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Open Access Highly Accessed Research article

Enhancement of fermentable sugar yield by competitive adsorption of non-enzymatic substances from yeast and cellulase on lignin

Yong Tang12, Fuhou Lei2, Carrasco Cristhian3, Zuguang Liu2, Hailong Yu1 and Jianxin Jiang1*

Author Affiliations

1 Department of Chemistry and Chemical Engineering, Beijing Forestry University, Beijing, China

2 GuangXi Key Laboratory of Chemistry and Engineering of Forest Products, Nanning 530006, China

3 Department of Chemical Engineering, Lund University, Lund, Sweden

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BMC Biotechnology 2014, 14:21  doi:10.1186/1472-6750-14-21

Published: 20 March 2014

Abstract

Background

Enhancement of enzymatic digestibility by some supplementations could reduce enzyme loading and cost, which is still too high to realize economical production of lignocellulosic biofuels. A recent study indicates that yeast hydrolysates (YH) have improved the efficiency of cellulases on digestibility of furfural residues (FR). In the current work, the components of YH were separated by centrifugation and size exclusion chromatography and finally characterized in order to better understand this positive effect.

Results

A 60.8% of nitrogen of yeast cells was remained in the slurry (YHS) after hydrothermal treatment. In the supernatant of YH (YHL), substances of high molecular weight were identified as proteins and other UV-absorbing compounds, which showed close molecular weight to components of cellulases. Those substances attributed to a synergetic positive effect on enzymatic hydrolysis of FR. The fraction of YHL ranged from 1.19 to 2.19 mL (elution volume) contained over 50% of proteins in YHL and had the best performance in stimulating the release of glucose. Experiment results proved the adsorption of proteins in YHL on lignin.

Conclusions

Supplementation of cellulases with YH enhances enzymatic digestibility of FR mainly by a competitive adsorption of non-enzymatic substances on lignin. The molecular weight of these substances has a significant impact on their performance. Different strategies can be used for a good utilization of yeast cells in terms of biorefinery concept.

Keywords:
Cellulases; Enzymatic hydrolysis; Yeast hydrolysate; Competitive adsorption