Effect of carbon dioxide on yeast growth and fermentation

Inhibition of yeast function by ethanol and by high substrate concentrations is well recognized and, to a limited extent, quantified. The role of carbon dioxide in affecting yeast metabolism (particularly growth processes) is not clear although inhibition is generally found at moderate to high concentrations of the dissolved gas. A similar situation exists with other microorganisms and with other fermentation systems. An understanding of the role of carbon dioxide, and particularly of its inhibitory effects on enzyme action and membrane function, is required if the observed global inhibition of yeasts and other fermentation systems is to be partitioned to its appropriate causes.     

Effect of carbon dioxide on growth of Pseudomonas fluorescens.

In minimal medium at 30 degrees C, growth of Pseudomonas fluorescens was stimulated when the pressure (p) of CO2 in solution was 100 mm of Hg, but at higher concentrations the growth rate declined linearly with increasing pCO2. All concentrations of CO2 were inhibitory for growth in complex medium, and at 30 degrees C the maximum degree of inhibition was attained when pCO2 was 250 mm of Hg. The degree of inhibition at a constant pCO2 in solution increased with decreasing temperature. The degree of inhibition was directly proportional to temperature for growth in complex medium, but not in minimal medium. The inhibition of cell respiration by CO2 was the same whether cells had been grown in air or in the presence of CO2, indicating that adaptive enzyme synthesis does not occur in response to CO2.     

Effect of carbon dioxide on growth of Pseudomonas fluorescens.

In minimal medium at 30 degrees C, growth of Pseudomonas fluorescens was stimulated when the pressure (p) of CO2 in solution was 100 mm of Hg, but at higher concentrations the growth rate declined linearly with increasing pCO2. All concentrations of CO2 were inhibitory for growth in complex medium, and at 30 degrees C the maximum degree of inhibition was attained when pCO2 was 250 mm of Hg. The degree of inhibition at a constant pCO2 in solution increased with decreasing temperature. The degree of inhibition was directly proportional to temperature for growth in complex medium, but not in minimal medium. The inhibition of cell respiration by CO2 was the same whether cells had been grown in air or in the presence of CO2, indicating that adaptive enzyme synthesis does not occur in response to CO2.     

Effect of carbon dioxide on the growth of cell suspensions ofCathakanthus roseus

Summary Growth parameters of Catharanthus roseus in suspension cultures were examined under various pCO₂ conditions. In CO₂-enriched environments (up to 2 %) for Erlenmeyer flask cultures, enhanced maximum growth rates and conversion yields were observed. Fermenter cultures with a constant pCO₂ of 2 %, gave high conversion yields although no growth-promoting activity was observed. High aeration rates led to decreased rates of growth due to CO₂ stripping.     

Effect of carbon dioxide on growth of Zymomonas mobilis in continuous culture

Summary Biomass production of Zymomonas mobilis in continuous cultivation on synthetic or complex glucose media was increased up to 100% when CO₂ partial pressure was reduced from 1,460 to 95 mbar at high dilution rates. Biomass yield increased and specific glucose uptake and ethanol production rates decreased approximately 6% when pCO₂ was lowered from 1,160 to 95 mbar. Product yield was not affected by pCO₂. Long time adaptation superimposing these effects was considered.     

New fossils of ascomycetous anamorphic fungi from Baltic amber

Three new fossils of saprotrophic fungi are presented and described from Baltic amber, dated to Eocene epoch (Paleogene, upper to mid-Eocene). All belong to Ascomycota and are represented by hyphae as well as asexual reproduction structures allowing to assign them to present genera, respectively Periconia, Penicillium and Scopulariopsis. These material provide both the first and the oldest known fossil record of the mentioned taxa, making these data valuable for the knowledge about the evolutionary history of the Ascomycota.     

Effect of carbon dioxide on photorespiration

The isotopic CO₂ technique for measuring photorespiration was shown to be a valid technique for measuring the unidirectional inward and outward fluxes of CO₂ from a sunflower (Helianthus annuus L.) leaf in the light. The rate of photorespiration was decreased little as the CO₂ concentration was increased from 20 to 1,150 microliters per liter. This finding contradicts the widely held assumption that photorespiration is suppressed at high CO₂ concentrations. Some discussion regarding this apparent conflict is presented.     

Effect of carbon dioxide on nitrification rates

Lab-scale ideal mixed, aerated reactors were employed to test the influence of carbon dioxide (CO(2)) on the growth rate of a nitrifier community. The buffer medium used did not contain any carbon sources. Reactors were inoculated alternatively with sludge from a nitrifying membrane assisted bioreactor, reflecting autotrophic material, or with sludge from a plant having denitrification and nitrification steps, which reflects mixed heterotrophic and autotrophic material. CO(2) was added as a gas with the intake air supply. Nitrification rates were related to the CO(2) in the intake air as well as to the total inorganic carbon in the medium. The batch experiments show a relationship between CO(2) concentration and growth rate. The optimum growth rate occurred at 5 mg CO(2)/L, corresponding to 0.4% (V/V) CO(2) in the inlet air. Different CO(2) optima for autotrophic and mixed sludges were found. In the case of the autotrophic sludge, the observed optimum growth rate was about 0.47/d and the optimum for the mixed sludge was about 0.75/d. Higher CO(2) concentrations lead to a decreasing growth rate. The first part of the kinetic graph can be described by Monod kinetics. Overall, the resulting graph can be described by Haldane kinetics.     

Effect of elevated oxygen and carbon dioxide on the surface growth of vegetable-associated micro-organisms

The impact of a novel type of Modified Atmosphere (MA), referred to as high O2-MA, on micro-organisms associated with the spoilage of minimally-processed vegetables was studied. Pure cultures of Pseudomonas fluorescens, Enterobacter agglomerans, Aureobacterium strain 27, Candida guilliermondii, C. sake, Salmonella typhimurium, Salm. enteritidis, Escherichia coli, Listeria monocytogenes, Leuconostoc mesenteroides var. mesenteroides, Lactobacillus plantarum and Lactococcus lactis were cultured on an agar-surface model system and incubated at 8 degrees C under an atmosphere composed of O2 (80 or 90%, balanced with N2), CO2 (10 or 20%, balanced with N2), or a combination of both gases. In general, exposure to high O2 alone did not inhibit microbial growth strongly, while CO2 alone reduced growth to some extent in most cases. Consistently strong inhibition was observed only when the two gases were used in combination. With minimally-processed vegetables, where CO2 levels of around 20% or above cannot be used because of physiological damage to the produce, the combined treatment of high O2 and 10-20% CO2 may provide adequate suppression of microbial growth, allowing a safe, prolonged shelf-life.     

Effect of dissolved carbon dioxide on penicillin fermentations: Mycelial growth and penicillin production

The effect of dissolved carbon dioxide on the specific growth rate and the penicillin production rate of Penicillium chrysogenum was examined experimentally. The dissolved carbon dioxide was found to inhibit the specific growth rate and the penicillin production rate when the aerated submerged penicillin fermentation was exposed to influent gases of 12.6 and 20% carbon dioxide, respectively. Upon exposure to influent gases of 3 and 5% carbon dioxide, no pronounced metabolic inhibition was noted.     

Effect of elevated dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum on D-glucose and L-lactate

The effect of increased dissolved carbon dioxide concentrations on growth of Corynebacterium glutamicum was studied with continuous turbidostatic cultures. The carbon sources were either l-lactate or d-glucose. To increase the dissolved carbon dioxide concentration the carbon dioxide partial pressure of the inlet gas stream pCO2,IN was increased stepwise from 0.0003 bar (air) up to 0.79 bar, while the oxygen partial pressure of the inlet gas stream was kept constant at 0.21 bar. For each resulting carbon dioxide partial pressure pCO2 the maximum specific growth rate mu(max) was determined from the feed rate resulting from the turbidostatic control. On d-glucose and pCO2 up to 0.26 bar, mu(max) was mostly constant around 0.58 h(-1). Higher pCO2 led to a slight decrease of mu(max). On l-lactate mu(max) increased gradually with increasing carbon dioxide partial pressures from 0.37 h(-1) under aeration with air to a maximum value of 0.47 h(-1) at a pCO2 of 0.26 bar. At very high pCO2 (0.81 bar) mu(max) decreased down to 0.35 h(-1) independent of the carbon source.     

甲烷菌对厌氧真菌不同碳源代谢的影响

【目的】探讨碳源和甲烷菌对厌氧真菌碳代谢的影响。【方法】利用体外批次厌氧发酵法,比较厌氧真菌纯培养(Orpinomyces sp.和Neocallimastix sp.)及其与甲烷菌共培养(F1:Orpinomyces sp.+Methanobrevibacter sp.和N3:Neocallimastix sp.+Methanobrevibacter sp.)发酵不同类型碳水化合物代谢产物的差异。【结果】对厌氧真菌和甲烷菌共培养F1和N3的研究显示,F1发酵木薯粉[(26.44±0.22)mmol/L]的乳酸产量是发酵玉米芯[(1.31±0.04)mmol/L]的20.18倍,是N3发酵木薯粉[(1.59±0.03)mmol/L]的16.63倍,玉米芯[(0.79±0.08)mmol/L]的33.47倍。当F1和N3中的厌氧真菌纯培养时,各组乳酸产量均1.90 mmol/L。对F1进一步研究,结果显示发酵体系中木薯粉添加量在0.8%–2.0%之间时,乳酸产量随木薯粉添加量增加而增加。当含量在1.0%–2.4%之间时,随木薯粉添加量增加,甲烷和乙酸产量逐渐降低。比较F1发酵大米粉、木薯粉、玉米粉、小麦粉和土豆粉的发酵结果,发现乳酸产量与底物中支链淀粉的含量成正相关(R2=0.9554)。当F1发酵葡萄糖和麦芽糖时,乳酸产量5.00 mmol/L。当以麦芽糊精为底物时,乳酸产量高达(28.00±0.95)mmol/L。【结论】本文首次报道碳源和甲烷菌能够增强厌氧真菌的乳酸代谢途径并且这种增强存在种属特异性。     

Catabolism of benzene compounds by ascomycetous and basidiomycetous yeasts and yeastlike fungi

A literature review is given on growth of yeasts on benzene compounds and on the catabolic pathways involved. Additionally, a yeast collection was screened for assimilation of phenol and 3-hydroxybenzoic acid. Fifteen ascomycetous and thirteen basidiomycetous yeast species were selected and were tested for growth on 84 benzene compounds. It appeared that 63 of these compounds supported growth of one or more yeast species. The black yeastExophiala jeanselmei assimilated 54 of these compounds.The catechol branch of the 3-oxoadipate pathway and its hydroxyhydroquinone variant were involved in phenol and resorcinol catabolism of ascomycetes as well as of basidiomycetes. However, these two groups of yeasts showed characteristic differences in hydroxybenzoate catabolism. In the yeastlike fungusE. jeanselmei and in basidiomycetes of the generaCryptococcus, Leucosporidium andRhodotorula, the protocatechuate branch of the 3-oxoadipate pathway was induced by growth on 3- and 4-hydroxybenzoic acids. In threeTrichosporon species and in all ascomycetous yeasts tested, 4-hydroxybenzoic acid was catabolyzed via protocatechuate and hydroxyhydroquinone. These yeasts were unable to cleave protocatechuate. 3-Hydroxybenzoic and 3-hydroxycinnamic acids were catabolized in ascomycetous yeasts via the gentisate pathway, but in basidiomycetes via protocatechuate.Incomplete oxidation of phenol, some chlorophenols, cresols and xylenols was observed in cultures ofCandida parapsilosis growing on hydroquinone. Most compounds transformed by the growing culture were also converted by the phenol monooxygenase present in cell-free extracts of this yeast. They did not support growth.The relationship between the ability of ascomycetous yeasts to assimilate n-alkanes, amines and benzene compounds, and the presence of Coenzyme Q₉ is discussed.