Continuous production of l (+)-lactic acid by Lactobacillus casei in two-stage systems

Abstract

A two-stage two-stream chemostat system and a two-stage two-stream immobilized upflow packed-bed reactor system were used for the study of lactic acid production by Lactobacillus casei subsp casei. A mixing ratio of D12/D2 = 0.5 (D = dilution rate) resulted in optimum production, making it possible to generate continuously a broth with high lactic acid concentration (48 g l-1) and with a lowered overall content of initial yeast extract (5 g l-1), half the concentration supplied in the one-step process. In the two-stage chemostat system, with the first stage at pH 5.5 and 37 degrees C and a second stage at pH 6.0, a temperature change from 40 degrees C to 45 degrees C in the second stage resulted in a 100% substrate consumption at an overall dilution rate of 0.05 h-1. To increase the cell mass in the system, an adhesive strain of L. casei was used to inoculate two packed-bed reactors, which operated with two mixed feedstock streams at the optimal conditions found above. Lactic acid fermentation started after a lag period of cell growth over foam glass particles. No significant amount of free cells, compared with those adhering to the glass foam, was observed during continuous lactic acid production. The extreme values, 57.5 g l-1 for lactic acid concentration and 9.72 g l-1 h-1 for the volumetric productivity, in upflow packed-bed reactors were higher than those obtained for free cells (48 g l-1 and 2.42 g l-1 h-1) respectively and the highest overall L(+)-lactic acid purity (96.8%) was obtained in the two-chemostat system as compared with the immobilized-cell reactors (93%).

High-rate continuous production of lactic acid byLactobacillus rhamnosus in a two-stage membrane cell-recycle bioreactor

“…The advantages of the CSTRs-in-series against a single CSTR especially in lactic acid production were revealed by others in two-and three-stage CSTRs (Aeschlimann et al, 1990;Bruno-Bárcena et al, 1999;Mulligan et al, 1991): increased productivity and concentration of lactic acid via partly separating cell growth and lactic acid production phases; increased lactic acid yield at the expense of biomass formation at a latter stage; high purity of the lactic acid isomer, L(+)-lactic acid via increased population of fresh cells; and reduced usage of a costly nutrient, yeast extract.…”

Open Fermentative Production of L-Lactic Acid from Distillers’ Grains by Lactobacillus casei CICC 6056

“…This might be due to the sharp decrease in pH during the first 24 h. As shown in Fig. 1c, the pH sharply decreased from 6.5 to 4.5 in the sterilized fermentation, and to 4.9 in the open fermentation at 24 h, and pH in both methods decreased gradually to approximately 4.1 at 144 h. Although L. casei was reported to be acid-tolerant and is relatively insensitive to product inhibition by lactic acid (Bruno-Barcena et al 1999), the optimal pH for L. casei to produce a significantly higher level of acid was above 5.0 (Yoo et al 1996;Roberto et al 2007). In this experiment, the pH of the broth was below 5.0 after 24 h of fermentation, which may adversely affect the growth of L. casei.…”

Producción de acido láctico por Lactobacillus plantarum L10 en cultivos batch y continuo

“…Teóricamente esta vía origina a partir de un mol de glucosa, dos moles de lactato. Sin embargo, el rendimiento real a condiciones de laboratorio e incluso de operación es de aproximadamente el 90% del rendimiento teórico (Bruno-Bárcena et al, 1999;Akeberg et al, 1998). Algunas especies del género Lactobacillus son heterofermentativos facultativos; en condiciones de anaerobiosis y microaerobiosis se comportan como homofermentativos, y en condiciones aeróbicas forman además de ácido láctico, ácido acético, acetoina y peroxido de hidrógeno (Li et al, 2006;Porro et al, 1999).…”