Abstract
Lactic acid, a widely used organic acid was produced from groundnut shells using Bacillus coagulans and the process was optimized with response surface methodology (RSM) by examining the relationships between time/temperature on the concentration of the Lactic acid produced. The experiment involved preparing the microorganism in a YEX medium (containing xylose and yeast extract) and combining it with treated groundnut shells, fermentation medium, and yeast extract and leaving it to ferment at a pH of 6.0 and temperature range of 350C of 500C for a 24hr period; producing lactic acid. The concentration of the product was measured using titrimetric and spectrophotometric methods at different conditions of temperature and time and the highest concentrations achieved were 5.92 g/l (titrimetric) and 13.02 g/l (spectrophotometric) at 42.5°C and 55 hours and the lowest concentrations were 2.16 g/l (titration) at 54°C and 8.86 g/l (spectrophotometric) at 31°C, consistent with the survivable temperature range of the microorganism (35°C to 50°C). The integration of the two techniques was to offer a dual-confirmation approach to ensure the reliability and accuracy of the concentration measurements. The optimum conditions for the titration method were 21.68 hours and 38.32°C, yielding a concentration of 4.434 g/l and for the spectrophotometric method, the optimal conditions were determined as 21.347 hours and 38.35°C, with a concentration of 11.332 g/l. Quadratic models were developed for both methods, yielding significant and well-fitting responses with the sequential p-value below 5% (p < 0.05) showing that the model is a fit. These findings indicate that groundnut shells can be effectively utilized for lactic acid production, within an optimal temperature range, showing that this process holds promise as a viable method for lactic acid production.

Key words: Lactic acid, Bacillus coagulans, groundnut shells, foodwaste, biomaterials.