Improving probiotic spore yield using rice straw hydrolysate

Spore‐forming Bacillus sp. has been extensively studied for their probiotic properties. In this study, an acid‐treated rice straw hydrolysate was used as carbon source to produce the spores of Bacillus coagulans. The results showed that this hydrolysate significantly improved the spore yield compared with other carbon sources such as glucose. Three significant medium components including rice straw hydrolysate, MnSO4 and yeast extract were screened by Plackett–Burman design. These significant variables were further optimized by response surface methodology (RSM). The optimal values of the medium components were rice straw hydolysate of 27% (v/v), MnSO4 of 0·78 g l−1 and yeast extract of 1·2 g l−1. The optimized medium and RSM model for spore production were validated in a 5 l bioreactor. Overall, this sporulation medium containing acid‐treated rice straw hydrolysate has a potential to be used in the production of B. coagulans spores. Significance and Impact of the Study: Endospore‐forming Bacillus sp. as probiotic supplements in human and animals has received increasing attentions in the last decade. Nevertheless, low spore yield has limited the commercial application. We found a novel sporulation medium containing acid‐pretreated rice straw hydrolysate, which greatly improved the spore yield of Bacillus coagulans. Then, various components in sporulation medium were further optimized for high spore yield using response surface methodology. This low cost and easily available medium from agricultural residues has a potential in large‐scale production of B. coagulans spores. To our knowledge, the production of Bacillus spores using lignocellulosic hydrolysate has not been reported in the previous researches.