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增强酿酒酵母对单萜的耐受性对于利用其生产单萜和利用含有单萜的生物质均具有重要意义.深入了解酿酒酵母应对单萜胁迫机理有助于构建一株较高单萜耐受性的酵母菌株,该菌株将有助于更高效率的单萜生产效率.研究表明,单萜会破坏酿酒酵母体内的氧化还原平衡,造成活性氧积累并进而导致菌体死亡.为了应对单萜诱发氧胁迫造成的损伤,酿酒酵母需要系统提升其抗氧化能力.本文归纳了酿酒酵母耐受多种典型单萜化合物胁迫机制的研究进展,并从酿酒酵母自身抗氧化机制方面,介绍了酿酒酵母应对氧胁迫的策略,并提出了进一步研究的方向. 相似文献
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萜类化合物具有可观的商业价值,但生产过程复杂,产量低,利用微生物异源合成萜类化合物已成为热点。谷氨酸棒状杆菌内含合成萜类色素的途径,具有异源合成萜类化合物的天然优势和研究前景。首次对谷氨酸棒状杆菌合成萜类化合物进行了综述,从萜类合成途径、关键酶和全局调控机制三个方面进行了途经介绍。概述了谷氨酸棒状杆菌中单萜、倍半萜、四萜类化合物的异源合成,并对利用谷氨酸棒状杆菌高效合成萜类化合物所需解决的问题进行讨论,为谷氨酸棒状杆菌高效合成萜类化合物提供建议。 相似文献
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植物萜类化合物广泛应用于食品、医药、化妆品、农业等行业,在人们生活中起着越来越重要的作用,但因植物资源有限、生长缓慢、提取工艺复杂、生产成本高等影响,萜类物质在应用上受到很大限制。酵母作为一种简单的真核生物,不但具有遗传背景清晰、生长快、容易操作等优点,而且其本身存在萜类合成途径。因此,酵母常被用作宿主菌,在不影响正常生长的情况下,优化其萜类合成途径,使之适合植物萜类药物的生物合成。本文就萜类的生物合成、近几年改造酵母生产萜类取得的成果和面临的一些问题及建议做一综述。 相似文献
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萜类化合物种类繁多、结构复杂,在医药、能源等领域具有重要的应用价值。当前萜类化合物主要是从植物中提取或化学法合成,费效比较高,而微生物合成成本低、效率高,更具有发展潜力,但由于萜类代谢通路复杂、微生物自身代谢调控精细以致难以人为操控,多数萜类化合物尚未通过微生物合成获得可观的产量。对此,对提高微生物合成萜类化合物的策略进行综述,旨在为萜类化合物在微生物中的生产与研究提供参考。 相似文献
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Carrau FM Medina K Boido E Farina L Gaggero C Dellacassa E Versini G Henschke PA 《FEMS microbiology letters》2005,243(1):107-115
This paper reports the production of monoterpenes, which elicit a floral aroma in wine, by strains of the yeast Saccharomyces cerevisiae. Terpenes, which are typical components of the essential oils of flowers and fruits, are also present as free and glycosylated conjugates amongst the secondary metabolites of certain wine grape varieties of Vitis vinifera. Hence, when these compounds are present in wine they are considered to originate from grape and not fermentation. However, the biosynthesis of monoterpenes by S. cerevisiae in the absence of grape derived precursors is shown here to be of de novo origin in wine yeast strains. Higher concentration of assimilable nitrogen increased accumulation of linalool and citronellol. Microaerobic compared with anaerobic conditions favored terpene accumulation in the ferment. The amount of linalool produced by some strains of S. cerevisiae could be of sensory importance in wine production. These unexpected results are discussed in relation to the known sterol biosynthetic pathway and to an alternative pathway for terpene biosynthesis not previously described in yeast. 相似文献
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【目的】研究酿酒酵母(Saccharomycesc erevisiae)中乙酰辅酶A合成酶基因ACS1和ACS2的生理作用。【方法】将来源于S.cerevisiae的ACS1和ACS2分别进行过量表达,研究过量表达ACS1和ACS2后S.cerevisiae胞内乙酰辅酶A含量、ATP水平、甲羟戊酸途径转录和乙醇耐受性等生理学特性变化。【结果】与出发菌株相比,过量表达ACS1和ACS2使得:(1)胞内乙酰辅酶A含量提高了2.19倍(ACS1)和5.02倍(ACS2);(2)胞内ATP含量提高了3.93倍(ACS1)和2.05倍(ACS2);(3)甲羟戊酸途径8个关键基因表达量显著上调;(4)S.cerevisiae对乙醇胁迫抵御能力显著增强。过量表达ACS1对乙醇胁迫的耐受能力强于过量表达ACS2。【结论】增加胞内乙酰辅酶A的含量可以显著增加甲羟戊酸途径碳代谢流量,并增强S.cerevisiae对发酵过程主要副产物乙醇的耐受能力。 相似文献
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Kalaivani Paramasivan 《Critical reviews in biotechnology》2017,37(8):974-989
Terpenes are natural products with a remarkable diversity in their chemical structures and they hold a significant market share commercially owing to their distinct applications. These potential molecules are usually derived from terrestrial plants, marine and microbial sources. In vitro production of terpenes using plant tissue culture and plant metabolic engineering, although receiving some success, the complexity in downstream processing because of the interference of phenolics and product commercialization due to regulations that are significant concerns. Industrial workhorses’ viz., Escherichia coli and Saccharomyces cerevisiae have become microorganisms to produce non-native terpenes in order to address critical issues such as demand-supply imbalance, sustainability and commercial viability. S. cerevisiae enjoys several advantages for synthesizing non-native terpenes with the most significant being the compatibility for expressing cytochrome P450 enzymes from plant origin. Moreover, achievement of high titers such as 40?g/l of amorphadiene, a sesquiterpene, boosts commercial interest and encourages the researchers to envisage both molecular and process strategies for developing yeast cell factories to produce these compounds. This review contains a brief consideration of existing strategies to engineer S. cerevisiae toward the synthesis of terpene molecules. Some of the common targets for synthesis of terpenes in S. cerevisiae are as follows: overexpression of tHMG1, ERG20, upc2-1 in case of all classes of terpenes; repression of ERG9 by replacement of the native promoter with a repressive methionine promoter in case of mono-, di- and sesquiterpenes; overexpression of BTS1 in case of di- and tetraterpenes. Site-directed mutagenesis such as Upc2p (G888A) in case of all classes of terpenes, ERG20p (K197G) in case of monoterpenes, HMG2p (K6R) in case of mono-, di- and sesquiterpenes could be some generic targets. Efforts are made to consolidate various studies (including patents) on this subject to understand the similarities, to identify novel strategies and to contemplate potential possibilities to build a robust yeast cell factory for terpene or terpenoid production. Emphasis is not restricted to metabolic engineering strategies pertaining to sterol and mevalonate pathway, but also other holistic approaches for elsewhere exploitation in the S. cerevisiae genome are discussed. This review also focuses on process considerations and challenges during the mass production of these potential compounds from the engineered strain for commercial exploitation. 相似文献
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In a foregoing paper we have shown the presence in the yeast Saccharomyces cerevisiae of an enzyme catalyzing the hydrolysis of L-gamma-glutamyl-p-nitroanilide, but apparently distinct from gamma-glutamyltranspeptidase. The cellular level of this enzyme was not regulated by the nature of the nitrogen source supplied to the yeast cell. Purification was attempted, using ion exchange chromatography on DEAE Sephadex A 50, salt precipitations and successive chromatographies on DEAE Sephadex 6B and Sephadex G 100. The apparent molecular weight of the purified enzyme was 14,800 as determined by gel filtration. As shown by kinetic studies and thin layer chromatography, the enzyme preparation exhibited only hydrolytic activity against gamma-glutamylarylamide and L-glutamine with an optimal pH of about seven. Various gamma-glutamylaminoacids, amides, dipeptides and glutathione were inactive as substrates and no transferase activity was detected. The yeast gamma-glutamylarylamidase was activated by SH protective agents, dithiothreitol and reduced glutathione. Oxidized glutathione, ophtalmic acid and various gamma-glutamylaminoacids inhibited competitively the enzyme. The activity was also inhibited by L-gamma-glutamyl-o-(carboxy)phenylhydrazide and the couple serine-borate, both transition-state analogs of gamma-glutamyltranspeptidase. Diazooxonorleucine, reactive analog of glutamine, inactivated the enzyme. The physiological role of yeast gamma-glutamylarylamidase-glutaminase is still undefined but is most probably unrelated to the bulk assimilation of glutamine by yeast cells. 相似文献
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Asadollahi MA Maury J Møller K Nielsen KF Schalk M Clark A Nielsen J 《Biotechnology and bioengineering》2008,99(3):666-677
The yeast Saccharomyces cerevisiae was chosen as a microbial host for heterologous biosynthesis of three different plant sesquiterpenes, namely valencene, cubebol, and patchoulol. The volatility and low solubility of the sesquiterpenes were major practical problems for quantification of the excreted sesquiterpenes. In situ separation of sesquiterpenes in a two-phase fermentation using dodecane as the secondary phase was therefore performed in order to enable quantitative evaluation of different strains. In order to enhance the availability of the precursor for synthesis of sesquiterpenes, farnesyl diphosphate (FPP), the ERG9 gene which is responsible for conversion of FPP to squalene was downregulated by replacing the native ERG9 promoter with the regulatable MET3 promoter combined with addition of 2 mM methionine to the medium. This strategy led to a reduced ergosterol content of the cells and accumulation of FPP derived compounds like target sesquiterpenes and farnesol. Adjustment of the methionine level during fermentations prevented relieving MET3 promoter repression and resulted in further improved sesquiterpene production. Thus, the final titer of patchoulol and farnesol in the ERG9 downregulated strain reached 16.9 and 20.2 mg/L, respectively. The results obtained in this study revealed the great potential of yeast as a cell factory for production of sesquiterpenes. 相似文献
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Aidar D. Satroutdinov Hiroshi Kuriyama Harumi Kobayashi 《FEMS microbiology letters》1992,98(1-3):261-267
Short-period (40-50 min) synchronized metabolic oscillation was found in a continuous culture of yeast Saccharomyces cerevisiae under aerobic conditions at low-dilution rates. During oscillation, many parameters changed cyclically, such as dissolved oxygen concentration, respiration rate, ethanol and acetate concentrations in the culture, glycogen, ATP, NADH, pyruvate and acetate concentrations in the cells. These changes were considered to be associated with glycogen metabolism. When glycogen was degraded, the respiro-fermentative phase was observed, in which ethanol was produced and the respiration rate decreased. In this phase, the levels of intracellular pyruvate and acetate became minimum, ATP became high and intracellular pH at its lowest level. When glycogen metabolism changed from degradation to accumulation, the respiratory phase started, during which ethanol was re-assimilated from the culture and the respiration rate increased. Intracellular pyruvate and acetate became maximum, ATP decreased and the intracellular pH appeared high. These findings may indicate new aspects of the control mechanism of glycogen metabolism and how respiration and ethanol fermentation are regulated together under aerobic conditions. 相似文献
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Accumulation and secretion of beta-glucanases have been studied in vivo by using a thermosensitive secretory mutant of Saccharomyces cerevisiae blocked at the endoplasmic reticulum level (sec 18-1). When incubated at the restrictive temperature no accumulation of active glucanases was observed. Following a shift to permissive conditions in the presence of cycloheximide a rise in the internal activity took place. The increase in total glucanase activity was partially due to the activation of an exo-glucanase that hydrolyzes PNPG. It is concluded that glucanases are synthesized in inactive precursor forms and are converted to the active forms in their secretory pathway. 相似文献