Safety and probiotic evaluation of two Bacillus strains producing antioxidant compounds.

Bacillus species are becoming increasingly relevant for use as probiotics or feed additives where their heat stability can ensure survival in the food matrix or enable long-term storage at ambient temperature. Some Bacillus species are pigmented and in this study, we have examined two strains, one Bacillus pumilus (pigmented red) and the other Bacillus megaterium (pigmented yellow) for their safety for potential use in humans as dietary supplements. In addition, we have set out to determine if they might confer any potential health benefits. Both strains produce C30 carotenoids while the B. pumilus strain also produced large quantities of riboflavin equivalent to genetically modified Bacillus strains and most probably contributing to this strain's pigmentation. Riboflavin's and carotenoids are antioxidants, and we have evaluated the ability of vegetative cells and/or spores to influence populations of Faecalibacterium prausnitzii in the colon of mice. While both strains increased levels of F. prausnitzii, spores of the B. pumilus strain produced a significant increase in F. prausnitzii levels. If found to be reproducible in humans such an effect might, potentially, confer health benefits particularly for those suffering from inflammatory bowel disease.