Pestalotiopsis mangiferae isolated from cocoa leaves and concomitant tannase and gallic acid production

Abstract

The enzyme tannase is of great industrial and biotechnological importance for the hydrolysis of vegetable tannins, reducing their undesirable effects and generating products for a wide range of processes. Thus, the search for new microorganisms that permit more stable tannase production is of considerable importance. A strain of P. mangiferae isolated from cocoa leaves was selected and investigated for its capacity to produce tannase enzymes and gallic acid through submerged fermentation. The assessment of the variables affecting tannase production by P. mangiferae showed that tannic acid, ammonium nitrate and temperature were the most significant (8.4 U/mL). The variables were analyzed using Response Surface Methodology - RSM (Box-Behnken design), with the best conditions for tannase production being: 1.9% carbon source, 1% nitrogen source and temperature of 23 °C. Tannase activity doubled (16.9 U/mL) after the optimization process when compared to the initial fermentation. A pH of 7.0 was optimal for the tannase and it presented stability above 80% with pH between 4.0 and 7.0 after 2h of incubation. The optimal temperature was 30 °C and activity remained at above 80% at 40–60 °C after 1 h. Production of gallic acid was achieved with 1% tannic acid (0.9 mg/mL) and P. mangiferae had not used up the gallic acid produced by tannic acid hydrolysis after 144 h of fermentation. A 5% tannic acid concentration was the best for gallic acid production (1.6 mg/mL). These results demonstrate P. mangiferae’s potential for tannase and gallic acid production for biotechnological applications.