Thermoascus aurantiacus is a promising source of enzymes for biomass deconstruction under thermophilic conditions

McClendon, Shara; Batth, Tanveer S.; Kim, Young-Mo; Adams, Paul D.; Simmons, Blake A.; Singer, Steven W.

doi:10.1186/1754-6834-5-54

Cited by 87 publications

(57 citation statements)

References 29 publications

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“…These results were surprising, since enzymatic assays of the supernatant recovered much higher levels of xylanase activity than cellulase activity. Therefore, it is possible that cellulase activity is underestimated based on measurement of the supernatants using model cellulase substrates and that such estimates do not necessarily reflect the cellulose hydrolysis activity in the consortia (29).…”

Section: Discussionmentioning

confidence: 99%

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Eichorst

Joshua

Sathitsuksanoh

et al. 2014

Appl Environ Microbiol

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e Microbial communities that deconstruct plant biomass have broad relevance in biofuel production and global carbon cycling. Biomass pretreatments reduce plant biomass recalcitrance for increased efficiency of enzymatic hydrolysis. We exploited these chemical pretreatments to study how thermophilic bacterial consortia adapt to deconstruct switchgrass (SG) biomass of various compositions. Microbial communities were adapted to untreated, ammonium fiber expansion (AFEX)-pretreated, and ionicliquid (IL)-pretreated SG under aerobic, thermophilic conditions using green waste compost as the inoculum to study biomass deconstruction by microbial consortia. After microbial cultivation, gravimetric analysis of the residual biomass demonstrated that both AFEX and IL pretreatment enhanced the deconstruction of the SG biomass approximately 2-fold. Two-dimensional nuclear magnetic resonance (2D-NMR) experiments and acetyl bromide-reactive-lignin analysis indicated that polysaccharide hydrolysis was the dominant process occurring during microbial biomass deconstruction, and lignin remaining in the residual biomass was largely unmodified. Small-subunit (SSU) rRNA gene amplicon libraries revealed that although the dominant taxa across these chemical pretreatments were consistently represented by members of the Firmicutes, the Bacteroidetes, and Deinococcus-Thermus, the abundance of selected operational taxonomic units (OTUs) varied, suggesting adaptations to the different substrates. Combining the observations of differences in the community structure and the chemical and physical structure of the biomass, we hypothesize specific roles for individual community members in biomass deconstruction.

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Section: Discussionmentioning

confidence: 99%

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Eichorst

Joshua

Sathitsuksanoh

et al. 2014

Appl Environ Microbiol

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“…In this study, we characterize the thermophilic GH family 3 BGs from Acremonium thermophilum ( At BG3) and Thermoascus aurantiacus ( Ta BG3) [15,16] in terms of cellobiose hydrolysis and glucose inhibition; a well-characterized BG from Aspergillus sp , purified from Novozyme®188 ( N188 BG), was used for comparison. A literature survey was also performed to identify correlations between the kinetic parameters of cellobiose hydrolysis and glucose inhibition.…”

Section: Introductionmentioning

confidence: 99%

Selecting β-glucosidases to support cellulases in cellulose saccharification

Teugjas

Väljamaë

2013

Biotechnol Biofuels

132

100

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BackgroundEnzyme end-product inhibition is a major challenge in the hydrolysis of lignocellulose at a high dry matter consistency. β-glucosidases (BGs) hydrolyze cellobiose into two molecules of glucose, thereby relieving the product inhibition of cellobiohydrolases (CBHs). However, BG inhibition by glucose will eventually lead to the accumulation of cellobiose and the inhibition of CBHs. Therefore, the kinetic properties of candidate BGs must meet the requirements determined by both the kinetic properties of CBHs and the set-up of the hydrolysis process.ResultsThe kinetics of cellobiose hydrolysis and glucose inhibition of thermostable BGs from Acremonium thermophilum (AtBG3) and Thermoascus aurantiacus (TaBG3) was studied and compared to Aspergillus sp. BG purified from Novozyme®188 (N188BG). The most efficient cellobiose hydrolysis was achieved with TaBG3, followed by AtBG3 and N188BG, whereas the enzyme most sensitive to glucose inhibition was AtBG3, followed by TaBG3 and N188BG. The use of higher temperatures had an advantage in both increasing the catalytic efficiency and relieving the product inhibition of the enzymes. Our data, together with data from a literature survey, revealed a trade-off between the strength of glucose inhibition and the affinity for cellobiose; therefore, glucose-tolerant BGs tend to have low specificity constants for cellobiose hydrolysis. However, although a high specificity constant is always an advantage, in separate hydrolysis and fermentation, the priority may be given to a higher tolerance to glucose inhibition.ConclusionsThe specificity constant for cellobiose hydrolysis and the inhibition constant for glucose are the most important kinetic parameters in selecting BGs to support cellulases in cellulose hydrolysis.

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“…The GH61 from T. aurantiacus exhibits high activity in a boosting assay (Harris et al 2010). The high cellulolytic potential of this fungus is underpinned by the report that extracellular enzymes from T. aurantiacus release the same amount of sugars from pretreated switchgrass as the commercial cellulase blend Cellic Ctec2 (Novozymes, Bagsvaerd, Denmark) at the same protein load (McClendon et al 2012). In addition to the high activity, the T. aurantiacus enzymes have higher thermostability than Cellic Ctec2, which probably consists mostly of enzymes from mesophilic fungi although the precise composition has not been disclosed by the manufacturer.…”

Section: Introductionmentioning

confidence: 99%

Cellulolytic potential of thermophilic species from four fungal orders

Busk

Lange

2013

AMB Express

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Elucidation of fungal biomass degradation is important for understanding the turnover of biological materials in nature and has important implications for industrial biomass conversion. In recent years there has been an increasing interest in elucidating the biological role of thermophilic fungi and in characterization of their industrially useful enzymes. In the present study we investigated the cellulolytic potential of 16 thermophilic fungi from the three ascomycete orders Sordariales, Eurotiales and Onygenales and from the zygomycete order Mucorales thus covering all fungal orders that include thermophiles. Thermophilic fungi are the only described eukaryotes that can grow at temperatures above 45°C. All 16 fungi were able to grow on crystalline cellulose but their secreted enzymes showed widely different cellulolytic activities, pH optima and thermostabilities. Interestingly, in contrast to previous reports, we found that some fungi such as Melanocarpus albomyces readily grew on crystalline cellulose and produced cellulases. These results indicate that there are large differences in the cellulolytic potential of different isolates of the same species. Furthermore, all the selected species were able to degrade cellulose but the differences in cellulolytic potential and thermostability of the secretome did not correlate to the taxonomic position. PCR amplification and sequencing of 22 cellulase genes from the fungi showed that the level of thermostability of the cellulose-degrading activity could not be inferred from the phylogenetic relationship of the cellulases.

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Thermoascus aurantiacus is a promising source of enzymes for biomass deconstruction under thermophilic conditions

Cited by 87 publications

References 29 publications

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Substrate-Specific Development of Thermophilic Bacterial Consortia by Using Chemically Pretreated Switchgrass

Selecting β-glucosidases to support cellulases in cellulose saccharification

Cellulolytic potential of thermophilic species from four fungal orders

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