Purpose: The purpose is to examine the dominant aerobic sporeformers during traditional maari productions, in order to select starter cultures.
Methods: The dominant microorganisms isolated from maari were screened for antimicrobial activity by agar well diffusion method. Then, SDS-PAGE and PCR were used to characterize the antimicrobial substances. Finally, the kinetics of bacteriocin production and the effect of aeration on bacteriocin production were studied.
Results: Three Bacillus subtilis strains (B3, B122 and B222) in particular had antimicrobial activity against some Gram positive organisms and were selected for further studies. It was found that the antimicrobial substances produced were heat-stable, insensitive to catalase, sensitive to protease and trypsin but resistant to the proteolytic action of papain and proteinase K and equally active at pH values ranging from 3 to 11. Bacteriocin secretion started in late exponential growth phase and maximum activity was detected during the stationary growth phase. Maximum production of bacteriocin was observed under reduced aeration. Specific primers were used to screen isolates B3, B122 and B222 for genes involved in the synthesis of the bacteriocins subtilosin A, subtilin, sublancin and ericin. Amplicons of the expected sizes were detected for iywB, sboA, sboX, albA and spaS involved in the biosynthesis of subtilosin and subtilin, respectively.
Significance: The present study contributes to the selection of Bacillus strains to be used as starter cultures for controlled production of maari.