Reduction of Biodiesel Cost Indirectly by Biological Treatment: Improving the Nutritive Value of Deoiled Jatropha Curcas Seed Meal for Potential Feed Use

The deoiled Jatropha curcas seed meal (DJSM) was fermented by mixed strains of Candida utilis and Geotrichum candidum under solid-state fermentation to improve their nutritive value. Maximum crude protein (CP) content in substrate was observed at 100% (w/w) substrate moisture and a growth period of 4 days. The statistic analysis results showed that the CP growth rate, in vitro CP digestibility, ammonia nitrogen content and protease activity in fermented DJSM was enhanced significantly (p<0.05) when the substrate supplemented with carbon source. Compared with non-fermented DJSM, the CP content, in vitro CP digestibility and ammonia nitrogen content of fermented DJSM were increased by 0.48-fold, 15.6-fold and 37-fold, respectively, and the protease activity was enhanced up to 2100 U/gds. In addition, the total amino acids (TAA) and essential amino acids (EAA) contents were raised by 18.55% and 20.47%, respectively. Especially, the levels of valine, lysine and isoleucine were increased greatly (P<0.05). These results demonstrated that the nutritive value of DJSM was improved significantly after solid-state fermentation by mixed strains.