Continuous d-lactic acid production by a novelthermotolerant Lactobacillus delbrueckii subsp. lactis QU 41

Abstract

We isolated and characterized a D-lactic acid-producing lactic acid bacterium (D-LAB), identified as Lactobacillus delbrueckii subsp. lactis QU 41. When compared to Lactobacillus coryniformis subsp. torquens JCM 1166 (T) and L. delbrueckii subsp. lactis JCM 1248 (T), which are also known as D-LAB, the QU 41 strain exhibited a high thermotolerance and produced D-lactic acid at temperatures of 50 °C and higher. In order to optimize the culture conditions of the QU 41 strain, we examined the effects of pH control, temperature, neutralizing reagent, and initial glucose concentration on D-lactic acid production in batch cultures. It was found that the optimal production of 20.1 g/l D-lactic acid was acquired with high optical purity (>99.9% of D-lactic acid) in a pH 6.0-controlled batch culture, by adding ammonium hydroxide as a neutralizing reagent, at 43 °C in MRS medium containing 20 g/l glucose. As a result of product inhibition and low cell density, continuous cultures were investigated using a microfiltration membrane module to recycle flow-through cells in order to improve D-lactic acid productivity. At a dilution rate of 0.87 h(-1), the high cell density continuous culture exhibited the highest D-lactic acid productivity of 18.0 g/l/h with a high yield (ca. 1.0 g/g consumed glucose) and a low residual glucose (<0.1 g/l) in comparison with systems published to date.

Production, optimization and characterization of lactic acid by Lactobacillus delbrueckii NCIM 2025 from utilizing agro-industrial byproduct (cane molasses)

“…Lactic acid (2-hydroxypropanoic acid, CH 3 -CH (OH)-COOH) is a natural organic acid with a long history of use in cosmetic and pharmaceutical industries, and also for the production of oxygenated chemicals, plant growth regulators, and special chemical intermediates (Dumbrepatil et al 2008;Oshiro et al 2009;Singhvi et al 2010;Tashiro et al 2011). Lactic acid is considered a specialty chemical with various applications both in the food and non-food industries.…”

Efficient Homofermentative l -(+)-Lactic Acid Production from Xylose by a Novel Lactic Acid Bacterium, Enterococcus mundtii QU 25

“…pH-controlled fermentations were carried out at 30°C to reduce the inhibitory effects of free lactate on the producer cells according to the method described previously (21). pH 7.0 provided the highest lactate concentration produced (131 mM) and the maximum lactate productivity (12.1 mM/h), which increased by 274% and 365%, respectively, compared to the levels for non-pH-controlled batches (Table 1).…”

Microbial production of lactic acid

“…For example, an L. delbrueckii strain isolated from a sink tolerated 50°C. Using continuous culture with membrane recycle at 43°C, this strain generated 20 g D-lactic acid l -1 continuously from 20 g glucose l -1 at a productivity of 18 g l -1 h -1 and a yield of 1 g/g (Tashiro et al 2011). In batch culture 87.4 g D-lactic acid l -1 accumulated in 168 h from 100 g glucose l -1 .…”