A Novel Endo-Polygalacturonase from Penicillium rolfsii with Prebiotics Production Potential: Cloning, Characterization and Application

Exploring the Biogenic Transformation Mechanism of Polyphenols by Lactobacillus plantarum NCU137 Fermentation and Its Enhancement of Antioxidant Properties in Wolfberry Juice

This study investigated the transformation of polyphenols, including free and bound polyphenols during the fermentation of wolfberry juice by Lactobacillus plantarum NCU137. Results indicated that fermentation significantly increased the free polyphenols content and released bound polyphenols, enhancing the antioxidant activity. Analysis showed that there were 19 free polyphenols, mainly scopoletin, pyrogallol, and dihydroferulic acid, and 16 bound polyphenols, especially p-coumaric acid, feruloyl hexoside, and caffeic acid. A significant correlation was observed between the generation and degradation of polyphenols, and specific bound polyphenols peaked during the 24-48 h fermentation. Furthermore, reduced surface roughness and galacturonic acid content in wolfberry residue, along with increased pectinase activity, suggested substantial pectin degradation in the cell wall, which may be associated with the release of polyphenols, due to pectin serving as carriers for bound polyphenols. The fermentation also increased polyphenol oxidase and peroxidase activity, contributing to polyphenol breakdown. These findings provide insights for improving wolfberry juice production.

Improvement of fruit juice quality: novel endo-polygalacturonase II from Aspergillus tubingensis FAT 43 for enhanced liquefaction, clarification, and antioxidant potential

This study focuses on the isolation, purification, and characterisation of endo-polygalacturonase II from Aspergillus tubingensis FAT43, particularly emphasising its potential applications in the fruit juice industry. A comprehensive screening test revealed the temporal dynamics of endo-polygalacturonase production during a 96-hour fermentation process. The purification process, involving ammonium sulfate and ethanol precipitation followed by ion-exchange chromatography, resulted in a 3.3-fold purification of PG II with a yield of 16% and a specific activity of 6001.67 U mg-1. Molecular analysis confirmed the identity of PG II, its gene (pgaII), and a high degree of sequence identity with Aspergillus tubingensis in the SWISS-PROT database. The optimal pH for PG II activity was 3.5-4.5, with robust stability across a broad pH spectrum (3-7). The enzyme exhibited optimal temperature activity at 45 °C, with a retention of 90% activity at 50 °C. The calculated activation energy for PG II was 62.1 kJ mol-1, indicating good stability. Inactivation kinetics revealed a half-life of 13.7 h at 40 °C, 5.4 h at 50 °C, and 0.85 h at 60 °C, with an activation energy of denaturation of 32.8 kJ mol-1. Compared to literature-reported PGs, PG II from A. tubingensis FAT43 demonstrated superior thermal stability. Hydrolysis experiments on different pectins revealed the highest specificity for non-methylated substrates (polygalacturonic acid). In fruit juice processing, PG II significantly increased juice yield and clarity, with the highest impact observed in strawberry juice. Antioxidant activity assays indicated enhanced antioxidant potential in enzyme-treated juices, especially strawberry, quince, and apple juices. The study highlights PG II's potential as an industrially valuable enzyme for fruit juice processing, offering improved thermostability and versatility across various fruit types.