Extraction, Purification, and Characterization of Tannase Produced by Aspergillus terreus PQ344456 and Its Textile Dye Degradation and Juice Clarification Features

Aspergillus terreus is a filamentous fungus of high biotechnological value, noted for its strong biosynthetic and fermentative capacities. In this study, tannase was produced via submerged fermentation using a soil-derived Aspergillus terreus strain (GenBank: PQ344456) identified through morphological and molecular screening. Tannase activity was markedly higher in submerged fermentation at 136.8 U/mL compared with liquid surface fermentation at 62.7 U/mL, confirming its superior performance. Kinetic analysis during the exponential phase revealed that tannase formation proceeded slightly faster than biomass accumulation, indicating partially growth-associated enzyme production. Optimal production was achieved at pH 5, 30 °C, and 1.5% tannic acid. Partial purification using organic solvents enhanced specific activity, and native PAGE analysis revealed a prominent high-molecular-weight band exceeding 250 kDa, suggesting the presence of a multimeric enzyme complex. FTIR analysis confirmed characteristic protein functional groups, including O–H and N–H stretching vibrations as well as an amide I band corresponding to peptide backbone integrity. Kinetic characterization using tannic acid followed Michaelis–Menten behavior and yielded a Km of 8.4 mg mL–1 and a Vmax of 4256 U mL–1. The partially purified enzyme demonstrated concentration-dependent dye decolorization in agar diffusion assays. Furthermore, application in fruit juices resulted in enhanced tannin hydrolysis, particularly in pomegranate, pineapple, and guava juices, and was accompanied by reduced turbidity and viscosity, improved clarity, and decreased microbial load.