Influence of hyperbaric oxygen tension on growth parameters of Candida tropicalis and Rhodococcus erythropolis

Summary Oxygen-limited growth was avoided by means of oxygen-enriched aeration in aerobic fermentation processes. Studies were carried out with Candida tropicalis (Cast.) Berkhout and Rhodococcus erythropolis (DSM 43215). The effect of hyperbaric dissolved oxygen tension on growth parameters was examined by varying the dissolved oxygen concentration and the carbon source (glucose, ethanol, and n-alkanes). Up to an oxygen concentration of 40 mg/l in the culture suspension no impairment of the economic coefficients and no promotion of cell lysis was found. It was observed that raised oxygen concentrations in the aeration gas led to enhanced specific growth rates. At cell concentrations above 20 g/l dry weight an uncoupling of carbon source dissimilation and biomass production was observed even at non-limiting oxygen concentrations.     

Flux-based analysis of sulfur metabolism in desulfurizing strains of Rhodococcus erythropolis

Rhodococcus erythropolis has been studied widely for potential applications in biodesulfurization. Previous works have been largely experimental with an emphasis on the characterization and genetic engineering of desulfurizing strains for improved biocatalysis. A systems modeling approach that can complement these experimental efforts by providing useful insights into the complex interactions of desulfurization reactions with various other metabolic activities is absent in the literature. In this work, we report the first attempt at reconstructing a flux-based model to analyze sulfur utilization by R. erythropolis. The model includes the 4S pathway for dibenzothiophene (DBT) desulfurization. It predicts closely the growth rates reported by two independent experimental studies, and gives a clear and comprehensive picture of the pathways that assimilate the sulfur from DBT into biomass. In addition, it successfully elucidates that sulfate promotes higher cell growth than DBT and its presence in the medium reduces DBT desulfurization rates. A study using eight carbon sources suggests that ethanol and lactate yield higher cell growth and desulfurization rates than citrate, fructose, glucose, gluconate, glutamate, and glycerol.     

Influence of hyperbaric oxygen therapy on bone metabolism in patients with neoplasm

BackgroundHyperbaric oxygen therapy (HBOT) is useful in the treatment of complications due to radiotherapy in patients with neoplasm. Its effects on bone metabolism are unclear. In our study, we analyzed the effects of HBOT on bone remodeling in oncological patients with radiotherapy.Materials and methodsProspective clinical study in 23 patients with neoplasms undergoing treatment with HBOT due to complications of radiotherapy (hemorrhagic cystitis, proctitis or radionecrosis) and 25 patients with chronic anal fissure. The average number of HBOT sessions was 20 ± 5 (100% oxygen, 2.3 atmospheres and 90 min per day). Serum levels of aminoterminal propeptide of type I collagen (P1NP), C terminal telopeptide of type I collagen (CTX), alkaline phosphatase (AP), 25hydroxyvitamin D (25-OHD), parathyroid hormone (PTH), were measured at 3 time points: T0 (before beginning HBOT), T1 (at the end of HBOT) and T2 (6 months after HBOT).ResultsAt baseline, the patients with neoplasm have higher bone turnover than those with anal fissure. These differences were 41% in CTX (0.238 ± 0.202 ng/mL in neoplasm and 0.141 ± 0.116 ng/mL in fissure; p = 0.04), 30% for PTH (46 ± 36 pg/mL in neoplasm and 32 ± 17 pg/mL in fissure; p = 0.04) and 15% for alkaline phosphatase (80 ± 24 U/L in neoplasm and 68 ± 16 U/L in fissure; p = 0.04). In the group with neoplasm, the values of P1NP decreased 6% after HBOT (T0: 49 ± 31 ng/mL, T2: 46 ± 12 ng/mL; p = 0.03). Also, there were non-significant decreases in PTH (−34%) and CTX (−30%).ConclusionsPatients with neoplasm and complications with radiotherapy have an increase in bone remodeling that may be diminished after HBOT.     

Preparatory metabolism of p-hydroxybenzoic acid in Candida tropicalis

A technique of experimental adaptation was used to obtain mutants of Candida tropicalis which were able to utilize p-hydroxybenzoic acid as the sole source of carbon and energy. The preparatory metabolism of p-hydroxybenzoic acid involves the following stages: PHBA leads to quinol leads to hydroxyquinol leads to maleylacetic acid leads to beta-ketoadipic acid. The enzyme system which catalyzes oxidative decarboxylation of PHBA mediates also oxidative decarboxylation of protocatechuic, beta-resorcylic and gallic acids, i.e. compounds having a hydroxyl group in para position with respect to the carboxyl of hydroxyl derivatives of benzoic acid. Benzoic, salicyclic and gentisic acids are not substrates of this enzyme system. A technique is proposed for rapid indentification of beta-ketoadipic acid by thin-layer chromatography. The authors believe that methods used to study preparatory metabolism, on the basis of the Stanier theory of "simultaneous adaptation", are not quite reliable and may lead to erroneous conclusions.     

Molecular Genetic Markers for Identification of Rhodococcus erythropolis and Rhodococcus qingshengii

Microbiology - The application of restriction analysis of amplification products of the genes rpoC and alkB, encoding the synthesis of the DNA-dependent RNA polymerase β'-subunit and...     

Biological properties of the alpha-mannanase of Rhodococcus erythropolis

When Rhodococcus erythropolis is cultivated under the submerged conditions in a medium containing yeast mannan as a sole carbon source, it synthesizes exocellular alpha-mannanase which hydrolyzes alpha-1,2 and alpha-1,3 bonds in a mannan molecule. The alpha-mannanase of R. erythropolis exerts distinct lectin properties under the conditions which entirely exclude its enzyme activity.     

Influence of oxygen and substrate supply on the metabolism of Candida maltosa during cultivation on n-alkanes

Summary The influence of different states of oxygen and alkane substrate supply on the metabolism of Candida maltosa during cultivation on n-alkanes has been investigated. At sufficient oxygen and substrate supply a nearly equimolar ratio between the formation of biomass and alkane oxidation was observed. About 45% of the carbon source utilized was incorporated into the biomass. Strong oxygen limitation decreased protein formation and carbon incorporation into the biomass with a simultaneous increase in CO₂ formation, whereas periodic changes of oxygen supply only caused a decrease in carbon incorporation into the biomass and an increase in CO₂ formation. During cultivation in the presence of an inert hydrocarbon (pristane) it was found that carbon limitation and oxygen saturation diminished the formation of total and nitrogen-containing biomass, whereas carbon and oxygen limitation reduced the formation of total biomass.Offprint requests to: P. Riege     

Kinetics of the degradation of aliphatic hydrocarbons by the bacteria Rhodococcus ruber and Rhodococcus erythropolis

Consumption of aliphatic hydrocarbons by the bacteria Rhodococcus ruber Ac-1513-D and Rhodococcus erythropolis Ac-1514-D grown on mixed n-alkanes and diesel fuel was studied. Consumption of diesel fuel hydrocarbons by the strains was less intense in comparison with the n-alkane mixture. The strains showed differences in growth rate and consumption of the substrates, which suggests that they possess different mechanisms of hydrocarbon uptake.     

Kinetics of the degradation of aliphatic hydrocarbons by the bacteria Rhodococcus ruber and Rhodococcus erythropolis

Consumption of aliphatic hydrocarbons by the bacteria Rhodococcus ruber Ac-1513-D and Rhodococcus erythropolis Ac-1514-D grown on mixed n-alkanes and diesel fuel was studied. Consumption of diesel fuel hydrocarbons by the strains was less intense in comparison with the n-alkane mixture. The strains showed differences in growth rate and consumption of the substrates, which suggests that they possess different mechanisms of hydrocarbon uptake.     

Construction of Rhodococcus expression vectors and expression of the aminoalcohol dehydrogenase gene in Rhodococcus erythropolis

NADP⁺-dependent aminoalcohol dehydrogenase (AADH) of Rhodococcus erythropolis MAK154 produces double chiral aminoalcohols, which are used as pharmaceuticals. However, the genetic manipulation of Rhodococcus strains to increase their production of such industrially important enzymes is not well studied. Therefore, I aimed to construct Rhodococcus expression vectors, derived from the Rhodococcus–Escherichia coli shuttle vector pRET1102, to express aadh. The plasmid pRET1102 could be transformed into many actinomycete strains, including R. erythropolis. The transformation ef?ciency for a species closely related to R. erythropolis was higher than that for other actinomycete strains. Promoters of various strengths, hsp, 1200rep, and TRR, were obtained from Gram-positive bacteria. The activity of TRR was stronger than that of hsp and 1200rep. The aadh-expressing plasmid pRET1172 with TRR could be transformed into many actinomycete strains to increase their AADH production. The Rhodococcus expression vector, pRET11100, constructed by removing aadh from the pRET1172 plasmid may be useful for bioconversion.     

The effect of hyperbaric oxygen on metabolism of the GABA shunt

Abstract— —The GABA-α-ketoglutarate transaminase pathway provides, in the brain, an alternative route for the conversion of α-ketoglutarate to succinate. In vitro experiments with rat brain homogenates and either [¹⁴C]GABA or [¹⁴C]α-ketoglutarate showed the percentage metabolism via the transaminase pathway to be about 17 per cent in air and 10 per cent oxygen at high pressure. Since the transaminase shunt was more sensitive to hyperbaric oxygen than the direct pathway, these results do not support the hypothesis of an alternative route operating under conditions of oxygen poisoning.     

Isolation and Characterization of Carbendazim-degrading Rhodococcus erythropolis djl-11

Carbendazim (methyl 1H-benzimidazol-2-yl carbamate) is one of the most widely used fungicides in agriculture worldwide, but has been reported to have adverse effects on animal health and ecosystem function. A highly efficient carbendazim-degrading bacterium (strain dj1-11) was isolated from carbendazim-contaminated soil samples via enrichment culture. Strain dj1-11 was identified as Rhodococcus erythropolis based on morphological, physiological and biochemical characters, including sequence analysis of the 16S rRNA gene. In vitro degradation of carbendazim (1000 mg·L⁻¹) by dj1-11 in minimal salts medium (MSM) was highly efficient, and with an average degradation rate of 333.33 mg·L⁻¹·d⁻¹ at 28°C. The optimal temperature range for carbendazim degradation by dj1-11 in MSM was 25–30°C. Whilst strain dj1-11 was capable of metabolizing cabendazim as the sole source of carbon and nitrogen, degradation was significantly (P<0.05) increased by addition of 12.5 mM NH₄NO₃. Changes in MSM pH (4–9), substitution of NH₄NO₃ with organic substrates as N and C sources or replacing Mg²⁺ with Mn²⁺, Zn²⁺ or Fe²⁺ did not significantly affect carbendazim degradation by dj1-11. During the degradation process, liquid chromatography-mass spectrometry (LC-MS) detected the metabolites 2-aminobenzimidazole and 2-hydroxybenzimidazole. A putative carbendazim-hydrolyzing esterase gene was cloned from chromosomal DNA of djl-11 and showed 99% sequence homology to the mheI carbendazim-hydrolyzing esterase gene from Nocardioides sp. SG-4G.     

Expression of acylamidase gene in Rhodococcus erythropolis strains

The expression of a new acylamidase gene from R. erythropolis TA37 was studied in Rhodococcus erythropolis strains. This acylamidase, as a result of its unique substrate specificity, can hydrolyse N-substituted amides (4′-nitroacetanilide, N-isopropylacrylamide, N′N-dimethylaminopropylacrylamide). A new expression system based on the use of the promoter region of nitrile hydratase genes from R. rhodochrous M8 was created to achieve constitutive synthesis of acylamidase in R. erythropolis cells. A fourfold improvement in the acylamidase activity of recombinant R. erythropolis cells as compared with the parent wild-type strain was obtained through the use of the new expression system.     

Studies on utilization of acetonitrile by Rhodococcus erythropolis A10

A petrochemical wastewater isolate, capable of utilizing high concentrations of acetonitrile and acetamide as the sole source of carbon and nitrogen was identified as Rhodococcus erythropolis A10. Cell-free extracts of acetonitrile-grown cells exhibited activities corresponding to nitrile hydratase (EC 4.2.1.84) and amidase (EC 3.5.1.4), which mediate the two-step breakdown of acetonitrile into acetic acid and ammonia. Studies indicated that both these enzymes in R. erythropolis A10 are intracellular, inducible and capable of hydrolysing a wide range of nitriles, including simple (acetonitrile, propionitrile), branched-chain (isobutyronitrile) and dinitrile (succinonitrile). The specific activity of the amidase was found to be several-fold higher than nitrile hydratase.