Efficient Over-expression and Application of High-performance Pectin Lyase by Screening Aspergillus niger Pectin Lyase Gene Family

摘要

Acidic pectin lyase is of great application value in fruit-processing industry. In this study, five pectin lyase genes (pelA, pelB, pelC, pelD and pelF) from A. niger pectin lyase gene family were cloned and over-expressed in A. niger strain SH-2, respectively. The pelA recombinant strain (SH2-pelA) owns the highest acidic pectin lyase activity: 11069.2 U/mL in flask fermentation, and 65148.8 U/mL in submerged fermentation. The recombinant pectin lyase A (PelA) was purified by Ni-affinity chromatography, and specificity of the protein was confirmed by western blotting. The recombinant PelA exhibits maximum activity at pH 4.5 and 50 degrees C. The recombineant PelA shows increasing specific activity as the degree of methyl-esterization of the substrate raises. The maximum activity (22423.3 U/mL) was obtined using citrus pectin (85% esterified) as the substrate. After the treatment by PelA, the light transmittance of orange, apple and grape juice was increased 19.2-fold, 7.3-fold and 3.8-fold, respectively, suggesting that the recombinant acidic PelA had noticeable clarifying effects on orange, apple and grape juice.