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

构建和整合新的途径和系统到生物体中生产有用的代谢物是合成生物学的一个关键领域。酿酒酵母（Saccharomyces cerevisiae）是生物技术的主力；几个世纪以来，它一直被用于生产食品和饮料。最近，这种生物已经成为生物燃料，生物乙醇生产的核心。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基因组和后基因组时代的过渡。例如，酿酒酵母（S. cerevisiae）是第一个完成基因组测序的生物，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个酵母菌中发展起来的。漫长而成功的生物技术应用历史与前所未有的工具和资源相结合，使酿酒葡萄球菌成为合成生物学的理想宿主。我们已经介绍了一种途径，允许在酿酒酵母生产生物丁醇。生物丁醇被认为是优于生物乙醇的生物燃料；也许最根本的是，它可以直接用于车辆而无需改装发动机，而且它没有腐蚀性，可以通过现有管道运输。我们在整合这一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，在菌株适用于工业环境之前，还需要进一步的优化和开发。因此，本提案的第一个目标是优化该菌株的生物丁醇生产。我们将评估添加酶的效率，我们将改变内源性代谢，将代谢物引向丁醇生产途径，我们将尽量减少乙醇等污染物的产生。第二个目标是扩大原料范围，这样我们的丁醇生产菌株可以最大限度地利用木质纤维素原料中的可用资源。例如，像英国的那些以小麦为原料的生物乙醇精炼厂，只使用富含淀粉的胚乳（在种子内）。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建立数学模型，准确概括各种条件下不同突变体的丁醇生产水平。然后，该模型可用于预测基因变化，从而进一步提高丁醇产量。这些预测对丁醇产量的影响将最终进行评估。总的来说，该项目旨在产生具有从可再生能源生产环境清洁生物燃料的能力的酵母菌株。

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.