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

Biotechnology for Biofuels

Shara D McClendon²  Tanveer Batth²  Christopher J Petzold²  Paul D Adams²  Blake A Simmons³  Steven W Singer¹ 

[1] Deconstruction Division, Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, CA, 94608, USA

[2] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

[3] Biomass Science and Conversion Technology Department, Sandia National Laboratories, Livermore, CA, USA

关键词: Switchgrass (Panicum virgatum);    1-ethyl-3-methylimidazolium acetate;    Ionic liquid;    Ammonia fiber expansion;    Fungal secretome;    Polysaccharide monooxygenases;    GH 61;    Thielavia terrestris;    Thermoascus aurantiacus;   

Others  :  798254
DOI  :  10.1186/1754-6834-5-54

 received in 2012-06-06, accepted in 2012-07-13,  发布年份 2012

【 摘 要 】

Background

Thermophilic fungi have attracted increased interest for their ability to secrete enzymes that deconstruct biomass at high temperatures. However, development of thermophilic fungi as enzyme producers for biomass deconstruction has not been thoroughly investigated. Comparing the enzymatic activities of thermophilic fungal strains that grow on targeted biomass feedstocks has the potential to identify promising candidates for strain development. Thielavia terrestris and Thermoascus aurantiacus were chosen for characterization based on literature precedents.

Results

Thermoascus aurantiacus and Thielavia terrestris were cultivated on various biomass substrates and culture supernatants assayed for glycoside hydrolase activities. Supernatants from both cultures possessed comparable glycoside hydrolase activities when incubated with artificial biomass substrates. In contrast, saccharifications of ionic liquid pretreated switchgrass (Panicum virgatum) revealed that T. aurantiacus enzymes released more glucose than T. terrestris enzymes over a range of protein mass loadings and temperatures. Temperature-dependent saccharifications demonstrated that the T. aurantiacus proteins retained higher levels of activity compared to a commercial enzyme mixture sold by Novozymes, Cellic CTec2, at elevated temperatures. Enzymes secreted by T. aurantiacus released glucose at similar protein loadings to CTec2 on dilute acid, ammonia fiber expansion, or ionic liquid pretreated switchgrass. Proteomic analysis of the T. aurantiacus culture supernatant revealed dominant glycoside hydrolases from families 5, 7, 10, and 61, proteins that are key enzymes in commercial cocktails.

Conclusions

T. aurantiacus produces a complement of secreted proteins capable of higher levels of saccharification of pretreated switchgrass than T. terrestris enzymes. The T. aurantiacus enzymatic cocktail performs at the same level as commercially available enzymatic cocktail for biomass deconstruction, without strain development or genetic modifications. Therefore, T. aurantiacus provides an excellent platform to develop a thermophilic fungal system for enzyme production for the conversion of biomass to biofuels.

【 授权许可】

   
2012 McClendon et al.; licensee BioMed Central Ltd.

【 图 表 】

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