Optimization of Lactic Acid Fermentation from Overriped Plantain Using Response Surface Methodology (RSM)

Abstract

Lactic acid is a building block chemical used by many manufacturing industries. The search for cheap biochemical feedstock and process is of great concern to lactic acid producing industries. Plantain is a rich source of carbohydrate but the overriped plantains are thrown away as waste because of their non-firmness. This study evaluates the utilization of overripe plantain as biochemical feedstock for optimum production of lactic acid. Optimization of lactic acid production with overriped plantain was studied using Response Surface Methodology. The initial pH and reducing sugar content of the plantain hydrolysate were 4.89 and 166.05 g/l respectively. The response of lactic acid concentration to four factors: substrate concentration (138.25 – 166.05 g/L), initial pH (4 – 8), fermentation temperature (30 – 50°C) and time (24 – 168 h) was studied. The lactic acid concentration ranged from 123.50 – 163.00 g/l. A statistically significant [(<I>P</I>_model><I>F</I>) < 0.0001] second order quadratic polynomial regression model was obtained for lactic acid production; the <I>R</I>² and adjusted-<I>R</I>² were 0.9935 and 0.9896 respectively. Numerical optimization was used to obtain optimum lactic acid production (157.53 g/ L) at glucose concentration, pH, temperature and time of 159.10 g/l, 7.0, 42.3°C and 60 h respectively. Overriped plantain was a good biochemical feedstock for lactic acid production.