Self-directing optimization for enhanced caffeine degradation in synthetic coffee wastewater using induced cells of Pseudomonas sp.: Bioreactor studies

Abstract

Coffee wastewater poses a serious threat to the environment due to the presence of a large number of toxic compounds which necessitates the importance of developing suitable treatment methodologies. Although there are treatments available to treat the different wastewaters, the presence of caffeine in wastewater interrupts the complete treatment of coffee wastewater. Alternatively, Pseudomonas sp. showed an excellent capacity to withstand coffee wastewater and degrades caffeine completely in shake flask studies. In this study, we scaled up the coffee wastewater treatment to a 1 L in bioreactor and optimized for caffeine degradation using the self-directing optimization technique. Using self-directing optimization maximum degradation rate of 16.73 mg/L.h was obtained at 210 rpm, 1.16 vvm, and 0.383 g/L of initial biomass. A regression model was developed to predict the caffeine degradation rate with oxygen mass transfer coefficient (kLa) and initial biomass concentration. The regression model was solved and the optimal conditions of initial biomass concentration and kLa are 0.23 g/L and 64.26 h−1 respectively. Under those conditions, experiments were performed and maximum degradation rate was 16.9 mg/L.h was obtained, which is in comparison with model prediction (15.2 mg/L.h).