Microbial production of xylitol from the hydrolysis products of selected agricultural wastes

Date

2017

Abstract

Three kinds of lignocellulosic agricultural wastes, sugarcane bagasse (SB), corn cobs (CC) and corn stovers(CS) were hydrolyzed as sources of xylose sugars for biotechnogical production of xyitol. After comparing, different methods used to pretreat ground SB namely: Acid Hydrolysis using Oil Bath, acid Hydrolysis using Autoclave, Steam Explosion and Steam Explosion of Acid-Treated SB, highest xylose concentration was obtained from acid hydrolysis via autoclaving followed by acid hydrolysis using an oil bath. Acid hydrolysis combined with high temperature treatment using oil bath was used for future scale up purposes and to study statistically the effect of temperature, acid concentration and time on the hydrolysis and xylose yield. This is the first time that optimization studies on the hydrolysis of agricultural feedstocks were conducted using Response Surface methodology which combines factorial experiment designs, statistical models and actual experimentation. The optimum conditions for the high temperature-dilute acid hydrolysis of ground sugar cane bagasse, corn cobs and corn stovers were obtained. Initial detoxification of the resulting hydrolysate was done by pH adjustment. Based on the analysis of variance of the responses (final biomass concentration, final xylose concentration, final xylitol concentration, growth yield, xylitol yield, specific growth rate, and specific xylitol production rate), both Candida tropicalis BIOTECH 2085 or Canada guillermondii BIOTECH 2172, can be used for the fermentation experiments for the production of xylitol from xylose sugars. Using SB hydroysate as substrate and C. tropicalis BIOTECH 2085 as organism, the optimum conditions for the production of xylitol under shake flask scale was obtained with a yield of 4.95 g xylitol/L medium. The optimum conditions for the production of xylitol from CS hydrosylate and C. guilliermondii BIOTECH 2172 as organism was obtained resulting to a yield of 9.63 g xylitol/L medium. Optimization studies for the production of xylitol from CC hydrosylate and C. guilliermondii BIOTECH 2172 as organism were aso conducted, however problems with the growth of the organism in the fermentation medium were encountered. Using SB hydrosylate as substrate, C. tropicalis BIOTECH 2085 as organism and the determined optimum conditions, preliminary kinetic studies of xyitol production was done in a 5-L stirred tank bioreactor. The fermentation profile showed a rapid decrease in xylose concentration with concomitant increase in xylitol during the exponential phase of growth of the organism. At optimum biomass concentration, xylose concentration was the limiting factor for xylitol production. Interestingly, higher xylitol concentration was observed at lower aeration conditions.

Language

English

Document Type

Article

En – AGROVOC descriptors

SUGARCANE; MAIZE; BYPRODUCTS; LIGNOCELLULOSE; XYLOSE; GRICULTURAL WASTES; ENZYMATIC HYDROLYSIS; XYLOSE; XYLITOL

This document is currently not available here.

Share

COinS