Bio-detoxification ofJatropha curcasL. cake by a soil-borneMucor circinelloidesstrain using a zebrafish survival model and solid-state fermentation

Aims The aims of the study were to (i) improve the evaluation criteria of detoxifyingJatropha curcasL. cake (JCC), (ii) isolate and characterize a JCC tolerant strain, (iii) explore its JCC detoxifying potential. Methods and Results The zebrafish was employed as a survival model to screen the strains capable of detoxifying JCC. A strain identified asMucor circinelloidesSCYA25, which is highly capable of degrading all toxic components, was isolated from soil. Different solid-state fermentation parameters were optimized by response surface methodology. The optimal values for inoculation amount, moisture content, temperature, and time were found to be 18% (1 center dot 8 x 10(6)spores g(-1)cake), 66%, 26, and 36 days, respectively, to achieve maximum detoxification of the JCC (92%). Under optimal fermentation conditions, the protein content of JCC was increased, while the concentrations of ether extract, crude fiber, toxins, and anti-nutritional substances were all degraded considerably (P 0 center dot 05). Scanning electron microscopy and Fourier transform infrared spectrometer analysis revealed that the fermentation process could disrupt the surface structure and improve the ratio of alpha-helix to beta-folding in the JCC protein, which may improve the digestibility when the detoxified JCC is used as a feedstuff. Conclusions Our results indicate thatM. circinelloidesSCYA25 is able to detoxify JCC and improve its nutritional profile, which is beneficial to the safe utilization of JCC as a protein feedstuff. Significance and Impact of the Study The newly identifiedM. circinelloidesSCYA25 detoxified JCC in a safe manner to provide a potential alternative to soybean meal for the feed industry. These results also provide a new perspective and method for the toxicity evaluation and utilization of JCC and similar toxic agricultural by-products.