Enhanced degradation of caffeine and caffeine demethylase production by Pseudomonas sp. in bioreactors under fed-batch mode

The growth of Pseudomonas sp. was studied in fed-batch process with an aim to improve the caffeine degradation rate and caffeine demethylase activity. The effects of varying initial caffeine concentrations in the batch mode, increase in the number of feeds, varying feed flow rates, and added nutrients to the feed on the fed-batch process were investigated. A maximum caffeine degradation rate of 0.82 g/L h and maximum caffeine demethylase activity of 2.6 U/mg were achieved using manual intermittent pulse feeds of caffeine with substrate concentration as feedback parameter for the fed batch started with an initial caffeine concentration of 3 g/L. A slight increase in the caffeine degradation rate (0.85 g/L h) and caffeine demethylase activity (3.4 U/mg) was observed when the additional nutrients were added along with caffeine in the feed. This is the first report showing complete degradation of large magnitudes of caffeine amounting to 237 g in 75 h. These results show that the fed-batch conditions achieved in this study using Pseudomonas sp. facilitate the development of a sustainable bioprocess to degrade the high concentrations of caffeine in industrial effluents.