Degradation and selective ligninolysis of wheat straw and banana stem for an efficient bioethanol production using fungal and chemical pretreatment.

Shilpi Thakur,Bhuvnesh Shrivastava,Snehal Ingale,Akshaya Gupte,Ramesh C Kuhad

doi:10.1007/s13205-012-0102-4

Shilpi Thakur, Bhuvnesh Shrivastava + Show 3 more

Open Access

https://doi.org/10.1007/s13205-012-0102-4

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Abstract

Lignocelluloses from agricultural, industrial, and forest residues constitute a majority of the total biomass present in the world. Environmental concerns of disposal, costly pretreatment options prior to disposal, and increased need to save valuable resources have led to the development of value-added alternate technologies such as bioethanol production from lignocellulosic wastes. In the present study, biologically pretreated (with the fungus, Pleurotus ostreatus HP-1) and chemically pretreated (with mild acid or dilute alkali) wheat straw (WS) and banana stem (BS) were subsequently subjected to enzymatic saccharification (with mixture of 6.0 U/g of filter paper cellulase and 17 U/g of β-glucosidase) and were evaluated for bioethanol production using Saccharomyces cerevisiae NCIM 3570. Biological and chemical pretreatments removed up to 4.0–49.2 % lignin from the WS and BS which was comparatively higher than that for cellulose (0.3–12.4 %) and for hemicellulose (0.7–21.8 %) removal with an average 5.6–49.5 % dry matter loss. Enzymatic hydrolysis yielded 64–306.6 mg/g (1.5–15 g/L) reducing sugars from which 0.15–0.54 g/g ethanol was produced from Saccharomyces cerevisiae NCIM 3570.

Highlights

Industrial bioconversion of renewable resources to bioethanol is a promising alternative to petroleum-based chemical synthesis (Volynets and Dahman 2011)
Dilute acid and mild alkali pretreatments are effective in targeting hemicelluloses and lignin, respectively (Talebnia et al 2010)
Mild alkali (1 N NaOH) and dilute acid (1 N H2SO4) pretreatments were evaluated on each lignocellulosic substrate (WS and banana stem (BS)) separately

Summary

Introduction

Industrial bioconversion of renewable resources to bioethanol is a promising alternative to petroleum-based chemical synthesis (Volynets and Dahman 2011). In this context, lignocelluloses, the most abundant source of sugars, are a potential candidate for obtaining energy in the form of charcoal, hydrogen, ethanol, and biogas; the last three of which require hydrolysis of the lignocellulosic material. Considerable developments in pretreatment techniques for improving the rate of release and total yield of sugars in the hydrolysis step have been made (Hendriks and Zeeman 2009) and using these processes substantial amounts of lignin and Biological pretreatment comprises the use of microorganisms especially brown rot, soft rot and/or white-rot fungi to selectively degrade lignin and hemicellulose. Though the use of biological pretreatment is considered safe, environmentally friendly and less energy consuming compared to other pretreatment methods, the rate of hydrolysis is low and needs improvement to make it a commercially viable proposition

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