Resumo

Tannase (EC 3.1.1.20) is an extracellular inducible enzyme that hydrolyses ester and depside bonds of hydrolysable tannins, releasing gallic acid and glucose. It is an important key in the fruit juices industry and coffee-flavoured soft drinks as a clarifying agent, and in the production of gallic acid, a potent nutraceutical compound. Tannase is produced by various microorganisms, however, filamentous fungi are described as the best producers. The present study deals with the rapid screening of exophytic fungi from cocoa tannase producers by a simple plate assay and determination of its correlation with quantitative tannase production using submerged fermentation. Were tested 46 isolates, using simple agar plate method containing malt extract (15g/L), tannic acid (5 g/L) and agar (20g/L) at 28 ° C until 96 hours. Those plates that showed a dark brown color halo rounding the colony were considered positive, indicating the isolates utilization of tannic acid by producing tannase enzyme. The isolates that presented degradation halos with a diameter greater than 3 cm, after 72 hours, were using for submerged fermentation in Czapeck minimal medium and tannic acid 1% as sole carbon source, at 280C, 120 rpm until 120h. Tannase activity was assayed by the spectrophotometric method of methanolic rhodanine, and one tannase unit was defined as the enzyme amount able to release 1 μmol of gallic acid per ml per min. Out of the 46 isolates, eleven produced the better colony diameter and were selected for a submerged fermentation. Among the isolates the best tannase producer were unidentified fungi FC22 (23.28 U/mL), FC77 (22.56 U/mL) and FC16 (20.20 U/mL) in 120 hours of culture. These fungi presented tannase activity higher than others described in the literature. Thus, it is necessary the identification of the fungi since it showed great quantities of tannase, therefore, they have great potential for industrial application since the conditions used in this work have not yet been optimized.