Single cell protein production from stillage by saccharomyces cerevisiae using fed-batch fermentation

Abstract

Waste treatment was one of the important problems in ethanol fermentation plants. Due to the very high organic matter of yeast cell and sugar residue in the fermentation broth, treatment of the stillage was found difficult to meet the regulatory discharge limits. To reduce the amount of stillatge for the waste treatment, re-use of cane molasses alcohol stillage in single cell protein production using Saccharomyces cerevisiae M30 was investgated. The system variables in batch fermentation were investigated including pH, ammonium sulfate concentration, initial sugar concentration, and proportion of stillage replacement. The optimal initial pH and ammonium sulfate concentration for cell production was 4.5 anf 0.10% (w/v). respectively. It was found that in the production of biomass by Saccharomyces cerevisiae M30 with initial total inverse sugar 6-10% w/v, it was viable to replace 40-60% to total fresh water by cane molasses alcohol stillage. No inhibition effect due to the substitution of 0-40% stillage was observed. To achieve high mass concentration, cultivation of cell at stepwise addition of medium was used to optimize the cell production. Using single fed batch culture and repeated fed batch, biomass accumulation was increased by a factor of 1.3 and 2.1, respectively, relative to the vatch culture. The biomass productivities from batch. single fed-batch culture and repeated fed-batch, were 0.12, 0.17 and 0.21 g/l.h, respectively. The results indicated that there exists a good potential for the use of alsohol stillage to replace of fresh water for single cell protien production