Degradation of bamboo lignocellulose by bamboo snout beetle Cyrtotrachelus buqueti in vivo and vitro: efficiency and mechanism

Chaobing Luo,Yaojun Yang,Yuanqiu Li,Chun Fu,Ying Chen,Xiang Nong

doi:10.1186/s13068-019-1406-y

Chaobing Luo, Yaojun Yang + Show 4 more

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https://doi.org/10.1186/s13068-019-1406-y

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Abstract

BackgroundAs an important biomass raw material, the lignocellulose in bamboo is of significant value in energy conversion. The conversion of bamboo lignocellulose into fermentable reducing sugar, i.e. the degradation of bamboo lignocellulose, is an important step in lignocellulose conversion. However, little research has focussed on excavating the enzymes and microbes that are related to the degradation of bamboo lignocellulose, which is important for its utilisation. This study used Cyrtotrachelus buqueti (bamboo snout beetle) to evaluate the efficiency of bamboo lignocellulose degradation.ResultsRNA sequencing was conducted to sequence the transcriptome of the insect before and after feeding on bamboo shoots. The expression levels of genes encoding several carbohydrate-active enzymes, such as endoglucanase (evgtrinloc27093t1 and evgtrinloc16407t0) and laccase (evgtrinloc15173t0 and evgtrinloc11252t0), were found to be upregulated after feeding. Faecal component analysis showed that the degradation efficiencies of cellulose, hemicellulose and lignin were 61.82%, 87.65% and 69.05%, respectively. After 6 days of co-culture with crude enzymes in vitro, the degradation efficiencies of cellulose, hemicellulose and lignin in bamboo shoot particles (BSPs) were 24.98%, 37.52% and 26.67%, respectively. These results indicated that lignocellulosic enzymes and related enzymes within the insect itself co-degraded bamboo lignocellulose. These finding can potentially be used for the pre-treatment and enzymatic hydrolysis of bamboo lignocellulose.ConclusionOur results showed that intestinal digestive enzymes from C. buqueti degraded bamboo shoot lignocellulose both in vivo and in vitro. In addition, the expression levels of many carbohydrate-active enzyme (CAZyme) genes were upregulated in the transcriptome, including those for cellulase, xylanase and ligninase genes. Therefore, we proposed a scheme for applying the lignocellulolytic enzymes from C. buqueti to degrade bamboo lignocellulose using genetic, enzymatic and fermentation engineering techniques to overexpress the lignocellulolytic enzymes genes in vitro and obtain large quantities of enzymes that could efficiently degrade bamboo lignocellulose and be used for lignocellulose bioconversion.

Highlights

As an important biomass raw material, the lignocellulose in bamboo is of significant value in energy conversion
We reported that many carbohydrate-active enzyme (CAZyme) genes, which are primarily involved in lignocellulose degradation [12, 13], expressed and lignocellulosic enzyme system existed in the different developmental stages of the bamboo snout beetle Cyrtotrachelus buqueti [14]
Transcriptome sequencing and assembly Clean reads were obtained from raw reads after removing reads that were of low quality or were ambiguous; adapters and duplicates were removed

Summary

Introduction

As an important biomass raw material, the lignocellulose in bamboo is of significant value in energy conversion. Little research has focussed on excavating the enzymes and microbes that are related to the degradation of bamboo lignocellulose, which is important for its utilisation. This study used Cyrtotrachelus buqueti (bamboo snout beetle) to evaluate the efficiency of bamboo lignocellulose degradation. Many methods for bamboo lignocellulose degradation have been proposed, little research has been devoted to excavate the enzymes related to the degradation of bamboo lignocellulose, which is important for its utilisation. We reported that many carbohydrate-active enzyme (CAZyme) genes, which are primarily involved in lignocellulose degradation [12, 13], expressed and lignocellulosic enzyme system existed in the different developmental stages of the bamboo snout beetle Cyrtotrachelus buqueti [14]. More detailed knowledge about the degradation, like degradation efficiency, mechanism, and so on, still lacked

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