Optimization of fermentation condition for production of lactic acid from khat (“Catha edulis”) waste by using immobilized Lactobacillus plantarum

Production of lactic acid from lignocellulosic biomass is becoming more popular as a way to solve the problem associated with first-generation biomass. In the present study, the optimum fermentation parameters for maximum lactic acid production from khat waste biomass by using immobilized Lactobacillus plantarumwere investigated. The effect of immobilizing the cell on the yield of lactic acid has been investigated, and the yield obtained from immobilized Lactobacillus plantarumcell is 32.78% higher than the free cells. The effects of three process parameters (incubation temperature, pH, and incubation time) on lactic acid yield were investigated. The optimization of lactic acid yield and fermentation parameters was done via response surface methodology with a central composite design. Based on the analysis, the optimum fermentation parameters were found to be incubation temperature of 42.3 °C, incubation time of 40.0 h, and pH of 6.18. Under these conditions, the maximum lactic acid yield obtained was 23.05 g/L. The experimental yield of lactic acid (22.98 ± 0.10 g/L) is in smooth agreement with the predicted one (23.05 g/L), indicating the fitness of the quadratic model used. Generally, the findings of the study suggest that utilization of khat waste as a potential carbohydrate source and immobilization of Lactobacillus plantarumcells for lactic acid production is worthful.