Influence of cell-wall degrading enzyme treatment and Saccharomyces cerevisiae fermentation on the antioxidant and antibacterial activities of green tea leaf

Abstract

This study was conducted to suggest an extraction method for preparing the extract from green tea leaves that possess enhanced antioxidant and antibacterial activities. Different ethanol concentrations were tested to recover phenolics and flavonoids, and 50% ethanol was the best under heat treatment (121°C, 15 min). The ethanol extract exhibited excellent DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and growth inhibition against B. cereus, B. licheniformis, S. aureus subsp. aureus, and A. hydrophila subsp. hydrophila. To enhance the antioxidant and antibacterial activities, cell-wall degrading enzymes (2.5% cellulose + 2.5% pectinase, v/w dry sample) treatment and Saccharomyces cerevisiae fermentation were applied singly or in combination. The enzymatic treatment of green tea leaves notably increased extraction yield. However, the antioxidant and antibacterial activities of the extract were lower than those of the control (heat-treated 50% ethanol extract). In contrast, the yeast fermentation alone did not affect the yield, but enhanced antioxidant and antibacterial activities, contributing to the increase in the extract’s total phenolic and flavonoid contents.