Synthetic approaches towards the production of biofuels from lignocellulosic feedstocks in yeast

将新的途径和系统构建并整合到生物体中以产生有用的代谢产物是合成生物学的一个关键领域。酿酒酵母（Saccharomyces cerevisiae）是一种生物技术的主力;它已被用于食品和饮料的生产几个世纪。最近，这种生物体已经成为生产生物燃料生物乙醇的核心。酿酒酵母也是分子和细胞生物学、生物化学和遗传学的模式生物。对这种酵母的研究开创了向基因组和后基因组时代的过渡。例如，S.酿酒酵母是第一个对其基因组测序的生物体，它拥有最全面的基因表达数据汇编和系统的突变体收集。可能正因为如此，系统生物学的许多数据、工具和技术都是在这种酵母菌中发展起来的。生物技术应用的悠久而成功的历史和前所未有的工具和资源使S。酿酒酵母是合成生物学的理想宿主。我们已经引入了一种途径，使生产生物丁醇在S。啤酒。生物丁醇被认为是比生物乙醇更优越的上级生物燃料;也许最根本的是，因为它可以直接用于车辆而无需修改发动机，并且它是无腐蚀性的，允许通过现有管道运输。我们在整合该途径中采用的设计策略，相对于其他已发表的研究，产量提高了约100倍。然而，在菌株应用于工业环境之前，还需要进一步的优化和开发。因此，本提案的首要目标是优化该菌株的生物丁醇生产。我们将评估添加的酶的效率，我们将改变内源性代谢以将代谢物引导到丁醇生产途径，我们将最大限度地减少乙醇等污染物的产生。第二个目标是扩大原料范围，使我们的丁醇生产菌株能够最大限度地利用木质纤维素原料中的可用资源。例如，以小麦为原料的生物乙醇精炼厂，如英国的那些，只使用富含淀粉的胚乳（种子内）。我们提出的菌株可能会使用更大比例的植物作为原料。贯穿该提案的最后一个总体目标是开发数学模型，准确概括各种条件下各种突变体中丁醇生产的水平。然后，该模型可以用于预测将导致丁醇产率进一步提高的遗传改变。这些预测对丁醇产量的影响最终将被评估。总的来说，该项目的目标是产生酵母菌株，这些酵母菌株具有利用可再生能源生产环境清洁的生物燃料的能力。

The construction and integration of new pathways and systems into organisms for the production of useful metabolites is a key area of synthetic biology. The brewers' yeast (Saccharomyces cerevisiae) is a biotechnological workhorse; it has been used for the production of foods and beverages for centuries. More recently, this organism has been central to the production of the biofuel, bioethanol. Saccharomyces cerevisiae also serves as a model organism in molecular and cell biology, biochemistry and genetics. Studies on this yeast have pioneered the transition into the genomic and post-genomic era. For instance, S. cerevisiae was the first organism to have its genome sequenced and it has the most comprehensive compilation of gene expression data and systematic mutant collections. Probably as a result, much of the data, tools and technologies of systems biology have been developed in this yeast. This combination of a long, successful history of biotechnological application and unprecedented tools and resources make S. cerevisiae an ideal host for synthetic biology. We have introduced a pathway that allows the production of biobutanol in S. cerevisiae. Biobutanol is viewed as a superior biofuel to bioethanol; perhaps most fundamentally, as it can be used directly in vehicles without engine modification and it is non-corrosive allowing transportation via existing pipelines. The design strategies that we have employed in the integration of this pathway, have improved the yield about 100-fold relative to other published studies. However, there is further optimisation and development required before the strains would be applicable in an industrial context. Therefore, the first aim of this proposal is to optimise the production of biobutanol from this strain. We will assess the efficiency of the added enzymes, we will alter endogenous metabolism to channel metabolites towards the butanol production pathway and we will minimise the production of contaminants such as ethanol.A second goal is to extend the feedstock range such that our butanol producing strain can make maximal use of the resources available in lignocellulosic-based feedstocks. For example, wheat fed bioethanol refineries, like those in the UK, use only the starch rich endosperm (within the seed). Our proposed strain could potentially use a much greater proportion of the plant as a feedstock. A final overarching goal running through the proposal is to develop mathematical models that accurately recapitulate levels of butanol production in various mutants under a variety of conditions. The model can then be used to predict genetic alterations that would lead to further enhancements of butanol yield. The impact of these predictions on butanol yield would ultimately be assessed.Overall, the project aims to generate yeast strains with the capacity to produce an environmentally clean biofuel from renewable energy sources.