Fermentation of Soybean Meal Hydrolyzates with Saccharomyces cerevisiae and Zymomonas mobilis for Ethanol Production.

Most of the ethanol currently produced by fermentation is derived from sugar cane, corn, or beets. However, it makes good ecological and economic sense to use the carbohydrates contained in by-products and coproducts of the food processing industry for ethanol production. Soybean meal, a co-product of the production of soybean oil, has a relatively high carbohydrate content that could be a reasonable substrate for ethanol production after fermentable sugars are released via hydrolysis. In this research, the capability of Saccharomyces cerevisiae NRRL Y-2233 and Zymomonas mobilis subsp. mobilis NRRL B-4286 to produce ethanol was evaluated using soybean meal hydrolyzates as substrates for the fermentation. These substrates were produced from the dilute-acid hydrolysis of soybean meal at 135 °C for 45 min with 0, 0.5%, 1.25%, and 2% H2 SO4 and at 120 °C for 30 min with 1.25% H2 SO4 . Kinetic parameters of the fermentation were estimated using the logistic model. Ethanol production using S. cerevisiae was highest with the substrates obtained at 135 °C, 45 min, and 0.5% H2 SO4 and fermented for 8 h, 8 g/L (4 g ethanol/100 g fresh SBM), while Z. mobilis reached its maximum ethanol production, 9.2 g/L (4.6 g ethanol/100 g fresh SBM) in the first 20 h of fermentation with the same hydrolyzate.

Evaluación de la fermentación del lactosuero ácido (entero y desproteinizado) utilizando Lactobacillus casei / Evaluation of acid whey fermentation (whole and deproteinized) using Lactobacillus casei

El lactosuero acidificado espontáneamente pone en riesgo la salud del consumidor al utilizarlo como acidificante de la leche usada en la elaboración del queso tipo mozzarella, y además reduce la calidad del producto. El objetivo de esta investigación fue evaluar el proceso de fermentación del lactosuero ácido (entero y desproteinizado) con Lactobacillus casei, utilizando diferentes porcentajes de su inóculo. Se caracterizaron fisicoquímicamente los lactosueros, sometiéndolos a fermentación anaeróbica a 37°C y 120 rpm por 96 h. Se evaluó la concentración de biomasa celular, el consumo de lactosa, la producción de ácido láctico (AL) y se estimaron los parámetros cinéticos y estequiométricos. Se aplicó un diseño experimental completamente al azar con arreglo factorial 2x3, empleando la metodología de medidas repetidas. Los datos, se procesaron a través de los paquetes estadísticos SAS® versión 9 y Statgraphics Centurión XVI®. El lactosuero, entero y desproteinizado, se encontró dentro de los intervalos fisicoquímicos aceptables para su acidificación. Los valores de acidez fueron superiores a 120 Grados Dornic (120°D) con la inoculación de L. casei, excepto en lactosuero desproteinizado, inoculado con 15% de cultivo. El lactosuero entero con 15% de inóculo, alcanzo 120°D en el menor tiempo (34h). Altas concentraciones de inóculo (15%) favorecieron la acidificación en el lactosuero entero, mostrando la mayor producción (20.83gAL/l), Y´p/s=0.86, Qp=0.173gAL/l*h; mientras el lactosuero desproteinizado mostró un mayor crecimiento microbiano, menor conversión de lactosa (8.2%) y menor producción media de ácido láctico (8.19g/l).

The spontaneously acidified whey threatens consumer health and reduces quality of mozzarella cheese. The goal of this research was to evaluate the acidification process of acid whey (whole and deproteinized) by fermentation with different inoculum concentrations of Lactobacillus casei. The whey was physicochemically characterized and anaerobically fermented at 37°C and120 rpm during 96h. Cellular biomass was evaluated, as well as lactose consumption, lactic acid production, kinetic and stoichiometric parameters were estimated. A completely randomized design with factorial arrangement (2x3) was applied by using the repeated measures methodology. Data was processed by using SAS® statistical package, version 9 and Statgraphics Centurion XVI®. The acidification for the whole and deproteinized whey was found within the acceptable intervals. Acidification values were above 120 degrees Dornic (120°D) with L. casei inoculation, except in the deproteinized whey inoculated with 15% of inoculum. The whole whey with 15% of inoculum reached 120°D in the shortest time (34 hours). High concentrations of inoculum (15%) aided the acidification in whole whey and showed the highest production (20.83 g LA/l), and p/s=0.86, Qp=0.173 g AL/l*h; on the other hand, the deproteinized whey showed the highest microbial growth, lowest conversion of lactose (8.2%) and lowest lactic acid production (8.19g/l).

Tolerance of S. cerevisiae and Z. mobilis to inhibitors produced during dilute acid hydrolysis of soybean meal.

The objective of this research was to determine the minimum inhibitory concentration of 5-hydroxymethyl furfural, furfural, and acetic acid on Saccharomyces cerevisiae (NRRL Y-2233) and Zymomonas mobilis subspecies mobilis (NRRL B-4286) in both detoxified hydrolyzed soybean meal and synthetic YM broth spiked with the three compounds. Soybean meal was hydrolyzed with dilute sulfuric acid (0.0, 0.5, 1.25, and 2.0% wt v(-1)) at three temperatures (105, 120, and 135°C) and three durations (15, 30, and 45 min) followed by detoxification with activated carbon. Of all the combinations, only the treatments obtained at 135°C, 2.0% H2SO4, and 45 min and the one at 135°C, 1.25% H2SO4, and 45 min showed inhibition in the growth of the tested microorganisms. Spiked YM broths showed inhibition for the highest levels of inhibitors, either applied individually or in combination.