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首页> 外文期刊>Applied Microbiology >Contribution of Complex I NADH Dehydrogenase to Respiratory Energy Coupling in Glucose-Grown Cultures of Ogataea parapolymorpha
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Contribution of Complex I NADH Dehydrogenase to Respiratory Energy Coupling in Glucose-Grown Cultures of Ogataea parapolymorpha

机译：复合物I NADH脱氢酶对葡萄糖生长培养物呼吸能耦合的贡献

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摘要

The thermotolerant yeast Ogataea parapolymorpha (formerly Hansenula polymorpha ) is an industrially relevant production host that exhibits a fully respiratory sugar metabolism in aerobic batch cultures. NADH-derived electrons can enter its mitochondrial respiratory chain either via a proton-translocating complex I NADH-dehydrogenase or via three putative alternative NADH dehydrogenases. This respiratory entry point affects the amount of ATP produced per NADH/O_(2) consumed and therefore impacts the maximum yield of biomass and/or cellular products from a given amount of substrate. To investigate the physiological importance of complex I, a wild-type O. parapolymorpha strain and a congenic complex I-deficient mutant were grown on glucose in aerobic batch, chemostat, and retentostat cultures in bioreactors. In batch cultures, the two strains exhibited a fully respiratory metabolism and showed the same growth rates and biomass yields, indicating that, under these conditions, the contribution of NADH oxidation via complex I was negligible. Both strains also exhibited a respiratory metabolism in glucose-limited chemostat cultures, but the complex I-deficient mutant showed considerably reduced biomass yields on substrate and oxygen, consistent with a lower efficiency of respiratory energy coupling. In glucose-limited retentostat cultures at specific growth rates down to ～0.001 h~(?1), both O. parapolymorpha strains showed high viability. Maintenance energy requirements at these extremely low growth rates were approximately 3-fold lower than estimated from faster-growing chemostat cultures, indicating a stringent-response-like behavior. Quantitative transcriptome and proteome analyses indicated condition-dependent expression patterns of complex I subunits and of alternative NADH dehydrogenases that were consistent with physiological observations.IMPORTANCE Since popular microbial cell factories have typically not been selected for efficient respiratory energy coupling, their ATP yields from sugar catabolism are often suboptimal. In aerobic industrial processes, suboptimal energy coupling results in reduced product yields on sugar, increased process costs for oxygen transfer, and volumetric productivity limitations due to limitations in gas transfer and cooling. This study provides insights into the contribution of mechanisms of respiratory energy coupling in the yeast cell factory Ogataea parapolymorpha under different growth conditions and provides a basis for rational improvement of energy coupling in yeast cell factories. Analysis of energy metabolism of O. parapolymorpha at extremely low specific growth rates indicated that this yeast reduces its energy requirements for cellular maintenance under extreme energy limitation. Exploration of the mechanisms for this increased energetic efficiency may contribute to an optimization of the performance of industrial processes with slow-growing eukaryotic cell factories.
机译：Thermotoolerant酵母ogataeaAlabolymorpha（以前Hansenula Mationorpha）是一种工业相关的生产宿主，其在有氧批量培养物中表现出完全呼吸的糖代谢。 NADH衍生的电子可以通过质子转置的复合物I NADH-脱氢酶或通过三个推定的替代NADH脱氢酶进入其线粒体呼吸链。该呼吸系统入口点影响每NADH / O_（2）产生的ATP的量，因此影响来自给定量的基材的生物量和/或细胞产物的最大产率。为了探讨复合物I的生理重要性，在有氧批量，化学蛋白和生物反应器中的葡萄糖中生长野生型O. parabolymorpha菌株和先生络合物型突变体。在分批培养物中，两种菌株表现出完全呼吸的代谢，并显示出相同的生长速率和生物质产量，表明，在这些条件下，NADH氧化通过复合物的贡献可以忽略不计。两种菌株也表现出葡萄糖有限的化学蛋白培养物中的呼吸代谢，但络合物突变体呈显着降低的基材和氧气产生的生物质产量，与呼吸能耦合的效率较低一致。在葡萄糖限制的葡萄糖限制率下降至〜0.001h〜（β1），O. Parabolymorpha菌株显示出高可活力。这些极低的增长率的维护能量要求比从增长的化学蹄类培养物的估计低约3倍，表明严格响应的行为。定量转录组和蛋白质组分析表明络合物I亚基的条件依赖性表达模式以及与生理观察结果一致的替代NADH脱氢酶。由于通常未选择流行的微生物细胞工厂以获得有效的呼吸能耦合，其ATP产生来自糖分解代谢的ATP产量通常是次优。在有氧工业过程中，次优能耦合导致糖的产量降低，氧气转移的过程成本增加，由于气体转移和冷却的限制，氧气转移的含量增加。本研究提供了对不同生长条件下酵母细胞厂对酵母细胞厂综合鼠胶质渣中的呼吸能量耦合机制的思考，为酵母细胞工厂中的能量耦合的合理改善提供了基础。在极低的特异性生长率下O. ParaBolymorpha的能量代谢分析表明，该酵母在极端能量限制下降低了对细胞维护的能量要求。对这种能量效率提高的机制的探索可能有助于优化具有生长缓慢的真核细胞工厂的工业过程的性能。

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