Shandong Provincial Key Laboratory of Energy Genetics, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong, China.
PLoS One. 2013 Jul 30;8(7):e70631. doi: 10.1371/journal.pone.0070631. Print 2013.
Clostridium thermocellum is a major candidate for bioethanol production via consolidated bioprocessing. However, the low ethanol tolerance of the organism dramatically impedes its usage in industry. To explore the mechanism of ethanol tolerance in this microorganism, systematic metabolomics was adopted to analyse the metabolic phenotypes of a C. thermocellum wild-type (WT) strain and an ethanol-tolerant strain cultivated without (ET0) or with (ET3) 3% (v/v) exogenous ethanol. Metabolomics analysis elucidated that the levels of numerous metabolites in different pathways were changed for the metabolic adaption of ethanol-tolerant C. thermocellum. The most interesting phenomenon was that cellodextrin was significantly more accumulated in the ethanol-tolerant strain compared with the WT strain, although cellobiose was completely consumed in both the ethanol-tolerant and wild-type strains. These results suggest that the cellodextrin synthesis was active, which might be a potential mechanism for stress resistance. Moreover, the overflow of many intermediate metabolites, which indicates the metabolic imbalance, in the ET0 cultivation was more significant than in the WT and ET3 cultivations. This indicates that the metabolic balance of the ethanol-tolerant strain was adapted better to the condition of ethanol stress. This study provides additional insight into the mechanism of ethanol tolerance and is valuable for further metabolic engineering aimed at higher bioethanol production.
热纤梭菌是通过整合生物加工生产生物乙醇的主要候选菌株。然而，该生物体对乙醇的低耐受性极大地阻碍了其在工业中的应用。为了探索该微生物的乙醇耐受性机制，采用系统代谢组学方法分析了热纤梭菌野生型（WT）菌株和在无（ET0）或有（ET3）3%（v/v）外源乙醇培养的乙醇耐受菌株的代谢表型。代谢组学分析表明，对于乙醇耐受的热纤梭菌的代谢适应，不同途径的许多代谢物水平发生了变化。最有趣的现象是，与 WT 菌株相比，乙醇耐受菌株中纤维二糖的积累显著增加，尽管在乙醇耐受和野生型菌株中细胞二糖都完全消耗。这些结果表明，纤维二糖的合成是活跃的，这可能是一种潜在的应激抗性机制。此外，在 ET0 培养中，许多中间代谢物的溢出，表明代谢失衡，比在 WT 和 ET3 培养中更为显著。这表明乙醇耐受菌株的代谢平衡更好地适应了乙醇胁迫的条件。本研究为乙醇耐受性机制提供了更多的见解，对进一步的旨在提高生物乙醇产量的代谢工程具有重要价值。
