Talaromyces verruculosus tannase production, characterization and application in fruit juices detannification

A potential tannase producing fungus S3-07 was isolated from the tannin-rich soil sample and screened as better tannase producer with 38 +/- 3 mm diameter of hydrolysis zone formation. It was identified as T. verruculosus (accession number KX863699) on the basis of the internal transcribed spacer ribosomal DNA (ITS-rDNA) sequence analysis. Tannase was produced with 8.22 +/- 0.35 Unit per gram dry substrate (U/gds) activity in the unoptimized condition through solid state fermentation (SSF) using Babul (Acacia nilotica) bark as a solid substrate. Central composite design (CCD) was used to maximize the production and achieved 3.91 fold increments (32.18 +/- 1.31 U/gds). Ammonium sulfate precipitation with 70% saturation and DEAE fractionation obtained 13.289 specific activity, 47.489% yield and 6.896 purification fold. SDS-PAGE and zymographic analysis showed two bands of tannase with similar to 75 kDa and 58 kDa pH optima of tannase was measured at 8.00, whereas pH stability was recorded between 4.0 and 8.0. Tannase had temperature optima at 60 degrees C, however, stability was observed between 30 and 60 degrees C. In presence of ethanol, SDS, Mn2+ ions and gallic acid increased tannase activity, whereas ethyl acetate, tween 20, Ba2+ ion and urea inhibited maximum activity. Most of tannin reduction (93.27%) was measured in case of orange juice after 15 min incubation and 89.36% reduction in pomegranate juice after 30 min, whereas aonla juice was measured with 75.49% tannin reduction after 45 min incubation.