Regulation of the Activity of Lactate Dehydrogenases from Four Lactic Acid Bacteria

“…On the other hand, deletion of ldh‐ 2 kept the homolactic fermentation, suggesting that LDH‐2 plays only a minor role in the lactate production. Kinetic study showed that the K m values of LDH‐2 for both pyruvate and NADH are larger than those of LDH‐1, indicating the minor role in lactate production [27].…”

Section: Resultsmentioning

confidence: 96%

An alternative allosteric regulation mechanism of an acidophilic l‐lactate dehydrogenase from Enterococcus mundtii 15‐1A

et al. 2014

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“…e ability of E. faecalis to produce L(+)-lactic acid from glucose or lactose by homolactic fermentation was earlier demonstrated in the literature. Lactate is generated through pyruvate reduction and two enzymes are involved in this reaction; the cytosolic NAD + -dependent L-(+)-lactate dehydrogenases: ldh-1 and ldh-2 [32].…”

Section: Effect Of Culture Media and Scale-up On Lactic Acid And Biommentioning

confidence: 99%

Bioreactor Scale-Up and Kinetic Modeling of Lactic Acid and Biomass Production by Enterococcus faecalis SLT13 during Batch Culture on Hydrolyzed Cheese Whey

Ziadi

M’hir

Aydi

et al. 2020

Journal of Chemistry

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Kinetic modeling of biomass and lactic acid production by Enterococcus faecalis SLT13 have been developed during batch culture in M17 and Hydrolyzed Cheese Whey (HCW) in 2 L and 20 L bioreactors. The specific growth rate μmax was higher in 20 L bioreactor (1.09 h−1); however, the maximum specific lactic acid production rate qpmax and maximum specific sugar utilization rate qsmax were higher in 2 L bioreactor. Biomass and sugar utilization were affected by lactic acid inhibition in HCW. No effects of substrate inhibition have been observed. Substrate limitation of biomass has been observed on HCW in 20 L bioreactor; the substrate limitation constant for biomass Ksx was 4.229 g/L. Substrate limitation of sugar consumption has been observed on M17 in 2 L bioreactor; the substrate limitation constant for sugar consumption Kss was 2.73 g/L. Compared to experimental data, the model provided good predictions for biomass, sugar consumption, and lactic acid production.

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“…The bacterial LdhLs (NAD-dependent LdhL) include an FBPdependent LdhL and an FBP-independent LdhL (30), and LdhL1 of E. faecalis is the FBP-dependent LdhL (31). The activity of FBPdependent Ldh is highly dependent on FBP produced from fructose 6-phosphate by 6-phosphofructokinase (Pfk) using ATP in glycolysis (31); however FBP is not produced in the glycerol metabolic pathway because glycerol is converted to DHAP and then enters glycolysis (9).…”

Section: Discussionmentioning

confidence: 99%

l -Lactate Production from Biodiesel-Derived Crude Glycerol by Metabolically Engineered Enterococcus faecalis: Cytotoxic Evaluation of Biodiesel Waste and Development of a Glycerol-Inducible Gene Expression System

Doi

2015

Appl Environ Microbiol

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Biodiesel waste is a by-product of the biodiesel production process that contains a large amount of crude glycerol. To reuse the crude glycerol, a novel bioconversion process using Enterococcus faecalis was developed through physiological studies. The E. faecalis strain W11 could use biodiesel waste as a carbon source, although cell growth was significantly inhibited by the oil component in the biodiesel waste, which decreased the cellular NADH/NAD ؉ ratio and then induced oxidative stress to cells. When W11 was cultured with glycerol, the maximum culture density (optical density at 600 nm [OD 600 ]) under anaerobic conditions was decreased 8-fold by the oil component compared with that under aerobic conditions. Furthermore, W11 cultured with dihydroxyacetone (DHA) could show slight or no growth in the presence of the oil component with or without oxygen. These results indicated that the DHA kinase reaction in the glycerol metabolic pathway was sensitive to the oil component as an oxidant. The lactate dehydrogenase (Ldh) activity of W11 during anaerobic glycerol metabolism was 4.1-fold lower than that during aerobic glycerol metabolism, which was one of the causes of low L-lactate productivity. The E. faecalis pflB gene disruptant (⌬pfl mutant) expressing the ldhL1 LP gene produced 300 mM L-lactate from glycerol/crude glycerol with a yield of >99% within 48 h and reached a maximum productivity of 18 mM h ؊1 (1.6 g liter ؊1 h ؊1 ). Thus, our study demonstrates that metabolically engineered E. faecalis can convert crude glycerol to L-lactate at high conversion efficiency and provides critical information on the recycling process for biodiesel waste. Biodiesel is one of the alternatives to fossil fuel that reduces greenhouse effects and is being produced worldwide (1, 2). Biodiesel is produced from triacylglycerol, which is a main component of vegetable oils and animal fats, by either chemical or enzymatic reactions (1, 3, 4). When biodiesel is produced by a chemical process, triacylglycerol is exposed to methanol under highly alkaline conditions to cleave the ester bond between glycerol and fatty acids, and the resulting methylated fatty acids are used as biodiesel (3). Consequently, this chemical process generates a by-product containing a large amount of crude glycerol, together with methanol and salts, that is called biodiesel waste. Microbial bioconversion processes to convert glycerol to other valuable materials, such as alcohols and organic acids, are being actively developed to reuse the crude glycerol included in biodiesel waste (5). When biodiesel waste contains impurities, such as methanol and residual fatty acids, it is pretreated to remove these impurities (6, 7) because raw biodiesel waste may be cytotoxic to producers (7,8). However, cytotoxic substances have not been identified in biodiesel waste.Many microorganisms can use glycerol as a carbon source (9, 10, 11). The bacterial glycerol metabolic pathway is known as a dehydrogenation pathway and a phosphorylation pathway (9). In the dehydrogenation ...

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Regulation of the Activity of Lactate Dehydrogenases from Four Lactic Acid Bacteria

Cited by 53 publications

References 32 publications

An alternative allosteric regulation mechanism of an acidophilic l‐lactate dehydrogenase from Enterococcus mundtii 15‐1A

An alternative allosteric regulation mechanism of an acidophilic l‐lactate dehydrogenase from Enterococcus mundtii 15‐1A

Bioreactor Scale-Up and Kinetic Modeling of Lactic Acid and Biomass Production by Enterococcus faecalis SLT13 during Batch Culture on Hydrolyzed Cheese Whey

l -Lactate Production from Biodiesel-Derived Crude Glycerol by Metabolically Engineered Enterococcus faecalis: Cytotoxic Evaluation of Biodiesel Waste and Development of a Glycerol-Inducible Gene Expression System

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