Optimization of Polyphenol Oxidase and Peroxidase Production Using Native Bacillus spp. Isolated from Fully Fermented Tea

Tea (Camellia sinensis) is a species of evergreen shrub or small tree in the flowering plant family of Thecae. One of the major steps in black tea manufacturing is the fermentation process, which bacteria may incorporate. This study aimed at using the one-factor-at-a-time (OFAT) and Taguchi methods to optimize the production of polyphenol oxidase (PPO) and peroxidase (POD) by Bacillus spp. isolated from fully fermented tea. The results showed that sucrose and glucose exhibited the greatest effects on the production of polyphenol oxidase and peroxidase by the strains Bacillus sp. (TB3) and B. licheniformis (TB14), respectively. In addition, the results indicated that the best nitrogen sources for the production of PPO by Bacillus sp. (TB3) and POD by B. licheniformis (TB14) were sodium nitrate and ammonium carbonate, respectively. Based on the obtained results, the medium components for the production of PPO by Bacillus sp. (TB3) at a pH of 7 were as follows: 0.5% sucrose, 1.0% of peptone, 0.8% of yeast extract, 0.2% of hydrolyzed casein, 0.02% of potassium dihydrogen phosphate, 0.005% of magnesium sulfate heptahydrate, and 0.1% sodium nitrate. Moreover, the optimal culture medium for the production of POD by B. licheniformis (TB14) at a pH of 7 was as follows: 0.3% of glucose, 1.0% of peptone, 0.8% of yeast extract, 0.2% of hydrolyzed casein, 0.02% of potassium dihydrogen phosphate, and 0.005% of magnesium sulfate heptahydrate. Increased production of PPO and POD enzymes were obtained about 8 and 6 fold more than the basal culture media, respectively.