Optimisation of enzymatic saccharification of wheat straw pre-treated with sodium hydroxide

Zhiquan Wang,Wei Zhang,Hainan Kong,Chunzhen Fan,Deyi Wu,Xinze Wang,Suqing Wu,Xiangyong Zheng

doi:10.1038/s41598-021-02693-2

Zhiquan Wang, Wei Zhang + Show 6 more

Open Access

https://doi.org/10.1038/s41598-021-02693-2

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Abstract

To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis. The enzymatic hydrolysis was based on the cellulase from Trichoderma reesi ATCC 26921, the optimum NaOH pre-treatment conditions were an NaOH concentration of 1.0% (w/w), a solid content of 5.0% (w/v) and a pre-treatment time of 60 min. Various parameters that affect the enzymatic hydrolysis of wheat straw, including the solid content, enzyme loading, pH and hydrolysis time, were investigated and optimized through a Box–Behnken design and response surface methodology. The predicted optimum conditions for enzymatic hydrolysis were a solid content of 8.0% (w/v), an enzyme loading of 35 FPU/g substrate, a temperature of 50 °C, a pH of 5.3 and a hydrolysis time of 96 h. The experimental result showed that the maximum reducing sugar yield was 60.73% (53.35% higher than the wheat straw without NaOH pre-treatment), which is in accordance with the predicted conditions.

Highlights

To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis
The reducing sugar (RS) yield change in NaOH pretreatment operation with a temperature of 121 °C, solid content of 5.0% (w/v) and pre-treatment time of 50 min is shown in Fig. 1a, the RS yield increased with an increase in the NaOH concentration and reached a maximum value of 80.65% when the NaOH concentration was 1.0% (w/w)
It has been reported that a long soaking in a high concentration of NaOH causes the dissolution of pentose, which leads to a reduction of RS recovery

Summary

Introduction

To enhance the reducing sugar yield in enzymatic hydrolysis, various factors (NaOH concentration, solid content and pre-treatment time) that affect the pre-treatment process were investigated and evaluated based on the reducing sugar yield of the subsequent enzymatic hydrolysis. Lignocellulosic resources are considerably abundant, one promising way to convert abundant and renewable biomass materials to ethanol is an enzymatic hydrolysis process, which has been reported to exhibit high sugar yield, few by-products and low costs, but the structural properties of lignocellulose lead to the resistance of b ioconversion[4]. RSM using the BoxBehnken design (BBD) was exploited to identify the optimal conditions for reducing sugar (RS) production from NaOH-pre-treated WS through enzymatic hydrolysis This was accomplished by analyzing the relationships among the parameters that affect the process

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Results

Conclusion