Insight into the role of \u03b1-arabinofuranosidase in biomass hydrolysis: cellulose digestibility and inhibition by xylooligomers

Donglin Xin,Xiang Chen,Junhua Zhang,Peiyao Wen

doi:10.1186/s13068-019-1412-0

Donglin Xin, Xiang Chen + Show 2 more

Open Access

https://doi.org/10.1186/s13068-019-1412-0

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Abstract

Backgroundα-l-Arabinofuranosidase (ARA), a debranching enzyme that can remove arabinose substituents from arabinoxylan and arabinoxylooligomers (AXOS), promotes the hydrolysis of the arabinoxylan fraction of biomass; however, the impact of ARA on the overall digestibility of cellulose is controversial. In this study, we investigated the effects of the addition of ARA on cellulase hydrolytic action.ResultsWe found that approximately 15% of the xylan was converted into AXOS during the hydrolysis of aqueous ammonia-pretreated corn stover and that this AXOS fraction was approximately 12% substituted with arabinose. The addition of ARA removes a portion of the arabinose decoration, but the resulting less-substituted AXOS inhibited cellulase action much more effectively; showing an increase of 45.7%. Kinetic experiments revealed that AXOS with a lower degree of arabinose substitution showed stronger affinity for the active site of cellobiohydrolase, which could be the mechanism of increased inhibition.ConclusionsOur findings strongly suggest that the ratio of ARA and other xylanases should be carefully selected to avoid the strong inhibition caused by the less-substituted AXOS during the hydrolysis of arabinoxylan-containing biomass. This study advances our understanding of the inhibitory mechanism of xylooligomers and provides critical new insights into the relationship of ARA addition and cellulose digestibility.

Highlights

Biofuels from lignocellulosic biomass have been considered a promising alternative to traditional fossil fuels [1,2,3]
Debranched AXOS inhibited cellulase more strongly To assess whether substitution affects the inhibition of AXOS on cellulase, AXOS with or without debranching enzyme was added to the hydrolysis of Avicel
The results showed that the ratio of arabinose to xylose was 41:59, indicating that the AXOS was highly substituted with arabinose

Summary

Introduction

Biofuels from lignocellulosic biomass have been considered a promising alternative to traditional fossil fuels [1,2,3]. The conversion process is not cost-effective because the cost of the conversion process is high and the biofuels productivity is low, which makes the price of biofuels too high to compete with traditional fossil fuels [4]. To address this issue, numerous research studies have focused on how to economically produce biofuels from lignocellulosic biomass [5,6,7]. There was a nearly linear relationship between the increases in xylose and glucose yields during the hydrolysis of biomass after pretreatment by many technologies, such as ammonia fiber expansion, ammonia recycle, and hydrothermal [11, 12]. The effect of adding extra ARA on the conversion of lignocellulosic biomass into monosaccharides has attracted intensive research interest [11, 20, 22]

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Conclusion