Production of cellulosic ethanol from alkali treated wheat straw using P-SSF process and bioconversion of hemicellulosic fraction into high value products

Abstract

Lignocellulosic biomass is an attractive resource for production of ethanol because of its abundance and lower cost. The economics of lignocellulosic ethanol production can be improved by enhancing the ethanol titres along with utilisation of waste generated during bioconversion process. The present study was aimed at development of a bioconversion process for production high concentration of ethanol from alkali treated cellulose rich wheat straw (WS) and utilization of unused hemicellulosic fraction into value added products. WS was subjected to microwave assisted alkali (MAA) treatment. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to analyse structural changes in untreated and pretreated WS. Bioethanol production from pretreated WS was carried out by pre hydrolysis and simultaneous saccharification and fermentation (P-SSF) process using newly isolated Saccharomyces cerevisisae SM1. Liquid fraction generated during pretreatment was utilised for xylooligosaccharides (XOS) production using indigenously produced endoxylanase. MAA treatment of WS was successful in enriching cellulose content of WS by solubilizing hemicellulose and lignin. Ethanol fermentation by P-SSF method lead to high concentration of ethanol (42.10±1.15 g/L) in 48 h. Ethanol productivity and yield were, 0.88 g/L/h and 69.14%, respectively. It can be predicted that 7.143 tons of raw WS may be required to produce 1 ton of ethanol and for additional revenue 191.93 kg xylitol and 263.58 kg XOS (DP2 - DP5) can also be produced simultaneously. The study has demonstrated the feasibility of a bio-refinery process for production of value added compounds in addition to high ethanol yields.