Characterization of the stimulatory effects of PGF2alpha on the release of arachidonic acid

Fibroblasts derived from a rat carrageenin granuloma were cultured in the presence of radioactive arachidonic acid, palmitic acid and linoleic acid. More than 90% of each labeled fatty acid was incorporated into a phospholipid fraction by the cells in 18 hrs. Arachidonic acid was evenly incorporated into phosphatidylcholine and phosphatidylethanolamine, while both palmitic acid and linoleic acid were almost entirely incorporated into phosphatidylcholine. The position of phosphatidylcholine where the fatty acids were incorporated was different for each fatty acid. The ratio of the amount of fatty acid incorporated into the 2-position to the amount incorporated into the 1-position of phosphatidylcholine for each fatty acid was greater than 90% for arachidonic acid, 2:1 for palmitic acid and 5:1 for linoleic acid. In the case of phosphatidylethanolamine, most arachidonic acid (greater than 90%) was incorporated into the 2-position. PGF2alpha caused the stimulation of arachidonic acid release but not of palmitic acid and linoleic acid from pre-labeled fibroblasts. The serum in the medium was completely replaceable by bovine serum albumin. The effect of PGF2Alpha increased with an increasing concentration of bovine serum albumin, suggesting that serum only acts as a "trap" for released arachidonic acid. The effect of PGF2Alpha was greater than bradykinin, and no synergistic effect was seen, although an additive effect was observed. The effect of PGF2Alpha depended on the concentration of calcium ions under magnesium-supplemented conditions.     

Studies on the biochemistry of Penicillium charlesii. Influence of various dicarboxylic acids on galactocarolose synthesis

1. It has been shown that Penicillium charlesii continues to synthesize galactocarolose when l-malic acid, malonic acid, succinic acid, fumaric acid, maleic acid or oxaloglycollic acid is substituted for dl-tartaric acid in the Raulin-Thom nutrient medium. 2. The quantity of galactocarolose synthesized per g. of mycelia was markedly decreased by substitution of l-malic acid, malonic acid, succinic acid, fumaric acid or maleic acid for dl-tartaric acid. Substitution of oxaloglycollic acid for dl-tartaric acid did not depress the galactocarolose synthesized/g. of mycelia; however, the quantity of fungal mass formed was decreased approximately fivefold. 3. Based upon (14)C incorporation into galactocarolose, succinic acid, fumaric acid or malonic acid did not serve as direct precursors of galactose as did tartaric acid. Oxaloglycollic acid, l-malic acid and maleic acid were not tested. 4. The relative quantity of galactocarolose synthesized per g. of mycelia decreased as the concentration of diammonium dicarboxylate added to the growth medium was increased. Tartaric acid, oxaloglycollic acid, fumaric acid and malonic acid were tested. 5. The quantity of mycelia formed and the quantity of galactocarolose synthesized per g. of mycelia were greater when the growth medium contained l-tartrate than when it contained d-tartrate.     

Suppressive effect of alkyl ferulate on the oxidation of linoleic acid

The oxidation processes of linoleic acid in the presence of ferulic acid, and 1-pentyl, 1-hexyl and 1-heptyl ferulates were observed at various temperatures and different molar ratios of each additive to linoleic acid. The processes were analyzed based on a kinetic equation of the autocatalytic type to evaluate the oxidative rate constant, k, and the kinetic parameter, Y(0), by which the initiation period for the oxidation of linoleic acid was mainly governed. The k values for linoleic acid mixed with each of the alkyl ferulates were smaller than that for linoleic acid mixed with ferulic acid. The greater suppressive effect of the alkyl ferulates would be ascribable to their higher solubility in linoleic acid. Both the activation energy, E, and the frequency factor, k(0), for the oxidation of linoleic acid mixed with ferulic acid or pentyl ferulate decreased with increasing molar ratio of the additive to linoleic acid.     

A reassessment of the binding of napthaleneacetic acid by membrane preparations from maize

Naphthalene-1-acetic acid (NAA) binding by membrane fractions derived from maize has been re-evaluated. Using a computer curve-fitting procedure only one major type of NAA binding, in terms of binding affinity, could be identified. Auxins, antiauxins and structurally related compounds have been tested for their competitive effect on NAA binding and the inhibitor constants for a number of these have been determined. Extracts from various plant species have been examined for their NAA binding ability, but all showed much less binding than maize leaf or coleoptile preparations. The possibility of the NAA binding by maize extracts being due to a true hormone receptor is discussed.Abbreviations BA benzoic acid - CPIB p-chlorophenoxyisobutyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - DCB 2,4-dichlorobenzoic acid - IAA indolyl-3-acetic acid - NAA napthalene-1-acetic acid - 2-NAA napthalene-2-acetic acid - NAOA napthalene-2-oxyacetic acid - PA phenylacetic acid - PU phenylurea - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid - TIBA 2,3,5-triiodobenzoic acid     

Maturation of membrane function: transport of amino acid by rat erythroid cells.

The membrane changes which occur during cellular maturation of erythroid cells have been investigated. The transport of alpha-aminoisobutyric acid, alanine, and N-methylated-alpha-aminoisobutyric acid have been studied in the erythroblastic leukemic cell, the reticulocyte, and the erythrocyte of the Long-Evans rat. The dependence of amino acid transport on extracellular sodium concentration was investigated. Erythrocytes were found to transport these amino acids only by Na-independent systems. The steady state distribution ratio was less than 1. Reticulocytes were found to transport alpha-aminoisobutyric acid and alanine by Na-dependent systems, but only small amounts of N-methylated-alpha-aminoisobutyric acid. Small amounts of these amino acids were transported by Na-independent systems. The steady state distribution ratio was greater than one for Na-dependent transport. The erythroblastic leukemia cell, a model immature erythroid cell, showed marked Na-dependence (greater than 90%) for alpha-aminoisobutyric acid and alanine transport, and greater than 80% for the Na-dependent transport of N-methyl-alpha-aminoisobutyric acid. The steady state distribution ratio for the Na-dependent transport was greater than 4. In the erythroblastic leukemic cell, at least three Na-dependent systems are present: one includes alanine and alpha-aminoisobutyric acid, but excludes N-methyl-alpha-aminoisobutyric acid; one is for alpha-aminoisobutyric acid, alanine and also N-methyl-alpha-aminoisobutyric acid; and one is for N-methyl-alpha-aminoisobutyric acid alone. In the reticulocyte, the number of Na-dependent systems are reduced to two: one for alpha-aminoisobutyric acid and alanine; one for N-methyl-alpha-aminoisobutyric acid. In the erythrocytes, no Na-dependent transport was found. Therefore, maturation of the blast cell to the mature erythrocyte is characterized by a systematic loss in the specificity and number of transport system for amino acids.     

Augmenting effect of acetic acid for acidification on bactericidal activity of hypochlorite solution

AIMS: Bactericidal activity of chlorine solution is enhanced by weak acidification. We compared the effects of various acids on the bactericidal activity of hypochlorite solution to establish a method for safe and effective use of an acidic hypochlorite solution. METHODS AND RESULTS: The bactericidal activities of acidic hypochlorite solutions that had been adjusted to pH 5.0 with hydrochloric acid, acetic acid, citric acid, lactic acid, formic acid, phosphoric acid or sulphuric acid against Bacillus subtilis spores were compared. The acidic solutions prepared with hydrochloric acid and acetic acid showed the highest bactericidal activity, and all of the spores (5 x 106 cfu ml(-1)) were killed within 10 min. On the other hand, the solutions prepared with citric acid and lactic acid showed no bactericidal activity against any bacterial strains tested in this study despite the low pH. The amount of chlorine gas produced by the preparation using acetic acid was sixfold less than that produced from the preparation using hydrochloric acid. CONCLUSIONS: Acetic acid is the most suitable and safe acid for the preparation of an acidic hypochlorite solution. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide useful information for establishing a method for safe and effective use of an acidic hypochlorite solution.     

Tetrahydrofolate and other growth requirements of certain strains of Ruminococcus flavefaciens.

Two strains of Ruminococcus flavefaciens were studied. Each grew in a chemically defined minimal medium containing: minerals; ammonium sulfate as a nitrogen source; amino acids as a nitrogen source, a growth promotant(s) or as both; cellobiose as an energy and carbon source; isobutyric acid, isovaleric acid, carbonic acid, and bicarbonate as additional carbon sources; and biotin, thiamine, and tetrahydrofolic acid as vitamins. Tetrahydrofolic acid (5 ng/ml) served as a replacement for rumen fluid that was required in previous media tested for the growth of these bacteria. The present bacteria differ from many of the ruminococci previously studied in that they do not require either p-amino-benzoic acid or folic acid but do require tetrahydrofolic acid for maximum growth. Dihydrofolic acid and 5-methyltetrahydrofolic acid can substitute for tetrahydrofolic acid in minimal chemically defined medium. Thus, there must be extensive metabolic interaction between the microbes inhabitating the rumen, because the R. flavefaciens isolated had complex requirements for growth and yet was among the predominant bacteria in the rumen of cattle fed a simple vitamin B-deficient, nonprotein nitrogen, high-fiber, purified diet.     

Maturation of membrane function: Transport of amino acid by rat erythroid cells

The membrane changes which occur during cellular maturation of erythroid cells have been investigated. The transport of α-aminoisobutyric acid, alanine, and N-methylated-α-aminoisobutyric acid have been studied in the erythroblastic leukemic cell, the reticulocyte, and the erythrocyte of the Long-Evans rat. The dependence of amino acid transport on extracellular sodium concentration was investigated. Erythrocytes were found to transport these amino acids only by Na-independent systems. The steady state distribution ratio was less than 1. Reticulocytes were found to transport α-aminoisobutyric acid and alanine by Na-dependent systems, but only small amounts of N-methylated-α-aminoisobutyric acid. Small amounts of these amino acids were transported by Na-independent systems. The steady state distribution ratio was greater than one for Na-dependent transport. The erythroblastic leukemia cell, a model immature erythroid cell, showed marked Na-dependence (>90%) for α-aminoisobutyric acid and alanine transport, and >80% for the Na-dependent transport of N-methyl-α-aminoisobutyric acid. The steady state distribution ratio for the Na-dependent transport was >4. In the erythroblastic leukemic cell, at least three Na-dependent systems are present: one includes alanine and α-aminoisobutyric acid, but excludes N-methyl-α-aminoisobutyric acid; one is for α-aminoisobutyric acid, alanine and also N-methyl-α-aminoisobutyric acid; and one is for N-methyl-α-aminoisobutyric acid alone. In the reticulocyte, the number of Na-dependent systems are reduced to two: one for α-aminoisobutyric acid and alanine; one for N-methyl-α-aminoisobutyric acid. In the erythrocytes, no Na-dependent transport was found. Therefore, maturation of the blast cell to the mature erythrocyte is characterized by a systematic loss in the specificity and number of transport systems for amino acids.     

Synthesis and metabolism of arachidonyl- and eicosapentaenoyl-CoA in rat aorta

In studies on the metabolism of polyunsaturated fatty acids, acyl-CoA synthetase for 5,8,11,14-20:4 (arachidonic acid) and 5,8,11,14,17-20:5 (eicosapentaenoic acid) and the incorporation of these fatty acids into complex lipids and their conversion to CO2 were investigated in rat aorta. The activity of acyl-CoA synthetase was 35.9 for arachidonic acid and 63.0 for eicosapentaenoic acid (nmol/mg protein per 10 min) and the apparent Km values were 45 microM for arachidonic acid and 56 microM for eicosapentaenoic acid. Inhibition of eicosapentaenoyl-CoA synthesis by arachidonic acid was stronger than that of arachidonyl-CoA synthesis by eicosapentaenoic acid. Arachidonic acid and eicosapentaenoic acid were mostly incorporated into phospholipids. The incorporation of these fatty acids into cholesterol ester and their conversion to CO2 were less than those of palmitic acid, but their incorporation into triacyglycerol was greater. The incorporation of these fatty acids into phosphatidylserine + phosphatidylinositol and phosphatidylethanolamine was also greater than that of palmitic acid. The patterns of incorporation of arachidonic acid and eicosapentaenoic acid were similar. The physiological roles of these polyunsaturated fatty acids and the interference of eicosapentaenoic acid in arachidonic acid metabolism are discussed on the basis of these results.     

GLC analysis of Indian rapeseed-mustard to study the variability of fatty acid composition

Rapeseed-mustard is one of the most economically important oilseed crops in India. Speciality oils having high amounts of a specific fatty acid are of immense importance for both nutritional and industrial purposes. Oil high in oleic acid has demand in commercial food-service applications due to a long shelf-life and cholesterol-reducing properties. Both linoleic and linolenic acids are essential fatty acids; however, less than 3% linolenic acid is preferred for oil stability. High erucic acid content is beneficial for the polymer industry, whereas low erucic acid is recommended for food purposes. Therefore, it is important to undertake systematic characterization of the available gene pool for its variable fatty acid profile to be utilized for specific purposes. In the present study the Indian rapeseed-mustard germplasm and some newly developed low-erucic-acid strains were analysed by GLC to study the fatty acid composition in these lines. The GLC analysis revealed that the rapeseed-mustard varieties being commonly grown in India are characterized by high erucic acid content (30-51%) in the oil with low levels of oleic acid (13-23%). However, from among the recently developed low-erucic-acid strains, several lines were identified with comparatively high oleic acid (60-70%), moderate to high linoleic acid (13-40%) and low linolenic acid (< 10%) contents. Work is in progress at TERI (New Delhi, India) to utilize these lines for development of strains with particular fatty acid compositions for specific purposes.     

天冬氨酸提高乳酸乳球菌Lactococcus lactis NZ9000酸胁迫抗性的作用机制

【背景】乳酸菌作为重要的发酵微生物在应用过程中面临广泛存在的酸胁迫。【目的】确认天冬氨酸可有效提高乳酸乳球菌的酸胁迫抗性,通过解析天冬氨酸的作用机制,为进一步提高乳酸菌酸胁迫抗性提供可借鉴的思路。【方法】通过荧光定量PCR比较胁迫条件下天冬氨酸对L.lactisNZ9000产能和氨基酸代谢途径中关键基因转录水平的影响,并通过过量表达天冬酰胺酶增加胞内天冬氨酸的含量。【结果】天冬氨酸主要是在转氨酶的作用下生成草酰乙酸和谷氨酸。草酰乙酸参与三羧酸循环,为细胞提供更多的能量;谷氨酸经谷氨酸脱羧酶途径提高细胞的酸胁迫抗性。经pH4.0胁迫处理后,天冬氨酸使糖酵解和三羧酸循环产能途径中关键基因转录上调,胞内ATP含量为对照组的42倍;胞内谷氨酸含量为对照的1.99倍。通过过量表达天冬酰胺酶获得的重组菌株,在pH3.6条件下胁迫0.5h后,存活率约为对照组的11.11倍。【结论】在L. lactis NZ9000中探究了天冬氨酸提高酸胁迫抗性的作用机理,进一步完善了氨基酸代谢提高乳酸菌酸胁迫抗性的理论基础。     

Characterization of the stimulatory effects of PGF2α on the release of arachidonic acid

Fibroblasts derived from a rat carrageenin granuloma were cultured in the presence of radioactive arachidonic acid, palmitic acid and linoleic acid. More than 90% of each labeled fatty acid was incorporated into a phospholipid fraction by the cells in 18 hrs. Arachidonic acid was evenly incorporated into phosphatidylcholine and phosphatidylethanolamine, while both palmitic acid and linoleic acid were almost entirely incorporated into phosphatidylcholine. The position of phosphatidylcholine where the fatty acids were incorporated was different for each fatty acid. The ratio of the amount of fatty acid incorporated into the 2-position to the amount incorporated into the 1-position of phosphatidylcholine for each fatty acid was >90% for arachidonic acid, 2:1 for palmitic acid and 5:1 for linoleic acid. In the case of phosphatidylethanolamine, most arachidonic acid (>90%) was incorporated into the 2-position. PGF_2^α caused the stimulation of arachidonic acid release but not of palmitic acid and linoleic acid from pre-labeled fibroblasts.The serum in the medium was completely replaceable by bovine serum albumin. The effect of PGF_2^α increased with an increasing concentration of bovine serum albumin, suggesting that serum only acts as a ‘trap’ for released arachidonic acid. The effect of PGF_2^α was greater than bradykinin, and no synergistic effect was seen, although an additive effect was observed.The effect of PGF_2^α depended on the concentration of calcium ions under magnesium-supplemented conditions.     

Comparison of the requirements for ribonucleic acid synthesis with the requirements for deoxyribonucleic acid synthesis in animal tissues

Ribonucleic acid polymerase and deoxyribonucleic acid polymerase have been partially purified from bovine lymphosarcoma, lymph node, and thymus. An examination of the deoxyribonucleic acid requirements of the two enzymes indicates that “native” deoxyribonucleic acid is the preferred template for ribonucleic acid synthesis; heat-denatured deoxyribonucleic acid is considerably less active. The primer requirements for deoxyribonucleic acid synthesis differ: “native” deoxyribonucleic acid is usually inactive, while denatured deoxyribonucleic acid is active. The two enzymes also differ in pH optima and in their requirements for metal cofactors.     

Effect of L-Aspartic Acid and L-Glutamic Acid on Production of L-Proline

To elucidate the effect of aspartic acid on growth of Kurthia catenaforma during the proline fermentation, this organism was compared with other bacteria with respect to the rate of consumption of aspartic acid, and to the activities of enzymes concerned in the metabolism of aspartic acid. Although no marked difference in enzyme activities was observed, the aspartic acid consumption rate of K. catenaforma was markedly higher than that of other organisms. The consumption of glutamic acid by K. catenaforma was not detected at 24 hr of culture. The difference between the consumption of aspartic acid and glutamic acid in this strain might result from a difference in permeability to the amino acids. We considered that L-glutamic acid might substitute for L-aspartic acid if the uptake of glutamic acid could be increased. A number of detergents were screened for their effect on consumption of glutamic acid. Cetyltrimethylammonium bromide, sodium laurylphosphate, and polyoxyethylene sorbitan monolaurate were found to increase the transport rate of glutamic acid, but not of aspartic acid. A method of producing L-proline from glutamic acid was established with the aid of detergents.     

Ascorbic acid within chromaffin granules. In situ kinetics of norepinephrine biosynthesis

Ascorbic acid requirements for norepinephrine biosynthesis were investigated in intact bovine chromaffin granules using the physiologic substrate dopamine and a novel coulometric electrochemical detection high pressure liquid chromatography system for ascorbic acid. 10 mM external dopamine, 1 mM Mg-ATP, and 1 mM ascorbic acid produced maximal norepinephrine biosynthesis without granule lysis. When external ascorbic acid was omitted, intragranular ascorbic acid was consumed in a 1:1 ratio with respect to norepinephrine biosynthesis. The initial concentration of intragranular ascorbic acid was 10.5 mM, which was depleted in stepwise fashion to 15 lower concentrations over the range of 9.2-0.2 mM. Chromaffin granules containing these varying concentrations of intragranular ascorbic acid were then incubated with 1 mM exogenous ascorbic acid, and norepinephrine biosynthesis from dopamine was determined. The apparent Km of norepinephrine biosynthesis for intragranular ascorbic acid was 0.57 mM by Eadie-Hofstee analysis and 0.68 mM by Lineweaver-Burk analysis. These data indicate that intragranular ascorbic acid is available and required for norepinephrine biosynthesis, that ascorbic acid is a true co-substrate for dopamine beta-monooxygenase, and that intragranular ascorbic acid is maintained by extragranular ascorbic acid. Continued norepinephrine biosynthesis in granules is dependent on both intragranular and extragranular concentrations of the vitamin. Furthermore, in situ kinetics of dopamine beta-monooxygenase for ascorbic acid may be most accurately determined using intact granules and the true physiologic substrate.     

Effects of linoleic acid and mitogenic stimulation on the fatty acid composition of human lymphocytes

Perturbation of the fatty acid composition of human lymphocytes in vitro was investigated by addition of linoleic acid complexed to bovine serum albumin (BSA-LA) and by mitogenic stimulation with phytohaemagglutinin (PHA). BSA-LA resulted in a 45% increase in linoleic acid in phosphatidylethanolamine (PE) and over 100% in phosphatidylcholine (PC) in peripheral blood cells. Supplementation with BSA-LA in PHA-stimulated lymphocytes produced even greater changes: 100% increase in linoleic acid content for PE and over 300% for PC. There was a large decrease in oleic acid: 40% for PE and almost 100% in PC. Significant decreases in arachidonic acid occurred in both phospholipid fractions. PHA alone also altered membrane phospholipid fatty acid composition, with reductions in palmitic, stearic and linoleic acid for PE and increases in oleic acid and arachidonic acid (almost 100%). For PC, there were large decreases in stearic (40%), linoleic (30%) and arachidonic (40%) acids, together with an increase in oleic acid (65%). Cells supplemented with linoleic acid grown in the presence of PHA, compared with those grown in linoleic acid-supplemented medium alone, showed a 40% decrease in palmitic acid and a 55% increase in arachidonic acid in PE. For PC, there were large decreases in stearic acid (40%) and arachidonic acid (57%). Antibody-induced redistribution of surface molecules ('capping') was inhibited by some 14% after incubation with BSA-LA. However, no consistent alterations in PHA-induced cell proliferation were observed. These data suggest that profound alterations of membrane fatty acid composition occur spontaneously during the mitotic cycle, and may be further induced by experimental manipulation, without gross perturbation of cell function.     

不同晶型、旋光型氨基酸原料药的红外图谱分析

分析比较了 33种不同来源的氨基酸产品红外图谱的差异 ,其中丝氨酸、门冬氨酸、醋酸赖氨酸、谷氨酸 (白色结晶性粉末 )、苏氨酸、缬氨酸、丙氨酸、亮氨酸、脯氨酸、盐酸组氨酸、盐酸精氨酸、酪氨酸、胱氨酸等 13种与标准图谱完全一致 ;甲硫氨酸、盐酸赖氨酸、甘氨酸、谷氨酸 (白色结晶 )等 4种与标准图谱不一致 ,其原因是 :甘氨酸和谷氨酸由晶型不同造成 ,甲硫氨酸因旋光性不同而造成 ,盐酸赖氨酸与相应的生化试剂图谱一致。     

Metabolism of Benzoic Acid by Bacteria: 3,5- Cyclohexadiene-1,2-Diol-1-Carboxylic Acid Is an Intermediate in the Formation of Catechol

3,5-Cyclohexadiene-1,2-diol-1-carboxylic acid (1,2-dihydro-1,2-dihydroxy-benzoic acid) is converted enzymatically to catechol in cell extracts from Acinetobacter, Alcaligenes, Azotobacter, and three Pseudomonas species. This enzymatic activity is present only in cultures which have been grown in the presence of benzoic acid, and which convert benzoic acid to catechol rather than to protocatechuic acid. The reaction is assayed by the concomitant formation of reduced nicotinamide adenine dinucleotide from nicotinamide adenine dinucleotide. The conversion of [(14)C]benzoic acid to [(14)C]dihydrodihydroxybenzoic acid is demonstrated in cell extracts. A scheme for the conversion of benzoic acid to catechol in bacteria is presented, involving the formation of dihydrodihydroxybenzoic acid from benzoic acid by a dioxygenase which is unstable in cell extracts, followed by the dehydrogenation and decarboxylation of dihydrodihydroxybenzoic acid to catechol by a previously undescribed enzyme. Experiments with anthranilic acid and phthalic acid suggest that dihydrodihydroxybenzoic acid is a metabolite unique to benzoic acid metabolism. Two new methods for assaying benzoic acid dioxygenase are suggested.     

紫色小白菜有机酸的提取优化及UPLC定量分析

为建立一种紫色小白菜中精准的有机酸提取及定性定量分析方法。本研究在单因素试验的基础上,采用Box-Behnken的中心组合试验设计原理,设计响应面试验优化紫色小白菜有机酸的提取工艺。结果表明,紫色小白菜有机酸提取的最优工艺参数为:乙醇浓度73%,料液比1∶21,超声时间11 min,超声温度70℃。通过超高效液相色谱法(ultra performance liquid chromatography,UPLC)对紫色小白菜叶片和叶柄部位有机酸进行定性定量分析,检测出苹果酸、柠檬酸、丙二酸、琥珀酸和酒石酸,其中苹果酸含量最高,分别为15.968、5.019 mg/g;其次为柠檬酸,分别为9.293、1.385 mg/g。定性定量结果表明,紫色小白菜叶片及叶柄部位含有丰富有机酸类物质,叶片部位苹果酸、柠檬酸、丙二酸、酒石酸含量均高于叶柄部位,而琥珀酸含量较低。     

碳酸盐对谷氨酸产生菌在缺氧条件下产有机酸的影响

考察谷氛酸产生菌在缺氧条件下积累L-乳酸和琥珀酸的情况.结果表明:在缺氧条件下,嗜乙酰乙酸棒杆菌(Corynebacterium acetoacidophilum)ATCC 13870积累有机酸的浓度随菌体密度的增大而增加,其中琥珀酸和乳酸积累的最适pH分别为7.5和8.0,最高质量浓度分别为22.5和60g/L.碳酸盐是影响产酸与有机酸分布的主要因素.比较ATCC 13870在NaHC03浓度为40和400mmol/L时的代谢通量,发现后者合成琥珀酸的代谢通量比前者提高了214.1%,合成乳酸的代谢通量降低了61.8%,说明PEP节点处的代谢通量分配明显受NaHCO3浓度的影响,而PYR节点受环境因素的影响不明显.