THE PROPERTIES OF BACTERIOCINS OBTAINED UNDER THE DIFFERENT CONDITIONS

Bacteriocines are substances of protein nature, which are produced by many strains of microorgamisms. Due to the fact that bacteriocins are effectively used as antimicrobial agents in medicine and food industry, isolation and study of the properties of new bacteriocins-producing strains is very important. It should be noted that production of bacteriocins by microbial cells directly depends on strain cultivation conditions and methods of bacteriocin isolation. Among other cultivation parameters such as temperature and the active acidity of the culture medium, the duration of cultivation directly influences the synthesis of bacteriocins. Thus, the selection of the optimum duration of strains cultivation and method of bacteriocin isolation would allow us to increase significantly the bacteriocin production and, hence the antimicrobial activity of the strains. Therefore, determination of the optimum duration of cultivation and method of bacteriocins isolation is a very important step for getting bacteriocins with maximum activity. In this study, the isolation of microbial cultures from the fresh onion surface and the identification of these strains by sequencing of the 16S RNA gene were carried out. Also their morphological and physiological-and-biochemical properties were studied. The optimum cultivation duration was performed by using the determination of the antimicrobial activity in different time intervals. The strain cultivation was carried out during 24 hours. Three methods were used to isolate bacteriocins. They were based on the using of activated carbon, ammonium sulfate, and chloroform. The antimicrobial activity of bacteriocins was studied by means of the disk diffusion method. The identification of the isolated strains has revealed that the strains belong to Bacillus safensis and Bacillus pumilus species. It was found that the bacteriocins had the greatest antimicrobial activity when being cultivated for 18 hours and using method based on ammonium sulfate precipitation.