Evaluación técnica de la fermentación de suero lácteo para la producción de ácido láctico a nivel de laboratorio

Abstract

El presente trabajo de graduación evalúa técnicamente la fermentación de suero lácteo para la producción de ácido láctico a nivel de laboratorio. Se realizó la caracterización fisicoquímica del lactosuero, incluyendo humedad, cenizas, proteínas, grasas, densidad y azúcares. Posteriormente, se llevó a cabo la propagación del microorganismo Lactobacillus leichmannii y la fermentación del lactosuero bajo distintas condiciones de agitación y uso de buffer químico. Se generó un modelo cinético para describir el consumo de azúcares, la producción de ácido láctico y el desarrollo de biomasa, proporcionando una base técnica para futuras investigaciones en el área de la ingeniería química.

The objective of this graduation project was to conduct a technical study of whey fermentation using Lactobacillus leichmannii as the fermenting microorganism for the production of lactic acid. First, the whey was characterized in both its powdered form and as a 10% w/v solution. For the powdered whey, the moisture content (2.102% w/w) and ash content (30.789% w/w) were determined. For the solution, density (1.0210 g/mL), pH (5.90), fat content (0.00% w/v), protein content (0.13% w/v), initial lactose concentration (8.38205% w/v), and initial lactic acid concentration (0.19912% w/v) were measured. Based on these results, a theoretical stoichiometric product-to-substrate ratio of 1.076 was established, indicating that 1.076 g of lactic acid can theoretically be produced from each gram of lactose fermented.

Subsequently, fermentations were carried out at 38 °C under different operating conditions, varying the agitation speed (50, 100, and 150 rpm) and evaluating the use of a potassium hydrogen phthalate–hydrochloric acid buffer. The objective was to determine the conditions that maximized fermentation yield. The optimal conditions were found to be an agitation speed of 50 rpm with the addition of the buffer solution. Under these conditions, an experimental yield of 10.474% was obtained, indicating that, for every 100 g of lactic acid theoretically producible, only 10.474 g were obtained experimentally.

Finally, a kinetic model of the fermentation process was developed based on the experimental data obtained under the optimal fermentation conditions. The model was designed to predict the behavior of the species involved over time, including lactose consumption, the growth of the Lactobacillus leichmannii culture, and lactic acid production in the fermentation medium. The proposed equations are presented in the Results section as Equations R4, R5, and R6, respectively, and are illustrated in Figure 20.

To validate the model, the mean squared error (MSE) was calculated for each fitted curve. The lactose consumption curve yielded an MSE of 1.88275, the biomass growth curve an MSE of 0.51547, and the lactic acid production curve an MSE of 0.55300. This kinetic model provides a valuable tool for identifying both the strengths and limitations of the fermentation system under the evaluated conditions. Furthermore, it facilitates the identification of opportunities for process improvement in future research and supports the potential scale-up of the process to an industrial level.