Biodegradation of Gramineous Lignocellulose by Locusta migratoria manilensis (Orthoptera: Acridoidea)

Exploring an efficient and green pretreatment method is an important prerequisite for the development of biorefinery. It is well known that locusts can degrade gramineous lignocellulose efficiently. Locusts can be used as a potential resource for studying plant cell wall degradation, but there are few relative studies about locusts so far. Herein, some new discoveries were revealed about elucidating the process of biodegradation of gramineous lignocellulose in Locusta migratoria manilensis. The enzyme activity related to lignocellulose degradation and the content of cellulose, hemicellulose, and lignin in the different gut segments of locusts fed corn leaves were measured in this study. A series of characterization analyses were conducted on corn leaves and locust feces, which included field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction pattern (XRD), and thermogravimetric (TG) analysis. These results showed that the highest activities of carboxymethyl cellulase (CMCase), filter paper cellulase (FPA), and xylanase were obtained in the foregut of locusts, which strongly indicated that the foregut was the main lignocellulose degradation segment in locusts; furthermore, the majority of nutritional components were absorbed in the midgut of locusts. The activity of CMCase was significantly higher than that of xylanase, and manganese peroxidase (MnPase) activity was lowest, which might be due to the basic nutrition of locusts being cellulose and hemicellulose and not lignin based on the results of FE-SEM, FTIR, XRD, and TG analysis. Overall, these results provided a valuable insight into lignocellulosic degradation mechanisms for understanding gramineous plant cell wall deconstruction and recalcitrance in locusts, which could be useful in the development of new enzymatic pretreatment processes mimicking the locust digestive system for the biochemical conversion of lignocellulosic biomass to fuels and chemicals.

Bacterial cellulase from the intestinal tract of the sugarcane borer

Cellulolytic enzymes have wide use in several industrial segments (e.g. biofuels, pulp and paper, food, and cosmetics). However, one of the challenges is their large-scale production with high specific activity to eliminate the dependence of the purchase of enzymatic cocktails produced by commercial parties. The aims of this study were (1) isolation, selection, and partial characterization of bacterial cellulases present in the intestinal tract of the sugarcane borer and (2) to identify cellulase-producing bacteria by analyzing the 16S rDNA gene. Cellulase production and purification assays resulted in similar electrophoretic profiles between four bacterial strains. These strains were identified as Klebsiella pneumoniae, Klebsiella sp., and Bacillus sp. K. pneumoniae was the main cellulase-producing microorganism. Our results show the possibility of finding cellulolytic microorganisms that inhabit the gut of herbivorous animals, especially those that are predators of important crops of economic value. Furthermore, K. pneumoniae cellulase is of medical importance. In hospitals, health professionals, hospital technicians, patients and visitors wear clothes containing cellulose. Thus, K. pneumoniae within hospitals can contaminate these clothes and be spread to the environment. In that case, it would be important for the hospital's chemical sterilization products to have at least one cellulase inhibitor.

Enzymatic activity of a recombinant β-1,4-endoglucanase from the Cotton Boll Weevil (Anthonomus grandis) aiming second generation ethanol production

In the last years, the production of ethanol fuel has started to change with the introduction of second-generation ethanol (2 G Ethanol) in the energy sector. However, in Brazil, the process of obtaining 2 G ethanol did not reach a basic standard to achieve relevant and economically viable results. Several studies have currently been addressed to solve these issues. A critical stage in the bioethanol production is the deployment of efficient and stable enzymes to catalyze the saccharification step into the process of biomass conversion. The present study comprises a screening for genes coding for plant biomass degradation enzymes, followed by cloning a selected gene, addressing its heterologous expression, and characterizing enzymatic activity towards cellulose derived substrates, with a view to second-generation ethanol production. A cDNA database of the Cotton Boll Weevil, Anthonomus grandis (Coleoptera: Curculionidae), an insect that feeds on cotton plant biomass, was used as a source of plant biomass degradation enzyme genes. A larva and adult midgut-specific β-1,4-Endoglucanase-coding gene (AgraGH45-1) was cloned and expressed in the yeast Pichia pastoris. Its amino acid sequence, including the two catalytic domains, shares high identity with other Coleoptera Glycosyl Hydrolases from family 45 (GH45). AgraGH45-1 activity was detected in a Carboxymethylcellulose (CMC) and Hydroxyethylcellulose (HEC) degradation assay and the optimal conditions for enzymatic activity was pH 5.0 at 50 °C. When compared to commercial cellulase from Aspergillus niger, Agra GH45-1 was 1.3-fold more efficient to degrade HEC substrate. Together, these results show that AgraGH45-1 is a valid candidate to be engineered and be tested for 2 G ethanol production.

Enzymatic hydrolysis of cellulose using extracts from insects

The use of Zophobas morio extracts in the aspect of cellulose hydrolysis is presented for the first time. The aim of this study was to investigate the action of enzymes obtained from Z. morio on cellulose hydrolysis and to determine their influence on the structural properties of cellulose with use the Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Cellulose hydrolysis products were analyzed by high performance liquid chromatography (HPLC). This analysis indicated that microcrystalline cellulose with smaller particle size was more susceptible to enzymatically treatment. Moreover, our investigation of cellulase activity showed a different profile of the used enzyme during particular developmental stages of Z. morio. Midgut extracts obtained from adult insects are more effective in degrading cellulose than extracts from larvae. The analysis of cellulose hydrolysis confirms that the efficiency of this reaction also depends on the structure of cellulosic materials and internal conditions of enzymatic reaction. In this study the cellulolytic activity of Z. morio midgut extracts showed that these insects could be valuable sources of cellulases.

De novo transcriptome assembly of the bamboo snout beetle Cyrtotrachelus buqueti reveals ability to degrade lignocellulose of bamboo feedstock

BACKGROUND

The 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.

RESULTS

Analysis 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.

CONCLUSION

Cyrtotrachelus 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.

Efficient and Supplementary Enzyme Cocktail from Actinobacteria and Plant Biomass Induction

Actinobacteria plays a key role in the cycling of organic matter in soils. They secret biomass-degrading enzymes that allow it to produce the unique metabolites that originate in plant biomass. Although past studies have focused on these unique metabolites, a large-scale screening of Actinobacteria is yet to be reported to focus on their biomass-degrading ability. In the present study, a rapid and simple method is constructed for a large-scale screening, and the novel resources that form the plant biomass-degrading enzyme cocktail are identified from 850 isolates of Actinobacteria. As a result, Nonomuraea fastidiosa secretes a biomass degrading enzyme cocktail with the highest enzyme titer, although cellulase activities are lower than a commercially available enzyme. So the rich accessory enzymes are suggested to contribute to the high enzyme titer for a pretreated bagasse with a synergistic effect. Additionally, an optimized cultivation method of biomass induction caused to produce the improved enzyme cocktail indicated strong enzyme titers and a strong synergistic effect. Therefore, the novel enzyme cocktails are selected via the optimized method for large-scale screening, and then the enzyme cocktail can be improved via the optimized production with biomass-induction.