Production of Polygalacturonase Using Carica Papaya Peel Biowaste and Its Application for Pomegranate Juice Clarification

The present study focuses on utilization of papaya peel for polygalacturonase production in solid-state fermentation (SSF). Papaya peel was screened as optimum solid substrate and valorized under SSF for polygalacturonase production by Aspergillus niger AN07 and the effect of different fermentation parameters viz. fermentation time, particle size, moisture content and agitation speed on the enzyme production was investigated. Two fermentation variables viz. moisture content and fermentation time have been identified to significantly affect polygalacturonase production as predicted using Plackett–Burman Design (PBD). It was further optimized by Response Surface Methodology (RSM) using Rotatory Central Composite Design (RCCD). An overall 5.4-fold increase (264.20 U/g dried substrate) in enzyme production was achieved after optimization at fermentation time 144 h and moisture content 90%. The results of RSM showed that the model was in good agreement with experimental results with R2 = 99.6% (P < 0.05). A. niger AN07, A. tubingensis MP30, A. fumigatus M1 and A. sydowii indicated a high growth rate of 0.55, 0.52, 0.39 and 0.25 mm/h, respectively on the optimized solid substrate in SSF. Native PAGE and Zymogram study showed predominant presence of polygalacturonase in the purified preparation. The purified polygalacturonase enzyme significantly increased pomegranate juice clarification by 3.6-fold and prevented haze formation during storage conditions.