Enhancing Biobutanol Production from biomass willow by pre-removal of water extracts or bark

Jinze Dou,Vijaya Chandgude,Tapani Vuorinen,Sandip Bankar,Sami Hietala,Huy Quang Lê

doi:10.1016/j.jclepro.2021.129432

Jinze Dou, Vijaya Chandgude + Show 4 more

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https://doi.org/10.1016/j.jclepro.2021.129432

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Abstract

Aiming to understand the importance of debarking on the controlled utilization of phenolic-rich willow biomass, biobutanol was produced from it by using Clostridium acetobutylicum. Acid-catalysed steam explosion and enzymatic hydrolysis (EH) were investigated before the acetone-butanol-ethanol (ABE) fermentation. The hydrolysable sugar yield and ABE fermentation efficiency were found to decline progressively from willow wood (WW) to HWE WB (hot water extracted willow biomass), WB (willow biomass) and the WW + HWE (willow wood plus the artificial willow bark water extracts), indicating that the pre-removal of water extracts or the bark can significantly improve ABE yield. Notably, the ABE productivity of WW achieved 12.7 g/L at the solvent yield of 31%, and the butanol concentration (i.e. 8.5 g/L) generated by WW is relatively high among the reported lignocellulosic-derived biomass. Additionally, it is hypothesized that under acidic conditions and high temperatures the fructose present in willow water extracts form hydroxymethylfurfural during steam explosion, which then spontaneously condenses with phenolic substances of willow bark to form a solid furanic precipitate. The formed furanic precipitates play inhibitory role in the enzymatic hydrolysis and are thereby deleterious to the ABE fermentation.

Highlights

Clean energy alternatives are of prime importance because of detri mental environmental impacts caused by conventional fossil fuels
Four types of materials (i.e. willow wood (WW), WB, HWEWB and WW + HWE of Fig. 1) were comparatively chemically evaluated during the stages of steam explosion pre-treatment, enzymatic hydrolysis and ABE fermentation, the chemical characteristics of the formed phenol-aldehyde condensate are all together discussed in the subsequent sections
The relative content of the cellulose and lignin in the recovered solid residues has increased in comparison to the untreated biomass due to the degradation of hemi celluloses

Summary

Introduction

Clean energy alternatives are of prime importance because of detri mental environmental impacts caused by conventional fossil fuels. Lignocellulose is mainly composed of cellulose, hemicellulose, lignin, and extractives. The primary hemicellulose in hardwood is glucuronoxylan, containing xylose and glucuronic acid as the main constituents. It is a linear polymer composed of β-D-xylopyranosyl units linked by β-(1,4)-glycosidic bonds and substituted by 4-O-methyl-D-glu copyranosyluronic acid and acetyl groups. Alde hydes (e.g. HMF and furfural) and phenols can condense, forming condensed precipitate (Koch and Pein, 1985). Lignin, another amorphous polymer, is composed mainly of three phenylpropanoid units, that is p-hydroxyphenol (H), guaiacyl (G) and syringyl (S) units. Extractives, rich in bioactive phenolic compounds and mono saccharides, exhibit high occurrence in the bark of trees, such as spruce (Kemppainen et al, 2014), willow (Dou et al, 2018b) and eucalyptus (Dou et al, 2021a)

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