Background: Bamboo, a lignocellulosic feedstock, is considered as a potentially excellent raw material and evaluated for lignocellulose degradation and bioethanol production, with a focus on using physical and chemical pre-treatment. However, studies reporting the biodegradation of bamboo lignocellulose using microbes such as bacteria and fungi are scarce. Results:In the present study, Bacillus velezensis LC1 was isolated from Cyrtotrachelus buqueti, in which the symbiotic bacteria exhibited lignocellulose degradation ability and cellulase activities. We performed genome sequencing of B. velezensis LC1, which has a 3929,782-bp ring chromosome and 46.5% GC content. The total gene length was 3,502,596 bp using gene prediction, and the GC contents were 47.29% and 40.04% in the gene and intergene regions, respectively. The genome contains 4018 coding DNA sequences, and all have been assigned predicted functions. Carbohydrate-active enzyme annotation identified 136 genes annotated to CAZy families, including GH, GTs, CEs, PLs, AAs and CBMs. Genes involved in lignocellulose degradation were identified. After a 6-day treatment, the bamboo shoot cellulose degradation efficiency reached 39.32%, and the hydrolysate was subjected to ethanol fermentation with Saccharomyces cerevisiae and Escherichia coli KO11, yielding 7.2 g/L of ethanol at 96 h. Conclusions:These findings provide an insight for B. velezensis strains in converting lignocellulose into ethanol. B. velezensis LC1, a symbiotic bacteria, can potentially degrade bamboo lignocellulose components and further transformation to ethanol, and expand the bamboo lignocellulosic bioethanol production.
Background Gut symbiotic microbiota plays a critical role in nutrient supply, digestion, and absorption. The bamboo snout beetle, Cyrtotrachelus buqueti , a common pest of several bamboo species, exhibits high lignocellulolytic enzyme activity and contains various CAZyme genes. However, to date, no studies have evaluated the role of gut symbiotic microbiota of the snout beetle on bamboo lignocellulose degradation. Therefore, the present study investigated the role of gut symbiotic microbiota of C . buqueti on bamboo lignocellulose degradation. Results Gut symbiotic microbiota of female (CCJ), male (XCJ), and larvae (YCJ) beetles was used to treat bamboo shoot particles (BSPs) in vitro for 6 days. Scanning electron microscopy (SEM) revealed significant destruction of the lignocellulose structure after treatment, which was consistent with the degradation efficiencies of CCJ, XCJ, and YCJ for cellulose (21.11%, 17.58% and 18.74%, respectively); hemicellulose (22.22%, 27.18% and 34.20%, respectively); and lignin (19.83%, 24.30% and 32.97%, respectively). Gut symbiotic microbiota of adult and larvae beetles was then identified using 16sRNA sequencing, which revealed that four microbes: Lactococcus , Serratia , Dysgonomonas and Enterococcus , comprise approximately 84% to 94% of the microbiota. Moreover, the genomes of 45 Lactococcus , 72 Serratia , 86 Enterococcus and 4 Dysgonomonas microbes were used to analyse resident CAZyme genes. These results indicated that gut symbiotic microbiota of adult and larvae C . buqueti is involved in the lignocellulose degradation traits shown by the host. Conclusions This study shows that the gut symbiotic microbiota of C . buqueti participates in bamboo lignocellulose degradation, providing innovative findings for bamboo lignocellulose bioconversion. Furthermore, the results of this study will allow us to further isolate lignocellulose-degrading microbiota for use in bamboo lignocellulose bioconversion. Electronic supplementary material The online version of this article (10.1186/s13068-019-1411-1) contains supplementary material, which is available to authorized users.
BackgroundThe bamboo weevil Cyrtotrachelus buqueti, which is considered a pest species, damages bamboo shoots via its piercing–sucking mode of feeding. C. buqueti is well known for its ability to transform bamboo shoot biomass into nutrients and energy for growth, development and reproduction with high specificity and efficacy of bioconversion. Woody bamboo is a perennial grass that is a potential feedstock for lignocellulosic biomass because of its high growth rate and lignocellulose content. To verify our hypothesis that C. buqueti efficiently degrades bamboo lignocellulose, we assessed the bamboo lignocellulose-degrading ability of this insect through RNA sequencing for identifying a potential route for utilisation of bamboo biomass.ResultsAnalysis of carbohydrate-active enzyme (CAZyme) family genes in the developmental transcriptome of C. buqueti revealed 1082 unigenes, including 55 glycoside hydrolases (GH) families containing 309 GHs, 51 glycosyltransferases (GT) families containing 329 GTs, 8 carbohydrate esterases (CE) families containing 174 CEs, 6 polysaccharide lyases (PL) families containing 11 PLs, 8 auxiliary activities (AA) families containing 131 enzymes with AAs and 17 carbohydrate-binding modules (CBM) families containing 128 CBMs. We used weighted gene co-expression network analysis to analyse developmental RNA sequencing data, and 19 unique modules were identified in the analysis. Of these modules, the expression of MEyellow module genes was unique and the module included numerous CAZyme family genes. CAZyme genes in this module were divided into two groups depending on whether gene expression was higher in the adult/larval stages or in the egg/pupal stages. Enzyme assays revealed that cellulase activity was highest in the midgut whereas lignin-degrading enzyme activity was highest in the hindgut, consistent with findings from intestinal gene expression studies. We also analysed the expression of CAZyme genes in the transcriptome of C. buqueti from two cities and found that several genes were also assigned to CAZyme families. The insect had genes and enzymes associated with lignocellulose degradation, the expression of which differed with developmental stage and intestinal region.ConclusionCyrtotrachelus buqueti exhibits lignocellulose degradation-related enzymes and genes, most notably CAZyme family genes. CAZyme family genes showed differences in expression at different developmental stages, with adults being more effective at cellulose degradation and larvae at lignin degradation, as well as at different regions of the intestine, with the midgut being more cellulolytic than the hindgut. This degradative system could be utilised for the bioconversion of bamboo lignocellulosic biomass.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1291-9) contains supplementary material, which is available to authorized users.
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