Optimization of cell yield of Candida krusei SO1 and Saccharomyces sp. LK3G cultured in sorghum hydrolysate

The fed-batch approach to the production of single-cell protein (SCP) from synthetic glucose medium or sorghum hydrolysate by Candida krusei SO1 and Saccharomyces sp. LK3G was studied in aerobic conditions. The results obtained with a synthetic glucose showed better growth parameters under fed-batch conditions than under batch conditions. Biomass yield (Yx/s) was increased by as much as 64% for Candida krusei and for Saccharomyces sp. LK3G by as much as 70%. Volumetric cell productivity was also improved for both yeasts: 0.75 g/l.h in fed-batch conditions against 0.68 g/l.h in batch conditions for Candida krusei SO1 and 0.63 g/l.h against 0.56 g/l.h for Saccharomyces sp. LK3G. Chemical analyses of yeast cells grown on either synthetic medium or on sorghum hydrolysate showed that the fed-batch process did not alter the nutritional quality of either yeast strain: in these conditions their protein content (47–50%) and their amino acid profiles compared favourably with the Food and Agricultural Organization references. Furthermore, both yeast strains were good sources of mineral salts.