Production of polymalic acid and malic acid by Aureobasidium pullulans fermentation and acid hydrolysis

Malic acid is a dicarboxylic acid widely used in the food industry and also a potential C4 platform chemical that can be produced from biomass. However, microbial fermentation for direct malic acid production is limited by low product yield, titer, and productivity due to end‐product inhibition. In this work, a novel process for malic acid production from polymalic acid (PMA) fermentation followed by acid hydrolysis was developed. First, a PMA‐producing Aureobasidium pullulans strain ZX‐10 was screened and isolated. This microbe produced PMA as the major fermentation product at a high‐titer equivalent to 87.6 g/L of malic acid and high‐productivity of 0.61 g/L h in free‐cell fermentation in a stirred‐tank bioreactor. Fed‐batch fermentations with cells immobilized in a fibrous‐bed bioreactor (FBB) achieved the highest product titer of 144.2 g/L and productivity of 0.74 g/L h. The fermentation produced PMA was purified by adsorption with IRA‐900 anion‐exchange resins, achieving a ～100% purity and a high recovery rate of 84%. Pure malic acid was then produced from PMA by hydrolysis with 2 M sulfuric acid at 85°C, which followed the first‐order reaction kinetics. This process provides an efficient and economical way for PMA and malic acid production, and is promising for industrial application. Biotechnol. Bioeng. 2013; 110: 2105–2113. © 2013 Wiley Periodicals, Inc.     

Lactobionic and cellobionic acid production profiles of the resting cells of acetic acid bacteria

Lactobionic acid was produced by acetic acid bacteria to oxidize lactose. Gluconobacter spp. and Gluconacetobacter spp. showed higher lactose-oxidizing activities than Acetobacter spp. Gluconobacter frateurii NBRC3285 produced the highest amount of lactobionic acid per cell, among the strains tested. This bacterium assimilated neither lactose nor lactobionic acid. At high lactose concentration (30%), resting cells of the bacterium showed sufficient oxidizing activity for efficient production of lactobionic acid. These properties may contribute to industrial production of lactobionic acid by the bacterium. The bacterium showed higher oxidizing activity on cellobiose than that on lactose and produced cellobionic acid.     

Lipoic acid and diabetes II: Mode of action of lipoic acid

Intraperitoneal administration of lipoic acid (10 mg/100 g) does not effect changes in serum insulin levels in normal and alloxan diabetic rats, while normalising increased serum pyruvate, and impaired liver pyruvic dehydrogenase characteristic of the diabetic state. Dihydrolipoic acid has been shown to participate in activation of fatty acids with equal facility as coenzyme A. Fatty acyl dihydrolipoic acid however is sparsely thiolyzed to yield acetyl dihydrolipoic acid. Also acetyl dihydrolipoic acid does not activate pyruvate carboxylase unlike acetyl coenzyme A. The reduced thiolysis of Β-keto fatty acyl dihydrolipoic acid esters and the lack of activation of pyruvic carboxylase by acetyl dihydrolipoic acid could account for the antiketotic and antigluconeogenic effects of lipoic acid     

果胶d-半乳糖醛酸生物转化制备黏酸研究进展

黏酸属于己糖二酸,可以由果胶的主要成分D-半乳糖醛酸氧化制备.黏酸结构、性质与葡萄糖二酸类似,可应用于重要平台化合物、聚合物、高分子材料的制备.与目前受到广泛关注的葡萄糖二酸合成相比,黏酸合成的研究工作尚处于起步阶段.果胶是一种廉价、丰富的可再生生物质资源,以果胶为原料生物转化制备黏酸具有重要的经济价值和环保意义.文中...     

产琥珀酸重组解脂酵母发酵副产物乙酸的代谢控制

琥珀酸是一种高附加值的有机酸,广泛用于食品、化工和农药领域。解脂酵母Yarrowia lipolytica作为新型强健的非传统酵母,近年来逐渐吸引了研究者的注意。前期通过基因敲除琥珀酸脱氢酶基因构建了一株产琥珀酸的重组解脂酵母PGC01003。由于糖酵解和TCA循环流量不协调,PGC01003分泌大量副产物乙酸,限制了琥珀酸产量的进一步提高。为降低乙酸的溢出,实现自然低pH值发酵生产琥珀酸,首先干扰旁路代谢,异源表达来自鼠沙门氏菌的乙酰辅酶A合酶,乙酸的产量下降至4.6 g/L,比对照降低了24.6%。而基因敲除乙酰辅酶A水解酶基因得到的重组菌PGC11505,发酵96 h乙酸分泌量只有0.4 g/L,琥珀酸产量提高到7.0 g/L,琥珀酸的转化率为0.30 g/g,为进一步构建高产琥珀酸的细胞工厂奠定基础。     

酸解法制取甘草次酸及其纯化工艺

以甘草酸单铵盐为原料,酸解制取甘草次酸并利用低温冷析法对其进行精制纯化.通过L9(34)正交试验,确定了酸解甘草次酸的最佳条件:H2SO4体积分数8％、料液比(g/mL)1:100、温度100℃、12 h,在此条件下,转化率可达80.24％:通过对比实验,获得了低温冷析法精制甘草次酸的纯化工艺:酸解产物经水洗、氯仿溶提后,在体积分数30％乙醇溶液中80℃热溶15 min,再在冰水中冷析10 min,最终得到甘草次酸的质量分数为95.79％,得率40.87％.     

Molecularly imprinted polymer using-p-hydroxybenzoic acid, p-hydroxyphenylacetic acid and p-hydroxyphenylpropionic acid as templates.

Molecularly imprinted polymers (MIPs) using p-hydroxybenzoic acid (p-HB), p-hydroxyphenylacetic acid (p-HPA) and p-hydroxyphenylpropionic acid (p-HPPA) as templates were synthesized. The performance of the templates and their analogues on polymer-based high performance liquid chromatography (HPLC) columns was studied. The imprinting effect of the MIP using p-HB as template is more obvious than that of MIP using either p-HPA or p-HPPA as template, and the mixture of p-HB and p-HPA can be well separated on the MIP using p-HB as template, but not on the blank. Interestingly, the recognition of MIP (p-HB as the template) to p-HB showed a synergistic effect. The retention factor of p-HB is not the sum of those of phenol and benzoic acid. We also found that the imprinting effect decreased when increasing the concentration of acetic acid in mobile phase. The possible reason is that acetic acid molecules occupied the binding sites of the polymer, thereby decreasing the concentration of binding sites. Furthermore, polymers, which showed specificity to 3,4-dihydroxybenzoic acid, can be prepared with p-HB as template. It is thus possible to synthesize a specific polymer for a compound that is either expensive or unstable by using a structurally similar compound as template.     

Analysis of creatinine, vanilmandelic acid, homovanillic acid and uric acid in urine by micellar electrokinetic chromatography

A simultaneous determination of vanilmandelic acid, homovanillic acid, creatinine and uric acid using capillary electrophoresis was investigated. The optimum conditions of buffer concentration, pH and surfactant concentration were studied, and high resolution was obtained using a 30 mM phosphate buffer (pH 7.0) containing 150 mM sodium dodecyl sulfate. The detection was by UV absorbance at 245 nm and the column was a fused-silica capillary of 67 cm×75 μm I.D.. The determination of these metabolites in human urine was completed within 15 min without any interferences.     

生物基乳酸生物转化研究进展

乳酸的发酵生产技术已取得了长足的进步,作为一种重要生物基化学品,乳酸除了可用于食品工业及生产聚乳酸外,亦可作为一种重要的平台化合物,用于生产丙烯酸、丙酮酸、1,2-丙二醇、乳酸酯等。文中重点综述了以生物基乳酸为原料经脱水、脱氢、还原及酯化反应生产乳酸衍生物的生物转化工艺,对该领域的发展趋势进行了展望。     

Docosahexaenoic acid synthesis from n-3 fatty acid precursors in rat hippocampal neurons

Docosahexaenoic acid (DHA), the most abundant n-3 polyunsaturated fatty acid in the brain, has important functions in the hippocampus. To better understand essential fatty acid homeostasis in this region of the brain, we investigated the contributions of n-3 fatty acid precursors in supplying hippocampal neurons with DHA. Primary cultures of rat hippocampal neurons incorporated radiolabeled 18-, 20-, 22-, and 24-carbon n-3 fatty acid and converted some of the uptake to DHA, but the amounts produced from either [1-¹⁴C]α-linolenic or [1-¹⁴C]eicosapentaenoic acid were considerably less than the amounts incorporated when the cultures were incubated with [1-¹⁴C]22:6n-3. Most of the [1-¹⁴C]22:6n-3 uptake was incorporated into phospholipids, primarily ethanolamine phosphoglycerides. Additional studies demonstrated that the neurons converted [1-¹⁴C]linoleic acid to arachidonic acid, the main n-6 fatty acid in the brain. These findings differ from previous results indicating that cerebral and cerebellar neurons cannot convert polyunsaturated fatty acid precursors to DHA or arachidonic acid. Fatty acid compositional analysis demonstrated that the hippocampal neurons contained only 1.1–2.5 mol% DHA under the usual low-DHA culture conditions. The relatively low-DHA content suggests that some responses obtained with these cultures may not be representative of neuronal function in the brain.     

GC-MS identification of abscisic acid and abscisic acid metabolites in seed of Vigna unguiculata

Abscisic acid, phaseic acid and 4′-dihydrophaseic acid were identified by GC-MS of derivatized (Me, MeTMSi) extracts from immature fruits of Vigna unguiculata. The fruits also contained some other ABA-related compounds, one of which might be epi-4′-dihydrophaseic acid while another was tentatively identified as 6′-hydroxymethylabscisic acid.     

一株耐受低pH、高浓度乳酸及琥珀酸菌株的筛选与鉴定

【目的】通过构建的人工耐酸系统,筛选耐受低pH值、乳酸及琥珀酸的菌株。【方法】构建人工耐酸系统长期驯化菌株,利用不同p H的酸性平板进行筛选,从环境中筛选出一株对低p H值、高浓度乳酸以及琥珀酸有很好耐受性的菌株。通过形态学特征、生理生化特征研究,并结合18S rDNA基因序列分析及分子系统发育树的构建结果,确定菌株的种类。【结果】经过酸性人工系统的长期驯化,筛选分离出一株耐受低pH值、高浓度乳酸以及琥珀酸的菌株WJ-2,经鉴定该菌株为酿酒酵母(Saccharomyces cerevisiae),其最适生长温度为30°C。酸性平板实验显示该菌株能够耐受pH2.5的酸性环境,同时对9%的乳酸及8%的琥珀酸也有很好的耐受性。另外,耐酸菌株WJ-2在pH 2.5、9%乳酸和8%琥珀酸的培养环境中仍能保持相对中性的细胞内pH值。【结论】通过构建人工酸性系统,成功筛选出一株对低pH值、高浓度乳酸以及琥珀酸具有耐受性的菌株——酿酒酵母菌WJ-2,该方法可为筛选具有特定耐受能力菌株提供一个新思路。     

Inverse correlation between jasmonic acid and salicylic acid during early wound response in rice

This study presents a kinetic analysis of the response to wounding in rice plants. In particular, jasmonic acid, salicylic acid, and lipoxygenase activity were measured in leaves of wounded rice plants during the early tillering phase. The results show that endogenous jasmonic acid transiently increases to a maximum 30 min after wounding (jasmonic acid burst) and lipoxygenase activity increases after the jasmonic acid burst, but not after the second smaller peak of endogenous jasmonic acid 23 h after wounding. In contrast, endogenous salicylic acid decreases during the jasmonic acid burst, such that the kinetic profiles of jasmonic acid and salicylic acid are inversely correlated during the early response to wounding. It is proposed here that the increase in endogenous jasmonic acid and the decrease in endogenous salicylic acid may contribute for establishing the efficient negative cross-talk between jasmonic acid and salicylic acid signaling pathways during the early response to wounding in rice.     

Sempervirenic acid,a diterpene acid from Solidago sempervirens

Sempervirenic acid, a new diterpene has been isolated from Solidago sempervirens and its structure determined by spectroscopic methods and chemical conversions to be 3β-acetoxy-labda-7,13-diene-15-oic acid.     

The problem of 4,5-dioxovaleric acid as a precursor of 5-aminolevulinic acid and chlorophyll in green algae

During chlorophyll biosynthesis, 4,5-dioxovaleric acid is supposed to be an intermediate between 2-oxoglutarate and 5-aminolevulinic acid. Although the occurrence of 4,5-dioxovaleric acid in cells and culture filtrates of unicellular green algae treated with levulinic acid has been previously reported, improvement of the analytical method now shows that 4,5-dioxovaleric acid does not occur in these organisms but arises due to interference of 5-aminolevulinic acid in 4,5-dioxovaleric acid analysis. The significance of 4,5-dioxovaleric acid as a free metabolite in 5-aminolevulinic acid biosynthesis must therefore be reconsidered.     

Stomatal responses to jasmonic acid, linolenic acid and abscisic acid in wild-type and ABA-deficient tomato plants

Wild-type and abscisic acid (ABA) -deficient (sitiens) tomato plants were used to analyse the effects of abscisic acid (ABA), butyric acid (BA), jasmonic acid (JA) and linolenic acid (LA) on assimilation and transpiration rates in detached leaves taking up those substances into the transpiration stream. BA did not affect assimilation and transpiration rates. ABA decreased assimilation and transpiration in both wild-type and ABA-deficient mutants. JA reduced the assimilation rate in both lines but induced a significant reduction of transpiration in the wild type only. The response to LA in both lines was slower than that to JA.     

Alanyl turnover from lipoteichoic acid to teichoic acid in Staphylococcus aureus

Abstract The metabolism of d -alanyl substituents of lipoteichoic acid (LTA) and teichoic acid was studied in Staphylococcus aureus . Double labelling with [³H]glycerol and d -[¹⁴C]alanine revealed that during the chase LTA was stable whereas its ¹⁴C label rapidly decreased. Half-time comparison indicated an enzyme- rather than a base-catalyzed process. Correlated with the loss of [¹⁴C]alanine from LTA was an increase of the radioactivity in wall-linked alanine ester which, after hydrolysis with HF, proved to be linked to teichoic acid. These results suggest that LTA-alanine is the donor for alanine esterification of teichoic acid. In connection with previous data we hypothesize that the loss of alanine from LTA is compensated by de novo incorporation.     

3-Hydroxy-3-phenylpropanoic acid is an intermediate in the biosynthesis of benzoic acid and salicylic acid but benzaldehyde is not

Stable-isotope-labelled (²H₆,¹⁸O) 3-hydroxy-3-phenylpropanoic acid, a putative intermediate in the biosynthesis of benzoic acid (BA) and salicylic acid (SA) from cinnamic acid, has been synthesized and administered to cucumber (Cucumis sativus L.) and Nicotiana attenuata (Torrey). Analysis of the products by gas chromatography-mass spectrometry revealed incorporation of labelling into BA and SA, but not into benzaldehyde. In a separate experiment, 3-hydroxy- 3-phenylpropanoic acid was found to be a metabolite of phenylalanine, itself the primary metabolic precursor of BA and SA. These data suggest that cinnamic acid chain shortening is probably achieved by β-oxidation, and that the proposed “non-oxidative” pathway of side-chain degradation does not function in the biosynthesis of BA and SA, in cucumber and N. attenuata. Received: 10 February 2000 / Accepted: 18 April 2000