Uncovering the Potential of Termite Gut Microbiome for Lignocellulose Bioconversion in Anaerobic Batch Bioreactors

Molecular unraveling of polysaccharide digestion in wood-feeding termites: A solid-state NMR perspective

Termites are among the most efficient organisms utilizing polysaccharides from wood and play a significant role in global carbon recycling, especially within tropical and subtropical ecosystems. Yet, the molecular details in polysaccharide degradation by termites remain largely unexplored. In this work, we have elucidated the shared and distinct molecular details in polysaccharides digestion by the higher termite Nasutitermes on poplar and the lower termite Cryptotermes on pine using high resolution solid-state nuclear magnetic resonance spectroscopy. For the first time, structural polymers are partitioned into the minor mobile and dominant rigid phases for individual examination. The mobile polysaccharides receive less structural impacts and exhibit greater digestibility compared to the rigid counterparts. While both termites effectively degrade cellulose, Nasutitermes significantly outperforms Cryptotermes in hemicellulose breakdown. In the rigid phase, cellulose is comprehensively degraded into a fragmented and more dynamically consistent structure; As Nasutitermes breaks down hemicellulose in a similar manner to cellulose, Cryptotermes selectively digests hemicellulose at its interfaces with cellulose. Additionally, crystalline cellulose undergoes selective degradation, and the digestion of amorphous cellulose might involve sugar chain detachment within microfibrils. Overall, our findings offer significant advancements and fresh perspectives on the polysaccharide digestion strategies of different termite lineages.

Sustainable structural polysaccharides conversion: How does DES pretreatment affect cellulase adsorption, thereby improving enzymatic digestion of lignocellulose?

Biomass conversion aims at degrading the structural polysaccharides of lignocellulose into reducing sugars. Pretreatment is necessary to overcome the recalcitrance of lignocellulose. The DES La/ChCl in this paper was selected based on our previous study. To examine cellulase adsorption of lignocellulose after DES pretreatment, sorghum straw was pretreated with DES under different condition. The adsorption improvement of cellulase on lignocellulose after DES pretreatment has positive impact on reducing sugar production of biomass. After DES pretreatment, 1. pore corrosion caused the upward trend of pore radius and the downward trend of SSA. 2. the hydrogen bounding force of pretreated sorghum straw and MCC decreased, the hydrogen bounding force of pretreated lignin increased. 3. although the unsaturation of pretreated lignin increased, DES pretreatment is helpful for the removal of lignin. 4. The decrease in the hydrophobicity of sorghum straw make it easier to disperse. 5. the Zeta potential of pretreated sorghum straw shifted towards the positively charged region, while pretreated lignin shifted towards the negatively charged region. 6. different adsorption behaviors were observed in specific components of cellulase mixtures (BGs, CBHs, EGs and xlylanase). These results revealing the mechanism of enzyme adsorption are conductive for understanding the role of pretreatment in biomass conversion.

Changes in the Bacterial Communities of Biocomposites with Different Flame Retardants

In today's world, the use of environmentally friendly materials is strongly encouraged. These materials derive from primary raw materials of plant origin, like fibrous hemp, flax, and bamboo, or recycled materials, such as textiles or residual paper, making them suitable for the growth of microorganisms. Here, we investigate changes in bacterial communities in biocomposites made of hemp shives, corn starch, and either expandable graphite or a Flovan compound as flame retardants. Using Next Generation Sequencing (NGS), we found that after 12 months of incubation at 22 °C with a relative humidity of 65%, Proteobacteria accounted for >99.7% of the microbiome in composites with either flame retardant. By contrast, in the absence of flame retardants, the abundance of Proteobacteria decreased to 32.1%, while Bacteroidetes (36.6%), Actinobacteria (8.4%), and Saccharobacteria (TM7, 14.51%) appeared. Using the increasing concentrations of either expandable graphite or a Flovan compound in an LB medium, we were able to achieve up to a 5-log reduction in the viability of Bacillus subtilis, Pseudomonas aeruginosa, representatives of the Bacillus and Pseudomonas genera, the abundance of which varied in the biocomposites tested. Our results demonstrate that flame retardants act on both Gram-positive and Gram-negative bacteria and suggest that their antimicrobial activities also have to be tested when producing new compounds.

Whole-Genome Analysis of Termite-Derived Bacillus velezensis BV-10 and Its Application in King Grass Silage

Bacillus velezensis (B. velezensis) is a cellulose-degrading strain that has the potential as an additive in fermented feed. B. velezensis BV-10 was isolated and screened from the termite gut. We sequenced the whole genome of this new source of B. velezensis to reveal its potential for use in cellulose degradation. Whole-genome sequencing of B. velezensis BV-10 showed that it has a circular chromosome of 3929792 bp containing 3873 coding genes with a GC content of 45.51% and many genes related to cellulose, hemicellulose, and lignin degradation. King grass silage was inoculated with B. velezensis BV-10 and mixed with other feed additives to assess the effect of B. velezensis BV-10 on the fermentation quality of silage. Six treatment groups were established: the control, B. velezensis BV-10, molasses, cellulase, B. velezensis BV-10 plus molasses, and B. velezensis BV-10 plus cellulase groups. After 30 days of silage-fermentation testing, B. velezensis BV-10 was found to rapidly reduce the silage pH value and significantly reduce the acid-detergent fiber (ADF) content (p < 0.05). The addition of B. velezensis BV-10 plus molasses and cellulase in fermented feed significantly reduced the silage neutral-detergent fiber and ADF content and promoted organic-acid accumulation (p < 0.05). The above results demonstrate that B. velezensis BV-10 promotes the fermentation quality of silage and that this effect is greater when other silage-fermentation additives are included. In conclusion, genes involved in cellulose degradation in B. velezensis BV-10 were identified by whole-genome sequencing and further experiments explored the effects of B. velezensis BV-10 and different feed additives on the fermentation quality of king grass silage, revealing the potential of Bacillus velezensis as a new silage additive.

Microbiome Diversity and Cellulose Decomposition Processes by Microorganisms on the Ancient Wooden Seawall of Qiantang River of Hangzhou, China

Archaeological wood, also known as wooden cultural relics, refers to ancient wood that has been worked by humans. Further insights into the decomposition mechanism of archaeological wood are needed for its preventive conservation. In this study, we assessed the microbiome diversity and cellulose decomposition processes on a 200-year-old ancient wooden seawall - the Qiantang River of Hangzhou, China. We used high-throughput sequencing (HTS) to deduce the metagenomic functions, particularly the cellulose-decomposing pathway of the microbial communities, through bioinformatical approaches. The predominant cellulose-decomposing microorganisms were then verified with traditional isolation, culture, and identification method. The results showed that the excavation of archaeological wood significantly altered the environment, accelerating the deterioration process of the archaeological wood through the carbohydrate metabolism and the xenobiotic biodegradation and metabolism pathways, under the comprehensive metabolism of complex ecosystem formed by bacteria, archaea, fungi, microfauna, plants, and algae. Bacteroidetes, Proteobacteria, Firmicutes, and Actinobacteria were found to be the predominant source of bacterial cellulose-decomposing enzymes. Accordingly, we suggest relocating the wooden seawall to an indoor environment with controllable conditions to better preserve it. In addition, these results provide further evidence for our viewpoints that HTS techniques, combined with rational bioinformatical data interpretation approaches, can serve as powerful tools for the preventive protection of cultural heritage.

Host-Specific Diversity of Culturable Bacteria in the Gut Systems of Fungus-Growing Termites and Their Potential Functions towards Lignocellulose Bioconversion

Fungus-growing termites are eusocial insects that represent one of the most efficient and unique systems for lignocellulose bioconversion, evolved from a sophisticated symbiosis with lignocellulolytic fungi and gut bacterial communities. Despite a plethora of information generated during the last century, some essential information on gut bacterial profiles and their unique contributions to wood digestion in some fungus-growing termites is still inadequate. Hence, using the culture-dependent approach, the present study aims to assess and compare the diversity of lignocellulose-degrading bacterial symbionts within the gut systems of three fungus-growing termites: Ancistrotermes pakistanicus, Odontotermes longignathus, and Macrotermes sp. A total of 32 bacterial species, belonging to 18 genera and 10 different families, were successfully isolated and identified from three fungus-growing termites using Avicel or xylan as the sole source of carbon. Enterobacteriaceae was the most dominant family represented by 68.1% of the total bacteria, followed by Yersiniaceae (10.6%) and Moraxellaceae (9%). Interestingly, five bacterial genera such as Enterobacter, Citrobacter, Acinetobacter, Trabulsiella, and Kluyvera were common among the tested termites, while the other bacteria demonstrated a termite-specific distribution. Further, the lignocellulolytic potential of selected bacterial strains was tested on agricultural waste to evaluate their capability for lignocellulose bioconversion. The highest substrate degradation was achieved with E. chengduensis MA11 which degraded 45.52% of rice straw. All of the potential strains showed endoglucanase, exoglucanase, and xylanase activities depicting a symbiotic role towards the lignocellulose digestion within the termite gut. The above results indicated that fungus-growing termites harbor a diverse array of bacterial symbionts that differ from species to species, which may play an inevitable role to enhance the degradation efficacy in lignocellulose decomposition. The present study further elaborates our knowledge about the termite-bacteria symbiosis for lignocellulose bioconversion which could be helpful to design a future biorefinery.

The tropical cookbook: Termite diet and phylogenetics—Over geographical origin—Drive the microbiome and functional genetic structure of nests

Termites are key decomposers of dead plant material involved in the organic matter recycling process in warm terrestrial ecosystems. Due to their prominent role as urban pests of timber, research efforts have been directed toward biocontrol strategies aimed to use pathogens in their nest. However, one of the most fascinating aspects of termites is their defense strategies that prevent the growth of detrimental microbiological strains in their nests. One of the controlling factors is the nest allied microbiome. Understanding how allied microbial strains protect termites from pathogen load could provide us with an enhanced repertoire for fighting antimicrobial-resistant strains or mining for genes for bioremediation purposes. However, a necessary first step is to characterize these microbial communities. To gain a deeper understanding of the termite nest microbiome, we used a multi-omics approach for dissecting the nest microbiome in a wide range of termite species. These cover several feeding habits and three geographical locations on two tropical sides of the Atlantic Ocean known to host hyper-diverse communities. Our experimental approach included untargeted volatile metabolomics, targeted evaluation of volatile naphthalene, a taxonomical profile for bacteria and fungi through amplicon sequencing, and further diving into the genetic repertoire through a metagenomic sequencing approach. Naphthalene was present in species belonging to the genera Nasutitermes and Cubitermes. We investigated the apparent differences in terms of bacterial community structure and discovered that feeding habits and phylogenetic relatedness had a greater influence than geographical location. The phylogenetic relatedness among nests' hosts influences primarily bacterial communities, while diet influences fungi. Finally, our metagenomic analysis revealed that the gene content provided both soil-feeding genera with similar functional profiles, while the wood-feeding genus showed a different one. Our results indicate that the nest functional profile is largely influenced by diet and phylogenetic relatedness, irrespective of geographical location.

Effect of Alkaline and Mechanical Pretreatment of Wheat Straw on Enrichment Cultures from Pachnoda marginata Larva Gut

In order to partially mimic the efficient lignocellulose pretreatment process performed naturally in the gut system of Pachnoda marginata larvae, two wheat straw pretreatments were evaluated: a mechanical pretreatment via cutting the straw into two different sizes and an alkaline pretreatment with calcium hydroxide. After pretreatment, gut enrichment cultures on wheat straw at alkaline pH were inoculated and kept at mesophilic conditions over 45 days. The methanogenic community was composed mainly of the Methanomicrobiaceae and Methanosarcinaceae families. The combined pretreatment, size reduction and alkaline pretreatment, was the best condition for methane production. The positive effect of the straw pretreatment was higher in the midgut cultures, increasing the methane production by 192%, while for hindgut cultures the methane production increased only by 149% when compared to non-pretreated straw. Scanning electron microscopy (SEM) showed that the alkaline pretreatment modified the surface of the wheat straw fibers, which promoted biofilm formation and microbial growth. The enrichment cultures derived from larva gut microbiome were able to degrade larger 1 mm alkaline treated and smaller 250 µm but non-pretreated straw at the same efficiency. The combination of mechanical and alkaline pretreatments resulted in increased, yet not superimposed, methane yield.

Enhanced protein degradation by black soldier fly larvae (Hermetia illucens L.) and its gut microbes

Black soldier fly larvae (BSFL) can convert a variety of organic wastes into biomass, and its gut microbiota are involved in this process. However, the role of gut microbes in the nutrient metabolism of BSFL is unclear. In this study, germ-free BSFL (GF) and gnotobiotic BSFL (GB) were evaluated in a high-protein artificial diet model. We used 16S rDNA sequencing, ITS1 sequencing, and network analysis to study gut microbiota in BSFL that degrade proteins. The protein reduction rate of the GB BSFL group was significantly higher (increased by 73.44%) than that of the GF BSFL group. The activity of gut proteinases, such as trypsin and peptidase, in the GB group was significantly higher than the GF group. The abundances of different gut microbes, including Pseudomonas spp., Orbus spp. and Campylobacter spp., were strongly correlated with amino acid metabolic pathways. Dysgonomonas spp. were strongly correlated with protein digestion and absorption. Issatchenkia spp. had a strong correlation with pepsin activity. Campylobacter spp., Pediococcus spp. and Lactobacillus spp. were strongly correlated with trypsin activity. Lactobacillus spp. and Bacillus spp. were strongly correlated with peptidase activity. Gut microbes such as Issatchenkia spp. may promote the gut proteolytic enzyme activity of BSFL and improve the degradation rate of proteins. BSFL protein digestion and absorption involves gut microbiota that have a variety of functions. In BSFL the core gut microbiota help complete protein degradation. These results demonstrate that core gut microbes in BSFL are important in protein degradation.

Hydrolysis of lignocellulose to succinic acid: a review of treatment methods and succinic acid applications

Succinic acid (SA) is an intermediate product of the tricarboxylic acid cycle (TCA) and is one of the most significant platform chemicals for the production of various derivatives with high added value. Due to the depletion of fossil raw materials and the demand for eco-friendly energy sources, SA biosynthesis from renewable energy sources is gaining attention for its environmental friendliness. This review comprehensively analyzes strategies for the bioconversion of lignocellulose to SA based on the lignocellulose pretreatment processes and cellulose hydrolysis and fermentation principles and highlights the research progress on acid production and SA utilization under different microbial culture conditions. In addition, the fermentation efficiency of different microbial strains for the production of SA and the main challenges were analyzed. The future application directions of SA derivatives were pointed out. It is expected that this research will provide a reference for the optimization of SA production from lignocellulose.

Development of different pretreatments and related technologies for efficient biomass conversion of lignocellulose

Lignocellulose, a kind of biological resource widely existing in nature, which can be transformed into value-added biochemical products through saccharification, fermentation or chemical catalysis. Pretreatments are the necessary step to increase the accessibility and digestibility of lignocellulose. This paper comprehensively reviewed different pretreatment progress of lignocellulose in recent year, including mechanical/thermal, biological, inorganic solvent, organic solvent and unconventional physical-chemical pretreatments, focusing on quantifying the influence of pretreatments on subsequent biomass conversion. In addition, related pretreatment techniques such as genetic engineering, reactor configurations, downstream process and visualization technology of pretreatment were discussed. Finally, this review presented the challenge of lignocellulose pretreatment in the future.

Enrichment of Anaerobic Microbial Communities from Midgut and Hindgut of Sun Beetle Larvae (Pachnoda marginata) on Wheat Straw: Effect of Inoculum Preparation

The Pachnoda marginata larva have complex gut microbiota capable of the effective conversion of lignocellulosic biomass. Biotechnological utilization of these microorganisms in an engineered system can be achieved by establishing enrichment cultures using a lignocellulosic substrate. We established enrichment cultures from contents of the midgut and hindgut of the beetle larva using wheat straw in an alkaline medium at mesophilic conditions. Two different inoculation preparations were used: procedure 1 (P1) was performed in a sterile bench under oxic conditions using 0.4% inoculum and small gauge needles. Procedure 2 (P2) was carried out under anoxic conditions using more inoculum (4%) and bigger gauge needles. Higher methane production was achieved with P2, while the highest acetic acid concentrations were observed with P1. In the enrichment cultures, the most abundant bacterial families were Dysgonomonadaceae, Heliobacteriaceae, Ruminococcaceae, and Marinilabiliaceae. Further, the most abundant methanogenic genera were Methanobrevibacter, Methanoculleus, and Methanosarcina. Our observations suggest that in samples processed with P1, the volatile fatty acids were not completely converted to methane. This is supported by the finding that enrichment cultures obtained with P2 included acetoclastic methanogens, which might have prevented the accumulation of acetic acid. We conclude that differences in the inoculum preparation may have a major influence on the outcome of enrichment cultures from the P. marginata larvae gut.

Intercolony Comparisons of Gut Microbiome Composition From Lab Reared Eastern Subterranean Termites (Blattodea: Rhinotermitidae)

Termites are social insects living in colonies composed of worker, soldier, and reproductive castes. Termite hindguts are inhabited by all three domains of life- Eukarya (protists), Bacteria, and Archaea. These gut microorganisms are horizontally and vertically transferred by nestmates and reproductives, respectively. Prior evidence suggests that every colony potentially has a different gut microbiome that was transferred vertically and horizontally over time. However, we do not know if different colonies reared in the laboratory on the same diet will ultimately demonstrate similar microbial composition and structure. Therefore, we looked at gut bacteria in Eastern subterranean termite (Reticulitermes flavipes) colonies that were reared in the laboratory with identical diets and rearing conditions. Based on16S rRNA gene sequencing, the observed features, and Shannon's diversity were significantly different between the colonies while differences in Pielou evenness and Faith phylogenetic diversity were not statistically significant. In addition, the microbial community structures were significantly different between colonies. Based on ANCOM (Analysis of Composition of Microbiomes), the taxa Elizabethkingia (Bacteroidetes: Flavobacteriales) and Chryseobacterium (Bacteroidetes: Flavobacteriales) were differentially abundant between the colonies. These results suggest that providing the exact same diet and rearing environment for >2 yr cannot result in identical gut microbiomes between termite colonies.

Harnessing the potential use of cellulolytic Klebsiella oxytoca (M21WG) and Klebsiella sp. (Z6WG) isolated from the guts of termites (Isoptera)

Background

For many years, denim-heavy quality cotton twill colored with indigo colors and with a well-worn/faded look has held a lot of appeal. Machine damage, drainage system blockage, and other issues come with the conventional usage of pumice stones for “stone-washing” denims. In view of the abovementioned information, a range of works has been done to investigate the economic prospects of bacterial cellulase enzymes for use in industrial processes, including biopolishing in the textile sector. Ethiopia has excellent termite diversity to isolate bacterial gut-associated cellulose enzymes for biostoning applications. The main purpose of this study was, therfore, to decipher how to isolate and characterize cellulase enzymes from termite (Isoptera) gut bacteria with the intention of employing it for biostoning of textiles.

Purpose

To use cellulolytic enzymes of Klebsiella oxytoca (M21WG) and Klebsiella sp. (Z6WG) isolated from termite guts in biostoning of textiles and improving garment quality.

Methods

Cellulase enzyme-producing bacteria were isolated and screened from the guts of worker termites sampled from Meki and Zeway termite mounds in the Central Rift Valley region of Ethiopia. Bacterial screening, biochemical, morphological, and 16S rRNA sequence identification techniques were employed to characterize the bacterial strains. In addition, the production, optimization, and purification of the associated cellulase enzymes were employed, and the potential application of the enzymes for biostoning of a textile was demonstrated.

Result

The isolated M21WG was found to be 99% identical to the Klebsiella oxytoca (MT104573.1) strain, while the isolated Z6WG showed 97.3% identity to the Klebsiella sp. strain (MN629242.1). At an ideal pH of 7, a temperature of 37 °C, a 72-h incubation time, and a substrate concentration of 1.5% carboxymethylcellulose sodium, the maximum activity of the crude cellulase extract from these bacteria was assessed. These bacteria produced cellulase enzymes that were moderately efficient. Consequently, it was determined that the cellulase enzymes were effective for biostoning of denim cloth.

Conclusion

It was determined that Klebsiella oxytoca (M21WG) and Klebsiella sp. (Z6WG) could be used as a doorway to better understand harnessing the use of these cellulase-producing bacteria from termite (Isoptera) guts. In this study, it was also attempted to assess the effectiveness of the two bacterial isolates in biostoning in anticipation of their potential application in the textile realm.

Investigating the potential of fish oil as a nutraceutical in an animal model of early life stress

Background: Early life stress is a key predisposing factor for depression and anxiety disorders. Selective serotonin re-uptake inhibitors (SSRI) are frequently used as the first line of pharmacology treatment for depression but have several negative qualities, i.e. a delay or absence of effectiveness and negative side-effects. Therefore, there is a growing need for new nutraceutical-based strategies to blunt the effects of adverse-life events.Objectives: This study aimed to use the maternal separation model in rats to test the efficacy of fish oil dietary supplementation, on its own and in conjunction with the SSRI anti-depressant fluoxetine, as a treatment for depressive and anxiety-like symptoms associated with early life stress.Methods: Behavioural tests (open field test, elevated plus maze test and forced swim test) and biochemical markers (corticosterone, BDNF, brain fatty acids and short chain fatty acids) were used to analyse the effects of the dietary treatments. Gut microbial communities and relating metabolites (SCFA) were analysed to investigate possible changes in the microbiota-gut-brain axis.Results: Maternally separated rats showed depressive-like behaviours in the forced swim and open field tests. These behaviours were prevented significantly by fluoxetine administration and in part by fish oil supplementation. Associated biochemical changes reported include altered brain fatty acids, significantly lower plasma corticosterone levels (AUC) and reduced brain stem serotonin turnover, compared to untreated, maternally separated (MS) rats. Untreated MS animals had significantly lower ratios of SCFA producers such as Caldicoprobacteraceae, Streptococcaceae, Rothia, Lachnospiraceae_NC2004_group, and Ruminococcus_2, along with significantly reduced levels of total SCFA compared to non-separated animals. Compared to untreated MS animals, animals fed fish oil had significantly higher Bacteroidetes and Prevotellaceae and reduced levels of butyrate, while fluoxetine treatment resulted in significantly higher levels of Neochlamydia, Lachnoclostridium, Acetitomaculum and Stenotrophomonas and, acetate and propionate.Conclusion: Despite the limitations in extrapolating from animal behavioural data and the notable differences in pharmacokinetics between rodents and humans, the results of this study provide a further advancement into the understanding of some of the complex systems within which nutraceuticals and pharmaceuticals effect the microbiota-gut-brain axis.

Advances in pretreatment of lignocellulosic biomass for bioenergy production: Challenges and perspectives

As a clean and renewable energy, bioenergy is one of the most promising alternatives to fossil fuels. Lignocellulose possesses great potential for bioenergy production, but the recalcitrant and heterogeneous structure limits its application. Pretreatment technology offers an effective solution to fractionate the main components of the lignocellulose and uncover the available cellulose. The obtained feedstock can be applied to bioconversion into energy, e.g., bioethanol, biogas, biohydrogen, etc. Here, the current state of lignocellulose pretreatment technologies was comprehensively reviewed, the advances in bioenergy production from pretreated lignocellulose was described, with particular attention to key challenges involved. Several new strategies for overcoming pretreatment barriers to realize highly efficient lignocellulose bioconversion were highlighted. The insights given in this review will facilitate further development on lignocellulosic bioenergy production, towards addressing the global energy crisis and climate change related to the use of fossil fuels.

Multipartite symbioses in fungus-growing termites (Blattodea: Termitidae, Macrotermitinae) for the degradation of lignocellulose

Fungus-growing termites are among the most successful herbivorous animals and improve crop productivity and soil fertility. A range of symbiotic organisms can be found inside their nests. However, interactions of termites with these symbionts are poorly understood. This review provides detailed information on the role of multipartite symbioses (between termitophiles, termites, fungi, and bacteria) in fungus-growing termites for lignocellulose degradation. The specific functions of each component in the symbiotic system are also discussed. Based on previous studies, we argue that the enzymatic contribution from the host, fungus, and bacteria greatly facilitates the decomposition of complex polysaccharide plant materials. The host-termitophile interaction protects the termite nest from natural enemies and maintains the stability of the microenvironment inside the colony.

Current Progress in Production of Building-Block Organic Acids by Consolidated Bioprocessing of Lignocellulose

Several organic acids have been indicated among the top value chemicals from biomass. Lignocellulose is among the most attractive feedstocks for biorefining processes owing to its high abundance and low cost. However, its highly complex nature and recalcitrance to biodegradation hinder development of cost-competitive fermentation processes. Here, current progress in development of single-pot fermentation (i.e., consolidated bioprocessing, CBP) of lignocellulosic biomass to high value organic acids will be examined, based on the potential of this approach to dramatically reduce process costs. Different strategies for CBP development will be considered such as: (i) design of microbial consortia consisting of (hemi)cellulolytic and valuable-compound producing strains; (ii) engineering of microorganisms that combine biomass-degrading and high-value compound-producing properties in a single strain. The present review will mainly focus on production of organic acids with application as building block chemicals (e.g., adipic, cis,cis-muconic, fumaric, itaconic, lactic, malic, and succinic acid) since polymer synthesis constitutes the largest sector in the chemical industry. Current research advances will be illustrated together with challenges and perspectives for future investigations. In addition, attention will be dedicated to development of acid tolerant microorganisms, an essential feature for improving titer and productivity of fermentative production of acids.

Cellulase Addition and Pre-hydrolysis Effect of High Solid Fed-Batch Simultaneous Saccharification and Ethanol Fermentation from a Combined Pretreated Oil Palm Trunk

In the current study, alkaline hydrogen peroxide pretreated oil palm trunk fibers were subjected to ethanol production via simultaneous saccharification and fermentation (SSF). The effect of high substrate loading, enzyme and substrate feeding strategy, and influence of a pre-hydrolysis step in SSF was studied to scale up ethanol production. In the enzyme feeding strategy, the addition of an enzyme at the start of fed-batch SSF significantly (p < 0.05) increased ethanol concentration to 51.05 g/L, ethanol productivity (Q_P ) to 0.61 g/L·h, and ethanol yield (Y _P/S) to 0.31 g/g, with a theoretical ethanol yield of 60.65%. Furthermore, the initial velocity of the enzyme (V ₀) in the first 8 h was 2.27 (g/h) with a glucose concentration of 18.17 g/L. On the other hand, the substrate feeding strategy and pre-hydrolysis simultaneous saccharification and fermentation (PSSF) process were studied in a 1 L fermenter. PSSF in fed batch with 10 and 20% (w/v) significantly improved enzyme hydrolysis, circumvent the problems of high viscosity, reduced overall fermentation time, and gave the highest ethanol concentration of 51.66 g/L, ethanol productivity (Q_P ) of 0.72 g/L·h, ethanol yield (Y _P/S) of 0.31 g/g, and theoretical ethanol yield of 60.66%. In addition, PSSF with 10 and 20% significantly increased the initial velocity of the enzyme (V ₀) to 4.64 and 4.40 (g/h) and glucose concentration to 37.14 and 35.27 g/L, respectively. This result indicated that ethanol production by PSSF along with substrate feeding could enhance ethanol production efficiently.

Characterization of the gut microbiome in wild rocky mountainsnails (Oreohelix strigosa)

Background

The Rocky Mountainsnail (Oreohelix strigosa) is a terrestrial gastropod of ecological importance in the Rocky Mountains of western United States and Canada. Across the animal kingdom, including in gastropods, gut microbiomes have profound effects on the health of the host. Current knowledge regarding snail gut microbiomes, particularly throughout various life history stages, is limited. Understanding snail gut microbiome composition and dynamics can provide an initial step toward better conservation and management of this species.

Results

In this study, we employed 16S rRNA gene amplicon sequencing to examine gut bacteria communities in wild-caught O. strigosa populations from the Front Range of Colorado. These included three treatment groups: (1) adult and (2) fetal snails, as well as (3) sub-populations of adult snails that were starved prior to ethanol fixation. Overall, O. strigosa harbors a high diversity of bacteria. We sequenced the V4 region of the 16S rRNA gene on an Illumina MiSeq and obtained 2,714,330 total reads. We identified a total of 7056 unique operational taxonomic units (OTUs) belonging to 36 phyla. The core gut microbiome of four unique OTUs accounts for roughly half of all sequencing reads returned and may aid the snails’ digestive processes. Significant differences in microbial composition, as well as richness, evenness, and Shannon Indices were found across the three treatment groups.

Conclusions

Comparisons of gut microbiomes in O. strigosa adult, fetal, and starved samples provide evidence that the host internal environments influence bacterial community compositions, and that bacteria may be transmitted vertically from parent to offspring. This work provides the first comprehensive report on the structure and membership of bacterial populations in the gastropod family Oreohelicidae and reveals similarities and differences across varying life history metrics. Strong differentiation between these life history metrics demonstrates the need for wider sampling for studies of dynamics of the snail gut microbiome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00111-6.

Unlocking the potential of insect and ruminant host symbionts for recycling of lignocellulosic carbon with a biorefinery approach: a review

Uprising fossil fuel depletion and deterioration of ecological reserves supply have led to the search for alternative renewable and sustainable energy sources and chemicals. Although first generation biorefinery is quite successful commercially in generating bulk of biofuels globally, the food versus fuel debate has necessitated the use of non-edible feedstocks, majorly waste biomass, for second generation production of biofuels and chemicals. A diverse class of microbes and enzymes are being exploited for biofuels production for a series of treatment process, however, the conversion efficiency of wide range of lignocellulosic biomass (LCB) and consolidated way of processing remains challenging. There were lot of research efforts in the past decade to scour for potential microbial candidate. In this context, evolution has developed the gut microbiota of several insects and ruminants that are potential LCB degraders host eco-system to overcome its host nutritional constraints, where LCB processed by microbiomes pretends to be a promising candidate. Synergistic microbial symbionts could make a significant contribution towards recycling the renewable carbon from distinctly abundant recalcitrant LCB. Several studies have assessed the bioprospection of innumerable gut symbionts and their lignocellulolytic enzymes for LCB degradation. Though, some reviews exist on molecular characterization of gut microbes, but none of them has enlightened the microbial community design coupled with various LCB valorization which intensifies the microbial diversity in biofuels application. This review provides a deep insight into the significant breakthroughs attained in enrichment strategy of gut microbial community and its molecular characterization techniques which aids in understanding the holistic microbial community dynamics. Special emphasis is placed on gut microbial role in LCB depolymerization strategies to lignocellulolytic enzymes production and its functional metagenomic data mining eventually generating the sugar platform for biofuels and renewable chemicals production.

Microbial enrichment and meta-omics analysis identify CAZymes from mangrove sediments with unique properties

Although lignocellulose is the most abundant and renewable natural resource for biofuel production, its use remains under exploration because of its highly recalcitrant structure. Its deconstruction into sugar monomers is mainly driven by carbohydrate-active enzymes (CAZymes). To develop highly efficient and fast strategies to discover biomass-degrading enzymes for biorefinery applications, an enrichment process combined with integrative omics approaches was used to identify new CAZymes. The lignocellulolytic-enriched mangrove microbial community (LignoManG) established on sugarcane bagasse (SB) was enriched with lignocellulolytic bacteria and fungi such as Proteobacteria, Bacteroidetes, Basidiomycota, and Ascomycota. These microbial communities were able to degrade up to 55 % of the total SB, indicating the production of lignocellulolytic enzymes. Metagenomic analysis revealed that the LignoManG harbors 18.042 CAZyme sequences such as of cellulases, hemicellulases, carbohydrate esterases, and lytic polysaccharide monooxygenase. Similarly, our metaproteomic analysis depicted several enzymes from distinct families of different CAZy families. Based on the LignoManG data, a xylanase (coldXynZ) was selected, amplified, cloned, expressed, and biochemically characterized. The enzyme displayed psicrofilic properties, with the highest activity at 15 °C, retaining 77 % of its activity when incubated at 0 °C. Moreover, molecular modeling in silico indicated that coldXynZ is composed of a TIM barrel, which is a typical folding found in the GH10 family, and displayed similar structural features related to cold-adapted enzymes. Collectively, the data generated in this study represent a valuable resource for lignocellulolytic enzymes with potential biotechnological applications.

Evaluation of cellulose degrading bacteria isolated from the gut-system of cotton bollworm, Helicoverpa armigera and their potential values in biomass conversion

Background

Cotton bollworm, Helicoverpa armigera is a widely distributed, devastating pest of over 200 crop plants that mainly consist of some cellulosic materials. Despite its economic importance as a pest, little is known about the diversity and community structure of gut symbiotic bacteria potentially functioned in cellulose digestion in different gut-sections of H. armigera. In view of this lacuna, we attempted to evaluate and characterize cellulose-degrading bacteria (CDB) from foregut, midgut, and hindgut -regions of H. armigera by using a culture-dependent approach.

Methodology

The symbiotic bacteria were isolated from different gut-systems of H. armigera by enrichment techniques using Carboxymethyl cellulose sodium salt (CMC) as carbon source. The isolated bacteria were purified and subsequently screened for cellulose-degradation by plate-based method to display the zones of CMC clearance around the colonies. The identification and phylogeny of the gut-bacteria were reconstructed by using 16S rRNA gene sequencing. Different enzymes such as endoglucanase, exoglucanase, β-glucosidase, and xylanase were assayed to determine the cellulolytic repertoire of the isolated bacteria.

Results

The enrichment of CDB and subsequent plate based screening methods resulted in isolation of 71 bacteria among which 54% of the bacteria were obtained from foregut. Among the isolated bacteria, 25 isolates showed discernible cellulose-degradation potential on CMC-agar plates. The phylogenetic analysis based on 16S rRNA gene amplification and sequencing affiliated these cellulolytic bacteria to two major phyla viz., Firmicutes and Proteobacteria. The members of the genus Klebsiella accounted for 39.43% of the total isolated bacteria while 31% of the Bacillus strains were enriched from hindgut region. The principal component analysis (PCA) further suggested that the members of Bacillus and Klebsiella together dominated the foregut and hindgut regions as they accounted for 68% of the total CDB. The four potential isolates selected on the basis of plate-based activities were further evaluated for their lignocellulases production by using various agricultural wastes as substrates. The PCA of the enzyme activities demonstrated that potential isolates majorly secreted endoglucanase and xylanase enzymes. Among the agro-wastes, multivariate analysis validated wheat husk (WH) and sugarcane bagasse (SCB) as most favorable substrates for xylanase and endoglucanase productions respectively. The overall findings suggest that H. armigera harbors diverse bacterial communities in different gut-sections that could assist the host in digestion processes, which may potentially serve as a valuable reservoir of some unique symbionts applied for biomass conversion in biofuel industry.

Development and application of aerobic, chemically defined media for Dysgonomonas

Members of Dysgonomonas are Gram-stain-negative, non-motile, facultatively anaerobic coccobacilli originally described in relation to their isolation from stool and wounds of human patients (CDC group DF-3). More recently, Dysgonomonas have been found to be widely distributed in terrestrial environments and are particularly enriched in insect systems. Their prevalence in xylophagous insects such as termites and wood-feeding cockroaches, as well as in soil-fed microbial fuel cells, elicit interest in lignocellulose degradation and biofuel production, respectively. Their occurrence in mosquito and fruit fly have implications relating to symbiosis, host immunology and developmental biology. Additionally, their presence in termite, mosquito and nematode present novel opportunities for pest and vector control. Currently, the absolute growth requirements of Dysgonomonas are unknown, and they are commonly cultured under anaerobic conditions on complex media containing blood, peptones, tryptones, and yeast, plant or meat extracts. Restrictive and undefined culturing conditions preclude physiological and genetic studies, and thus further understanding of their metabolic potential. Here we describe the requirements for growth of termite-derived Dysgonomonas isolates and create parallel complex, defined and minimal media that permit vigorous and reliable aerobic growth. Furthermore, we show that these media can be used to easily enrich for Dysgonomonas isolates from densely-colonized and microbially-diverse environmental samples.

Multi-omic Directed Discovery of Cellulosomes, Polysaccharide Utilization Loci, and Lignocellulases from an Enriched Rumen Anaerobic Consortium

The lignocellulolytic ERAC displays a unique set of plant polysaccharide-degrading enzymes (with multimodular characteristics), cellulosomal complexes, and PULs. The MAGs described here represent an expansion of the genetic content of rumen bacterial genomes dedicated to plant polysaccharide degradation, therefore providing a valuable resource for the development of biocatalytic toolbox strategies to be applied to lignocellulose-based biorefineries.

Lignocellulose is one of the most abundant renewable carbon sources, representing an alternative to petroleum for the production of fuel and chemicals. Nonetheless, the lignocellulose saccharification process, to release sugars for downstream applications, is one of the most crucial factors economically challenging to its use. The synergism required among the various carbohydrate-active enzymes (CAZymes) for efficient lignocellulose breakdown is often not satisfactorily achieved with an enzyme mixture from a single strain. To overcome this challenge, enrichment strategies can be applied to develop microbial communities with an efficient CAZyme arsenal, incorporating complementary and synergistic properties, to improve lignocellulose deconstruction. We report a comprehensive and deep analysis of an enriched rumen anaerobic consortium (ERAC) established on sugarcane bagasse (SB). The lignocellulolytic abilities of the ERAC were confirmed by analyzing the depolymerization of bagasse by scanning electron microscopy, enzymatic assays, and mass spectrometry. Taxonomic analysis based on 16S rRNA sequencing elucidated the community enrichment process, which was marked by a higher abundance of Firmicutes and Synergistetes species. Shotgun metagenomic sequencing of the ERAC disclosed 41 metagenome-assembled genomes (MAGs) harboring cellulosomes and polysaccharide utilization loci (PULs), along with a high diversity of CAZymes. The amino acid sequences of the majority of the predicted CAZymes (60% of the total) shared less than 90% identity with the sequences found in public databases. Additionally, a clostridial MAG identified in this study produced proteins during consortium development with scaffoldin domains and CAZymes appended to dockerin modules, thus representing a novel cellulosome-producing microorganism.

IMPORTANCE The lignocellulolytic ERAC displays a unique set of plant polysaccharide-degrading enzymes (with multimodular characteristics), cellulosomal complexes, and PULs. The MAGs described here represent an expansion of the genetic content of rumen bacterial genomes dedicated to plant polysaccharide degradation, therefore providing a valuable resource for the development of biocatalytic toolbox strategies to be applied to lignocellulose-based biorefineries.

Changes in the gut microbiome and enzymatic profile of Tenebrio molitor larvae biodegrading cellulose, polyethylene and polystyrene waste

Recent studies have demonstrated the ability of mealworm (Tenebrio molitor) for plastic degradation. This study is focused on changes in microbiome structure depending on diets. Microbial community obtained from oat and cellulose diet formed similar group, two kinds of polyethylene formed another group, while polystyrene diet showed the highest dissimilarity. The highest relative abundance of bacteria colonizing gut was in PE-oxodegradable feeding, nevertheless all applied diets were higher in comparison to oat. Dominant phyla consisted of Proteobacteria, Bacteroides, Firmicutes and Actinobacteria, however after PS feeding frequency in Planctomycetes and Nitrospirae increased. The unique bacteria characteristic for cellulose diet belonged to Selenomonas, while Pantoea were characteristic for both polyethylene diets, Lactococcus and Elizabethkingia were unique for each plastic diet, and potential diazotropic bacteria were characteristic for polystyrene diet (Agrobacterium, Nitrosomonas, Nitrospira). Enzymatic similarity between oatmeal and cellulose diets, was shown. All three plastics diet resulted in different activity in both, digestive tract and bacteria. The enzymes with the highest activity were included phosphatases, esterases, leucine arylamidase, β-galactosidase, β-glucuronidase, α-glucosidase, β-glucosidase, chitinase, α-mannosidase and α-fucosidase. The activity of digestive tract was stronger than cultured gut bacteria. In addition to known polyethylene degradation methods, larvae may degrade polyethylene with esterase, cellulose and oatmeal waste activity is related with the activity of sugar-degrading enzymes, degradation of polystyrene with anaerobic processes and diazotrophs.

Microbiome profiling of the onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae)

The gut microbial community structure of adult Thrips tabaci collected from 10 different agro-climatically diverse locations of India was characterized by using the Illumina MiSeq platform to amplify the V3 region of the 16S rRNA gene of bacteria present in the sampled insects. Analyses were performed to study the bacterial communities associated with Thrips tabaci in India. The complete bacterial metagenome of T. tabaci was comprised of 1662 OTUs of which 62.25% belong to known and 37.7% of unidentified/unknown bacteria. These OTUs constituted 21 bacterial phyla of 276 identified genera. Phylum Proteobacteria was predominant, followed by Actinobacteria, Firmicutes, Bacteroidetes and Cyanobacteria. Additionally, the occurrence of the reproductive endosymbiont, Wolbachia was detected at two locations (0.56%) of the total known OTUs. There is high variation in diversity and species richness among the different locations. Alpha-diversity metrics indicated the higher gut bacterial diversity at Bangalore and lowest at Rahuri whereas higher bacterial species richness at T. tabaci samples from Imphal and lowest at Jhalawar. Beta diversity analyses comparing bacterial communities between the samples showed distinct differences in bacterial community composition of T. tabaci samples from different locations. This paper also constitutes the first record of detailed bacterial communities associated with T. tabaci. The location-wise variation in microbial metagenome profile of T. tabaci suggests that bacterial diversity might be governed by its population genetic structure, environment and habitat.

Degradation profile of nixtamalized maize pericarp by the action of the microbial consortium PM-06

The nixtamalized maize pericarp (NMP) is a plentiful by-product of the tortilla industry and an important source of fermentable sugars. The aim of this study was to describe the degradation profile of NMP by the action of a consortium (PM-06) obtained from the native microbial community of this residue. The degradation was analyzed in terms of the changes in the community dynamics, production of enzymes (endo-xylanase and endo-cellulase), physicochemical parameters, and substrate chemical and microstructural characteristics, to understand the mechanisms behind the process. The consortium PM-06 degraded 86.8 ± 3.3% of NMP after 192 h of growth. Scanning electron microscopy images, and the composition and weight of the residual solids, showed that degradation was sequential starting with the consumption of hemicellulose. Xylanase was the highest enzyme activity produced, with a maximum value of 12.45 ± 0.03 U mL⁻¹. There were fluctuations in the pH during the NMP degradation, starting with the acidification of the culture media and finishing with a pH close to 8.5. The most abundant species in the consortium, at the moment of maximum degradation activity, were Aneurinibacillus migulanus, Paenibacillus macerans, Bacillus coagulans, Microbacterium sp. LCT-H2, and Bacillus thuringiensis. The diversity of PM-06 provided metabolic abilities that in combination helped to produce an efficient process. The consortium PM-06 generated a set of different tools that worked coordinated to increase the substrate availability through the solubilization of components and elimination of structural diffusion barriers. This is the first report about the degradation of NMP using a microbial consortium.

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.

Anaerobic lignocellulolytic microbial consortium derived from termite gut: enrichment, lignocellulose degradation and community dynamics

BACKGROUND

Lignocellulose is the most abundant renewable carbon resource that can be used for biofuels and commodity chemicals production. The ability of complex microbial communities present in natural environments that are specialized in biomass deconstruction can be exploited to develop lignocellulose bioconversion processes. Termites are among the most abundant insects on earth and play an important role in lignocellulose decomposition. Although their digestive microbiome is recognized as a potential reservoir of microorganisms producing lignocellulolytic enzymes, the potential to enrich and maintain the lignocellulolytic activity of microbial consortia derived from termite gut useful for lignocellulose biorefinery has not been assessed. Here, we assessed the possibility of enriching a microbial consortium from termite gut and maintaining its lignocellulose degradation ability in controlled anaerobic bioreactors.

RESULTS

We enriched a termite gut-derived consortium able to transform lignocellulose into carboxylates under anaerobic conditions. To assess the impact of substrate natural microbiome on the enrichment and the maintenance of termite gut microbiome, the enrichment process was performed using both sterilized and non-sterilized straw. The enrichment process was carried out in bioreactors operating under industrially relevant aseptic conditions. Two termite gut-derived microbial consortia were obtained from Nasutitermes ephratae by sequential batch culture on raw wheat straw as the sole carbon source. Analysis of substrate loss, carboxylate production and microbial diversity showed that regardless of the substrate sterility, the diversity of communities selected by the enrichment process strongly changed compared to that observed in the termite gut. Nevertheless, the community obtained on sterile straw displayed higher lignocellulose degradation capacity; it showed a high xylanase activity and an initial preference for hemicellulose.

CONCLUSIONS

This study demonstrates that it is possible to enrich and maintain a microbial consortium derived from termite gut microbiome in controlled anaerobic bioreactors, producing useful carboxylates from raw biomass. Our results suggest that the microbial community is shaped both by the substrate and the conditions that prevail during enrichment. However, when aseptic conditions are applied, it is also affected by the biotic pressure exerted by microorganisms naturally present in the substrate and in the surrounding environment. Besides the efficient lignocellulolytic consortium enriched in this study, our results revealed high levels of xylanase activity that can now be further explored for enzyme identification and overexpression for biorefinery purposes.

Screening of Phytophagous and Xylophagous Insects Guts Microbiota Abilities to Degrade Lignocellulose in Bioreactor

Microbial consortia producing specific enzymatic cocktails are present in the gut of phytophagous and xylophagous insects; they are known to be the most efficient ecosystems to degrade lignocellulose. Here, the ability of these consortia to degrade ex vivo lignocellulosic biomass in anaerobic bioreactors was characterized in term of bioprocess performances, enzymatic activities and bacterial community structure. In a preliminary screening, guts of Ergates faber (beetle), Potosia cuprea (chafer), Gromphadorrhina portentosa (cockroach), Locusta migratoria (locust), and Gryllus bimaculatus (cricket) were inoculated in anaerobic batch reactors, in presence of grounded wheat straw at neutral pH. A short duration fermentation of less than 8 days was observed and was related to a drop of pH from 7 to below 4.5, leading to an interruption of gas and metabolites production. Consistently, a maximum of 180 mg_eq.COD of metabolites accumulated in the medium, which was related to a low degradation of the lignocellulosic biomass, with a maximum of 5 and 2.2% observed for chafer and locust gut consortia. The initial cell-bound and extracellular enzyme activities, i.e., xylanase and β-endoglucanase, were similar to values observed in the literature. Wheat straw fermentation in bioreactors leads to an increase of cell-bounded enzyme activities, with an increase of 145% for cockroach xylanase activity. Bacterial community structures were insect dependent and mainly composed of Clostridia, Bacteroidia and Gammaproteobacteria. Improvement of lignocellulose biodegradation was operated in successive batch mode at pH 8 using the most interesting consortia, i.e., locust, cockroaches and chafer gut consortia. In these conditions, lignocellulose degradation increased significantly: 8.4, 10.5, and 21.0% of the initial COD were degraded for chafer, cockroaches and locusts, respectively in 15 days. Consistently, xylanase activity tripled for the three consortia, attesting the improvement of the process. Bacteroidia was the major bacterial class represented in the bacterial community for all consortia, followed by Clostridia and Gammaproteobacteria classes. This work demonstrates the possibility to maintain apart of insect gut biological activity ex vivo and shows that lignocellulose biodegradation can be improved by using a biomimetic approach. These results bring new insights for the optimization of lignocellulose degradation in bioreactors.

Biodelignification and hydrolysis of rice straw by novel bacteria isolated from wood feeding termite

In this study, two bacterial strains capable of degrading lignin, cellulose, and hemicellulose were isolated from wood feeding termite. The isolates were identified by 16S rRNA gene sequencing. A bacterium Ochrobactrum oryzae BMP03 capable of degrading lignin was isolated on alkali lignin medium and Bacillus sp. BMP01 strain capable of degrading cellulose and hemicellulose were isolated on carboxymethyl cellulose and xylan media. The efficiency of bacterial degradation was studied by evaluating the composition of rice straw both before and after degradation. The appearance of new cellulose bands at 1382, 1276, 1200, and 871 cm-1, and the absence of former lignin bands at 1726, 1307, and 1246 cm-1 was observed after biodelignification. This was further confirmed by the formation of channeling and layering of the microstructure of biodelignified rice straw observed under electron microscope. Maximum lignin removal was achieved in separate biodelignification and hydrolysis process after the 14th day of treatment by Ochrobactrum oryzae BMP03 (53.74% lignin removal). Hydrolysis of the biodelignified rice straw released 69.96% of total reducing sugars after the 14th day hydrolysis by Bacillus sp. BMP01. In simultaneous delignification and hydrolysis process, about 58.67% of total reducing sugars were obtained after the 13th day of biotreatment. Separate delignification and hydrolysis process were found to be effective in lignin removal and sugar released than the simultaneous process. The bacteria, Bacillus sp. BMP01, has the ability to degrade hemicellulose and cellulose simultaneously. Overall, these results demonstrate that the possibility of rice straw bioconversion into reducing sugars by bacteria from termite gut.

Harnessing microfluidic streak plate technique to investigate the gut microbiome of Reticulitermes chinensis

The termite gut microbiome is a model system to investigate microbial interactions and their associations with host. For decades, extensive research with molecular tools and conventional cultivation method has been carried out to define the microbial diversity in termite gut. Yet, many bacterial groups of the termite gut microbiome have not been successfully cultivated in laboratory. In this study, we adapted the recently developed microfluidic streak plate (MSP) technique for cultivation of termite gut microbial communities at both aerobic and anaerobic conditions. We found that 99 operational taxonomic units (OTUs) were cultivable by MSP approach and 18 OTUs were documented first time for termite gut microbiota. Further analysis of the bacterial diversities derived by culture‐dependent MSP approach and culture‐independent 16S rRNA gene typing revealed that both methods have bias in recovery of gut microbiota. In total 396 strains were isolated with MSP technique, and potential new taxa at species and/or genus levels were obtained that were phylogenetically related to Burkholderia, Micrococcus, and Dysgonomonas. Results from this study indicate that MSP technique is applicable for cultivating previously unknown and new microbial groups of termite gut microbiota.