Isolation and identification of a Bacillus megaterium strain with ochratoxin A removal ability and antifungal activity

Ochratoxin A (OTA) is a type of mycotoxin mainly produced by fungus belonging to the genus Aspergillus and Penicillium and plays a critical role in food safety since it causes serious health problem. Biological control by using microorganisms is considered a promising approach for detoxification of this mycotoxin. In order to find bacteria with efficient OTA elimination capability, one bacteria strain JSW-B1 with OTA removal ability was isolated from soil samples and was identified as Bacillus megaterium based on morphological and 16S rRNA analysis. After incubation of isolate JSW-B1 in liquid culture medium containing 2.5 mu g/mL OTA for 72 h, the OTA removal percentage was 80.3%. No degradation products of OTA could be detected by liquid chromatography. About 62.6% OTA could be removed by the viable cell fraction after incubation for 72 h compared to 13.7% by cell-free supernatant. Meanwhile, heat treatment significantly enhanced OTA removing capability of the cells, suggesting that the OTA removal activity of the isolate JSW-B1 was mainly attributed to the adsorption by bacterial cells. In addition, the antifungal experiments revealed that isolate JSW-B1 was able to suppress the mycelial growth of Aspergillus ochraceus on solid medium with an inhibition ratio of 41.9% and reduce the fungal incidence on maize corns with a reduction ratio of 15%. Taken together, our results indicated that B. megaterium JSW-B1 could be considered as potential biological agent to control toxigenic fungal growth and mycotoxin contamination in agricultural products.