Process optimization and kinetic modeling of ultrasound assisted lactic acid production

The impact of ultrasound-assisted fermentation using Lactobacillus species was investigated, for enhanced lactic acid production. The different ultrasound frequencies of 20, 30, and 40 Hz, with time intervals of 3, 4, and 5 min, and with corn steep liquor concentrations of 1%–3% were examined using response surface methodology-Box–Behnken design. The growth of lactic acid production was modeled by Contois model (linear) and Baranyi–Roberts model (nonlinear), assessing the suitability of Lactobacillus paracasei, Lactobacillus plantarum, and Lactobacillus acidophilus for industrial processes. At 34 h, the maximal lactic acid generation of L. paracasei, L. plantarum, and L. acidophilus was 85.2%, 82.1%, and 79.4%, respectively. The R², μ_max, and K_s values for L. paracasei and L. plantarum were found to be 0.9158, 0.574 h⁻¹, 54.27 g/L and 0.9426, 0.294 h⁻¹, 22.66 g/L, respectively, using Contois model. The observed R² values of Baranyi–Roberts model for the strains L. acidophilus, L. paracasei, and L. plantarum were 0.9947, 0.9954, and 0.9998, respectively.

Practical Applications

Lactic acid is crucial in the fermentation process for products like yogurt, sauerkraut, kimchi, and pickles, enhancing flavor, texture, and shelf life. As a precursor to biodegradable plastics, lactic acid contributes to the development of sustainable packaging materials and environmentally friendly alternatives to traditional plastics. Utilizing waste corn steep liquor (CSL) as a growth medium presents a sustainable and cost-effective solution for lactic acid production, capitalizing on its rich nutrient profile to enhance microbial growth. As a byproduct of corn wet milling, using CSL for fermentation processes promotes waste valorization and contributes to a circular economy. The optimization of fermentation conditions using the Box–Behnken design ensures maximum yield and efficiency by systematically evaluating the effects of key process variables. Integrating advanced growth curve models like the Contois and Baranyi models further refines the understanding and prediction of microbial dynamics, enabling precise control over the fermentation process. This comprehensive approach not only promotes the efficient use of industrial by-products but also advances the development of environmentally friendly and economically viable bioprocesses.