Cellulases without carbohydrate-binding modules in high consistency ethanol production process

Biotechnology for Biofuels

Annukka Pakarinen¹  Mai Østergaard Haven³  Demi Tristan Djajadi¹  Anikó Várnai⁴  Terhi Puranen²  Liisa Viikari¹ 

[1] Department of Food and Environmental Sciences, University of Helsinki, PO 27, 00014 Helsinki, Finland

[2] Roal Oy, Tykkimäentie 15, FIN-05200 Rajamäki, Finland

[3] DONG Energy A/S, Kraftværksvej 53, 7000 Fredericia, Denmark

[4] Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, N-1432 Aas, Norway

关键词: High consistency;    Hydrolysis;    Lignocellulose;    Recyclability;    Cellobiohydrolases;    Cellulases;    CBM;    Carbohydrate-binding modules;   

Others  :  793556
DOI  :  10.1186/1754-6834-7-27

 received in 2013-11-05, accepted in 2014-02-06,  发布年份 2014

【 摘 要 】

Background

Enzymes still comprise a major part of ethanol production costs from lignocellulose raw materials. Irreversible binding of enzymes to the residual substrate prevents their reuse and no efficient methods for recycling of enzymes have so far been presented. Cellulases without a carbohydrate-binding module (CBM) have been found to act efficiently at high substrate consistencies and to remain non-bound after the hydrolysis.

Results

High hydrolysis yields could be obtained with thermostable enzymes of Thermoascus aurantiacus containing only two main cellulases: cellobiohydrolase I (CBH I), Cel7A and endoglucanase II (EG II), Cel5A. The yields were decreased by only about 10% when using these cellulases without CBM. A major part of enzymes lacking CBM was non-bound during the most active stage of hydrolysis and in spite of this, produced high sugar yields. Complementation of the two cellulases lacking CBM with CBH II (CtCel6A) improved the hydrolysis. Cellulases without CBM were more sensitive during exposure to high ethanol concentration than the enzymes containing CBM. Enzymes lacking CBM could be efficiently reused leading to a sugar yield of 90% of that with fresh enzymes. The applicability of cellulases without CBM was confirmed under industrial ethanol production conditions at high (25% dry matter (DM)) consistency.

Conclusions

The results clearly show that cellulases without CBM can be successfully used in the hydrolysis of lignocellulose at high consistency, and that this approach could provide new means for better recyclability of enzymes. This paper provides new insight into the efficient action of CBM-lacking cellulases. The relationship of binding and action of cellulases without CBM at high DM consistency should, however, be studied in more detail.

【 授权许可】

   
2014 Pakarinen et al.; licensee BioMed Central Ltd.

【 图 表 】

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