Functional and translational analyses of a beta-glucosidase gene (glycosyl hydrolase family 1) isolated from the gut of the lower termite Reticulitermes flavipes

Scharf, Michael E.; Kovaleva, E. S.; Jadhao, S. B.; Campbell, James H.; Buchman, George W.; Boucias, Drion G.

doi:10.1016/j.ibmb.2010.06.002

Cited by 66 publications

(61 citation statements)

References 36 publications

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“…Like G1NkBG (30), G1mgNtBG1 has broad substrate specificity and hydrolyzes both natural and synthetic substrates (Table 1). Since wood is the main diet source for termites, it is intuitive that cellobiose was hydrolyzed by all ␤-glucosidases (25,27,32). Activities of both laminaribiase and cellobiase emphasize the importance of G1mgNtBG1 in the hydrolysis of biomass.…”

Section: Discussionmentioning

confidence: 99%

“…However, termites have evolved their own system to degrade cellulose, independently of whether or not they maintain a relationship with symbiotic protists (34). To date, only a few endogenous cellulases of termite origin have been biochemically characterized (13,25,27,32,37). The properties of endogenous ␤-glucosidases from three termite species, Macrotermes muelleri (25), Neotermes koshunensis (20,29,32), and Reticulitermes flavipes (27), have been characterized.…”

mentioning

confidence: 99%

“…To date, only a few endogenous cellulases of termite origin have been biochemically characterized (13,25,27,32,37). The properties of endogenous ␤-glucosidases from three termite species, Macrotermes muelleri (25), Neotermes koshunensis (20,29,32), and Reticulitermes flavipes (27), have been characterized. Regarding the wood-feeding higher termite Nasutitermes takasagoensis, only the site of expression of endogenous ␤-glucosidases has been reported (28,30).…”

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confidence: 99%

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Heterologous Expression in Pichia pastoris and Characterization of an Endogenous Thermostable and High-Glucose-Tolerant β-Glucosidase from the Termite Nasutitermes takasagoensis

Uchima

Tokuda

Watanabe

et al. 2012

Appl Environ Microbiol

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ABSTRACTTermites are well-known cellulose decomposers and can give researchers insights into how to utilize lignocellulosic biomass in the actual scenario of energy consumption. In this work, an endogenous β-glucosidase from the midgut of the higher termiteNasutitermes takasagoensiswas purified to homogeneity by Ni2+affinity chromatography and its properties were characterized. This β-glucosidase (G1mgNtBG1), which belongs to glycoside hydrolase family 1, is a homotrimer in its native form, with a molecular mass of 169.5 kDa, as demonstrated by gel filtration chromatography. The enzyme displayed maximum activity at pH 5.5 and had broad substrate specificities toward several saccharides, including cellobiose. G1mgNtBG1 showed a relatively high temperature optimum of 65°C and one of the highest levels of glucose tolerance among several β-glucosidases already characterized, with aKiof 600 mM glucose. To examine the applicability of G1mgNtBG1 in biomass conversion, we compared the thermostability and glucose tolerance of G1mgNtBG1 with those of Novozym 188. We found that G1mgNtBG1 was more thermostable after 5 h of incubation at 60°C and more resistant to glucose inhibition than Novozym 188. Furthermore, our result suggests that G1mgNtBG1 acts synergistically with Celluclast 1.5 L in releasing reducing sugars from Avicel. Thus, G1mgNtBG1 seems to be a potential candidate for use as a supplement in the hydrolysis of biomass.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Heterologous Expression in Pichia pastoris and Characterization of an Endogenous Thermostable and High-Glucose-Tolerant β-Glucosidase from the Termite Nasutitermes takasagoensis

Uchima

Tokuda

Watanabe

et al. 2012

Appl Environ Microbiol

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“…Tubes were vented by melting a pinhole in the assay tube lids. All assay conditions are based on extensive preliminary work showing circum-neutral gut pH in R. flavipes, digestive enzyme pH optima around 7, and enzyme stability at 37°C (Zhou et al, 2007(Zhou et al, , 2010Tartar et al, 2009;Coy et al, 2010;Scharf et al, 2010Scharf et al, , 2011aSethi et al, 2013). A range of feedstock amounts was compared (0.2, 0.4, 0.8, 1, and 2% w/v).…”

Section: In Vitro Saccharification Assaysmentioning

confidence: 99%

“…There is ample evidence of termites having endogenous cellulases that aid in cellulose digestion independent of symbiont action (Watanabe et al, 1998;Zhou et al, 2007), but clearly a synergistic collaboration exists between the termite and its symbiota that achieves efficient lignocellulose digestion (Scharf et al, 2011a,b). Several GH families have been identified in termites with activity toward various cellulosic substrates (Tokuda et al, 1997;Zhou et al, 2007Zhou et al, , 2010Scharf et al, 2010). In contrast, little is known about lignin breakdown mechanisms of wood-feeding insects (Geib et al, 2008), which is a limiting step in biofuel production (Yang and Wyman, 2008).…”

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Saccharification of Agricultural Lignocellulose Feedstocks and Protein-Level Responses by a Termite Gut-Microbe Bioreactor

Rajarapu

Scharf

2017

Front. Energy Res.

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This study investigated saccharification and protein-level responses to the candidate biofuel feedstocks corn stover (CS) and soybean residue (SR) by the gut of a lower termite. The focus termite was Reticulitermes flavipes, which is a highly efficient digester of wood lignocellulose that houses a mixture of prokaryotic and eukaryotic microbes in its gut. Our specific objectives were to (i) measure saccharification potential of the CS and SR feedstocks by termite gut protein extracts, (ii) identify specific proteins in the termite gut responding to feeding on CS and SR diets, and (iii) evaluate gut lignocellulase and accessory enzyme activity responses to CS and SR feeding. Cellulose paper was the control diet. Although CS was saccharified at higher levels, termite gut protein extracts saccharified both CS and SR irrespective of feedstock loading. Consumption of the CS and SR feedstocks by termites resulted in surprisingly few differences in gut protein profiles, with the main exception being elevated myosin abundance with SR feeding. Activity of potential lignocellulases and accessory enzymes was generally similar between CS and SR fed guts as well; however, cellobiohydrolase/exoglucanase activity was higher with CS feeding and glutathione peroxidase activity with SR feeding. These findings have significance from two perspectives. First, SR feeding/digestion appears to cause physiological stress in the termite gut that likely would extend to other types of microbial environments including those within industrial bioreactors. Second, because termites can survive on exclusive CS and SR diets and their guts exhibit clear CS and SR saccharification activity, this validates the R. flavipes system as a potential source for CS and SR degrading enzymes; in particular, cellobiohydrolases/exoglucanases and glutathione peroxidases from this system may play roles in CS and SR breakdown.

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Biofuels: Fungal, Bacterial and Insect Degraders of Lignocellulose

Sethi

Scharf

2013

Encyclopedia of Life Sciences

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Lignocellulose is the main structural component of plant cell walls and can be degraded into simple sugars with the help of hydrolytic enzymes. Lignocellulose is composed of three polymers: cellulose, hemicellulose and lignin. Certain fungi, bacteria and insects have evolved the ability to degrade lignocellulose. Cellulose is degraded to glucose by the synergistic action of three distinct classes of enzymes: endoglucanases, exoglucanases and β‐glucosidases. Owing to its variable structure and organisation, hemicellulose degradation requires various enzymes with diverse modes of action, which include endoxylanases, endomannanases, β‐xylosidases, β‐mannosidases, β‐galactosidases, α‐glucuronidases, α‐arabinofurnosidases, α‐galactosidases, acetyl xylan esterases, feruloyl esterases and glucuronyl esterases. Lignin degradation is much more difficult due to its complex structure and bonding to carbohydrate complexes. It requires oxidative enzymes, such as lignin peroxidases, manganese peroxidases, versatile peroxidases, laccases, and several other auxiliary enzymes. Commercial biofuel production from lignocellulosic materials can be achieved by artificially producing these cellulases, hemicellulases and lignases in recombinant form. Key Concepts: Lignocellulose is the most abundant renewable resource of energy on the Earth. Lignocellulose is a general term referring to a natural complex of three biopolymers: cellulose, hemicellulose and lignin. Simple sugar can be released from lignocellulose using three categories of enzymes: cellulases, hemicellulase and lignases. Released sugars from lignocellulose can be fermented into biofuel (ethanol). Wood‐rotting fungi such as white‐rot, brown‐rot and soft‐rot fungi can degrade lignocellulose. Aerobic and anaerobic bacteria such as Bacillus, Streptomyces, Cellulomonas and Clostridium possess lignocellulose‐degrading enzymes. Wood and plant‐feeding insects such termites, roaches, longhorn beetles and grasshoppers are rich sources of novel lignocellulases genes. Lignocellulases of fungal, bacterial and insect origin can be artificially/recombinantly produced in various protein expression systems. Fungal, bacterial and insect lignocellulases are expected to play important roles in the development of successful lignocellulose conversion technologies.

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Functional and translational analyses of a beta-glucosidase gene (glycosyl hydrolase family 1) isolated from the gut of the lower termite Reticulitermes flavipes

Cited by 66 publications

References 36 publications

Heterologous Expression in Pichia pastoris and Characterization of an Endogenous Thermostable and High-Glucose-Tolerant β-Glucosidase from the Termite Nasutitermes takasagoensis

Heterologous Expression in Pichia pastoris and Characterization of an Endogenous Thermostable and High-Glucose-Tolerant β-Glucosidase from the Termite Nasutitermes takasagoensis

Saccharification of Agricultural Lignocellulose Feedstocks and Protein-Level Responses by a Termite Gut-Microbe Bioreactor

Biofuels: Fungal, Bacterial and Insect Degraders of Lignocellulose

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