Optimization of fermentation conditions for lactic acid production by Lactiplantibacillus plantarum OM510300 using plantain peduncles as substrate

Lactic acid (LA) is the most common hydroxycarboxylic acid with optically active chiral carbon atoms, with numerous applications across pharmaceutical, food, textile, chemical, and medical sectors. LA has been used as an antioxidant, decontaminant, acidulant, and cryoprotectant among other functions. This study was aimed at optimizing fermentation conditions for LA production by Lactiplantibacillus plantarum (accession number OM510300) using plantain peduncles. The plantain peduncles were subjected to pre-treatment using alkaline and enzymatic hydrolysis. The physical and chemical properties of the pre-treated plantain peduncles were observed using X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Through the design expert, a central composite design was set up and used in designing the experimental runs for fermentation conditions. The results from the runs were analyzed using ANOVA. SEM, XRD, and FTIR analysis revealed changes in the structural arrangement of the untreated and pre-treated plantain peduncles. Results from the ANOVA revealed different levels of interaction by each fermentation condition independently and collaboratively. The reliability of the reduced quadratic model used in the central composite design was observed to be significant with an F-value of 13.25 and a p-value of < 0.0001. This implies that the model can accurately predict the concentration of LA under the investigated experimental settings. Upon conducting a submerged LA production, 483 ml of LA was obtained at the end of the extraction using the phase partitioning technique. Fermentation conditions such as pH and temperature have a significant effect on LA production with optimal conditions observed for the pH to be 9.8 to 10 and for incubation periods of 6 to 7 h with a temperature range of 40 °C to 42 °C.