Optimisation of lactic acid production using cost effective agro residue for food applications†

Abstract

Lactic acid (LA) (CH₃CHOHCOOH) is utilised in a variety of industrial processes, including production of polymers, emulsifiers, pharmaceutical, and cosmetic formulations. Biological synthesis of useful products by fermentation of renewable resources has advantages over chemical methods. Focus on optimised usage of cost effective regional substrates is necessary to achieve environmentally sustainable practices and efficient biomass fermentation for production of organic acid such as lactic acid. The present study was carried out to optimize lactic acid production using Limosilactobacillus fermentum DFRM8 with cost effective regional carbon substrate (sugarcane bagasse). Experimental design used for the optimization of lactic acid production was 3⁴ full factorial design using four factors such as sugarcane bagasse (%), inoculation level (%), incubation temperature (°C) and pH. The conditions optimized with sugarcane bagasse hydrolysate at 5.0% (v/v), inoculum level at 5.0% (v/v), and incubation temperature at 30 °C with an initial pH of 6.0 produced the maximum lactic acid (22.2 g L⁻¹ on dry weight basis) after 48 h. Simple sugars when used as carbon source in fermentation medium produced (g L⁻¹) LA in the range of 4.5 to 13.5 while agro residues such as mango peel, grape peel and banana peel produced (g L⁻¹) LA at 18.0, 4.5 and 2.7 on dry weight basis. Lactic acid synthesised by the isolate L. fermentum DFRM8 is suitable for food and biomedical applications as the bacterium has GRAS status.