Biosynthesis of Lactic Acid by Mutagenetic Lactic Acid Bacteria Strains Isolated From Processed Milk

Abstract Lactic acid, a valuable weak natural organic acid extensively utilized in various industries has been conventionally synthesized through chemical processes. However, the growing demand for sustainable and eco-friendly production methods has stimulated interest in microbial synthesis. The study was to explore the potential of multi-strain lactic acid bacteria isolated from processed liquid milk to synthesize lactic acid. Microorganisms were isolated and screened on deMan Rogosa Sharpe (MRS) agar and were identified according to morphological and biochemical characteristics. Mutagenesis of positive isolate using chemical and physical means, quantitative and qualitative production using High-Performance Liquid Chromatography (HPLC) were investigated. The isolate was discovered to have a clear zone on MRS agar, which allowed for its identification as Lactobacillus sp. It was then chosen for mutagenesis using ethidium bromide (EB) and UV light. Thirteen mutants were identified, and three of those were examined to see if they could generate lactic acid using various substrates. HPLC confirmed mutants and parent strain to produce significant homo-fermentative lactic acid in cheese whey substrate. The parent strain gave a significant yield of 2004.87ugml-1 as compared to UV and EB mutant strains with 1457.67ugml-1 and 239.10ugml-1 respectively. Optimum lactic acid yields were produced at 37°C, pH 4.5, and 150 rpm 16 h fermentation period. This study showed that mutagenesis did not influence optimum lactic acid production. The yield improvement that occurred via mutations might have diverted the metabolism from lactic acid production towards mixed acid fermentation, hence produce reduced levels of lactic acid.