Enhanced viability of Lactobacillus reuteri for probiotics production in mixed solid-state fermentation in the presence of Bacillus subtilis

In order to develop a multi-microbe probiotic preparation of Lactobacillus reuteri G8-5 and Bacillus subtilis MA139 in solid-state fermentation, a series of parameters were optimized sequentially in shake flask culture. The effect of supplementation of B. subtilis MA139 as starters on the viability of L. reuteri G8-5 was also explored. The results showed that the optimized process was as follows: water content, 50 %; initial pH of diluted molasses, 6.5; inocula volume, 2 %; flask dry contents, 30 similar to 35 g/250 g without sterilization; and fermentation time, 2 days. The multi-microbial preparations finally provided the maximum concentration of Lactobacillus of about 9.01 +/- 0.15 log CFU/g and spores of Bacillus of about 10.30 +/- 0.08 log CFU/g. Compared with pure fermentation of L. reuteri G8-5, significantly high viable cells, low value of pH, and reducing sugar in solid substrates were achieved in mixed fermentation in the presence of B. subtilis MA139 (P < 0.05). Meanwhile, the mixed fermentation showed the significantly higher antimicrobial activity against E. coli K88 (P < 0.05). Based on the overall results, the optimized process enhanced the production of multi-microbe probiotics in solid-state fermentation with low cost. Moreover, the viability of L. reuteri G8-5 could be significantly enhanced in the presence of B. subtilis MA139 in solid-state fermentation, which favored the production of probiotics for animal use.