Tween 40 pretreatment of unwashed water-insoluble solids of reed straw and corn stover pretreated with liquid hot water to obtain high concentrations of bioethanol

Jie Lu,Xuezhi Li,Jian Zhao,Ruifeng Yang,Yinbo Qu

doi:10.1186/1754-6834-6-159

Abstract

BackgroundLiquid hot water (LHW) pretreatment is an effective and environmentally friendly method to produce bioethanol with lignocellulosic materials. In our previous study, high ethanol concentration and ethanol yield were obtained from water-insoluble solids (WIS) of reed straw and corn stover pretreated with LHW by using fed-batch semi-simultaneous saccharification and fermentation (S-SSF). However, high cellulase loading and the large amount of wash water possibly limit the practical application of LHW pretreatment. To decrease cellulase loading and the amount of wash water, we performed Tween 40 pretreatment before WIS was subjected to bioethanol fermentation.ResultsResults showed that the optimum conditions of Tween 40 pretreatment were as follows: Tween 40 concentration of 1.5%, WIS-to-Tween 40 ratio of 1:10 (w/v), and pretreatment time of 1 hour at ambient temperature. After Tween 40 pretreatment, cellulase loading could be greatly reduced. After Tween 40 pretreatment, the residual liquid could be recycled for utilization but slightly affected ethanol concentration and yield. The unwashed WIS could obtain a high ethanol concentration of 56.28 g/L (reed straw) and 52.26 g/L (corn stover) by Tween 40 pretreatment using fed-batch S-SSF. Ethanol yield reached a maximum of 69.1% (reed straw) and 71.1% (corn stover).ConclusionsTween 40 pretreatment was a very effective and less costly method with unwashed WIS. This pretreatment could greatly reduce cellulase loading and save wash water. Higher ethanol concentration was obtained almost without reducing ethanol yield.

Highlights

Liquid hot water (LHW) pretreatment is an effective and environmentally friendly method to produce bioethanol with lignocellulosic materials
The ethanol concentration was approximately equal to that of the washed water-insoluble solids (WIS) when the unwashed WIS was pretreated with Tween 40, but the washed WIS was treated with Tween 40 to slightly increase ethanol concentration compared with washed WIS without Tween 40, indicating that Tween 40 pretreatment is more suitable for unwashed WIS
Ethanol concentrations obtained from water-pretreated unwashed WIS were 22.11 g/L and 28.14 g/L, respectively

Summary

Introduction

Liquid hot water (LHW) pretreatment is an effective and environmentally friendly method to produce bioethanol with lignocellulosic materials. High ethanol concentration and ethanol yield were obtained from water-insoluble solids (WIS) of reed straw and corn stover pretreated with LHW by using fed-batch semi-simultaneous saccharification and fermentation (S-SSF). To decrease cellulase loading and the amount of wash water, we performed Tween 40 pretreatment before WIS was subjected to bioethanol fermentation. Lignocellulosic materials are subjected to bioethanol conversion performed in three steps: pretreatment; enzymatic hydrolysis; and fermentation [1]. Studies about the mechanism of Tween additives on enzymatic hydrolysis and fermentation of lignocellulosic materials have been proposed [18,19,20,21]. Different methods of applying Tween additives produce different results of bioethanol fermentation.

Methods

Results

Conclusion