Vol. 7, Issue 11, Part A (2025)

Lactic acid is an industrially significant organic acid with broad applications in food preservation, pharmaceuticals, and biodegradable plastics. The high cost of conventional carbon substrates, however, limits the economic feasibility of its microbial production. In the present study, various agro-industrial wastes molasses, corn starch hydrolysate, fruit peel hydrolysate, and whey were evaluated as low-cost substrates for lactic acid production using Lactobacillus plantarum. Fermentation was carried out at 37 °C, pH 6.0, and 5% inoculum for 72 h under anaerobic conditions. Among the substrates tested, molasses supported the highest lactic acid yield of 45.2 g L⁻¹, with a productivity of 0.63 g L⁻¹ h⁻¹ and a conversion efficiency of 77.2%. Optimization of substrate concentration revealed 6% (w/v) molasses as the most effective level for maximum yield. These findings demonstrate that agro-industrial residues can be effectively valorised as renewable feedstocks for sustainable lactic acid production, contributing to cost reduction and waste management in a circular bioeconomy framework.