d-Glucose does not catabolite repress a transketolase-deficientd-ribose-producingBacillus subtilis mutant strain

Wulf, Peter De; Soetaert, Wim; Schwengers, Dieter; Vandamme, Erick

doi:10.1007/bf01570052

Cited by 15 publications

(21 citation statements)

References 4 publications

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“…For example, cometabolism of glucose and citrate in batch cultures and continuous B. subtilis cultures was shown to prevent the formation of overflow products and to increase the carbon yield more than twofold (25). Moreover, the simultaneous use of glucose and gluconate in batch cultures of a recombinant Dribose-producing B. subtilis strain led to higher yields of Dribose and by-products (15). Our interest, however, was to evaluate the influence of cofeeding on yields under processrelevant conditions.…”

Section: Discussionmentioning

confidence: 99%

Intracellular Carbon Fluxes in Riboflavin-Producing Bacillus subtilis during Growth on Two-Carbon Substrate Mixtures

Dauner

Sonderegger

Hochuli

et al. 2002

Appl Environ Microbiol

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Metabolic responses to cofeeding of different carbon substrates in carbon-limited chemostat cultures were investigated with riboflavin-producing Bacillus subtilis. Relative to the carbon content (or energy content) of the substrates, the biomass yield was lower in all cofeeding experiments than with glucose alone. The riboflavin yield, in contrast, was significantly increased in the acetoin-and gluconate-cofed cultures. In these two scenarios, unusually high intracellular ATP-to-ADP ratios correlated with improved riboflavin yields. Nuclear magnetic resonance spectra recorded with amino acids obtained from biosynthetically directed fractional 13 C labeling experiments were used in an isotope isomer balancing framework to estimate intracellular carbon fluxes. The glycolysis-to-pentose phosphate (PP) pathway split ratio was almost invariant at about 80% in all experiments, a result that was particularly surprising for the cosubstrate gluconate, which feeds directly into the PP pathway. The in vivo activities of the tricarboxylic acid cycle, in contrast, varied more than twofold. The malic enzyme was active with acetate, gluconate, or acetoin cofeeding but not with citrate cofeeding or with glucose alone. The in vivo activity of the gluconeogenic phosphoenolpyruvate carboxykinase was found to be relatively high in all experiments, with the sole exception of the gluconate-cofed culture.During batch growth on mixtures of carbon substrates, bacteria frequently first consume almost exclusively their preferred substrate. Consumption of any other substrate(s) occurs only after depletion of the preferred one, leading to a diauxic pattern of growth. The primary molecular mechanisms that inhibit the simultaneous utilization of substrates are catabolite repression (9) and inducer exclusion (47). Under carbon-limited conditions in chemostat cultures, in contrast, mixtures of carbon sources are often utilized simultaneously at low and intermediate dilution rates (D) (18). Thus, for the most frequently used paradigm catabolite repression sugar, glucose, such coutilization occurs at concentrations below a critical repression level (29). Consequently, many catabolic enzymes are relieved from repression so that alternative substrates can be catabolized (32,34).While many biotechnological processes operate on a single carbon source, substrate mixtures may help to diagnose potential bottlenecks in the biosynthetic pathways to a desired product (10). For the production of riboflavin (vitamin B 2 ), which is a commercially important additive in the feed and food industries, such cofeeding experiments were used to identify potential limitations in building block supply (55) (Fig. 1). Generally, cofeeding experiments are evaluated on the basis of physiological analysis, with a primary focus on production. Much information on the underlying metabolic network response, however, is not accessible from extracellular physiological data but requires knowledge of intracellular carbon fluxes.The classical approach to analyzing intracellular car...

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Section: Discussionmentioning

confidence: 99%

Intracellular Carbon Fluxes in Riboflavin-Producing Bacillus subtilis during Growth on Two-Carbon Substrate Mixtures

Dauner

Sonderegger

Hochuli

et al. 2002

Appl Environ Microbiol

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“…Glucose and corn steep liquor are particularly effective for production of D-ribose [9,32]. To increase D-ribose production, some substrates metabolized only via the pentose phosphate pathway, such as D-gluconic acid, D-xylose, D-xylitol, and D-arabinose, were supplied together with glucose [7,10,28,29]. For example, 50 g l -1 of D-gluconic acid were supplied together with 100 g l -1 of D-glucose to obtain 45 g l -1 of D-ribose in 84 h [10], and the yield of D-ribose was increased from 0.24 to 0.37 mol mol -1 based on total carbon sources consumed.…”

mentioning

confidence: 99%

Enhanced d-ribose biosynthesis in batch culture of a transketolase-deficient Bacillus subtilis strain by citrate

2009

J Ind Microbiol Biotechnol

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In this study, the effects of citrate addition on D-ribose production were investigated in batch culture of a transketolase-deficient strain, Bacillus subtilis EC2, in shake flasks and bioreactors. Batch cultures in shake flasks and a 5-l reactor indicated that supplementation with 0.2-0.5 g l(-1) of citrate enhanced D: -ribose production. When B. subtilis EC2 was cultivated in a 15-l reactor in a complex medium, the D: -ribose concentration was 70.9 g l(-1) with a ribose yield of 0.497 mol mol(-1). When this strain was grown in the same medium supplemented with 0.3 g l(-1) of citrate, 83.4 g l(-1) of D-ribose were obtained, and the ribose yield was increased to 0.587 mol mol(-1). Addition of citrate reduced the activities of pyruvate kinase and phosphofructokinase, while it increased those of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Metabolic flux distribution in the stationary phase indicated that citrate addition resulted in increased fluxes in the pentose phosphate pathway and TCA cycle, and decreased fluxes in the glycolysis and acetate pathways.

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“…AraR regulates arabinose metabolism in a similar manner as XylR (81). Successful diversion of glucose flux from glycolysis to the oxidative branch of the pentose phosphate pathway (PPP) in B. subtilis favored the co-metabolism of glucose and other carbon sources like arabinose and xylose that is extensively utilized via non-oxidative branch of PPP (82).…”

Section: Bacillus Subtilismentioning

confidence: 99%

Rewiring carbon catabolite repression for microbial cell factory

Parisutham¹,

Kim²,

Lee³

et al. 2012

BMB Reports

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Carbon catabolite repression (CCR) is a key regulatory system found in most microorganisms that ensures preferential utilization of energy-efficient carbon sources. CCR helps microorganisms obtain a proper balance between their metabolic capacity and the maximum sugar uptake capability. It also constrains the deregulated utilization of a preferred cognate substrate, enabling microorganisms to survive and dominate in natural environments. On the other side of the same coin lies the tenacious bottleneck in microbial production of bioproducts that employs a combination of carbon sources in varied proportion, such as lignocellulose-derived sugar mixtures. Preferential sugar uptake combined with the transcriptional and/or enzymatic exclusion of less preferred sugars turns out one of the major barriers in increasing the yield and productivity of fermentation process. Accumulation of the unused substrate also complicates the downstream processes used to extract the desired product. To overcome this difficulty and to develop tailor-made strains for specific metabolic engineering goals, quantitative and systemic understanding of the molecular interaction map behind CCR is a prerequisite. Here we comparatively review the universal and strain-specific features of CCR circuitry and discuss the recent efforts in developing synthetic cell factories devoid of CCR particularly for lignocellulose-based biorefinery. [BMB reports 2012; 45(2): 59-70]

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d-Glucose does not catabolite repress a transketolase-deficientd-ribose-producingBacillus subtilis mutant strain

Cited by 15 publications

References 4 publications

Intracellular Carbon Fluxes in Riboflavin-Producing Bacillus subtilis during Growth on Two-Carbon Substrate Mixtures

Intracellular Carbon Fluxes in Riboflavin-Producing Bacillus subtilis during Growth on Two-Carbon Substrate Mixtures

Enhanced d-ribose biosynthesis in batch culture of a transketolase-deficient Bacillus subtilis strain by citrate

Rewiring carbon catabolite repression for microbial cell factory

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