Department of Chemical and Biological Engineering, Industrial Biotechnology, Chalmers University of Technology, Gothenburg, Sweden.
PLoS One. 2013 Sep 4;8(9):e73936. doi: 10.1371/journal.pone.0073936. eCollection 2013.
When using microorganisms as cell factories in the production of bio-based fuels or chemicals from lignocellulosic hydrolysate, inhibitory concentrations of acetic acid, released from the biomass, reduce the production rate. The undissociated form of acetic acid enters the cell by passive diffusion across the lipid bilayer, mediating toxic effects inside the cell. In order to elucidate a possible link between lipid composition and acetic acid stress, the present study presents detailed lipidomic profiling of the major lipid species found in the plasma membrane, including glycerophospholipids, sphingolipids and sterols, in Saccharomyces cerevisiae (CEN.PK 113_7D) and Zygosaccharomyces bailii (CBS7555) cultured with acetic acid. Detailed physiological characterization of the response of the two yeasts to acetic acid has also been performed in aerobic batch cultivations using bioreactors. Physiological characterization revealed, as expected, that Z. bailii is more tolerant to acetic acid than S. cerevisiae. Z. bailii grew at acetic acid concentrations above 24 g L(-1), while limited growth of S. cerevisiae was observed after 11 h when cultured with only 12 g L(-1) acetic acid. Detailed lipidomic profiling using electrospray ionization, multiple-reaction-monitoring mass spectrometry (ESI-MRM-MS) showed remarkable changes in the glycerophospholipid composition of Z. bailii, including an increase in saturated glycerophospholipids and considerable increases in complex sphingolipids in both S. cerevisiae (IPC 6.2×, MIPC 9.1×, M(IP)2C 2.2×) and Z. bailii (IPC 4.9×, MIPC 2.7×, M(IP)2C 2.7×), when cultured with acetic acid. In addition, the basal level of complex sphingolipids was significantly higher in Z. bailii than in S. cerevisiae, further emphasizing the proposed link between lipid saturation, high sphingolipid levels and acetic acid tolerance. The results also suggest that acetic acid tolerance is associated with the ability of a given strain to generate large rearrangements in its lipid profile.
当使用微生物作为细胞工厂，从木质纤维素水解物中生产生物基燃料或化学品时，生物质释放的抑制浓度的乙酸通过穿过脂质双层的被动扩散进入细胞，介导细胞内的毒性作用。为了阐明脂质组成与乙酸胁迫之间的可能联系，本研究对在含有乙酸的条件下培养的酿酒酵母（CEN.PK 113_7D）和毕赤酵母（CBS7555）的质膜中主要脂质种类的详细脂质组学进行了分析，包括甘油磷脂、鞘脂和甾醇。还使用生物反应器进行了有氧分批培养，对这两种酵母对乙酸的响应进行了详细的生理特性分析。生理特性分析表明，与酿酒酵母相比，毕赤酵母对乙酸的耐受性更强，如预期的那样。毕赤酵母在乙酸浓度高于 24 g/L 时生长，而当仅用 12 g/L 乙酸培养时，酿酒酵母的生长受到限制，11 h 后观察到生长受限。使用电喷雾电离、多反应监测质谱（ESI-MRM-MS）的详细脂质组学分析显示，毕赤酵母的甘油磷脂组成发生了显著变化，包括饱和甘油磷脂增加，以及酿酒酵母（IPC 增加 6.2 倍，MIPC 增加 9.1 倍，M(IP)2C 增加 2.2 倍）和毕赤酵母（IPC 增加 4.9 倍，MIPC 增加 2.7 倍，M(IP)2C 增加 2.7 倍）中复杂鞘脂的含量显著增加。此外，毕赤酵母中复杂鞘脂的基础水平明显高于酿酒酵母，进一步强调了脂质饱和度、高鞘脂水平与乙酸耐受性之间的联系。结果还表明，乙酸耐受性与特定菌株在其脂质谱中产生大的重排的能力有关。
