Rapid detoxification of Jatropha curcas cake by fermentation with a combination of three microbial strains and characterization of their metabolic profiles.

Abstract

Our previous study reported a strain that can detoxify Jatropha curcas L. cake (JCC), but the detoxification duration is long. This study intends to explore the efficient detoxification of JCC through multi-strain collaborative fermentation to accelerate the detoxification process. Mucor circinelloides SCYA25 strain that we previously reported can effectively degrade the toxicity of JCC, and the newly screened Bacillus megaterium SCYA10 and Geotrichum candidum SCYA23 strains were used to detoxify JCC. Different solid-state-fermentation (SSF) parameters were optimized by single-factor tests and response surface methodology. A detoxification rate established by zebrafish toxicity of JCC at 96% was achieved under the following optimized conditions: the combination ratio of B. megaterium SCYA10, G. candidum SCYA23 and M. circinelloides SCYA25 at 2:3:1, a total injection amount of 15.25%, a feed to water ratio of 1:0.68, a fermentation temperature of 30.3°C and fermentation duration of 21.5 days. The protein content of fermented JCC (FJCC) increased, while the concentrations of ether extract, crude fibre and toxins were all degraded considerably. Metabolomics analysis revealed that the fermentation increased the contents of neurotransmitter receptor modulator, emulsifier, aromatic substances and insecticidal compounds, as well as decreasing the contents of oxidative stress and neurotoxic substances. A rat feeding trial showed that the growth performance of the rats provided with the FJCC diet was similar to that of the corn-soybean meal group, and no lesions in the liver and kidney were observed. The co-bio-fermentation process can effectively detoxify JCC and improve its nutritional value, which means it could be served as a protein feed in animal husbandry. The combination of three microbial strains can detoxify JCC in a safe and effective manner to provide a great potential alternative to soybean meal. The research also suggests that metabonomics and bioinformatics are useful tools for revealing the bio-detoxification mechanism.