Production of single cell protein from rice polishings using Candida utilis

Microbial protein was produced from defatted rice polishings using Candida utilis in shake-flasks and a 14-l fermentor to optimize fermentation conditions before producing biomass in a 50-l fermentor. The organism supported maximum values of 0.224 h−1, 0.94, 1.35, 1.75, 2.12 g l−1 h−1, 0.62 g cells g−1 substrate utilized and 0.38 g g−1 for specific growth rate, true protein productivity, crude protein productivity, cell mass productivity, substrate consumption rate, cell yield, crude protein yield, respectively in 50-l fermentor studies using optimized cultural conditions. Maximum values compared favourably or were superior to published data in literature. The biomass protein in the 50-l fermentor contained 22.3, 27.8, 19.2, 9.5, 38.12, 8.5 and 0.27% true protein, crude protein, crude fibre, ash, carbon, cellulose and RNA content, respectively. The dried biomass showed a gross metabolizable energy value of 2678 kcal kg−1 and contained all essential and non-essential amino acids. Yeast biomass as animal feed may replace expensive feed ingredients currently being used in poultry feed and may improve the economics of feed produced in countries like Pakistan.