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

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°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.