Abstract
Debaryomyces nepalensis NCYC 3413, halotolerant yeast isolated from rotten apple, was capable of utilizing components of hemicellulose hydrolysate such as glucose, galactose, mannose, xylose and arabinose. The organism utilizes xylose as a sole carbon source and produces xylitol. The Plackett-Burman design was applied to determine the specific medium components affecting xylitol production and found that xylose, K2HPO4, and ZnSO4 were critical in augmenting xylitol production. These significant parameters were further optimized using response surface methodology. The optimum concentrations of xylose, K2HPO4, and ZnSO4 were found to be 100 g/l, 10.6 g/l and 8.9 mg/l respectively. Under these optimal conditions the xylitol production increased from 27 g/l to 36 g/l with a yield of 0.44 g/g (57% increase in total yield). In addition, formation of the by product (glycerol) was decreased under optimal conditions.
Highlights
Lignocelluloses are the largest renewable source of energy and bioconversion of lignocelluloses to commercial products is a rational way of making use of this source
Debaryomyces nepalensis NCYC 3413, halotolerant yeast isolated from rotten apple, was capable of utilizing components of hemicellulose hydrolysate such as glucose, galactose, mannose, xylose and arabinose
A total of 14 components were screened for their effect on xylitol production by D. nepalensis NCYC 3413 using the Plackett-Burman design
Summary
Lignocelluloses are the largest renewable source of energy and bioconversion of lignocelluloses to commercial products is a rational way of making use of this source. Agricultural residues contain 37% of hemicelluloses which can be used as raw material for the production of useful compounds using chemical and biotechnological processes. One such compound is xylitol which has application in medical and food industries. The current industrial production of xylitol is by chemical reduction of D-xylose in the presence of a nickel catalyst at high temperature and pressure, which is laborious and expensive [1,2]. Microbial xylitol production from renewable sources like plant biomass rich in hemicelluloses is worthwhile since it is environment-friendly and economically viable [3]. The efficient bioconversion of both glucose and xylose components of the hemicellulose hydrolysate is essential for the economic production of industrially important metabolites.
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