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This work aims to select biological treatments and conditions for the bioconversion of rape straw by the mixed-strain fermentation of Ganoderma lucidum and yeasts (Saccharomyces cerevisiae, Candida tropicalis and Candida utilis), into an enriched substrate with increased crude protein and digestibility. Orthogonal experiment showed that the optimal experimental condition for the crude protein enrichment was: 10% (v/w) C. utilis inoculum was added to the rape straw medium after 7 days of G. lucidum growth; the crude protein content of the substrate was 16.23%; the yield rate were increased by 75.70 and 225.90%, respectively when compared to the G. lucidum individual-fermentation and without fermentation substrate. The results in this study also indicated that: the co-culture of 2 fungi (G. lucidum + C. utilis) was better than individual (G. lucidum) culture on the degradation of cellulose and lignin of rape straw substrate and the secretion of ligninolytic enzyme system including laccase (Lac), manganese peroxidase (MnP) and lignin peroxidase (LiP).
Key words: Bioconversion, rape straw, nutritionally enrichment, Ganoderma lucidum, yeast.