Investigations on microbial fermentation of hemicellulose hydrolysate for xylitol production.

Abstract

A crude trial on microbial fermentation of dilute acid treated hemicellulose hydrolysate of water hyacinth (Eichhornia crassipes) biomass was performed in batch culture in a BOD rotary shaker using four different species as Candida shehatae, Pichia stipitis, Candida tropicalis and Debaromyces hansenii under various parameters to check the optimal xylitol production. The hydrolysate was concentrated using a vacuum evaporator at 70C and detoxified using activated charcoal (5 %) which efficiently removed 83 % of inhibitory phenolic biproducts. Effect of nutrients concentration, pH (4.5, 5.5, 6.5), temperature (20, 30, 40C) and agitation speed (150, 200, 250 rpm) on growth of different yeast and xylitol production was studied and compared. The optimal xylitol yield was found to be 0.65 g xylitol/g of xylose from Candida tropicalis at 30C, pH 5.5 with an agitation of 200 rpm, 2.5 g/L ammonium sulphate as a nutrient and 0.615 xylitol/g of xylose from Pichia stipitis respectively after 72 h of incubation. Keyword: Microbial fermentation, water hyacinth biomass, xylitol production, yeast, detoxification.