Pectinolytic activity of aspergillus niger and Aspergillus flavus grown on grapefruit (citrus Parasidis) peel in solid state fermentation

Abstract

The present study was aimed at studying pectinolytic activity of resident fungi isolated from decomposing grapefruit (Citrus parasidis) peels in solid state fermentation. Grape fruit peel was subjected to natural fermentation and the fermenting fungi were isolated, characterized and identified using standard microbiological methods. The isolated fungi were in turn used for fermentation to determine their pectinolytic activity through solid state fermentation technique. Culture parameters such as incubation period, temperature, moisture content and addition of salts supplements were optimized during the research for five days. The identified fungi were Aspergillus Niger and Aspergillus flavus. The peak of pectinolytic activity was at day three of fermentation when the highest pectinase activity of 13.32 μmol/mg/min was recorded for A. Niger and 11.32 μmol/mg/min for A. flavus. Optimum temperature and pH for pectinase activity by A. Niger and A. flavus was at 40 0C and pH 7.5 and 7.7 respectively. The use of salt supplemented substrate did not alter enzyme activity. In conclusion, the isolated fungi could be promising organisms for pectinolytic enzyme production on grape peel as substrate. Keywords: Grapefruit, Pectinolytic Activity, Fungi, Fermentation, Aspergillus