Fermentative production of butanol and butyric acid from cheese whey using a mixed culture
Authors:   , Stevens David Keith 
Published: July 2024

Some of the most ubiquitous and persistent environmental contaminants belong to the class of organochlorine compounds called polychlorinated biphenyls (PCBs). An estimated 1.4 billion pounds of PCBs were commercially manufactured in the United States from 1929-1977 primarily for use as dielectric fluids in transformers and capacitors, hydraulic fluids, and plasticizers. In 1977, PCBs were the only group of chemicals specifically mentioned by the Toxic Substances Control Act, and in 1979, the U.S. Environmental Protection Agency (EPA) banned the manufacture, processing, distribution in commerce, and use of these chemicals in totally unenclosed systems. Despite the fact that production of PCBs has decreased steadily since 1971, a 10-year survey by the U.S. Fish and Wildlife Service revealed that although mean residue values of PCBs have declined in fish, maximum values have increased in highly contaminated areas (Schmitt et al. 1981). Therefore, the estimated one billion pounds residing in serviceable equipment and landfills may continue to threaten our aquatic resources for some time. The presence of PCBs in the environment is well documented in the literature. They have been isolated from a variety of aquatic and terrestrial species throughout the world. Although the mode of action is still unknown for PCBs, several toxicological trends have been established. Among aquatic organisms, PCBs are more toxic to some invertebrates than to fishes (Sanders and Chandler 1972; Stalling and Mayer 1972), and toxicity to fishes varies from species to species (Hansen et al. 1971; Mayer et al. 1977a). Furthermore, PCBs are more toxic to early life stages of fishes than to later life stages (Nebeker et al. 1974; Schimmel et al. 1974; Mauck et al. 1978). Since PCBs are highly lipophilic, even low concentrations entering the environment can accumulate in the food chain (Mayer et al. 1977a). Thus, predators at higher trophic levels, such as fishes, can become affected directly from the surrounding water and indirectly via the food chain. In addition, PCBs have been shown to suppress avian and mammalian immune responses (Vos, 1972; Vos and Driel�"Crootenhuis 1972; Vos and de Roij 1972; Koller and Thigpen 1973; Wasserman et al. 1973; Fishbein 1974; Harris et al. 1976), and are therefore suspected of increasing disease susceptibility in higher animals. The increased occurrence of diseased fishes inhabiting polluted ecosystems catalyzed a number of contaminant-disease interaction studies on aquatic organisms. Ishikawa et al. (1975) and Ishikawa and Takayama (1979) induced liver neoplasms in medaka Oryzias latipes by the addition of diethyInitrosamine to water. Exposure to Aroclor 1254 (Couch and Courtney 1977) and mirex (Couch et al. 1975) increased the incidence of a shrimp-specific Baculovirus in feral pink shrimp Paneaus durarum. Similarly, bacterial Proteus vulgaris and viral (infectious pancreatic necrosis-IPN) infections were induced in zebrafish Brachydanio rerio by zinc (Sarot and Perlmutter 1976), and copper increased the susceptibility of rainbow trout Salmo gairdneri to IPN virus (Hetrick et al. 1979) and to enteric redmouth Yersinia ruckeri bacterial disease (Knittel 1980, 1981). Knittel (1980) also found that cadmium increased susceptibility of rainbow trout to Y. ruckeri, but zinc (98 ug/liter) either decreased disease susceptibility or had no effect (59 ug/liter). However, in studies that were not intended to assess contaminant-disease interactions, coincidental development of disease was observed in fish exposed to Aroclor 1254 (Hansen et al. 1971, 1973; Schimmel et al. 1974; Couch 1975; Snarski and Puglisi 1976). Even though the toxicity of PCBs to fishes has been intensively studied, only pure technical PCBs have been utilized in most experiments. The majority of PCBs enter the environment after long-term use, and the resulting waste oil may contain not only PCBs, but other chemicals and impurities even more toxic than PCBs (Buser et al. 1978). Consequently, we conducted a laboratory study to compare the toxicity of technical PCBs and used transformer oil containing PCBs to rainbow trout and the effects of these two PCB materials on disease susceptibility.