Discovery and characterization of ionic liquid-tolerant thermophilic cellulases from a switchgrass-adapted microbial community

Biotechnology for Biofuels

John M Gladden³  Joshua I Park⁴  Jessica Bergmann²  Vimalier Reyes-Ortiz¹  Patrik D’haeseleer⁷  Betania F Quirino⁵  Kenneth L Sale³  Blake A Simmons³  Steven W Singer⁶ 

[1] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Joint BioEnergy Institute (JBEI), 1 Cyclotron Road, Berkeley, CA 94720, USA

[2] Department of Genomics Science and Biotechnology, Universidade Católica de Brasília, Brasília DF 70790-160, Brazil

[3] Biological and Materials Science Center, Sandia National Laboratories, Livermore, CA, USA

[4] Current address: Department of Biological Sciences, Takeda California, Inc., San Diego, CA, USA

[5] Embrapa-Agroenergy, Brasilia DF 70770-901, Brazil

[6] Department of Geochemistry & Department of Ecology, Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

[7] Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA

关键词: Biofuel;    Thermophilic;    Ionic liquid;    Cellulase;   

Others  :  793820
DOI  :  10.1186/1754-6834-7-15

 received in 2013-10-14, accepted in 2014-01-15,  发布年份 2014

【 摘 要 】

Background

The development of advanced biofuels from lignocellulosic biomass will require the use of both efficient pretreatment methods and new biomass-deconstructing enzyme cocktails to generate sugars from lignocellulosic substrates. Certain ionic liquids (ILs) have emerged as a promising class of compounds for biomass pretreatment and have been demonstrated to reduce the recalcitrance of biomass for enzymatic hydrolysis. However, current commercial cellulase cocktails are strongly inhibited by most of the ILs that are effective biomass pretreatment solvents. Fortunately, recent research has shown that IL-tolerant cocktails can be formulated and are functional on lignocellulosic biomass. This study sought to expand the list of known IL-tolerant cellulases to further enable IL-tolerant cocktail development by developing a combined in vitro/in vivo screening pipeline for metagenome-derived genes.

Results

Thirty-seven predicted cellulases derived from a thermophilic switchgrass-adapted microbial community were screened in this study. Eighteen of the twenty-one enzymes that expressed well in E. coli were active in the presence of the IL 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) concentrations of at least 10% (v/v), with several retaining activity in the presence of 40% (v/v), which is currently the highest reported tolerance to [C₂mim][OAc] for any cellulase. In addition, the optimum temperatures of the enzymes ranged from 45 to 95°C and the pH optimum ranged from 5.5 to 7.5, indicating these enzymes can be used to construct cellulase cocktails that function under a broad range of temperature, pH and IL concentrations.

Conclusions

This study characterized in detail twenty-one cellulose-degrading enzymes derived from a thermophilic microbial community and found that 70% of them were [C₂mim][OAc]-tolerant. A comparison of optimum temperature and [C₂mim][OAc]-tolerance demonstrates that a positive correlation exists between these properties for those enzymes with a optimum temperature >70°C, further strengthening the link between thermotolerance and IL-tolerance for lignocelluolytic glycoside hydrolases.

【 授权许可】

   
2014 Gladden et al.; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

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