Current research on the genetics of lactic acid production in lactic acid bacteria

Davidson, Barrie E.; Llanos, Roxana M.; Cancilla, Michael R.; Redman, Natalie; Hillier, Alan J.

doi:10.1016/0958-6946(95)00031-3

Cited by 43 publications

(16 citation statements)

References 90 publications

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“…Enhancing the ldh expression resulted in a minor increase in the amount of lactate produced, which is in agreement with an earlier study; in L. lactis the expression of ldh [26] was increased on low copy-number plasmids from 1.05-to 1.8-fold, which is close to the range applied in this study and they found only a small increase in the production of lactate. Gradually lowering the expression of ldh from the wild-type level towards zero did not affect the amount of lactate produced until almost a twofold reduction had taken place, and after this point a proportional reduction in lactate production occurred.…”

Section: Physiological Effects Of Large Changes In the Expression Of Ldhsupporting

confidence: 93%

Lactate dehydrogenase has no control on lactate production but has a strong negative control on formate production in Lactococcus lactis

Andersen

Pedersen

Hammer

et al. 2001

European Journal of Biochemistry

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A series of mutant strains of Lactococcus lactis were constructed with lactate dehydrogenase (LDH) activities ranging from below 1% to 133% of the wild-type activity level. The mutants with 59% to 133% of lactate dehydrogenase activity had growth rates similar to the wild-type and showed a homolactic pattern of fermentation. Only after lactate dehydrogenase activity was reduced ninefold compared to the wild-type was the growth rate significantly affected, and the ldh mutants started to produce mixed-acid products (formate, acetate, and ethanol in addition to lactate). Flux control coefficients were determined and it was found that lactate dehydrogenase exerted virtually no control on the glycolytic flux at the wild-type enzyme level and also not on the flux catalyzed by the enzyme itself, i.e. on the lactate production. As expected, the flux towards the mixed-acid products was strongly enhanced in the strain deleted for lactate dehydrogenase. What is more surprising is that the enzyme had a strong negative control (C J F1 LDH ¼ 2 1.3) on the flux to formate at the wild-type level of lactate dehydrogenase. Furthermore, we showed that L. lactis has limited excess of capacity of lactate dehydrogenase, only 70% more than needed to catalyze the lactate flux in the wild-type cells.Keywords: lactic acid bacteria; metabolic control analysis; gene expression; fermentation.Lactococcus lactis plays an important role in dairy fermentations, mainly in the production of cheeses. In these fermentation processes, lactose is present at high concentrations (50 g·L 21 ) and is converted through glycolysis to lactic acid, with minor amounts of other compounds being produced in addition (homolactic fermentation). The resulting low pH contributes to the texture and flavor of cheeses and inhibits the growth of other bacterial species. Under conditions where sugar becomes limiting for growth of Lactococcus lactis, the metabolism shifts to mixed-acid products, i.e. formate, acetate and ethanol along with smaller amounts of lactate [1,2].Work has been performed in the past to study the mechanisms involved in the shift between the two different fermentation modes in L. lactis. In the presence of excess sugar, the concentration of fructose 1,6-bisphosphate, the triose-phosphates, pyruvate, and the NADH/NAD þ ratio are high, whereas the concentration of phosphoenolpyruvate and inorganic phosphate are relative low [3 -6]. In contrast, when sugar is limiting the concentration of these metabolites and cofactors are reversed to the opposite, high or low level. Particularly, the level of fructose-1,6-bisphosphate, which is known to activate both pyruvate kinase and lactate dehydrogenase, has been suggested to play a key role in the regulation of the fermentation mode [1].Work has also been performed to determine the factors that control the flux through glycolysis by applying metabolic control analysis [7,8]. Based on inhibitor titration, Poolman et al. [9] suggested that glyceraldehyde 3-phosphate dehydrogenase had a large amount of control ove...

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Section: Physiological Effects Of Large Changes In the Expression Of Ldhsupporting

confidence: 93%

Lactate dehydrogenase has no control on lactate production but has a strong negative control on formate production in Lactococcus lactis

Andersen

Pedersen

Hammer

et al. 2001

European Journal of Biochemistry

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“…This unique organization could in principle allow for coordinated regulation of the expression of these genes, and it was suggested that expression of the las operon might be involved in regulating energy production and lactate flux in L. lactis (5). Indeed, a fivefold up-regulation of expression of the las operon was recently demonstrated at the onset of the stationary growth phase (1).…”

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confidence: 99%

Twofold Reduction of Phosphofructokinase Activity in Lactococcus lactis Results in Strong Decreases in Growth Rate and in Glycolytic Flux

et al. 2001

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Two mutant strains of Lactococcus lactis in which the promoter of the las operon, harboring pfk, pyk, and ldh, were replaced by synthetic promoters were constructed. These las mutants had an approximately twofold decrease in the activity of phosphofructokinase, whereas the activities of pyruvate kinase and lactate dehydrogenase remained closer to the wild-type level. In defined medium supplemented with glucose, the growth rate of the mutants was reduced to 57 to 70% of wild-type levels and the glycolytic flux was reduced to 62 to 76% of wild-type levels. In complex medium growth was even further reduced. Surprisingly, the mutants still showed homolactic fermentation, which indicated that the limitation was different from standard glucose-limited conditions. One explanation could be that the reduced activity of phosphofructokinase resulted in the accumulation of sugar-phosphates. Indeed, when one of the mutants was starved for glucose in glucose-limited chemostat, the growth rate could gradually be increased to 195% of the growth rate observed in glucosesaturated batch culture, suggesting that phosphofructokinase does affect the concentration of upstream metabolites. The pools of glucose-6-phosphate and fructose-6-phosphate were subsequently found to be increased two-to fourfold in the las mutants, which indicates that phosphofructokinase exerts strong control over the concentration of these metabolites.Lactococcus lactis plays an important role in dairy fermentations, mainly in the production of cheeses. During such fermentation processes, lactose is present at very high concentrations (50 g/liter) and is converted through glycolysis to primarily form lactic acid as well as minor amounts of other compounds (homolactic fermentation). The resulting low pH contributes to the texture and flavor of cheeses and inhibits the growth of other bacterial species. During homolactic fermentation more than 90% of the lactose consumed is recovered as by-products (42), which shows that the glycolytic pathway functions almost exclusively as a catabolic pathway to supply ATP to the cells. When sugar becomes limiting for growth, or in the presence of a less readily metabolized carbon source, the pattern of product formation switches from homolactic to mixedacid fermentation, i.e., to the formation of formate, ethanol, and acetate with smaller amounts of lactate (43).The mechanisms responsible for regulation of glycolytic flux and the shift between different fermentation modes in L. lactis have been studied intensively. The concentrations of intermediary metabolites and cofactors are affected by the external sugar concentration (8,10,37,46). In the presence of excess sugar, the concentrations of fructose-1,6-bisphosphate, the triose-phosphates, and pyruvate and the NADH/NAD ϩ ratio are high, whereas the concentrations of phosphoenolpyruvate and inorganic phosphate are relatively low. The glycolytic flux was proposed to be regulated through the level of fructose-1,6-bisphosphate (43), which is known to activate both pyruvate kinase ...

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“…Lactic acid can be produced by either microbial fermentation or chemical synthesis . Chemical synthesis using petrochemical resources produce always racemic dl ‐lactic acid, but an optically pure l (+)‐ or d (−)‐lactic acid can be obtained through microbial fermentation when the appropriate microorganism is selected .…”

Section: Analyte Classes Important In Bioprocess Analysismentioning

confidence: 99%

Capillary electrophoresis for monitoring bioprocesses

2013

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Chemical characterization and monitoring of fermentation broths and cell culture media provide significant information on the changes occurring within these complex and dynamic systems. Analytical methods based on CE in capillaries and microchips are attractive for integration in instrumental tools to obtain this critical data, improving the understanding and control of bioprocesses. In this review, the use of CE for chemical characterization and monitoring fermentations is discussed, organized by analyte class, including organic acids, pharmaceuticals, proteins, sugars, amino acids, and metabolites published between 1992 and October 2012. A section is dedicated to the roles CE plays throughout the wine making process, where applications range from characterization and increase in fundamental understanding of the fermentation to forensic applications, verifying the authenticity of the wine.

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Current research on the genetics of lactic acid production in lactic acid bacteria

Cited by 43 publications

References 90 publications

Lactate dehydrogenase has no control on lactate production but has a strong negative control on formate production in Lactococcus lactis

Lactate dehydrogenase has no control on lactate production but has a strong negative control on formate production in Lactococcus lactis

Twofold Reduction of Phosphofructokinase Activity in Lactococcus lactis Results in Strong Decreases in Growth Rate and in Glycolytic Flux

Capillary electrophoresis for monitoring bioprocesses

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