## 1 Introduction  
Foodborne illnesses are caused by consuming food that is contaminated by the presence of bacteria, viruses, or parasites that have entered the body [1]. Preservatives are used for heating and drying, but they can reduce the quality and change the texture of the food [2]. The shelf life of foods is currently being extended by the use of preservative chemicals, many of which are dangerous. Such chemicals are especially dangerous in non-food groups. In addition, some people think that these chemicals are not good for health because they can cause diseases, such as cancer. These drawbacks have triggered the discovery and development of natural preservatives [3].  
A biopreservative involves the use of microorganisms or natural products [3]. Biopreservative substances such as lactic acid bacteria (LAB), which have antibacterial properties, have long been used [1]. However, during the process of using biopreservatives, changes in the taste, texture, and odor of a product take place, so the use of lactic acid bacteria as a biological preservative has been limited. It can safely extend the shelf life of food without causing health effects and it can produce other compounds with antibacterial properties, specifically other bacteria, so research regarding the isolation and potency of LAB is currently underway.  
Bacteriocins are antibacterial peptides that have received GRAS (generally recognized as safe) status from the FDA, so it is safe to use them as biological preservatives [4]. Bacteriocins, as biological preservatives, can be used to control microbial contaminants in foods, but their commercial potential is limited and their costs are relatively high. Bacterial production in Indonesia requires much more exploration and innovation. Among the efforts undertaken to explore the production of bacteria is the production of bacteria from food. Bacteria-producing LAB, such as _Lactobacillus pentosus_, have been found in some fermented foods. The bacterium _L. pentosus_ can be isolated from fermented products such as dadih, which is made from the milk of buffalo that are native to West Sumatra, Indonesia [5].  
The bacterium _L. pentosus_ was isolated from the feces of healthy infants and showed potent antibacterial activity and probiotic compounds [6]. The newly studied dadih bacteriocin _L. pentosus_ is a crude bacteriocin, showing antibacterial activity against _Salmonella_ sp., _Escherichia coli_, and _Staphylococcus aureus_[7].  
A purification process can increase the specific activity of bacteriocins, so that the resulting activity is purely that of bacteriocins and is safer for consumption because it reduces other components that are not safe to eat or are of non-food grade [8; 9]. In addition, to determine the activity of pure bacteriocin, it is necessary to test the antimicrobial activity against indicator bacteria [8; 10]. A partial bacteriocin characterization was carried out to determine the characteristics of partial bacteriocins through testing on pH, temperature, surfactant, and salt. A food test can predict the properties of bacteriocins at the level of partial purification for application. Exploration and purification of bacteriocins from food will always present new alternatives, so characterization is carried out.  
In this study, _L. pentosus_ was isolated from fermented buffalo milk. The bacteriocin was produced in three steps: the production of crude bacteriocin, the partial purification by ammonium sulfate precipitation, and the purification by gel filtration chromatography with Sephadex LH-20. The antibacterial activity, specific activity, and molecular weight of bacteriocins were determined. In addition, the effects of temperature, pH, surfactants, and salt were also considered to determine the stability of bacteriocin.