Abstract

This study investigated lactic acid production using starch-based substrates by lactic acid bacteria. Starchy substrates; yam, cassava, corn, potatoes and rice were used for lactic acid fermentation. Isolation of microorganisms was done using de Man, Rogosa, and Sharpe (MRS) medium. Ten pure colonies were identified and classified presumptively using standard morphological and biochemical identification processes. Optimization of culture conditions was done by varying temperature (25^oC, 30^oC, 35^oC and 40^oC), pH (6.0, 6.5, 7.0, 7.5, 8.0, 8.5 and 9.0), and fermentation Time (24, 48, 96 and 122hrs). Optimal culture conditions were obtained at 35^oC, pH 6.0 and 122hrs. At optimal conditions, Lactiplantibacillus pentosus strain BSR3 (SL2) produced the highest concentration of lactic acid (0.43 ± 0.10 g/L) in yam broth. Lactiplantibacillus plantarum strain Z2 (SL1) produced the highest concentration of lactic acid (0.55 ± 0.12 g/L) in cassava broth. In corn broth, the highest quantity of lactic acid (0.55 ± 0.14 g/L) was produced by Lactiplantibacillus plantarum strain Z2 (SL1).  Lactiplantibacillus plantarum strain Z2 (SL1) produced the highest concentration of lactic acid (0.56 ± 0.35g/L) in potato broth. In rice broth, the highest concentration of lactic acid (0.46 ± 0.40 g/L) was produced by Lactiplantibacillus pentosus strain BSR3 (C3P). Overall highest concentration of lactic acid (0.56 ± 0.35g/L) was produced by Lactiplantibacillus plantarum strain Z2 (SL1) in potato broth. This study shows that fermentation of potatoes, a low-cost substrate by Lactiplantibacillus plantarum strain Z2 (SL1) has a high-rate lactic acid production. This bacterium and substrate can be used in large-scale production of lactic acid for many industrial uses.