Impact of particle size reduction on high gravity enzymatic hydrolysis of steam-exploded wheat straw

Luis Hoppert,Daniel Einfalt

doi:10.1007/s42452-021-04870-4

Abstract

Economically feasible bioethanol production from lignocellulosic biomass requires solid loadings ≥ 15% dry matter (DM, w/w). However, increased solid loadings can lead to process difficulties, which are characterized by high apparent slurry viscosity, insufficient substrate mixing and limited water availability, resulting in reduced final glucose yields. To overcome these limitations, this study focused on enzymatic hydrolysis of 10–35% DM solid loadings with steam-exploded wheat straw in two different particle sizes. At solid loadings of 20 and 25% DM small particle size of ≤ 2.5 mm yielded 16.9 ± 1.1% and 10.2 ± 1.4% increased final glucose concentrations compared to large particle size of 30 ± 20 mm. Small particle size also positively influenced slurry viscosity and, therefore, miscibility. As a key finding of this investigation, high gravity enzymatic hydrolysis with solid loadings of 30–35% DM was indeed successfully employed when wheat straw was applied in small particle size. Here, the highest final glucose yield was achieved with 127.9 ± 4.9 g L−1 at 35% DM solid loading. An increase in the solid loading from 10 to 35% DM in small particle size experiments resulted in a 460% increase in the final glucose concentration.

Highlights

Lignocellulose is the most abundant source of renewable biomass and an attractive material for bioethanol production [1]
Enzymatic hydrolysis was performed with small fiber size (SFS), when the substrate was milled after steam explosion, to investigate the effect of particle size on the severity of the pretreatment
The experiments showed the importance of particle size on the yield of high gravity enzymatic hydrolysis

Summary

Introduction

Lignocellulose is the most abundant source of renewable biomass and an attractive material for bioethanol production [1]. One approach to improve monosaccharide yields and, in-terms, economic feasibility is to apply high gravity enzymatic hydrolysis [6,7,8]. High gravity enzymatic hydrolysis is defined as a saccharification step at solid loadings ≥ 15% dry matter (DM, w/w). It offers advantages over hydrolysis at low solid loadings [3]. A major advantage of high gravity enzymatic hydrolysis is that it can result in a slurry with a bioethanol concentration of ≥ 4% w/w, which is required for an economically feasible and efficient distillation step [10, 12]

Methods

Results

Conclusion