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过量的副产物形成 工程酿酒酵母菌株的低异丁醇产量的关键因素-外文文献论文翻译

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发布于 2017-1-28 18:13:34 | 显示全部楼层 |阅读模式
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外文标题: Excessive by-product formation: A key contributor to low isobutanol yields of engineered Saccharomyces cerevisiae strains
外文摘要: It is theoretically possible to engineer Saccharomyces cerevisiae strains in which isobutanol is the pre- dominant catabolic product and high-yielding isobutanol-producing strains are already reported by in- dustry. Conversely, isobutanol yields of engineered S. cerevisiae strains reported in the scientific literature typically remain far below 10% of the theoretical maximum. This study explores possible reasons for these suboptimal yields by a mass-balancing approach. A cytosolically located, cofactor-balanced iso- butanol pathway, consisting of a mosaic of bacterial enzymes whose in vivo functionality was confirmed by complementation of null mutations in branched-chain amino acid metabolism, was expressed in S. cerevisiae. Product formation by the engineered strain was analysed in shake flasks and bioreactors. In aerobic cultures, the pathway intermediate isobutyraldehyde was oxidized to isobutyrate rather than
reduced to isobutanol. Moreover, significant concentrations of the pathway intermediates 2,3-dihy- droxyisovalerate and α-ketoisovalerate, as well as diacetyl and acetoin, accumulated extracellularly. While the engineered strain could not grow anaerobically, micro-aerobic cultivation resulted in iso-
butanol formation at a yield of 0.01870.003 mol/mol glucose. Simultaneously, 2,3-butanediol was produced at a yield of 0.64970.067 mol/mol glucose. These results identify massive accumulation of pathway intermediates, as well as overflow metabolites derived from acetolactate, as an important, previously underestimated contributor to the suboptimal yields of ‘academic’ isobutanol strains. The observed patterns of by-product formation is consistent with the notion that in vivo activity of the iron– sulphur-cluster-requiring enzyme dihydroxyacid dehydratase is a key bottleneck in the present and previously described ‘academic’ isobutanol-producing yeast strains.
英关键词: Saccharomyces cerevisiae Isobutanol Catabolic pathway By-product formation 2,3-butanediol Diacetyl
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译文标题: 过量的副产物形成: 工程酿酒酵母菌株的低异丁醇产量的关键因素
译文概要: -
译文摘要: 酿酒酵母菌株主要的分解代谢产物是异丁醇,工程改造酿酒酵母菌株在理论上是可行的, 工业上也早有能够大量产出异丁醇的菌株的报道。与其相反,科学文献中报道的经过改造的酿酒酵母一般只能产出远远低于理论上最大值的10%的异丁醇。通过质量平衡法,本文研究探索造成次优产量的可能原因。位于细胞溶胶中辅因子平衡的异丁醇生产途径在酿酒酵母中表达,这种途径包含不同细菌酵母的混杂,支链氨基酸代谢中无效突变的互补确认这些细菌在活体中的功能。在摇瓶和生物反应器中分析工程菌株是如何形成产物的。在需氧培养物中,中间物异丁醛被氧化成异丁酸而不是还原成异丁醇。此外,高度集中的中间物2,3-二羟基异戊酸,α-酮异戊酸,二乙酰和乙偶姻在细胞外积聚。而工程菌株不能厌氧生长,微氧培养使异丁醇产量保持在0.018±0.003摩尔/每摩尔葡萄糖。同时,2,3-丁二醇的产量保持在0.649±0.067摩尔/每摩尔葡萄糖。本文研究将中间物的积聚和乙酰乳酸溢出的代谢物判断为重要因素,这些因素在之前未得到重视.造成学术中异丁醇菌株的次好产量。现在和之前所说的“学术性”生产异丁醇的酵母菌株的关键瓶颈是铁硫簇酶二羟酸脱水酶在活体内的活性,这一概念与观察到的副产物形成的方式相符。
译文格式: WORD
中关键词: 关键词: 酿酒酵母 分解代谢途径 副产物形成 2,3-丁二醇 二乙酰
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