Screening of Potential Tannase-producing Fungi from Local Agri-industrial By-products using a Plate Assay and Submerged Fermentation

Tannase (Tannin Acyl Hydrolase EC 3.1.1.20) is an industrial inducible enzyme capable of hydrolyzing hydrolyzable tannin ester linkage gallotannin and ellagitannin, producing gallic acid and glucose. Tannase is extensively used in the pharmaceutical, chemical, cosmetics, textile, leather, food, feed, and beverage industries. In the beverage industry, tannase is used as a clarifying agent to clarify tannin present in coffee, coffee-flavored soft drinks, tea, and fruit juices by removing phenolic compounds. In the pharmaceutical industry, tannase is used to produce gallic acid, an intermediary compound in the production of antibacterial drug, trimethoprim, while in the food industry, tannase is used to synthesize crucial antioxidant food preservative propyl gallate (3,4,5-trihydroxybenzoate). Most of the tannase production utilizes bacteria such as Bacillus sp. as tannase producer under submerged fermentation, SmF. Despite the immense industrial potential of tannase, it has not fully been exploited due to lack of knowledge, and fewer studies reported filamentous fungi for tannase production. This study aimed to screen potential tannase-producing fungi from various agri-industrial by-products such as rice by-products, spent tea, spent coffee ground, banana peels, mango peels, desiccated coconut residue, soybean residue, sweet potato peels, and onions. Fungal isolate, J1 (Aspergillus niger) was identified as the efficient tannase-producing fungus due to the hydrolytic zone's largest diameter (60.7 ± 0.6) mm. It achieved high tannase activity with (6.86 ± 0.04) U/ml in submerged fermentation, SmF. In conclusion, filamentous fungi isolated from agri-industrial by-products have huge potential as an efficient tannase producer.