STTR Phase I: Carbon capture and high-value isoprene production by fast-growing cyanobacteria

这个小型企业技术转移（STTR）第一阶段项目的更广泛的影响/商业潜力建议开发蓝藻（蓝绿色微藻）和光生物反应器（藻类培养）系统，有效地利用阳光、废水中的营养物质和光生物反应器（CO2）来生产可持续的、碳中性的异戊二烯来源。异戊二烯是数千种萜烯产品的高价值成分，包括合成橡胶、药品、香精、香料、油和生物燃料，年市场规模达20亿美元。到2017年，以类异戊二烯为主要成分的香精和香料的年销售额预计将达到100亿美元。目前，几乎所有的异戊二烯都是由石油生产的。由于人们越来越意识到气候变化的可怕影响，开发“碳中和”生物产品和生物燃料已成为全球经济和安全的当务之急。随着企业寻求减少碳足迹和提高其“绿色”证书，可再生的类异戊二烯将受到需求。一些生物异戊二烯是通过微生物发酵生产的，但这仍然会释放二氧化碳，目前还没有公司通过光合作用生产异戊二烯。因此，微藻利用来自阳光的能量和从大气或工业流感气体中捕获的碳生产的“光异戊二烯”将为社会和环境带来重大效益，并为商业发展提供重要潜力。STTR一期项目拟开发聚藻球菌（Synechococcus sp. PCC 7002）蓝藻，该蓝藻利用二氧化碳、阳光和废水高效生产可持续的“绿色”异戊二烯（C5H8）来源，C5H8是一种挥发性的高价值前体，可生产多种萜烯产品。蓝藻捕获而不是产生二氧化碳。聚珠球菌7002是地球上生长最快的藻类之一，它能忍受对许多藻类来说是致命的极端光强度，能在温度高达45°C的盐水中生长，而且很容易适应生物工程。这些特点使聚球菌7002成为在不适合作物生长的干旱地区的废水中生长的极好平台，并具有成本效益的碳捕获和“光异戊二烯”生产。该计划是利用聚球菌改良的2- c -甲基- d -赤藓糖醇-4-磷酸（MEP）途径和优化的异戊二烯合成基因，培养出连续数周生产异戊二烯的菌株，其速度远高于任何已发表的蓝藻细菌。商业化将需要进一步的生物工程和光生物反应器设计，以最大化生产和开发有效的异戊二烯捕获。第一阶段将：1)整合进一步的基因修饰，将异戊二烯的产量提高5倍，将捕获的碳转化为异戊二烯的10%；2)优化光生物反应器，用于CO2捕获和异戊二烯的生产；3)开发一个原型系统，从培养气体排出物中捕获至少50%的异戊二烯。

The broader impact/commercial potential of this Small Business Technology Transfer (STTR) Phase I project proposes to develop cyanobacteria (blue-green microalgae) and photobioreactor (algal culture) systems that efficiently use sunlight, nutrients from wastewater, and waste carbon dioxide (CO2) to produce a sustainable, carbon-neutral source of isoprene. Isoprene is a high-value component of thousands of terpene products including synthetic rubber, pharmaceuticals, flavors, fragrances, oils, and biofuels, and has an annual market of $2 billion. Ingredients for flavors and fragrances, of which isoprenoids are a large part, are expected to reach $10 billion annually by 2017. Currently, almost all isoprene is produced from petroleum. Because of growing awareness of the dire impacts of climate change, the development of "carbon neutral" bioproducts and biofuels has become a global economic and security imperative. Renewable isoprenoids will be in demand as companies seek to mitigate their carbon footprints and improve their "green" credentials. Some bio-isoprene is being produced by microbial fermentation, but this still releases CO2, and no company currently produces isoprene photosynthetically. Thus, "photo-isoprene" produced by microalgae with energy from sunlight and carbon captured from the atmosphere or industrial flu gases will offer significant benefits for society and the environment as well as important potential for business development. This STTR Phase I project proposes to develop Synechococcus sp. PCC 7002 cyanobacteria that use CO2, sunlight, and wastewater to efficiently produce a sustainable, "green" source of isoprene (C5H8), a volatile, high-value precursor for numerous terpene products. Cyanobacteria capture rather than produce CO2. Synechococcus 7002 is among the fastest growing algae on earth, tolerates extreme light intensities that are lethal to many algae, grows in saline waters at temperatures up to 45°C, and is readily amenable to bio-engineering. These features make Synechcoccus 7002 an excellent platform for growth on wastewaters in arid regions unsuitable for crops, and cost-effective carbon capture and "photo-isoprene" production. The plan is to use a modified 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway of Synechococcus and optimized genes for isoprene synthesis to develop strains that continuously produce isoprene for weeks at rates much higher than any published for cyanobacteria. Commercialization will require further bio-engineering and photobioreactor design to maximize production and develop efficient isoprene capture. Phase I will: 1) integrate further genetic modifications to increase isoprene production 5-fold to convert 10% of captured carbon into isoprene 2) optimize photobioreactors for CO2 capture and isoprene production, and 3) develop a prototype system that captures at least 50% of the isoprene from the culture gas effluent.