Enhanced Lactic Acid Production by Adaptive Evolution of Lactobacillus paracasei on Agro-industrial Substrate

Abstract

The aim of this study was to perform the adaptation of Lactobacillus paracasei NRRL B-4564 to substrate through adaptive evolution in order to ensure intensive substrate utilization and enhanced L (+)-lactic acid (LA) production on molasses-enriched potato stillage. To evaluate the strain response to environmental conditions exposed during the adaptation process and to select the best adapted cells, the antioxidant activity and LA-producing capability were assessed in batch fermentation. The most promising adapted strain was further used in a pulsed fed-batch mode. Among three selected adapted strains, L. paracasei A-22 showed considerably improved antioxidant capacity, demonstrating more than onefold higher 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging rates compared to parent strain. This strain also exhibited superior LA production in batch fermentation and reached 89.4 g L of LA, with a yield of 0.89 g g, a productivity of 1.49 g L h, and an optical purity greater than 99%. Furthermore, in fed-batch mode L. paracasei A-22 resulted in 59% higher LA concentration (169.9 g L) compared to parent strain (107.1 g L). The strain adaptation to molasses environment, performed in this study, is a rather simple and promising method for enhancement of LA production on the complex agro-industrial substrate.

Bioprocessing of agro‐industrial residues into lactic acid and probiotic enriched livestock feed

“…The DPPH scavenging activity of L. paracasei was higher than that of L. casei (27.5%) and L. delbrueckii (24.0%) at the same cell concentration of 10 9 CFU mL −1 . We have previously shown that the antioxidant capacity of L. paracasei NRRL B‐4564 was highly dependent on environmental conditions, and a significant increase in antioxidant activity could be provoked by strain exposure to certain pro‐oxidative compounds . These findings indicate that L. paracasei may exert an important role in protection from oxidative stress, providing the benefit to the gut microbiota of host.…”

“…Cell disruption was performed by ultrasonic homogenizer (Sonopuls HD 2200, BANDELIN electronic, Berlin, Germany) for five 1 min intervals (1 min on/1 min off, 35% amplitude), ensuring a constant cooling. Cell debris was removed by centrifugation (8000 × g , 10 min, 4 °C) and the resulting supernatant (intracellular extract), along with intact cells, was subjected to 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging assay as previously described …”

Evolutionary Engineering of Lactobacillus Bulgaricus Reduces Enzyme Usage and Enhances Conversion of Lignocellulosics to D-lactic Acid by Simultaneous Saccharification and Fermentation

“…Some studies have attempted to evolve yeast strains for lactate production to leverage its property to tolerate lower pH [22]. There are also reports on L-LA production from lignocellulosic substrate by SSF using different strains evolved for improved antioxidant property [23] and e cient xylose assimilation [24]. Although enzyme loading is a critical techno-economic factor, there are not many detailed reports available on optimization or minimization of enzyme loading to achieve higher product to enzyme ratio.…”

Evolutionary engineering of Lactobacillus bulgaricus reduces enzyme usage and enhances conversion of lignocellulosics to D-lactic acid by simultaneous saccharification and fermentation

“…Some studies have attempted to evolve yeast strains for lactate production to leverage its property to tolerate lower pH [26]. There are also reports on L-LA production from lignocellulosic substrate by SSF using different strains evolved for improved antioxidant property [27] and e cient xylose assimilation [28]. Although enzyme loading is a critical techno-economic factor, there are not many detailed reports available on optimization or minimization of enzyme loading to achieve higher product to enzyme ratio (PER).…”