coefficient was reduced to .63 indicating “good” agreement (Fleiss, 1971 as cited in Pett, 1997).
Results
To contextualize survivors’ decisions to cease disclosing, vignettes summarizing their assault and disclosure experiences are presented first. Pseudonyms are used throughout.
Vignettes of survivors’ experiences
Natalie. Natalie was abducted from a bus stop by three men and taken to an abandoned building where she was assaulted both vaginally and anally. The ordeal lasted five hours and ended when they set the building on fire. After escaping, Natalie staggered home and passed out, injured and hemorrhaging. When she woke up, she was in the hospital and the police were there. The police took her back to the scene, but the woman who answered the door said she didn't know anything and that no-one else was there. The police did not investigate any further.
Natalie felt that the police didn't care and weren't going to do anything to help:They wasn't going to do shit, wasn't nothing going to be done.
She was also distressed by their lack of sensitivity when she was recounting her experience:I remember one of the police officer laughed.
Natalie also felt that the police doubted her story and held her accountable for the rape. These negative experiences with the police made her reluctant to have any further contact with them:The way they responded to me, I didn't want anything else to do with them.
Natalie's experiences with the police served to silence her and she didn't speak of the assault again for a year, in part due to a perceived lack of options and in part due to fear that others would react as badly. She finally began speaking about the assault again when she entered a drug treatment program and began working with a counselor who was also a rape survivor.
Karen. Karen was abandoned by her boyfriend at a coffee shop during a cross-country road trip. The manager offered her a room at the adjacent motel, but when the night watchman brought her food, he raped her. When Karen tried to tell her sister about the assault, her sister didn't seem to identify the experience as rape:Her comment was … you should never have sex with anybody you don't want to. I’m like, duh. Like I had a choice, you know?
This unsupportive interchange caused Karen to question the efficacy of disclosure:It's just that it didn't do any good, it just made me angry.
Her sister's response was so unsympathetic that she never spoke to her about the assault again. Believing that there was no-one in her life who would support her, Karen did not disclose again for 19 years. In effect, her sister's reaction confirmed her own doubts and fears about whether her experience qualified as rape:I never used the word rape ‘til like a year ago honestly.
The fact that she was unsure of whether the experience qualified as rape also affected Karen's perception of options for disclosure. For example, she described never even considering reporting the assault to the police, going to the emergency room, seeking mental health services, or contacting a rape crisis center.I just felt … that anybody would say, well, ah, you know, it was your own fault or you were vulnerable or, you know, not that you asked for it, but you were in that position, what did you expect, or something like that, you know. There was like, it's not going to be any help. And, well, you just laid there, you know.
After 19 years of silence, Karen began disclosing again after she ran into the ex-boyfriend who had abandoned her. After telling him, Karen was able to start telling other people.
Shawna. Shawna was a self-identified drug addict who prostituted when necessary to support her addiction. The assailant was a fellow drug user who assaulted her with a weapon one night when she was walking down the street. The first person Shawna told about the assault was her cousin who told her that she should have known better:She thought I knew about his, um, past. He was known to do that, take advantage of women.
This response reinforced Shawna's feelings of self-blame and fears of being blamed by others. Fears of being blamed were particularly salient because of her lifestyle, leading Shawna to believe that there was no-one out there that she could turn to:Being a drug, intravenous drug user, then you’re like, that's your fault. That's—what you coming here for? I mean, you keep using and you keep going on the streets, that's going to happen.
Feelings of self-blame led Shawna to cease disclosing altogether for three years, a decision that was reinforced by her distrust of the police and fears of retaliation:Then they kill you, beat you up, lay in the garbage, you won't hear nothing about it.
Shawna began disclosing again when she entered a drug rehab center.
Marie. Marie was assaulted by two strangers her boyfriend arranged to give her a ride home. They drove to a wooded area where they held a gun to her infant son's head and raped her. When she got home, she told her mother who told her to keep the rape a secret:And I went home, and it was my fault. Shut up and don't you tell anybody what you did.
Marie also told two friends, but they blamed her and told her to try and forget that it happened:Forget it, it's over, it was your fault, leave it alone.
She then turned to her priest and told him about the assault in confession. But, he blamed her for the assault and told her that God was punishing her:He was in confessional. And just, you know, I’m separated, I had no right dating.
Marie internalized the shame and blame communicated by both her mother and the priest:I felt really, really, really bad. Feeling very bad. I couldn't talk, look at your face. I would, I would look down ‘cause I’d think you’d look and I’d be filthy, dirty whore … feel less than a whore, dirtiest thing in God's earth.
Having exhausted all of the options she felt were available to her, Marie stopped disclosing for several years. Although Marie did begin to seek counseling several years later and has found some support among new friends, she relies mainly on herself and God for support.
Linda. After a party, Linda decided to spend the night on the sofa rather than take the bus home alone at night. She woke up to the host raping her anally. The next day, she told a counselor who had been helpful in the past. But, he was very judgmental and blaming:When I went to see him, he said, well, what do you expect? If you stay over at somebody's house like that that you barely know, that's an open invitation.
This experience was so traumatizing that Linda decided to stop disclosing altogether:After that, the red flag went up and I just said no, I’m not speaking to anybody about this.
Her inability to identify other support providers and her fears of similar negative reactions led her to stop disclosing for 13 years:Well, I figured they would do the same thing that this counselor did. They would just blame me and they would discount it.
These fears were reinforced by her own uncertainty about how to define her experience:I referred to it as an unfortunate incident. I … had a narrow view of what rape was.
Linda broke her silence when a therapist was able to validate her experience for her. She now runs support groups for sexual assault survivors.
Rita. Rita's ex-boyfriend invited her out on his boat where he and one of his friends assaulted her at gunpoint. She remained in a state of shock for three days and then contacted her church's prayer line who told her she must have wanted it to happen:Well, they told me that…that situation could not have occurred unless I’d attracted it by thinking about it … they said, probably, it must be in your subconscious.
Rita then turned to friends who told her she should have known what would happen and she shouldn't report the assault because she knew the assailant. Rita decided to file a report anyway, but the police dismissed her claims because she knew the assailants:It was as if because I knew the men that suddenly, then, somehow that was not a legitimate complaint or something.
Rita considered contacting a counselor, but the negative reactions she received from the police and her church led her to question the efficacy of such services:I just wasn't in a place where I wanted to invest my money in that. Particularly in as much as everybody along the way that I had sought help from, I mean, always blowing me off. So, I’m not going to pay money to have someone blow me off.
Since Rita was unaware that rape crisis centers existed and really didn't have any close friends or family that she trusted to have a good reaction, she felt she was out of options for support and justice. This led her to stop disclosing altogether for the next 4 years. Although she has disclosed the assault to researchers and has written a magazine article in the hopes of helping other women, she continues to mainly rely on herself and her spirituality for healing.
Vanessa. Vanessa was assaulted when her ex-boyfriend offered to help her see her sisters whom she had been separated from when she was placed in the foster care system. When she arrived at his home, her sisters were not there and he raped her while threatening her with weights. After the assault, she ran to the nearest phone and called 911. The police took both the assailant and Vanessa to the police station for questioning. Vanessa was then taken to the hospital for the rape exam, a traumatizing experience for her:Well, for me, I was already feeling nasty and dirty and there was semen. Um. It was just like another assault. Cold and impersonal.
She was then taken back to the police station where a sergeant accused her of lying:He told me that he know my kind and I was messin up this boy future for college. And I couldn’t-I know I heard what he said, but I couldn't understand. You know, like hey, I’m the one that's the victim, you know. And he was all, pulled out some papers and threw them down and say, you’re a repeated run-away, you in foster care. And all the time, I did not know what to say. I was just looking at him, like, why are you do this to me? He said, that boy have a future in there and you destroying it. You stay away from him.
The police refused to file rape charges but did file simple assault charges. When Vanessa arrived at the courthouse, however, one of the assailant's brothers pulled her aside:[He] said if I do not drop the charges, he will burn my mother house down and rape my little sisters.
Combined with Vanessa's negative experiences with the police, this threat of retaliation served to silence her:I came to them in my most vulnerable state. I’d just been victimized and I walked into a place that was male dominant and what they did or did not do for me hurt me. Emotionally, mentally, very bad. They formed an opinion that will probably take a lifetime to undo.
Although she considered disclosing to friends and family, she was afraid of being punished for skipping school. She did not reach out to the mental health system because she didn't know that the rape would continue to affect her for so long. As the aftermath of the rape became clear to her, however, she still did not contact a therapist because she wasn't sure that such services were appropriate for her:[I didn't know] that it was OK for African Americans to go to a mental place. Back then, not too many people I knew who were my color was going to therapists.
Rape crisis centers were also not an option for Vanessa, primarily because she was unaware that they existed:I didn't even know what that is. And still don’t.
Having nowhere else to turn, Vanessa stopped disclosing for 10 years. The current interview was the first time she told her story since her interactions with the legal system.
Therese. Therese was assaulted by a stranger when she went to the apartment of a man who claimed to be an old acquaintance. She tried to leave when she realized that she had never met him before, but he grabbed her and proceeded to rape her. She remained in shock for three days, feeling unable to talk to anyone. When she contacted her best friend, her friend was sympathetic, but extremely upset:She took it almost as bad as I did.
This reaction was difficult for Therese to deal with because she felt guilty for upsetting her friend and felt she had to comfort her:It kind of made me feel like I had to comfort her because she was taking it so hard.
Even though Therese's friend was trying to be supportive, she was more concerned about herself than Therese. Therese's own feelings of self-blame and shame were also too strong to be overcome. Unable to identify support providers she thought would react well, these high levels of self-blame were ultimately the reason Therese did not report the assault or contact any professional services:Cause I felt like it was my fault. And, ah, I really couldn’t. If I felt like it was my fault, I knew everybody else would be looking at me like, well, it's your fault anyway.
These feelings of self-blame and fears of being blamed by others led Therese to cease disclosing for nine months. Unfortunately, her initial effort to break her silence by disclosing to a boyfriend was met by a blaming response. Nonetheless, she decided to participate in the current interview as a first step toward receiving needed services.
Cross-case analysis: Common experiences and themes
The preceding vignettes provide rich, contextualized descriptions of each survivor's experiences with disclosure and silence. In-depth analysis of these survivors’ narratives revealed four general types of negative reactions experienced by these survivors: 1) being blamed; 2) receiving insensitive reactions; 3) experiencing ineffective disclosures; and 4) receiving inappropriate support.
All of the survivors described being blamed for the assault. These survivors were blamed for putting themselves in vulnerable positions and were frequently told that they should have known better. Such responses were particularly common from community system personnel, especially the legal system. Interactions with the legal system were characterized by questions about whether the assault qualified as rape, their role in the assault, and whether they deserved the assistance the legal system could provide.
All of the survivors also received insensitive reactions. These reactions included having a support provider question, doubt, or minimize their experience. Insensitive reactions also occurred when support providers showed no sympathy for her distress or didn't seem to consider what the survivor needed. Legal, medical, mental health, and religious system personnel were all described as reacting insensitively by at least half of the survivors who turned to them. Frequently, these insensitive reactions occurred in conjunction with blaming and doubting responses, reinforcing survivors’ perceptions that community systems didn't care and would not provide any help.
Ineffective disclosures were also quite common. Ineffective disclosures were characterized by a lack of help/support resulting from disclosure. This code was applied when support providers refused to help. In several cases, help-seeking attempts to counselors, church, or friends/family did not result in support. In other cases, the police refused to take a report or charge the assailant with rape. Indeed, all three cases that were reported to the police were dropped and none resulted in prosecution of the offender for rape.
All but one of the survivors also described inappropriate support, mainly from friends, family, and religious personnel. Inappropriate support referred to support attempts that may have been well-intentioned, but were nevertheless perceived as inappropriate or unhelpful. Being told to keep silent or not report the assault, being treated as though they couldn't take care of themselves, or having to comfort their support providers ultimately interfered with these survivors’ ability to receive support and comfort.
These negative reactions then affected survivors’ decisions to cease disclosing the assault. In-depth analysis of these survivors’ narratives revealed five common reasons for ceasing to disclose: 1) lack of options; 2) fears of negative reactions or consequences; 3) ineffectiveness of support; 4) self-blame or embarrassment; and 5) didn't qualify for support.
All of the survivors discussed a lack of options as a reason for not continuing to disclose the assault. Many of these survivors were unaware of services available in the community (e.g., rape crisis centers) and all of them felt that there were no additional sources of support available to them. Having evaluated the likelihood of receiving support from others and determined that such support was unlikely, these survivors described having nowhere else to turn.
Even when survivors could identify providers, they all expressed extreme distrust and fears of negative reactions. Fears of being blamed, doubted, and treated insensitively were pervasive. For many, these fears were directly related to their previous negative disclosure experiences, leading them to conclude that additional disclosures would be harmful.
Six of the survivors also feared that additional disclosures would be ineffective. These survivors believed that continued disclosure would be unhelpful or would not result in the type of support they needed. They didn't see the use of continued disclosure and felt that further discussion of the assault would be pointless. Combined with fears of negative reactions, their decision to cease disclosing was a form of self-protection.
Six of these survivors also cited self-blame or embarrassment as reasons for ceasing to disclose. They felt that it was embarrassing to talk about rape and didn't want to put themselves through additional disclosures. The fact that they had been blamed for the assault previously served to heighten feelings of self-blame. These survivors described feeling somewhat responsible for the assault prior to disclosing, a view that was enhanced when they were blamed by others.
Finally, two survivors described questioning whether their experience qualified as rape. Because these assaults were not particularly violent, these survivors were unsure whether their experience counted as rape even before they disclosed. The fact that their initial disclosure recipients also appeared to question whether their experiences were rape served to reinforce their own doubts.
The relationship between negative social reactions and reasons for ceasing to disclose
As the above analyses suggest, the survivors in this sample spontaneously referenced negative experiences from initial disclosure attempts when describing their reasons for ceasing to disclose (even though this question was never explicitly asked, suggesting that this was an extremely salient reason for ceasing to disclose). This suggests that these survivors were using their past experiences with disclosure to evaluate future disclosure opportunities. Receiving negative responses to their initial disclosures, these survivors became more cautious and critical of future disclosure opportunities and ultimately opted to remain silent rather than risk further harm.
The manner in which negative reactions led to being silenced, but, varied across survivors. Further examination of survivors’ narratives revealed three primary routes to silence. First, three of these survivors described negative reactions that made them question whether future disclosures would be effective. Each of these survivors had disclosed to formal support providers and felt that these disclosures had been ineffective. For example, Natalie, the woman raped by a group of men in an abandoned building, attributed her decision to stop disclosing to the negative reactions she received from the police and medical system. She felt that talking to others would be ineffective so she tried to forget about the assault and move on with her life. Similarly, Rita, the woman assaulted on a boat, described initially seeking help from multiple sources. She ultimately decided that help would not be forthcoming and turned inward to heal herself. Finally, Vanessa, the woman assaulted at her ex-boyfriend's home, also attributed her decision to stop disclosing to her experience with the legal and medical systems. The ineffectiveness of her contact with the legal system was particularly poignant in Vanessa's case and reinforced her fears that the legal system could do nothing to protect her from retaliation by the assailant and his brothers.
Second, two survivors described negative reactions that reinforced their own doubts about whether their experience qualified as rape. Both Karen, the woman assaulted by the night watchman, and Linda, the woman assaulted by the host of a party, questioned whether the assault qualified as rape. Their own doubts about whether their assault qualified as rape and the reactions of others combined to make them reluctant to risk further disclosures.
Finally, three survivors described disclosures which reinforced feelings of self-blame. These survivors’ initial disclosures were either inadequate for overcoming their sense of self-blame or actively reinforced feelings of self-blame. For example, both Shawna, the woman assaulted by a fellow drug addict, and Therese, the woman assaulted at a stranger's home, turned to informal support providers who provided inappropriate support that was inadequate for countering their fears and self-blame. For Marie, the woman who was raped in a car, the negative reactions she received from her mother, friends, and priest reinforced her feelings of self-blame, making her too ashamed to talk about the assault with anyone else.
Discussion
Unlike other crimes such as burglary and assault, rape survivors must prove not only that the crime did in fact occur, but that they had no role in its occurrence (Burt, 1980; Pollard, 1992; Ward, 1995). But, for most survivors, no matter what they did or how they behave, they are likely to be blamed for the assault. For some survivors, this blame may be so traumatizing that they are effectively silenced by the negative reactions they receive. Sadly, when rape survivors are silenced by negative reactions, their experiences and perspectives are concealed and our ability to identify the causes and consequences of rape are obscured. Such silences thereby obstruct our ability to engage in social change. A first step toward unearthing these untold stories may be to understand how and why rape survivors are silenced.
Results suggested that rape survivors are silenced by a range of negative reactions including blaming, ineffective, insensitive, and inappropriate responses. Specific reactions appeared to be more common from different support providers, however. For example, being blamed, receiving insensitive reactions, and experiencing ineffective disclosures were particularly common among survivors who turned to formal community systems (especially the legal and medical systems). These experiences are consistent with previous research which has documented high levels of victim blame, doubt, insensitivity, and refusal of services by community system personnel (Campbell et al., 1999; Madigan & Gamble, 1991; Filipas & Ullman, 2001). Such reactions may stem from organizational features of these systems. In an examination of unresponsive treatment of rape survivors by both legal and medical personnel, Martin and Powell (1994) argue that the organizational frameworks guiding these systems’ activities are oriented towards the needs of the organization rather than the needs of survivors. They suggest that the needs of the systems and rape survivors may run counter to one another. Whereas the survivor needs to be believed and supported, the legal system needs to win cases and the emergency room needs to treat emergent patients. These conflicting needs often result in insensitive and unresponsive treatment of rape survivors (Martin & Powell, 1994). In the current study, survivors described police, medical staff, counselors, and pastors who laughed at their account of the assault, were cold and unsympathetic, and overtly blamed them for the assault. For three of the survivors in the current study, being silenced was a direct result of the accumulation of blaming, insensitive, and ineffective reactions from community system personnel which led them to question the effectiveness of disclosure.
Inappropriate support attempts, on the other hand, were more common from informal support providers such as family and friends. Inappropriate support attempts included suggestions or behaviors that may have been intended to be helpful but were experienced by survivors as hurtful or simply not what they needed. Herbert and Dunkel-Schetter (1992) first noted the distinction between intentionally negative reactions (e.g., blame) and unintentional negative reactions resulting from altruistically motivated, but ineffective support attempts. This distinction was further validated by Ullman (Ullman, 1996a, 1996b, 1996c) in her survey of rape survivors. In the current study, several of the survivors described interactions with informal support providers that were inadequate for overcoming their own feelings of self-blame. In essence, these survivors internalized many of the cultural narratives about rape that emphasize victim culpability. When support providers were unable to counter these messages, the victims engaged in self-silencing, choosing to censor themselves and remain silent about an experience they considered shameful and stigmatizing (Jack, 1991). These survivors did not receive any benefits from disclosure and often felt worse after speaking about the assault. Having lost faith in the efficacy of disclosure, these survivors opted to heal themselves.
Finally, the current findings suggest that some rape survivors are silenced when disclosure recipients fail to confirm their victim status. Several of the survivors in the current study described knowing that something unwelcome had occurred, but they did not know whether the experience qualified as rape. This finding is consistent with previous research which suggests that rape survivors do not always identify as rape victims, particularly when their experiences do not conform to stereotypical rape myths (Allison & Wrightsman, 1993; Kahn, Jackson, Kully, Badger, & Halvorsen, 2003; Koss, Dinero, Seibel, & Cox, 1988; Layman, Gidycz, & Lynn, 1996). The results from the current study expand on this research, however, by suggesting that disclosure recipients play a role in how rape survivors interpret their experiences. For two of the rape survivors in this sample, initial disclosures were partially motivated by the desire to have others confirm or deny their victim status. Unfortunately, in these cases, the disclosure recipients failed to confirm their victim status and these survivors stopped disclosing as a result.
There are several limitations to this current research that are important to note. First, any effort to study silence is limited by the fact that, by definition, the population of interest is not disclosing the assault to anyone. As researchers, the best we can do is work to create recruitment strategies and interview environments that facilitate disclosure for previously silenced populations. In the current study, we went to great lengths to employ strategies that communicated support, understanding, and acceptance (see Campbell et al., 2004 for a complete description of these recruitment strategies). These strategies may have enabled previously silenced survivors to come forward and speak about their assaults. Indeed, many of these survivors mentioned the fact that this interview appeared to be a safe place to talk about their experiences. For one survivor, this interview was the first time she had spoken about the assault since being silenced by negative reactions. For others, they only began disclosing once supportive providers were found (most commonly, counselors). Thus, supportive recruitment strategies and interview environments may facilitate disclosure for some survivors. But, it is likely that many others continue to remain silent about their experiences. Important differences may exist between survivors who do and do not choose to disclose to researchers.
It should also be noted that these results are not intended to reflect the experiences of all rape survivors. To the contrary, this study sought to examine the experiences of a previously hidden subpopulation of rape survivors—those who have been silenced by negative disclosure experiences. This subpopulation has remained hidden due to both survivors’ own silence about their experiences as well as researchers’ overly simplistic conceptualizations of disclosure. To date, researchers have defined disclosure as a discrete yes/no event—a survivor disclosed or she didn't (Bachman, 1993, 1998; Binder, 1981; Feldman-Summers & Norris, 1984; Golding et al., 1989; McAuslan, 1998; Neville & Pugh, 1997; Ullman, 1996c; Ullman & Filipas, 2001; Washington, 2001). This conceptualization has obscured the experiences of survivors who initially disclose but are then silenced by negative social reactions. As a result, almost nothing is known about how negative reactions can silence rape survivors. While there may only be a small population that is ultimately silenced by negative disclosure experiences, the fact that their voices have been silenced and their stories hidden is problematic. This study was intended as a first step toward unearthing such stories to add to our knowledge of the devastating impact that negative social reactions can have on rape survivors. As is true of most qualitative research, the goal was not to generalize to the entire population of rape survivors. Rather, the goal was to gain an in-depth understanding of the phenomenon in question (in this case, being silenced) and the context in which the phenomenon occurred (Goetz & LeCompte, 1984; Guba & Lincoln, 1982; Miles & Huberman, 1994). Future research can examine the findings in different populations of rape survivors, particularly among other populations that are likely to experience high levels of silence such as child sexual abuse and incest survivors.
In spite of these limitations, this exploratory study offers several avenues for further research. First, future research could benefit from larger samples in order to examine the impact of race, socioeconomic status, lifestyle characteristics, and assault characteristics. Increasingly, social identity theorists have argued that social group memberships are interactive such that one's race may affect how social class is experienced and vice versa (Frable, 1997; Weber, 1998). In the current context, it is possible that race, class, lifestyle, and assault characteristics may interact in varying combinations to lead to different outcomes. Unfortunately, the current study did not include a large enough sample to examine all of these combinations. This makes it difficult to interpret some of the racial, class, lifestyle, and assault characteristics that emerged in the current study. For example, all of the survivors who contacted the police were African American—but they also experienced the most brutal assaults. All of the survivors who had difficulty defining their experiences were White—but these assaults also involved less resistance by the survivor. Without comparison groups of White survivors who reported to the police or African Americans whose assaults were not as severe, it is not possible to determine the impact of race and type of assault on disclosure choices or outcomes. Similarly, there is some evidence that race and social class may have interacted in the current study: the police were far more blaming toward Vanessa, who was a young African American girl in the foster care system, than toward Rita, who was a middle-class African American professional. A larger sample would help confirm this possibility.
Future research could also further examine the role of support provider gender on the types of reactions provided and the impact these reactions have on survivors. In the current study, gender of support provider was not specifically assessed, leading to two cases where it was not clear whether the hospital personnel and police were comprised entirely of men or were a mixture of men and women. Although this prohibited a direct examination of support provider gender, the information that was available suggests that the vast majority of professionals who provided negative reactions were men. This is in line with previous research that suggests that men tend to respond more negatively than women (Ahrens & Campbell, 2000; Davis & Brickman, 1996). In contrast to previous research, however, the vast majority of informal support providers who provided negative reactions were women. Future research is needed to examine this distinction more methodically.
Future research should also compare the impact of positive and negative reactions. The current study focused on the impact of negative social reactions on rape survivors’ decision to stop disclosing. This was, in part, because previous research has suggested that negative reactions are far more impactful than positive reactions (Campbell et al., 2001; Davis et al., 1991; Ullman, 1996b). It was therefore hypothesized that negative reactions would play an important role in rape survivors’ decisions to stop speaking about the assault, a proposition that had yet to be examined in the literature. Future research is needed to determine how positive reactions affect this relationship, however. If victims receive both positive and negative reactions, how do they weigh these reactions when evaluating subsequent disclosure opportunities? Is there a threshold of positive disclosure experiences that serve to negate negative experiences? Is there a threshold of negative disclosure experiences that negate positive experiences? Or is a single positive or negative experience enough to determine whether victims will disclose? Future research on the impact of positive and negative social reactions on disclosure is needed to begin to answer these questions.
Finally, the impact of such extensive periods of silence on survivors’ recovery remains unknown. Predictions from Pennebaker's Psychoimmunology Theory of Disclosure would predict that the inhibition of emotional expression that accompanies such lengthy periods of silence would adversely affect survivors’ psychological and physical health (Pennebaker, 1988, 1989; Pennebaker & Susman, 1988). On the other hand, these survivors chose to stop disclosing in order to avoid negative reactions that have been found to relate to higher psychological and physical health symptoms (Campbell et al., 2001; Davis et al., 1991; Ullman, 1996b; Ullman & Filipas, 2001). Ceasing to disclose may therefore have a positive impact on survivors’ recovery by helping them avoid such negative reactions. Additional research is needed to understand the impact that their decision to stop disclosing has on their recovery.
On a more practical level, the results of the current study suggest that negative reactions are particularly detrimental as survivors use these reactions as a gauge for how others are likely to respond. These results attest to the importance of continued efforts to reduce rape myth acceptance and train support providers on how to effectively support rape victims. Combating rape myths, educating the public about sexual assault, and training potential support providers to avoid negative reactions may help reduce the trauma of the assault and increase the likelihood that victims receive the support they are seeking when they turn to others for help. Such efforts may be further enhanced by changes in the organizational context of formal community systems. Until the institutional orientation of the legal system is changed to reward prosecution of all rape cases rather than only those cases that are considered convictable, the legal system will likely continue to blame rape victims who come to their attention. Until the medical system comes to view providing support as part of their role, victims will likely continue to be treated insensitively. Thus, educational and training efforts should be used in conjunction with efforts to help shift the organizational orientation of formal community systems.

disclosure
rape
secondary victimization
social relations


Improving the batch-to-batch reproducibility in microbial cultures during recombinant protein production by guiding the process along a predefined total biomass profile

In industry Escherichia coli is the preferred host system for the heterologous biosynthesis of therapeutic proteins that do not need posttranslational modifications. In this report, the development of a robust high-cell-density fed-batch procedure for the efficient production of a therapeutic hormone is described. The strategy is to guide the process along a predefined profile of the total biomass that was derived from a given specific growth rate profile. This profile might have been built upon experience or derived from numerical process optimization. A surprisingly simple adaptive procedure correcting for deviations from the desired path was developed. In this way the batch-to-batch reproducibility can be drastically improved as compared to the process control strategies typically applied in industry. This applies not only to the biomass but, as the results clearly show, to the product titer also.
Introduction
Biologics are known to be rather complex products. Apparently small changes in the manufacturing processes can cause significant differences in their clinical properties. Hence, production processes for biologics are approved by authorities only with clearly defined constraints on their manufacturing procedures. Consequently, reproducibility is of utmost importance. Additionally, reproducibility is very important as it affects the downstream processing and thus quality of the final product.
From the engineering point of view there are two challenges in guaranteeing batch-to-batch reproducibility. First of all, within the given constraints, the operational procedure, most robust with respect to typically appearing process fluctuations, must be found. And, secondly, while running the process along this robust path, the remaining randomly appearing disturbances must be eliminated by means of feedback control.
With respect to batch-to-batch reproducibility, production processes for recombinant proteins are lagging far behind most other industrial processes. Figure 1 shows a typical example of the repeatability of biomass concentration profiles in a recombinant protein production process. The variability is quite high.
Fig. 1Biomass (open circles) and target protein (open triangles) concentration profiles from 13 fed-batch fermentations for the production of a recombinant protein. Typically the batch-to-batch reproducibility of these production processes is rather low
This fact was recognized by the FDA. The agency responded with a couple of measures. One essential reaction is FDA’s PAT initiative [2]. With PAT, improvements in pharmaceutical and biologics production processes with respect to real time automated process monitoring and control are demanded. A rigorous science-based approach to manufacturing is demanded, as better understanding is thought to lead to more efficient process control, lower process variability, thus high product quality and finally patient safety. For biologics it is particularly important to keep the processes under control early in the product synthesis process (e.g., [1]).
In bioprocess engineering, process monitoring and control is being developed since many years. A review was given by Lee et al. [8]. The objective was to keep the process on trajectories that finally lead to a high value of the desired mass mP of the product. Within a more or less well-defined production time tP, this can be related to biomass by the following expression:  where π is the specific product formation rate and x the total biomass. Both arguments of the integral are functions of time, but more importantly, both are primarily dependent on the specific biomass growth rate μ in most industrial production systems. The growth rate that a specific medium supports determines the physiological state of the cells, and particularly the cell’s protein-synthesizing machinery that is important to recombinant protein production is also under growth rate control [12]. Hence, the variable that rules the final outcome of the process is the specific biomass growth rate μ. Thus, design of effective cultivation processes should be based on an optimal or at least a quasi-optimal profile of the specific growth rate. This can be obtained by means of numerical optimization procedures (e.g., [10]) or simply by deriving a profile from data records and experience with the production system under consideration. In order to make sure that the process follows this profile it is straightforward to control μ in the engineering sense (e.g., [5–7, 11, 13, 14, 16–18]).
Direct control of μ works perfectly as long as there are no severe disturbances in the process. When, however, some disturbances lead to a significant deviation of the biomass from its desired path, one must correct it before one can proceed with the desired optimal or quasi-optimal μ profile. Otherwise reproducible process trajectories cannot be obtained.
The decisive innovation in this paper is to show that the batch-to-batch reproducibility of the production processes can be significantly enhanced when the process is controlled to a predefined profile of the biomass x. This does not mean to stay away from keeping the μ profiles found to be optimal from the physiological point of view. The x-setpoint profiles are simply derived from predefined μ profiles. Using start biomass and desired specific biomass growth rate profile it is easy to estimate total biomass profile during the cultivation:
A given biomass profile xset(t) is then in close relationship with the specific biomass growth rate μ. Hence, controlling the process to an x profile should satisfy the corresponding specific growth rate profile μset(t) as well. In this case the cultivation process is more robust because the deviations in biomass concentration can be eliminated directly by controlling the integral variable x.
As x cannot be measured directly with sensors that work reliably at a production fermenter and provide biomass values representative for the culture, it should be measured indirectly. This is a further advantage as compared to the μ-control because we are able to estimate x much more reliably than the specific growth rate μ [4]. In production environments, where sufficiently many data records are available from the process under consideration, artificial neural networks (ANNs) yield very accurate estimates. Hence we use ANNs to estimate biomass x. The ANN was trained on 26 data sets measured during a process development project with the strain used in this work.
Materials and methods
Experiments were performed with Escherichia coli BL21(DE3) as the host cell. The recombinant target protein was coded on the plasmid pET 28a and expressed under the control of the T7 promoter after induction with isopropyl-thiogalactopyranosid (IPTG). The strain was resistant to kanamycin. The product appears as inclusion body within the cytoplasm. The particular strain used did not produce measurable amounts of acetate under the cultivation conditions adjusted in the experiments reported. This was tested in the beginning by means of appropriate test kits.
The main substrate was glucose. It was fed at a concentration of 600 g/kg. The other components are compiled in Table 1.
Table 1Composition of the mineral mediumMineral salt solutionTrace element solutionComponentConcentration (g/kg)ComponentConcentration (g/kg)K2HPO414.60Na2-EDTA20.10NaH2PO4·H2O3.60FeCl3·6H2O16.70(NH4)2SO42.46CaCl2·2H2O0.74Na2SO42.00CoCl2·6H2O0.21MgSO4·7H2O1.20ZnSO4·7H2O0.18(NH4)2-H-citrate1.00CuSO4·5H2O0.10NH4Cl0.50MnSO4·H2O0.10Kanamycin0.10Thiamin0.10Trace element solution2 mL/kg
All experiments were performed within BBI Sartorius System’s BIOSTAT® ED 15 L bioreactor with 8 L working volume (Fig. 2). The fermenter was equipped with standard 6-blade Rushton turbines that could be operated at up to 1,400 rpm. The aeration rate could be increased up to 24 L/min. Aeration rate and then stirrer speed were increased one after the other in order to keep the dissolved oxygen concentration at 25% saturation. In order to suppress foam formation, increase oxygen solubility and reduce the risk of contamination, the fermenter head pressure was kept at 0.5 bar above the ambient pressure in the laboratory.
Fig. 2Experimental setup of the cultivation equipment
The fermentations were operated in the fed-batch mode from the early beginning with an initial volume of 5 L at pH 7 and a temperature of 35°C. All fermentations were started in the night by automatic transfer of the inoculation biomass from a refrigerator into the reactor. Substrate feeding starts immediately after inoculation with a fixed exponential profile. According to Jenzsch et al. [3], the specific growth rate setpoint was chosen as 0.5 h−1. Thus the glucose concentration appeared to be at a very low value just from the beginning on. Its value is in the order of the Ks value and thus below the values that can be measured during the fermentation. After the biomass concentration reached values of about 35 g/kg, the culture was induced with 1 mM IPTG. From the seventh fermentation hour on, the growth rate was kept under feedback control along an x profile that was derived from a predefined profile of the specific growth rate. The corresponding profile of the substrate feed rate was determined from the profiles of μ and x. This was taken as reference feeding profile Fref for all the fermentations described.
Temperature was measured with a Pt-100, pH with an Ingold-pH-probe, pO2 with an Ingold pO2-Clark-electrode, CO2 in the vent line with MAIHAK®’s Unor 610 and O2 there with MAIHAK®’s Oxor 610. Further, the total ammonia consumption during pH control was recorded by means of a balance beneath the base reservoir. All these quantities were measured online. Additionally, enhanced foam levels could be detected with a foam sensor and, if the critical level was reached, a silicone antifoaming emulsion (ROTH®) was added.
Biomass concentrations were measured offline (via the optical density at 600 nm) with a Shimadzu® photo-spectrometer (UV-2102PC). In preceding experiments a correlation was established between these values and the biomass dry weights, which were determined with the standard drying and weighting technique. Glucose was determined enzymatically with a YSI 2700 Select Bioanalyzer. The product was measured with SDS-PAGE after separation of the inclusion bodies and their solubilization.
Results
Preliminary simulations and experiments showed that the total biomass x(t) is better suited as the controlled variable than the biomass concentration X(t) itself. The control can then be performed with a simple adaptive control algorithm comprising the following steps:Estimate the total biomass xest at the current time instant t using the artificial neural network trained before on the available data records [4]. A simple feedforward artificial neural network with a single hidden layer was used which makes use of the online measured signals OUR, CPR, total base consumption resulting from pH control. With an additional bias node in the input layer the network has four input nodes. Five hidden layer nodes were used where the nonlinear response function of these nodes was chosen to be tangens hyperbolicus (tanh) functions. A single output, namely the biomass x, was taken, where the weighted sum of its input signals was directly used as the output signal.Compute the deviation of estimated biomass xest from its setpoint xset: The deviation Δx in x was used to correct the growth yield value Yxs in the feed function, which itself was limited to the interval given in order to avoid too big variations in cases where the measurements are disturbed in an unusual way: The concrete limits to F were chosen by experience in control practice.In order to determine the controller variable α by which the growth yield is adapted to the current state of the process we found that it is better to make use not only of the deviation Δx but also the smoothing action of an integral correction term to the deviation: Again, the correction was limited. Here the limitation was chosen by experience in such a way that the resulting yield values are kept within reasonable limits. The parameters k1 and k2 were initially determined in simulation studies. Later, during preliminary control experiments, they were slightly adapted. Their final values are k1 = 0.1 (kg(S))−1 and k2 = 0.02 (kg(S))−1 h−1.
The controlled biomass profiles depicted in Fig. 3 show that this simple control approach leads to a very good reproducibility of the total biomass profiles.
Fig. 3Total biomass signals from five fermentations performed sequentially using the same setpoint profile
As one is usually not interested in the total biomass, the corresponding biomass concentrations are depicted in Fig. 4. As can easily be seen from both plots, the batch-to-batch variability of the trajectories is rather small, i.e., the process total biomass control works well.
Fig. 4Measurements of the biomass concentration during five experiments in which the total biomass was controlled. The induction time was tind = 11 h in all cases
In order to get a better impression of the controller action, the deviations from the desired profile, i.e., the relative deviations between the total biomass and its setpoint, are plotted in Fig. 5. In all the experiments, the controller was switched on at t = 7 h. In the first 4 h thereafter, the relative deviations remain within a 5% interval. The controller action then improves so that finally the relative deviation of the total biomass remains within a 2% interval around the mean. The feed rate profiles F(t) applied in the experiments are shown in Fig. 6.
Fig. 5Relative deviations of the total biomass from the mean. The controller was switched on 7 h after the cultivation was inoculatedFig. 6Substrate feed rate profiles for the six x-controlled fed-batch experiments
There is one exception. In the last experiment (S330) feed pump was switched off from 3 to 5 h in order to test the controller performance under process conditions with an extremely hard disturbance. The controller appeared to be robust enough to cope with this disturbance. Again in the end the relative deviation from the mean remained in the 2% interval.
The next question is what does this mean for the profiles of the specific biomass growth rate, which was initially chosen to determine the setpoint profiles for the total biomass. This comparison essentially should demonstrate data consistency. The specific growth rate μ was determined from a Luedeking–Piret type relationship between the biomass concentration, carbon dioxide production or oxygen uptake rate and the specific growth rate:
Both equations can be resolved for μ. The parameters were already known from a fit of the models to the fermentation data.
Hence, with the biomass concentration profiles estimated and the measured OUR(t) and CPR(t) signals, μ can easily be computed. The result is depicted in Fig. 7. In the decisive phase of the process, the product formation phase, the resulting trajectories of the specific biomass formation rate μ(t) resemble quite well the original setpoint profiles. It should be recalled that rather high noise is to be expected when computing μ(t). However, the results depicted in Fig. 7 nevertheless clearly show that the data are consistent.
Fig. 7Specific biomass growth rate profiles determined from the measurement profiles of OUR, CPR as well as from the estimates for biomass concentration X(t). Note that the study 330 was the test case where the substrate supply was interrupted for some period during the biomass growth phase
Finally the question arises what does a high batch-to-batch reproducibility in the biomass profiles mean for the variance in the product formation profiles. Results corresponding to the data shown before are depicted in Fig. 8.
Fig. 8Product concentration profiles for the cultivation processes already mentioned. All protein data stay within the error bar ranges representing the confidential interval of the protein analysis method
The corresponding protein concentration profiles are rather close together saying that the improved reproducibility in biomass profiles by means of x control also leads to an improved batch-to-batch reproducibility in the product concentration profiles. All profiles stay within the confidence interval of the analytical protein detection method. The relative error of ±15% of target protein analysis by SDS-PAGE was estimated from a fivefold analysis using the same fermentation samples.
Discussion
Previous work on controlling the fermentation processes performed to manufacture recombinant proteins focused on keeping the cultures on tracks that guaranteed a high productivity or yield. The obviously first quantity influencing the amount of protein that is produced in a cultivation run is the biomass employed, hence high-cell-density cultures are required (e.g., [9, 15]). As the cells’ protein-synthesizing machinery that is particularly important to recombinant protein production is under growth rate control [12], the performance of the cells is ruled by the specific biomass growth rate μ. Hence, much work has been put into closed loop control of fermentation processes along appropriate profiles μset(t) of the specific biomass growth rate [5–7, 11, 13, 16–18]. While advantageous from the cell physiological point of view, controlling the specific growth rate directly has the disadvantage of leading to a relatively low reproducibility of the fermentations [6]. This is a significant disadvantage from the process quality point of view.
We wished to extend the work on fermentation control towards quality assurance of process and thus product formation. This first of all requires improving the batch-to-batch reproducibility of the processes. There are two motivations for this. First, the product quality in recombinant protein manufacturing processes can be affected by changes in the fermentation operational procedure, hence the authorities link process approval with tight constraints on the process trajectories. Thus, good reproducibility increases product quality. Secondly the downstream processing can work much more efficiently when the cultivation results are highly reproducible. Therefore, having the same culture each time should be beneficial to the overall product yield as well.
The results of the new control procedure discussed below show that the batch-to-batch reproducibility is significantly improved. The procedure controls the biomass along a profile that is directly derived from the specific growth rate profile that was found to be desirable. The first decisive advantage of this approach is that the control procedure is robust to distortions usually appearing in practice. This is opposite to control along a predefined profile of the specific biomass growth rate. Practically all distortions lead to changes in the biomass and this is the controlled variable. A second advantage is that the actual biomass values can be estimated with higher accuracy than the specific growth rate from the online measurement signals available at most fermenters. As shown previously [4] x can be representatively estimated with a root mean square error of about 0.5 g/kg by means of simple artificial neural networks.
The reason for the robustness of the x control is easy to understand. The x-setpoint profile for the control was determined from a μ profile. This μ profile leads to a feed rate profile F(t) and a biomass profile x(t). The F(t) profile is taken as the feed forward component of the process and programmed in the programmable controller at the fermenter. If due to distortion the biomass becomes smaller as expected, the cells will see more substrate than expected and respond temporarily by increasing their growth rate. If, on the other hand, the distortion leads to a higher biomass concentration, the cells see less substrate than expected and reduce their growth rate, thus correcting for their deviation in the total biomass. The feedback component of the process has thus only to correct for larger deviations.
Control of the specific biomass growth rate or qualitatively similar control technique that uses the substrate feed rate F as the manipulated variable is currently not generally used in production practice. Its adoption is now supported by recent initiatives of the FDA in its PAT initiative [2], but will critically depend on the ease of the control algorithm. The algorithm used in this work is an extremely simple adaptive control approach which only corrects the biomass-on-substrate yield in the basic feed rate expression. The control algorithm proved to be stable in many fermentation runs with many different organisms and several different fermenter scales up to the large production scale.
It is very important to note again that the new x control approach does not require refraining from taking the μ profile of the process as the basic process control variable. This basic concept can be maintained and it is easy to derive the x profile from a given μ profile. As clearly shown in the examples, not only does this x-based control keep biomass and specific growth rate in tight limit, but also the batch-to-batch reproducibility with respect to the desired product concentration is high.

reproducibility
recombinant proteins
pat
e. coli fed batch