Abstract: In order to screen the strains suitable for producing biological feed by solid-state fermentation with grape skin residues, the grape skin residues were used as the main raw material, and the true protein content was used as the evaluation index. To screen the optimal strains for fermentation use, the solid-state fermentation experiment was conducted with single stain or multi-strain combinations of Candida utilis, Saccharomyces cerevisiae, Lactobacillus acidophilus and Lactobacillus plantarum. Furthermore, the effect of solid medium sterilization or non-sterilisation process on the true protein content of the fermentation products was assessed. The results showed that the non-sterilized solid medium containing grape skin residues had higher true protein content in the fermentation products. For single strain fermentation experiment, the highest true protein content （13.75%） was observed in the products fermented with Candida utilis. For mixed strains fermentation experiment, the dual-combination of Candida utilis and Lactobacillus acidophilus had the highest true protein content （13.88%） in fermentation products, and showed better fermentation effect compared to the triple- or quadruple-combination of other strains. It was indicated that the best strains combination for the solid-state fermentation of grape skin residues was Candida utilis and Lactobacillus acidophilus.

Key words: strain, screening, solid-state fermentation, true protein, grape skin residues