Antibacterial activity of lactic acid bacteria community SFC-2 used for fer-mentation of air-dried crop straws

Abstract:

[Objective] To evaluate the antibacterial activity of lactic acid bacteria community SFC-2 in fermented crop straw. [Methods] Total 13 isolates were obtained from spontaneous fermented rice straw by plating, paper diffusion and Denaturing Gradient Gel Electrophoresis. All these strains were used to determine the antibacterial activity of SFC-2. [Results] (1) Phylogenetic analysis of the 13 strains based on 16S rDNA gene sequence data indicated that 9 strains belong to Enterobacter cloacae, Klebsiella oxytoca, Bacillus cereus, Klebsiella pneumoniae, Citrobacter freundii, Klebsiella terrigena and Citrobacter sp., which were all common pathogens or opportunistic pathogens. (2) Indicating bacteria selected from the pathogens were used to detect antibacterial activity of SFC-2 cell-free culture supernatant. The results showed that: SFC-2 community had stronger antibacterial activity than isolated strains from SFC-2 community or man-made communities against indicating bacteria. (3) Antibacterial activities of seven different cell-free culture supernatants, which were extracted at intervals from the culture of SFC-2 community during 14-48 hours, were no obvious difference, but the content of organic acids were obvious differences during 14-48 hours; the antibacterial substances were stable after heating and sensitive partly to protease K.