Investigation of extracted cellulase effects from Symbiotic tea fungus on Iranian northern tea quality

Aspergillus niger is one of the important symbiotic fungus of tea leaves. The fungal extracellular cellulase could be used as a cellulolytic agent during tea processing. Tea is the most consuming beverage in the world and different qualities are due to complex metabolic pathways occurring during fermentation process so investigation of tea fungal enzyme effects as an important part of fermentation is valuable. The final goal of this research is investigation of cellulolytic effects of fungal enzymes on tea leaves in order to improvement of tea quality factors. The cellulase enzymes isolated from Aspergillus niger was used for fermentation of tea leaves. The somogyi–nelson assay was used to determine enzyme activity. Other parameters such as Km and Vmax, optimum amounts of pH and temperature and finally thermo stability of enzyme was determined and compared with two other enzyme samples. Effects of both crude enzyme preparation and purified cellulase enzymes on the improvement of tea leaf fermentation were determined in terms of theaflavin, thearubigin, total liquor color and dry matter content of the tea produced. Enzyme specific activity and total protein as well as evaluated quality factors of tea was observed to increased by using more purified preparation of enzyme. The crude enzyme preparations obtained from ethanol precipitation were found to be more effective in improving tea leaf fermentation than crude extract of enzyme preparation.