Acetyl xylan esterases are among the key enzymes in the xylan degradation enzyme system. However, acetyl xylan esterases from natural microorganisms have low expression and low enzyme activity and are impure. In this study, a new xylanase gene, est1051, from the metagenomic library, was expressed in the prokaryotic system. Its enzymatic properties were explored, including optimum temperature and pH, thermal and pH stability, and tolerance against organic solvents, metal ions and salt solutions. Then the fermentation conditions of EST1051 were optimized by the response surface method, and the maximum enzyme yield reached 1909.32 U/L. Finally, the synergism with cellulase on straw degradation was evaluated. EST1051 displays high homology with acetylxylan esterases in terms of amino acid sequences and conserved active sites. EST1051 shows high stability across a broad temperature range, and retains more than 60% of its enzymatic activity between 4 and 60°C after 24 h of incubation. Single-factor analysis and orthogonal design were conducted to determine the optimal conditions for the maximizing the saccharification rate of wheat straws. Interestingly, the synergism of EST1051 with cellulase contributes to the efficient transformation of wheat straws. These findings may open the door to significant industrial applications of this novel acetylxylan esterase.

Cellulose is the cheapest, natural, renewable organic substance that is used as a carbon source in various elds. Water hyacinth, an aquatic plant rich in cellulose, is often used as a raw material in fuel production. However, natural cellulase can be hardly used in industrial production on account of its low thermal stability and activity. In this study, a metagenomic library was constructed. Then a new cellulase gene, cel1029, was screened by Congo red staining and expressed in the prokaryotic system. Enzymatic properties of Cel1029 were explored, including optimum temperature and pH, thermal and pH stability, and tolerance against organic solvents, metal ions and salt solutions. Finally, its ability of degrading water hyacinth was identi ed and evaluated. Cel1029 displayed high homology with endoglucanase in the glycoside hydrolase family 5 (GH5) and had high stability across a broad temperature range. More than 86% of its enzymatic activities were retained between 4 and 60°C after 24 h of incubation. Singlefactor analysis and orthogonal design were further conducted to determine the optimal conditions for the highest reducing sugar yield of water hyacinth. Interestingly, Cel1029 e ciently transformed water hyacinth with a reducing sugar yield of 430.39 mg/g in 22 h. These ndings may open the door for signi cant industrial applications of a novel GH5 cellulase (NCBI Reference Sequence: MK051001, Cel1029) and help identify more e cient methods to degrade cellulose-rich plants.

Cellulose is the cheapest, natural, renewable organic substance that is used as a carbon source in various fields. Water hyacinth, an aquatic plant rich in cellulose, is often used as a raw material in fuel production. However, natural cellulase can be hardly used in industrial production on account of its low thermal stability and activity. In this study, a metagenomic library was constructed. Then a new cellulase gene, cel1029, was screened by Congo red staining and expressed in the prokaryotic system. Enzymatic properties of Cel1029 were explored, including optimum temperature and pH, thermal and pH stability, and tolerance against organic solvents, metal ions and salt solutions. Finally, its ability of degrading water hyacinth was identified and evaluated. Cel1029 displayed high homology with endoglucanase in the glycoside hydrolase family 5 (GH5) and had high stability across a broad temperature range. More than 86% of its enzymatic activities were retained between 4 and 60°C after 24 h of incubation. Single-factor analysis and orthogonal design were further conducted to determine the optimal conditions for the highest reducing sugar yield of water hyacinth. Interestingly, Cel1029 efficiently transformed water hyacinth with a reducing sugar yield of 430.39 mg/g in 22 h. These findings may open the door for significant industrial applications of a novel GH5 cellulase (NCBI Reference Sequence: MK051001, Cel1029) and help identify more efficient methods to degrade cellulose-rich plants.