PRODUCTION OF MICROBIOLOGICAL PROTEIN FEED FROM SWEET POTATO (Ipomoea batatas L. Lam) RESIDUE BY CO-CULTIVATION SACCHAROMYCES CEREVISIAE AND CANDIDA UTILIS

Sweet potato residue (SPR), a byproduct generated during starch extraction from sweet potato, is usually treated as an agro-waste, resulting in lower economic benefits and serious environmental pollution. To promote resource recycling, SPR was used as a starting material to prepare a microbiological protein feed (MPF) by co-cultivating Saccharomyces cerevisiae and Candida utilis . The cultivation conditions were investigated, and the optimum conditions were determined as follows: inoculation amount of S. cerevisiae , 5%; inoculation amount of C. utilis , 5%; water content of SPR, 75%; urea, 1%; cellulase, 0.5%; and isoamylase, 0.5%, at a culture temperature of 32°C. Under these conditions, true protein content in fermented SPR was enhanced to 18.08%, which was 6.34 times that of the original SPR. Amino acid composition and the essential amino acid index (EAAI) indicated the high nutritive value of MPF to cattle, rabbits, and lambs. This simple method provides a strategy for recycling and reusing agricultural residues in an economical and environment-friendly manner.