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 center dot 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 degrees C and pH 4 center dot 5. PNLZJ5B activity improved with increasing degrees of methyl esterification of pectin. The K-m and V-max values were 0 center dot 81 mg ml(-1) and 372 center dot 8 mu mol 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.