Thompson Olivia A, Hawkins Gary M, Gorsich Steven W, Doran-Peterson Joy
Department of Microbiology, University of Georgia, Athens, GA 30602 USA.
Department of Biology, Central Michigan University, Mount Pleasant, MI 48859 USA.
Biotechnol Biofuels. 2016 Sep 20;9:200. doi: 10.1186/s13068-016-0614-y. eCollection 2016.
Lignocellulosic biomass continues to be investigated as a viable source for bioethanol production. However, the pretreatment process generates inhibitory compounds that impair the growth and fermentation performance of microorganisms such as Saccharomyces cerevisiae. Pinewood specifically has been shown to be challenging in obtaining industrially relevant ethanol titers. An industrial S. cerevisiae strain was subjected to directed evolution and adaptation in pretreated pine biomass and resultant strains, GHP1 and GHP4, exhibited improved growth and fermentative ability on pretreated pine in the presence of related inhibitory compounds. A comparative transcriptomic approach was applied to identify and characterize differences in phenotypic stability of evolved strains.
Evolved strains displayed different fermentative capabilities with pretreated pine that appear to be influenced by the addition or absence of 13 inhibitory compounds during pre-culturing. GHP4 performance was consistent independent of culturing conditions, while GHP1 performance was dependent on culturing with inhibitors. Comparative transcriptomics revealed 52 genes potentially associated with stress responses to multiple inhibitors simultaneously. Fluorescence microscopy revealed improved cellular integrity of both strains with mitochondria exhibiting resistance to the damaging effects of inhibitors in contrast to the parent.
Multiple potentially novel genetic targets have been discovered for understanding stress tolerance through the characterization of our evolved strains. This study specifically examines the synergistic effects of multiple inhibitors and identified targets will guide future studies in remediating effects of inhibitors and further development of robust yeast strains for multiple industrial applications.
木质纤维素生物质仍在作为生物乙醇生产的可行原料进行研究。然而，预处理过程会产生抑制性化合物，这些化合物会损害酿酒酵母等微生物的生长和发酵性能。具体而言，已证明松木在获得与工业相关的乙醇滴度方面具有挑战性。一株工业酿酒酵母菌株在预处理的松木生物质中进行定向进化和适应性培养，所得菌株GHP1和GHP4在存在相关抑制性化合物的情况下，对预处理松木的生长和发酵能力有所提高。应用比较转录组学方法来鉴定和表征进化菌株在表型稳定性方面的差异。
进化菌株在预处理松木上表现出不同的发酵能力，这似乎受到预培养期间是否添加13种抑制性化合物的影响。GHP4的性能不受培养条件的影响，表现稳定，而GHP1的性能则取决于与抑制剂一起培养。比较转录组学揭示了52个可能与同时对多种抑制剂的应激反应相关的基因。荧光显微镜显示，与亲本相比，这两种菌株的细胞完整性均有所改善，线粒体对抑制剂的破坏作用具有抗性。
通过对我们进化菌株的表征，发现了多个潜在的新遗传靶点，用于理解应激耐受性。本研究特别考察了多种抑制剂的协同作用，所确定的靶点将指导未来关于抑制剂修复作用的研究以及用于多种工业应用的稳健酵母菌株的进一步开发。
