Bio‐detoxification of Jatropha curcas L. cake by a soil‐borne Mucor circinelloides strain using a zebrafish survival model and solid‐state fermentation

Abstract

Aims The aims of the study were to (i) improve the evaluation criteria of detoxifying Jatropha curcas L. 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 as Mucor circinelloides SCYA25, 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% (1·8 × 106 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 < 0·05). Scanning electron microscopy and Fourier transform infrared spectrometer analysis revealed that the fermentation process could disrupt the surface structure and improve the ratio of α‐helix to β‐folding in the JCC protein, which may improve the digestibility when the detoxified JCC is used as a feedstuff. Conclusions Our results indicate that M. circinelloides SCYA25 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 identified M. circinelloides SCYA25 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.

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

“…A 50 μl of the dilutions were spread onto beef extract peptone agar plates and potato dextrose agar plates to cultivate bacteria and fungi, respectively. The strain screening process was carried out the same as previously described (Zhang et al, 2021). The bacteria were observed routinely by light microscopy and gram staining, according to Bergey's manual of determinative bacteriology (Bergey et al, 1923).…”

“…As shown in Table 1, a total of 29 trials were set, with five replicates at the centre. The operating procedures of the zebrafish toxicity test in this study were the same as in our previous study, with 50 zebrafish per tank (Zhang et al, 2021). A quadratic polynomial equation was applied to the experimental data, as shown in Equation .$$$$ Y=a0+a1A+a2B+a3C+a4D+a12 AB+a13 AC+a14 AD+a23 BC+a24 BD+a34 CD+a11{A}^2+a22{B}^2+a33{C}^2+a44{D}^2 $$$$where Y is the dependent variable, and a0 is the fitting response value of the design centre; a1, a2, a3 and a4 are linear coefficients; a12, a13, a14, a23, a24 and a34 are cross‐coefficients; a11, a22, a33 and a44 are quadratic coefficients.…”

“…detoxification, Jatropha curcas, metabolite, protein feed, rat feeding model, waste screening process was carried out the same as previously described (Zhang et al, 2021). The bacteria were observed routinely by light microscopy and gram staining, according to Bergey's manual of determinative bacteriology (Bergey et al, 1923).…”

“…In order to evaluate the detoxification rate of JCC, we applied a zebrafish survival model for JCC toxicity evaluation from a previous study, and a microbial strain, Mucor circinelloides SCYA25, was selected to detoxify JCC (Zhang et al, 2021). Although M. circinelloides SCYA25 has a high detoxification rate of JCC at 94%, it has a long fermentation duration, a common shortcoming of the fermentation process by single strains.…”

Benefits and Challenges of Jatropha Meal as Novel Biofeed for Animal Production

“…Rapeseed, cottonseed, and soybean meals are common by-products of the seed oil industry. The products have been recommended as a feed additive for livestock as it contains a high level of protein and low level of fiber [ 8 , 9 ]. Furthermore, it contains lignin, cellulose, amino acids, proteins, and polyphenolic compounds [ 10 ].…”