Impact of aeration on the metabolic end‐products formed from glucose and galactose by <i>Streptococcus lactis</i>

Cogan, J.F.; Walsh, D.; Condón, S.

doi:10.1111/j.1365-2672.1989.tb02457.x

Cited by 36 publications

(34 citation statements)

References 27 publications

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“…In some cases, LAB do not benefit from O # , but they are not inhibited by its presence, e.g. Lactobacillus plantarum (Murphy & Condon, 1984) and Lactococcus lactis (Cogan et al, 1989). However, O. oeni M42 …”

Section: Effect Of Anaerobic or Aerobic Conditions On Growth And Metamentioning

confidence: 99%

NAD(P)H regeneration is the key for heterolactic fermentation of hexoses in Oenococcus oeni

2002

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Oenococcus oeni (formerly Leuconostoc oenos) can perform malolactic fermentation, converting L-malate to L-lactate and carbon dioxide, in wines. The energy and redox potential required to support the growth of the microorganism are supplied mainly by the consumption of carbohydrates via the heterolactic pathway. In the first steps of hexose metabolism two molecules of NAD(P) M are consumed, which must be regenerated in later reactions. The aim of this work was to test if aerobic growth of O. oeni promotes higher cell yields than anaerobic conditions, as has been shown for other lactic acid bacteria. O. oeni M42 was found to grow poorly under aerobic conditions with glucose as the only carbohydrate in the medium. It was demonstrated that O 2 inactivates the enzymes of the ethanol-forming pathway, one of the two pathways which reoxidizes NAD(P) M cofactors in the heterolactic catabolism of glucose. These results suggest that the regeneration of cofactors is the limiting factor for the aerobic consumption of glucose. When external electron acceptors, such as fructose or pyruvate, were added to glucose-containing culture medium the growth of O. oeni was stimulated slightly ; fructose was converted to mannitol, oxidizing two molecules of NAD(P)H, and pyruvate was transformed to lactate, enabling the regeneration of NAD M . The addition of cysteine seemed to suppress the inactivation of the ethanol-forming pathway enzymes by O 2 , enabling glucose consumption in aerobic conditions to reach similar rates to those found in anaerobic conditions.

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Section: Effect Of Anaerobic or Aerobic Conditions On Growth And Metamentioning

confidence: 99%

NAD(P)H regeneration is the key for heterolactic fermentation of hexoses in Oenococcus oeni

2002

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Section: ؊1mentioning

confidence: 99%

“…In this light, it is surprising that, to our knowledge, no investigations have been carried out on the microaerobic physiology of starter cultures. A number of studies on the effect of oxygen in fully aerated cultures have been published, but little light has been shed on the window ranging from anaerobic to fully aerobic conditions of growth (4,7,8,20).Interest in the microaerobic physiology of LAB is furthermore spurred by reports on the extreme sensitivity of pyruvate formate-lyase (PFL) to oxygen (1, 25) and the negative effect of oxygen on pfl gene expression (2,19). Similarly, it has recently been reported that vigorous aeration reduces the transcription of the adhE gene, which encodes alcohol dehydrogenase (ADH) in Lactococcus lactis (3).…”

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confidence: 99%

Metabolic Behavior of Lactococcus lactis MG1363 in Microaerobic Continuous Cultivation at a Low Dilution Rate

Jensen

Melchiorsen

Jokumsen

et al. 2001

Appl Environ Microbiol

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Minute amounts of oxygen were supplied to a continuous cultivation of Lactococcus lactis subsp. cremoris MG1363 grown on a defined glucose-limited medium at a dilution rate of 0.1 h ؊1. More than 80% of the carbon supplied with glucose ended up in fermentation products other than lactate. Addition of even minute amounts of oxygen increased the yield of biomass on glucose by more than 10% compared to that obtained under anaerobic conditions and had a dramatic impact on catabolic enzyme activities and hence on the distribution of carbon at the pyruvate branch point. Increasing aeration caused carbon dioxide and acetate to replace formate and ethanol as catabolic end products while hardly affecting the production of either acetoin or lactate. The negative impact of oxygen on the synthesis of pyruvate formate lyase was confirmed. Moreover, oxygen was shown to down regulate the protein level of alcohol dehydrogenase while increasing the enzyme activity levels of the pyruvate dehydrogenase complex, ␣-acetolactate synthase, and the NADH oxidases. Lactate dehydrogenase and glyceraldehyde dehydrogenase enzyme activity levels were unaffected by aeration.Homofermentative lactic acid bacteria (LAB) are used primarily in the dairy industry but may also prove to be advantageous hosts for production of lactate as a bulk chemical or of food additives such as bacteriocins or amino acids using recombinant DNA technology (10, 15). The metabolism of these bacteria is constrained by the requirement for a balance between NADH-producing and -consuming reactions. In the absence of external electron acceptors (e.g., oxygen), the carbon fluxes of catabolism are tightly coupled. In anaerobic culture, glucose may be redox-neutrally converted to lactate or, alternatively, to the mixed acid products formate, acetate, and ethanol in a molar ratio of 2:1:1 (12, 26). However, when oxygen is present in the growth medium, the catabolic carbon fluxes are uncoupled from the redox metabolism due to the NAD ϩ -regenerating activity of NADH oxidases (NOX). This oxygenrelated potential for redirecting fluxes is used industrially in connection with the formation of other metabolites such as diacetyl in fermented milk products. Even submillimolar concentrations of diacetyl have a strong impact on the taste of buttermilk and cheese (22). Hence, minute amounts of oxygen may influence an industrial process greatly. In this light, it is surprising that, to our knowledge, no investigations have been carried out on the microaerobic physiology of starter cultures. A number of studies on the effect of oxygen in fully aerated cultures have been published, but little light has been shed on the window ranging from anaerobic to fully aerobic conditions of growth (4,7,8,20).Interest in the microaerobic physiology of LAB is furthermore spurred by reports on the extreme sensitivity of pyruvate formate-lyase (PFL) to oxygen (1, 25) and the negative effect of oxygen on pfl gene expression (2,19). Similarly, it has recently been reported that vigorous aeration reduces the...

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“…Furthermore, expression of the adhE gene, which encodes the alcohol dehydrogenase enzyme, is known to be reduced by aeration (2). In contrast, the in vitro specific activities of ␣-acetolactate synthase (ALS) and the pyruvate dehydrogenase (PDH) complex have been reported to increase with aeration (8, 17).For the most part, L. lactis has been studied under totally anaerobic conditions or, in some cases, under totally aerobic conditions (8,10,19,26,31). To the best of our knowledge, a recent study performed by Jensen et al (17) was the first study to look into the behavior of L. lactis under microaerobic conditions (i.e., with small amounts of oxygen dissolved in the cultures).…”

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confidence: 99%

Glucose Metabolism in Lactococcus lactis MG1363 under Different Aeration Conditions: Requirement of Acetate To Sustain Growth under Microaerobic Conditions

Nordkvist

Jensen

Villadsen

2003

Appl Environ Microbiol

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Lactococcus lactis subsp. lactis MG1363 was grown in batch cultures on a defined medium with glucose as the energy source under different aeration conditions, namely, anaerobic conditions, aerobic conditions, and microaerobic conditions with a dissolved oxygen tension of 5% (when saturation with air was used as the reference). The maximum specific growth rate was high (0.78 to 0.91 h ؊1 ) under all aeration conditions but decreased with increasing aeration, and more than 90% of the glucose was converted to lactate. However, a shift in by-product formation was observed. Increasing aeration resulted in acetate, CO 2 , and acetoin replacing formate and ethanol as end products. Under microaerobic conditions, growth came to a gradual halt, although more than 60% of the glucose was still left. A decline in growth was not observed during microaerobic cultivation when acetate was added to the medium. We hypothesize that the decline in growth was due to a lack of acetyl coenzyme A (acetyl-CoA) needed for fatty acid synthesis since acetyl-CoA can be synthesized from acetate by means of acetate kinase and phosphotransacetylase activities.The homofermentative lactic acid bacterium Lactococcus lactis is used primarily in the dairy industry to manufacture fermented milk products and cheese. The members of this species are facultative anaerobes and have limited biosynthetic capacity (7,18,30). Consequently, the main purpose of sugar metabolism is to produce ATP for biosynthesis, and more than 95% of the sugar metabolized ends up in fermentation products (24). If the small amount of NADH gained in anabolism is neglected, catabolism is constrained by a balance between NADH-producing and -consuming steps. Under anaerobic conditions this constraint results in conversion of glucose into lactate via lactate dehydrogenase (LDH) or into the mixed acid products formate, ethanol, and acetate at a C molar ratio of 1:1:1 via pyruvate formate lyase (PFL) depending on whether the specific sugar uptake rate is high or low (6,12,21). When oxygen is present in the medium, the tight coupling of catabolic carbon fluxes that is needed to satisfy the redox balance is alleviated, since NAD ϩ can be regenerated by the activity of NADH oxidases (NOX).Not only does the presence of oxygen in the medium influence metabolism by altering the NADH/NAD ϩ ratio, which has been proposed to play a key role in regulation of sugar metabolism (12,13,16,17,23), but the cellular content of key enzymes also changes with aeration. The negative effect of oxygen on expression of the pfl gene is well known (1, 22), and PFL is known to be very sensitive to oxygen (10,22,29). Furthermore, expression of the adhE gene, which encodes the alcohol dehydrogenase enzyme, is known to be reduced by aeration (2). In contrast, the in vitro specific activities of ␣-acetolactate synthase (ALS) and the pyruvate dehydrogenase (PDH) complex have been reported to increase with aeration (8, 17).For the most part, L. lactis has been studied under totally anaerobic conditions or, in some cas...

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Impact of aeration on the metabolic end‐products formed from glucose and galactose by Streptococcus lactis

Cited by 36 publications

References 27 publications

NAD(P)H regeneration is the key for heterolactic fermentation of hexoses in Oenococcus oeni

NAD(P)H regeneration is the key for heterolactic fermentation of hexoses in Oenococcus oeni

Metabolic Behavior of Lactococcus lactis MG1363 in Microaerobic Continuous Cultivation at a Low Dilution Rate

Glucose Metabolism in Lactococcus lactis MG1363 under Different Aeration Conditions: Requirement of Acetate To Sustain Growth under Microaerobic Conditions

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