Assessing the potential of sucrose production by genetically engineered cyanobacteria

与利用化石资源相比，利用光合作用生物体的可再生生物质生产生物燃料和生物化学品的过程几乎不会产生二氧化碳。蓝藻等光合作用生物将能量储存在高分子和低分子糖中，这些糖可以通过微生物发酵或化学催化转化为燃料或化学原料。由于蓝藻是一种光合作用、生长迅速的微生物，可以在特定条件下积累蔗糖，因此它们在生物质衍生的可再生燃料和化学品生产中具有潜在的糖源应用。两位申请人对糖合成的分子机制的理解(德国方面)及其在可溶性糖生产中的应用(中方合作伙伴用蓝藻实现了蔗糖L 5-6 mg/h-1)具有共同的兴趣。虽然蓝藻蔗糖生产潜力很大，但要实现工业化应用，蔗糖产量还需进一步提高。这种尝试受到蔗糖生物合成调节机制未知以及蔗糖合成和分泌效率低的限制。为了提高蔗糖产量，我们提出了以下研究任务：利用蓝藻代谢工程优化提高蔗糖生物合成效率的基因表达；阻断竞争途径，将碳流重新定向到蔗糖生物合成途径；筛选和表达不同来源的蔗糖转运蛋白，以提高蔗糖分泌效率。蔗糖生物合成酶在转录和生化水平上的调控研究比较不同来源生物体的酶和基因。研究将提高蔗糖产量的条件(盐、二氧化碳的有效性)。

The production of biofuels and biochemicals from renewable biomass of photosynthetic organisms results in an almost CO2-neutral process compared to utilizing fossil resources. Photosynthetic organisms such as cyanobacteria store their energy in high and low molecular mass sugars, which can be converted into fuels or chemical feedstock through microbial fermentation or chemical catalysis. Because cyanobacteria are photosynthetic, fast-growing microorganisms that can accumulate sucrose under specific conditions, they have a potential application as a sugar source for the biomass-derived production of renewable fuels and chemicals. The two applicants have mutual interests in the understanding of molecular mechanisms of sugar synthesis (German side) and its application for soluble sugar production (a rate of 5-6 mg sucrose L-1 h-1 was achieved with cyanobacteria by the Chinese partner). Although it is clear that cyanobacterial sucrose production has great potential, for the industrial scale application the sucrose production needs to be increased. Such attempts are limited by the unknown regulatory mechanism of sucrose biosynthesis as well as the low sucrose synthesis and secretion efficiency. To improve sucrose production, we propose the following research tasks: Metabolic engineering of cyanobacteria to optimize the expression of genes for enhancing the sucrose biosynthesis efficiency; to disrupt the competitive pathway for redirecting the carbon flux into sucrose biosynthesis pathway; to screen and express the sucrose transporters with different origins for improving the sucrose secretion efficiency. Study of the regulation of sucrose biosynthesis enzymes on transcriptional and biochemical level comparing enzymes and genes from different source organisms.Investigating conditions (salt, CO2 availability) which will improve sucrose production.