Production and Characterization of Natural Tannin-Degrading Aspergillus strains

Abstract

Among the different types of agrowastes, tannin biomass also contributes to significant amount. The tannin rich biomass can be exploited as the most economic substrate for the production of industrially important enzyme Tannase. Tannases are hydrolases which find applications in different industries such as leather, food, feed, beverage and pharmaceutical industry. Tannases are gaining importance as industrially-important biocatalyst. The present study focuses on the isolation of natural tannin degrading fungal strains including their characterization. Among the fifty fungal cultures isolated from soil samples, eleven tannase producing isolates were selected by qualitative screening. The selected isolates were cultivated by liquid surface fermentation for quantitative estimation of extracellular tannase activity. On the basis of quantitative screening, two isolates Aspergillus niger and Aspergillus flavus were identified as efficient tannase producers. To study natural tannin degradation efficiency of the isolates, different tannin rich agro-residues were tested as carbon source in the production medium for tannase production as well as substrate for the enzyme. Both isolates utilized natural tannins appreciably, producing significant tannase yield. Gauva leaves and ber leaves proved to be the best carbon source for Aspergillus niger and Aspergillus flavus respectively. The optimum incubation period for maximum tannin utilization was found to be 72 hrs for Aspergillus niger and 96 hrs for Aspergillus flavus. In conclusion, both fungal isolates exhibited potential for tannin biomass utilization and conversion to various valuable industrial products.