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PubMed1992

Spin trapping of free radical metabolites of carbon tetrachloride in vitro and in vivo: effect of acute ethanol administration.

A single dose of ethanol, when administered 18 hr prior to CCl4, potentiates the hepatotoxicity of the halocarbon. In these studies, spin trapping and electron spin resonance (ESR) spectroscopy methods were utilized to determine whether a single ethanol dose increased the metabolism of CCl4 to free radical intermediates. When hepatic microsomes from ethanol-treated or control rats were incubated with CCl4 and the spin trapping agent alpha-phenyl-N-tert-butylnitrone (PBN), the ESR signal of the trichloromethyl radical adduct of PBN was of similar intensity in both groups. The ethanol dose also failed to induce p-nitrophenol hydroxylase activity. When PBN and CCl4 were administered to rats, liver extracts contained ESR signals resulting primarily from the trichloromethyl radical adduct of PBN, and the signals were of similar intensity in both experimental groups. Higher concentrations of the carbon dioxide anion radical adduct of PBN were detected in plasma samples from ethanol-treated rats. However, when hepatocytes from ethanol-treated and control rats were incubated with PBN and CCl4, ESR signals of the carbon dioxide adduct were of similar intensity. These data suggest that the higher concentrations of the carbon dioxide adduct in the blood of ethanol-treated rats may be explained by early CCl4-induced damage to liver cell membranes, rather than increased rates of formation. The data in this report fail to support the hypothesis that a single dose of ethanol stimulates the hepatic metabolism of CCl4 to the trichloromethyl radical. Alternatively, ethanol may potentiate CCl4 toxicity by affecting some critical metabolic step subsequent to trichloromethyl radical formation.

Animals↗
PubMedDate not supplied

Role of ethanol exposure on cocaine metabolism in rat hepatocytes.

Cocaine remains a widely abused illicit substance in our society. Cocaine hepatotoxicity has been linked to cocaine metabolism. Cocaine can undergo hydrolytic inactivation via plasma and hepatic esterases or it can be N-oxidized by cytochrome P-450 and FAD-containing monooxygenases. Ethanol is frequently used in combination with cocaine. The presence of ethanol can affect the metabolism of other agents, depending on the dose and duration of exposure. In this investigation, hepatocytes isolated from male Sprague-Dawley rats were utilized to study the effect of ethanol exposure on cocaine metabolism. Hepatocytes were isolated using a two-step collagenase perfusion system. Hepatocytes (2 x 10(6) cells ml(-1)) were exposed to cocaine, ethanol or the combination of cocaine and ethanol for a 2-h period in a shaking water-bath at 30 oscillations per minute maintained at 37 degrees C. Sodium fluoride (NaF) was added to aliquots of cells which were removed from the incubation following 30, 60 and 120 min. The cells were homogenized on ice and immediately extracted for the quantification of cocaine, benzoylecognine, norcocaine and ethylcocaine by HPLC. Quantitative analysis revealed that there was a time-dependent increase in the disappearance of cocaine from hepatocytes. The rate of cocaine disappearance was not changed when ethanol was included in incubations containing cocaine. However, in the presence of ethanol there was a difference in the quantities of cocaine metabolites produced. When ethanol was included in incubations containing cocaine, the formation of norcocaine and benzoylecognine was less than that formed in hepatocytes exposed to cocaine alone. Additionally, when hepatocytes were exposed to cocaine in combination with ethanol, the formation of ethylcocaine was linear with time. This study revealed that in the presence of ethanol, cocaine qualitative metabolism is altered.

Animals↗
PubMedDate not supplied

Ethanol as a neurochemical surrogate of conventional reinforcers: the dopamine-opioid link.

Various lines of evidence support the view that ethanol is a neurochemical surrogate of conventional reinforcers, such as food and sex. In fact, ethanol activates central neuronal systems that utilize dopamine, opioids, and gamma-aminobutyric acid (GABA) as neurotransmitters and also are activated by conventional reinforcers. These neurotransmitter systems are likely to mediate specific aspects of ethanol's reinforcing properties. Activation of the mesolimbic dopamine and endogenous opioid systems might be the substrate of the incentive and rewarding (ergotropic) properties of ethanol (arousal, euphoria, motor stimulation) and of the process of acquiring ethanol-related secondary reinforcers (incentive learning) and ethanol self-administration habits. Stimulation of the endogenous GABAergic system might mediate the sedative and drive-reducing (trophotropic) properties of ethanol. The dopamine and opioid systems are largely interconnected. Thus, pharmacological blockade of the endogenous opioid system by mu- or delta-opioid receptor antagonists prevents ethanol's activation of the dopamine system and reduces ethanol consumption. This interaction might contribute to naltrexone's effectiveness in reducing alcohol craving in humans.

Animals↗
PubMed2006

Is using ethanol-glycine irrigating fluid monitoring and 'good surgical practice' enough to prevent harmful absorption during transurethral resection of the prostate?

OBJECTIVE: To evaluate the utility of using a tracer of 1% ethanol in 1.5% glycine for the early detection of irrigation fluid absorption during transurethral resection of the prostate (TURP). PATIENTS AND METHODS: In all, 126 men undergoing TURP were irrigated with a solution of 1% ethanol and 1.5% glycine; their expired air was tested for ethanol every 20 min, and again at the end of the procedure. Maximum absorption by the breath-ethanol reading was compared with the serum concentration of absorbed glycine (analysed by anion-exchange chromatography). RESULTS: Complete data on 120 men were assessed; 75% of the men absorbed irrigation fluid, with glycine levels above the normal range. The sodium levels tended to decrease with increasing glycine levels (Spearman's rank correlation coefficient, - 0.57; 120 men) and five men (4%) developed clinical features of the TUR syndrome. There was a weak correlation between breath-ethanol levels and serum glycine levels (Spearman's rank correlation coefficient, 0.54). The experience of the surgeon, the weight of the resected chips, and the operative duration were not significantly predictive of irrigation fluid absorption. CONCLUSIONS: A rising breath-ethanol level indicates irrigation fluid absorption. However, irrigating fluid absorption is unpredictable, supporting the case for alternative, potentially safer irrigants.

Aged↗
PubMed2003

Toward consistent and productive complex media for industrial fermentations: studies on yeast extract for a recombinant yeast fermentation process.

Yeast extract (YE) is commonly used as a key component in the complex media for industrial fermentations. However, the lot-to-lot variation of this raw material frequently requires extensive "use testing" of many lots to identify only the few that support desired fermentation performance. Through extensive fermentation studies and chemical analyses, we have identified adenine and two metabolizable carbon sources, trehalose and lactate, as the principle components in YE that affect the production of a recombinant protein antigen by a yeast strain. Adenine is required for culture growth and the relationship between biomass and measured adenine can be expressed by a Michaelis-Menten model, while the slowly metabolized trehalose serves to maintain the energy supply to the continued antigen synthesis. The rapidly utilized lactate exerts an indirect positive effect by sparing some of the accumulated ethanol from being consumed for growth to being utilized in the product formation. The effects of these YE components are mutually dependent. Based on the database generated from 40 lots at laboratory scale, a relatively high level of carbon sources in YE (trehalose plus lactate, >9.5% w/w) and an intermediate level of adenine (0.14-0.24% w/w) appear to be the minimal requirement of a good lot for this recombinant yeast fermentation. Many poor lots were improved in lab fermenters by rational supplementation of trehalose, lactate, or adenine to compensate for their insufficiencies. At the large production scale, predictions based on adenine and trehalose/lactate contents in various YE lots used correlated reasonably well with culture growth and antigen yield, illustrating the feasibility of such a simple chemical/biochemical analysis as a rapid and reliable initial screening tool. Without incurring any compositional change to an established manufacturing medium, this study demonstrates an effective approach to achieve consistency in fermentations employing complex nutrients and to improve fermentation productivities supported by suboptimal lots of raw material.

Adenine↗
PubMed1996

Ethanol exposure reduces the density of the low-affinity nerve growth factor receptor (p75) on pheochromocytoma (PC12) cells.

Although ethanol is detrimental to the developing nervous system, the mechanism(s) by which ethanol produces neuronal damage is (are) not clear. One potential mechanism is ethanol-induced inhibition of neurotrophic support. This study utilized an in vitro model, pheochromocytoma PC12 cells, to examine the effect of ethanol on the nerve growth factor (NGF) receptor. NGF binding studies indicated that ethanol exposure (400 mg/dl for 4 days) reduced the density of the low-affinity (p75) NGF receptor on PC12 cells, but had no effect on the density of the high-affinity NGF receptor. The equilibrium dissociation constants (Kd) for both the low-affinity and high-affinity NGF receptors were unaffected by ethanol. Low-affinity NGF binding is mediated by the p75 component of the NGF receptor. Quantification of p75 by immunoprecipitation revealed that ethanol reduced the level of p75 in PC12 cells. However, Northern analysis indicated that the p75 mRNA was not reduced by ethanol exposure, raising the possibilities that ethanol inhibited translation of p75 or incorporation of the p75 protein into the plasma membrane. This work is consistent with the hypothesis that ethanol's detrimental effects may be produced in part by inhibition of neurotrophic support at the receptor level.

Animals↗
PubMed2006

Maternal oral intake mouse model for fetal alcohol spectrum disorders: ocular defects as a measure of effect.

BACKGROUND: This work was conducted in an effort to establish an oral intake model system in which the effects of ethanol insult that occur during early stages of embryogenesis can be easily examined and in which agents that may modulate ethanol's teratogenicity can be readily tested in vivo. The model system described utilizes the alcohol deprivation effect to obtain teratogenic levels of maternal ethanol intake on days 7 and 8 of pregnancy in C57Bl/6J mice. Ocular defects including microphthalmia and uveal coloboma, which have previously been shown to result from ethanol administered by gavage or via intraperitoneal injection on these days, served as the developmental end point for this study. The ocular defects are readily identifiable and their degree of severity is expected to correlate with concurrently developing defects of the central nervous system (CNS). METHODS: Female C57Bl/6J mice were maintained on an ethanol-containing (4.8% v/v) liquid diet for 14 days and then mated during a subsequent abstinence period. Mice were then reexposed to ethanol on days 7 and 8 of pregnancy only. Control as well as ethanol-exposed dams were killed on their 14th day of pregnancy. Fetuses were then weighed, measured for crown rump length, photographed, and analyzed for ocular abnormalities. Globe size, palpebral fissure length, and pupil size and shape were noted for both the right and left eyes of all fetuses and informative comparisons were made. RESULTS: This exposure paradigm resulted in peak maternal blood alcohol concentrations that ranged from 170 to 220 mg/dL on gestational day (GD) 8. Compared with the GD 14 fetuses from the normal control group, the pair-fed, acquisition controls, as well as the ethanol-exposed fetuses, were developmentally delayed and had reduced weights. Confirming previous studies, comparison of similarly staged control and treated GD 8 embryos illustrated reductions in the size of the forebrain in the latter. Subsequent ocular malformations were noted in 33% of the right eyes and 25% of the left eyes of the 103 GD 14 ethanol-exposed fetuses examined. This incidence of defects is twice that observed in the control groups. Additionally, it was found that the palpebral fissure length is directly correlated with globe size. CONCLUSIONS: The high incidence of readily identifiable ocular malformations produced by oral ethanol intake in this model and their relevance to human fetal alcohol spectrum disorders (FASD) makes this an excellent system for utilization in experiments involving factors administered to the embryo that might alter ethanol's teratogenic effects. Additionally, the fact that early ethanol insult yields ocular and forebrain abnormalities that are developmentally associated allows efficient specimen selection for subsequent detailed analyses of CNS effects in this in vivo mammalian FASD model.

Abnormalities, Drug-Induced↗
PubMed2002

Investigations of outbreaks of contagious caprine pleuropneumonia in Eritrea.

Mycoplasmas were isolated from freeze-dried lung samples from goats from the western lowlands of Eritea suspected of being affected by contagious caprine pleuropneumonia. The goats belonged to two herds in which mortality and morbidity rates were high. Mycoplasma capricolum subsp. capripneumoniae was identified in most samples by the polymerase chain reaction and by conventional serological tests. The latex agglutination test detected more positive serum samples in both herds than did the complement fixation test. Following cloning, the isolates of M. capricolum subsp. capripneumoniae were analysed biochemically and shown to be metabolically similar. They oxidized glucose, N-acetylglucosamine, pyruvate and L-lactate with high affinity and mannose, glucosamine and 2-oxobutyrate with low affinity; they were unable to utilize maltose, trehalose, fructose or ethanol. Major improvements were seen in the growth yield of the Eritrean strains with the addition of pyruvate to the medium. Thus, it may be that organic acids are important energy sources for these strains and may be used in addition to or in place of glucose. In contrast to most other strains of the M. mycoides cluster, the Eritrean strains produced large amounts of hydrogen peroxide during the oxidation of NADH by lysed cells. This characteristic had previously been reported for strain M. F38, the type strain of M. capricolum subsp. capripneumoniae, although strain F38 did not metabolize sugars. Hydrogen peroxide has long been considered a pathogenicity factor in mycoplasma infections. This is the first isolation of M. capricolum subsp. capripneumoniae from Eritrea.

Animals↗
PubMed2002

Snf1 protein kinase regulates Adr1 binding to chromatin but not transcription activation.

The yeast transcriptional activator Adr1 controls the expression of genes required for ethanol, glycerol, and fatty acid utilization. We show that Adr1 acts directly on the promoters of ADH2, ACS1, GUT1, CTA1, and POT1 using chromatin immunoprecipitation assays. The yeast homolog of the AMP-activated protein kinase, Snf1, promotes Adr1 chromatin binding in the absence of glucose, and the protein phosphatase complex, Glc7.Reg1, represses its binding in the presence of glucose. A post-translational process is implicated in the regulation of Adr1 binding activity. Chromatin binding by Adr1 is not the only step in ADH2 transcription that is regulated by glucose repression. Adr1 can bind to chromatin in repressed conditions in the presence of hyperacetylated histones. To study steps subsequent to promoter binding we utilized miniAdr1 transcription factors to characterize Adr1-dependent transcription in vitro. Yeast nuclear extracts prepared from glucose-repressed and glucose-derepressed cells are equally capable of supporting miniAdr1-dependent transcription and pre-initiation complex formation. Nuclear extracts prepared from a snf1 mutant support miniAdr1-dependent transcription but are partially defective in the formation of pre-initiation complexes with Mediator components being particularly depleted. We conclude that Snf1 regulates Adr1-dependent transcription primarily at the level of chromatin binding.

Chromatin↗
PubMed2006

Acetobacter oeni sp. nov., isolated from spoiled red wine.

A bacterial strain, designated B13T, was isolated from spoiled red wine from the Dão region, Portugal. The strain was Gram-negative, strictly aerobic, rod-shaped and motile. Phylogenetic analysis on the basis of 16S rRNA gene sequences indicated that B13T belonged to the genus Acetobacter within the Alphaproteobacteria. The closest related species was Acetobacter aceti, with 98.4 % 16S rRNA gene sequence similarity. DNA-DNA hybridization showed that B13T constituted a taxon separate from the Acetobacter species with validly published names. The DNA G+C content of B13T was 58.1 mol%. Phenotypic characteristics of B13T allowed its differentiation from the recognized Acetobacter species. B13T produced 5-ketogluconic acid from glucose, but no 2-ketogluconic acid. It produced catalase, but no oxidase. It utilized glycerol, but not maltose, ethanol or methanol as carbon sources. On the basis of the results obtained, B13T represents a novel species for which the name Acetobacter oeni sp. nov. is proposed. The type strain is B13T (= LMG 21952T = CECT 5830T).

Acetobacter↗
PubMed1983

Effect of Sugar Concentration in Jerusalem Artichoke Extract on Kluyveromyces marxianus Growth and Ethanol Production.

The effect of inulin sugars concentration on the growth and ethanol production by Kluyveromyces marxianus UCD (FST) 55-82 was studied. A maximum ethanol concentration of 102 g/liter was obtained from 250 g of sugars per liter initial concentration. The maximum specific growth rate varied from 0.44 h at 50 g of sugar per liter to 0.13 h at 300 g of sugar per liter, whereas the ethanol yield remained almost constant at 0.45 g of ethanol per g of sugars utilized.

Journal Article↗
PubMed1984

Use of gas-liquid chromatography to determine the end products of growth of lactic Acid bacteria.

A simple gas-liquid chromatographic procedure for analyzing ethanol, acetic acid, acetoin, and racemic and meso-2,3-butylene glycol in broth media is described. Overnight broth cultures were filtered or centrifuged, and the filtrate or supernatant was treated with formic acid to aid separation of volatile fatty acids. Samples were then directly analyzed by gas-liquid chromatography on a 20% Tween 80-Chromosorb W-AW column and propionic acid as an internal standard. A complete analysis took ca. 8 min. The method can be used to distinguish homofermentative from heterofermentative lactic acid bacteria based on the level of ethanol produced and citrate-utilizing from non-citrate-utilizing lactic acid bacteria based on the levels of acetic acid produced. The method also has potential in distinguishing other bacterial fermentations. Of the 13 species of lactic acid bacteria tested, Streptococcus lactis subsp. diacetylactis was the major producer of 2,3-butylene glycol (total range, 0.3 to 3.5 mM), and, except for strain DRC1, both the racemic and meso isomers were produced in approximately equal amounts.

Journal Article↗
PubMed2003

Hydrogenotrophic methanogenesis by moderately acid-tolerant methanogens of a methane-emitting acidic peat.

The emission of methane (1.3 mmol of CH(4) m(-2) day(-1)), precursors of methanogenesis, and the methanogenic microorganisms of acidic bog peat (pH 4.4) from a moderately reduced forest site were investigated by in situ measurements, microcosm incubations, and cultivation methods, respectively. Bog peat produced CH(4) (0.4 to 1.7 micro mol g [dry wt] of soil(-1) day(-1)) under anoxic conditions. At in situ pH, supplemental H(2)-CO(2), ethanol, and 1-propanol all increased CH(4) production rates while formate, acetate, propionate, and butyrate inhibited the production of CH(4); methanol had no effect. H(2)-dependent acetogenesis occurred in H(2)-CO(2)-supplemented bog peat only after extended incubation periods. Nonsupplemented bog peat initially produced small amounts of H(2) that were subsequently consumed. The accumulation of H(2) was stimulated by ethanol and 1-propanol or by inhibiting methanogenesis with bromoethanesulfonate, and the consumption of ethanol was inhibited by large amounts of H(2); these results collectively indicated that ethanol- or 1-propanol-utilizing bacteria were trophically associated with H(2)-utilizing methanogens. A total of 10(9) anaerobes and 10(7) hydrogenotrophic methanogens per g (dry weight) of bog peat were enumerated by cultivation techniques. A stable methanogenic enrichment was obtained with an acidic, H(2)-CO(2)-supplemented, fatty acid-enriched defined medium. CH(4) production rates by the enrichment were similar at pH 4.5 and 6.5, and acetate inhibited methanogenesis at pH 4.5 but not at pH 6.5. A total of 27 different archaeal 16S rRNA gene sequences indicative of Methanobacteriaceae, Methanomicrobiales, and Methanosarcinaceae were retrieved from the highest CH(4)-positive serial dilutions of bog peat and methanogenic enrichments. A total of 10 bacterial 16S rRNA gene sequences were also retrieved from the same dilutions and enrichments and were indicative of bacteria that might be responsible for the production of H(2) that could be used by hydrogenotrophic methanogens. These results indicated that in this acidic bog peat, (i) H(2) is an important substrate for acid-tolerant methanogens, (ii) interspecies hydrogen transfer is involved in the degradation of organic carbon, (iii) the accumulation of protonated volatile fatty acids inhibits methanogenesis, and (iv) methanogenesis might be due to the activities of methanogens that are phylogenetic members of the Methanobacteriaceae, Methanomicrobiales, and Methanosarcinaceae.

Anaerobiosis↗
PubMedDate not supplied

[Desulfacinum subterraneum sp.nov.--a new thermophilic sulfate-reducing bacterium isolated from a high temperature oil field ].

A new thermophilic sulfate-reducing bacterium isolated from the high-temperature White Tiger oil field (Vietnam) is described. Cells of the bacterium are oval (0.4-0.6 by 0.6-1.8 microns), nonmotile, non-spore-forming, and gram-negative. Growth occurs at 45 to 65 degrees C (with an optimum at 60 degrees C) at NaCl concentrations of 0 to 50 g/l. In the course of sulfate reduction, the organism can utilize lactate, pyruvate, malate, fumarate, ethanol, salts of fatty acids (formate, acetate, propionate, butyrate, caproate, palmitate), yeast extract, alanine, serine, cysteine, and H2 + CO2 (autotrophically). In addition to sulfate, the bacterium can use sulfite, thiosulfate, and elemental sulfur as electron acceptors. In the absence of electron acceptors, the bacterium can ferment pyruvate and yeast extract (a yet unrecognized capacity of sulfate reducers) with the formation of acetate and H2. The G + C content of DNA is 60.8 mol %. The level of DNA-DNA hybridization of the isolate (strain 101T) and Desulfacinum infernum (strain B alpha G1T) is as low as 34%. Analysis of the nucleotide sequence of 16S rDNA places strain 101T in the phylogenetic cluster of the Desulfacinum species within the sulfate reducer subdivision of the delta subclass of Proteobacteria. All these results allowed the bacterium studied to be described as a new species, Desulfacinum subterraneum sp. nov., with strain 101 as the type strain.

Electron Transport↗
PubMed1995

Phenol degradation by Acinetobacter calcoaceticus NCIB 8250.

Acinetobacter calcoaceticus NCIB 8250 utilizes phenol as sole source of carbon and energy via an ortho-cleavage pathway. The presence of ethanol in mixed substrate cultivations repressed the utilization of phenol. In fed batch cultivation the phenol tolerance was increased at least 2-fold. Maximum degradation rates of 150 mg phenol/(1 h) and 280 mg phenol/(g h), respectively were observed. Phenol hydroxylase is induced by its substrate and in parallel the catechol-1,2-dioxygenase is detectable. The presence of active phenol hydroxylase is strongly connected with the phenol degradation. Using a spectrophotometric enzyme assay the partially purified phenol hydroxylase was characterized with respect to kinetic parameters. The apparent Km values for phenol, FAD and NADPH were estimated to be 147 microM, 35 microM and 416 microM, respectively. Both FAD and NADPH were essential for maximum activity of the cytoplasmically localized enzyme. No substrate inhibition of phenol hydroxylase by phenol was observed up to 0.8 mM. The pH and temperature optima were pH 7.8 and 33 degrees C, respectively. The partially purified enzyme showed a broad substrate specificity. It hydroxylated the three isomeric cresols, chlorophenols and methylated chlorophenols. Pyrogallol, 3,4-dihydroxy-L-phenylalanine and resorcinol were oxygenated with higher rates than phenol. With the exception of phenol all other enzyme substrates tested did not serve as growth substrates.

Acinetobacter calcoaceticus↗
PubMedDate not supplied

Evaluation of the Syva ETS-PLUS Ethyl Alcohol Assay with application to the analysis of antemortem whole blood, routine postmortem specimens, and synovial fluid.

A critical evaluation of the ETS-PLUS Ethyl Alcohol Assay indicates that it is simple to perform, sensitive enough to reliably detect ethanol above a concentration of 0.010 g/dL, and dynamic enough to reliably quantitate ethanol concentrations between 0.010 and 0.400 g/dL, correlating well with headspace gas chromatography. The technique is suitable for the analysis of relatively fresh (less than 1 month old) serum, plasma, urine, bile, vitreous humor, and gastric samples. With the aid of dilution, it is adaptable to the analysis of whole blood, relatively old specimens (more than 3 months old), viscous and highly pigmented plasma, bile, and the occasional extremely viscous vitreous humor specimens. Our evaluation further indicates that samples can remain in the system's covered sample wheel for up to 2 h without significant (less than 10%) diminution in ethanol concentration. This technique was further utilized to evaluate the suitability of synovial fluid as an alternative for vitreous humor.

Ethanol↗
PubMed1991

Ethanol production by recombinant Escherichia coli carrying genes from Zymomonas mobilis.

Efficient utilization of lignocellulosic feedstocks offers an opportunity to reduce the cost of producing fuel ethanol. The fermentation performance characteristics of recombinant Escherichia coli ATCC 11303 carrying the "PET plasmid" (pLOI297) with the lac operon controlling the expression of pyruvate decarboxylase (pdc) and alcohol dehydrogenase II (adhB) genes cloned from Zymomonas mobilis CP4 (Alterthum & Ingram, 1989) were assessed in batch and continuous processes with sugar mixtures designed to mimic process streams from lignocellulosic hydrolysis systems. Growth was pseudoexponential at a rate (generation time) of 1.28 h at pH 6.8 and 1.61 h at pH 6.0. The molar growth yields for glucose and xylose were 17.28 and 7.65 g DW cell/mol, respectively (at pH 6.3 and 30 degrees C), suggesting that the net yield of ATP from xylose metabolism is only 50% compared to glucose. In pH-stat batch fermentations (Luria broth with 6% sugar, pH 6.3), glucose was converted to ethanol 4-6 times faster than xylose, but the glucose conversion rate was much less than can be achieved with comparable cell densities of Zymomonas. Sugar-to-ethanol conversion efficiencies in nutrient-rich, complex LB medium were near theoretical at 98 and 88% for glucose and xylose, respectively. The yield was 10-20% less in a defined-mineral-salts medium. Acetate at a concentration of 0.1M (present in lignocellulosic hydrolysates from thermochemical processing) inhibited glucose utilization (about 50%) much more than xylose, and caused a decrease in product yield of about 30% for both sugars. With phosphate-buffered media (pH 7), glucose was a preferred substrate in mixtures with a ratio of hexose to pentose of 2.3 to 1. Xylose was consumed after glucose, and the product yield was less (0.37 g/g). Under steady-state conditions of continuous culture, the specific productivity ranged from 0.76-1.24 g EtOH/g cell/h, and the maximum volumetric productivity, 2.5 g EtOH/L/h, was achieved with a rich complex LB medium (glucose) at pH 6.0 (30 degrees C) and ethanol at 1.63% (v/v). Growth and fermentation were poor in a buffered-wood (aspen) "hemicellulose hydrolysate" containing 4% xylose and 0.1M acetate with added thiamine and mineral salts.

Alcohol Dehydrogenase↗
PubMed1978

Stimulation of lipase production during bacterial growth on alkanes.

Acinetobacter lwoffi strain O(16), a facultative psychrophile, can grow on crude oil, hexadecane, octadecane, and most alkanes when tested at 20 but not at 30 degrees C. Growth occurred on a few alkanes at 30 degrees C but after a longer lag than at 20 degrees C. Cells grown on alkanes as sole carbon sources had high levels of cell-bound lipase. In contrast, previous work has shown that those grown on complex medium produced cell-free lipase and those grown on defined medium without alkanes produced little or no lipase. Low concentrations of the detergent Triton X-100 caused the liberation of most of the lipase activity of alkane-grown cells and increased total lipase activity. When ethanol and hexadecane were both present in a mineral medium, diauxic growth occurred; until the ethanol was completely used up, hexadecane was not utilized, and the lipase activity was very low. When growth on hexadecane began, lipase activity increased, reaching a level 50- to 100-fold higher than that of cells growing on ethanol. A similar pattern of lipase formation and hexadecane utilization was observed with Pseudomonas aeruginosa. Whenever A. lwoffi and other bacteria degraded alkanes they exhibited substantial lipase activity. Not all bacteria that produced lipase, however, could attack alkanes. Bacteria that could not produce lipase did not attack alkanes. The results suggest that a correlation may exist between lipase formation and alkane utilization.

Acinetobacter↗