High-yield production of acidic pectin lyase PNLZJ5B for juice processing.

A pectin lyase gene pnlzj5b from Aspergillus niger ZJ5 was identified and overexpressed successfully in Pichia pastoris. Recombinant PNLZJ5B exhibited high activity towards citrus pectin (150 U ml -1 ). Through further codon optimization, the expression efficiency of PNLZJ5B in P. pastoris increased to 3·5-fold (532/150 U ml -1 ). PNLZJ5B was purified by ultrafiltration, anion exchange and gel chromatography. It showed optimal activity and good stability at 58°C and pH 4·5. PNLZJ5B activity improved with increasing degrees of methyl esterification of pectin. The K m and V max values were 0·81 mg ml -1 and 372·8 μmol min -1  mg -1 , respectively. In addition, PNLZJ5B effectively decreased the viscosity of apple juice. Compared with commercial pectin lyase, PNLZJ5B obtained a higher juice volume. These favourable enzymatic properties of PNLZJ5B show potential utility in juice-processing applications and other food-related fields.