Metabolic response of Bacillus stearothermophilus chemostat cultures to a secondary oxygen limitation

Martins, Meire Lélis Leal; Tempest, D. W.

doi:10.1099/00221287-137-6-1391

Cited by 12 publications

(9 citation statements)

References 17 publications

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“…Strain MFF4 differs, however, from other B. stearothermophilus strains with an absolute requirement for biotin, nicotinic acid and thiamin (Amartey et al 1991;Lee et al 1982;Rowe et al 1975), since from the vitamins tested only biotin was needed for growth of the organism. Strain MMF4 resembles other near-prototrophic B. stearothermophilus strains (Martins and Tempest 1991;Epstein and Grossowicz 1969). Unlike strain MFF4, however, B. stearothermophilus var.…”

Section: Discussionmentioning

confidence: 88%

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

Wind

Buitelaar

Eggink

et al. 1994

Appl Microbiol Biotechnol

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A novel strain of Bacillus stearothermophilus was isolated from samples of a potato-processing industry. Compared to known e-amylases from other B.stearothermophilus strains, the isolate was found to produce a highly thermostable e-amylase. The half-time of inactivation of this e-amylase was 5.1 h at 80°C and 2.4 h at 90°C. The temperature optimum for activity of the e-amylase was 70°C; the pH optimum for activity was relatively low, in the range 5.5-6.0. e-Amylase synthesis was regulated by induction and repression mechanisms. An inverse relationship was found between growth rate and e-amylase production. Low starch concentrations and low growth temperatures were favourable for enzyme production by the organism. At the optimal temperature for growth, 65°C, the e-amylase was a growth-associated enzyme. The optimal temperature for e-amylase production, however, was 40°C, with e-amylase increasing from 3.9 units (U)/ml to 143 U/ml when lowering the growth temperature from 65°C to 40°C. Maximal e-amylase production in a batch fermentor run at 65°C was 102 U/ml, which was 26-fold higher than in erlenmeyer flasks at 65°C. The dissolved 02 concentration was found to be a critical factor in production of the e-amylase.

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Section: Discussionmentioning

confidence: 88%

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

Wind

Buitelaar

Eggink

et al. 1994

Appl Microbiol Biotechnol

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“…Formation of low-molecular-weight by-products (excluding riboflavin) by so-called overflow metabolism was low in Climited culture (10), moderate in N-limited culture, and extensive in P-limited culture (Table 1), as was described for Bacillus spp. (28,35) and E. coli (31). The primary by-product was acetate, but diacyl and acetoin formation was also significant.…”

Section: Resultsmentioning

confidence: 99%

“…Although mostly studied in the gram-negative Enterobacteria, these findings are consistent with data from gram-positive Bacillus spp. (4,28,32,35).The uncoupling of anabolism and catabolism in excess-C cultures reduces the energetic growth efficiency of these cultures, which is attributed to so-called overflow metabolism, metabolic shifts of carbon or electron flow to less efficient pathways, and/or a variety of energy-spilling reactions (40, 57).While the magnitude of ATP dissipation via energy-spilling reactions is not well understood, several such processes that catalyze net loss of energy though cyclic reactions are known at the molecular level. Such cycles are frequently referred to as futile, simply because no clear metabolic function of such apparent waste of energy could be envisaged (22,30,40).…”

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Bacillus subtilis Metabolism and Energetics in Carbon-Limited and Excess-Carbon Chemostat Culture

2001

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The energetic efficiency of microbial growth is significantly reduced in cultures growing under glucose excess compared to cultures growing under glucose limitation, but the magnitude to which different energy-dissipating processes contribute to the reduced efficiency is currently not well understood. We introduce here a new concept for balancing the total cellular energy flux that is based on the conversion of energy and carbon fluxes into energy equivalents, and we apply this concept to glucose-, ammonia-, and phosphate-limited chemostat cultures of riboflavin-producing Bacillus subtilis. Based on [U-13 C 6 ]glucose-labeling experiments and metabolic flux analysis, the total energy flux in slow-growing, glucose-limited B. subtilis is almost exclusively partitioned in maintenance metabolism and biomass formation. In excess-glucose cultures, in contrast, uncoupling of anabolism and catabolism is primarily achieved by overflow metabolism, while two quantified futile enzyme cycles and metabolic shifts to energetically less efficient pathways are negligible. In most cultures, about 20% of the total energy flux could not be assigned to a particular energy-consuming process and thus are probably dissipated by processes such as ion leakage that are not being considered at present. In contrast to glucoseor ammonia-limited cultures, metabolic flux analysis revealed low tricarboxylic acid (TCA) cycle fluxes in phosphate-limited B. subtilis, which is consistent with CcpA-dependent catabolite repression of the cycle and/or transcriptional activation of genes involved in overflow metabolism in the presence of excess glucose. ATPdependent control of in vivo enzyme activity appears to be irrelevant for the observed differences in TCA cycle fluxes.The very basis of microbial growth resides in balanced fluxes through anabolic and catabolic reactions. These metabolic fluxes are highly variable and change with the environmental conditions and the rate of growth, since faster-growing cells demand a higher rate of metabolism. To delineate these influences, metabolic flux responses are typically studied in chemostat cultures that are maintained under different nutrient limitations. When microorganisms are limited for their energy source (usually the carbon source), catabolism is tightly coupled to anabolism and high biomass yields on the carbon source are achieved (40). Compared to those with carbon (C) limitation, excess-C cultures exhibit generally high rates of carbon consumption and low yields of biomass and thus have a low energetic growth efficiency (11,31,32,57). Most frequently excess-C cultures in chemostats are limited by other cellular macroelements such as nitrogen (N) and phosphorus (P) but also potassium, the predominant intracellular cation (11). Potassium or P limitation invokes usually a strong uncoupling of catabolic and anabolic processes that lead consequently to low biomass yields on the energy source, while N limitation has more moderate effects on cellular physiology (31, 68). Although mostly studied in the gr...

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“…Under oxygen-limited conditions, their metabolism switches to mixed fermentation in which alcohols and organic acids are formed (23,40,42). Since B. stearothermophilus strains are highly auxotrophic, they must be supplied with most amino acids and vitamins.…”

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confidence: 99%

Isolation of two physiologically induced variant strains of Bacillus stearothermophilus NRS 2004/3a and characterization of their S-layer lattices

et al. 1994

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Metabolic response of Bacillus stearothermophilus chemostat cultures to a secondary oxygen limitation

Cited by 12 publications

References 17 publications

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

Characterization of a new Bacillus stearothermophilus isolate: a highly thermostable α-amylase-producing strain

Bacillus subtilis Metabolism and Energetics in Carbon-Limited and Excess-Carbon Chemostat Culture

Isolation of two physiologically induced variant strains of Bacillus stearothermophilus NRS 2004/3a and characterization of their S-layer lattices

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