Current sources of fermentation feedstocks, i.e., corn, sugar cane, or plant biomass, fall short of demand for liquid transportation fuels and commodity chemicals in the United States. Aquatic phototrophs including cyanobacteria have the potential to supplement the supply of current fermentable feedstocks. In this strategy, cells are engineered to accumulate storage molecules including glycogen, cellulose, and/or lipid oils that can be extracted from harvested biomass and fed to heterotrophic organisms engineered to produce desired chemical products. In this manuscript, we examine the production of glycogen in the model cyanobacteria, Synechococcus sp. strain PCC 7002, and subsequent conversion of cyanobacterial biomass by an engineered Escherichia coli to octanoic acid as a model product. In effort to maximize glycogen production, we explored the deletion of catabolic enzymes and overexpression of GlgC, an enzyme that catalyzes the first committed step toward glycogen synthesis. We found that deletion of glgP increased final glycogen titers when cells were grown in diurnal light. Overexpression of GlgC led to a temporal increase in glycogen content but not in an overall increase in final titer or content. The best strains were grown, harvested, and used to formulate media for growth of E. coli. The cyanobacterial media was able to support the growth of an engineered E. coli and produce octanoic acid at the same titer as common laboratory media.

在美国，当前发酵原料的来源，即玉米，甘蔗或植物生物质，对液体运输燃料和商品化学品的需求不足。包括蓝细菌在内的水生营养生物有潜力补充当前可发酵原料的供应。在这种策略下，细胞经过工程设计以积累包括糖原，纤维素和/或脂质油在内的存储分子，这些分子可以从收获的生物质中提取出来，并喂入经工程改造以生产所需化学产品的异养生物中。在本手稿中，我们研究了模型蓝细菌中糖原的产生，球菌sp。PCC 7002菌株，然后通过工程技术转化蓝细菌生物质大肠杆菌以辛酸为模型产品。为了最大程度地提高糖原的产生，我们探索了分解代谢酶的缺失和GlgC的过表达，GlgC是一种催化糖原合成的第一步。我们发现删除了糖蛋白当细胞在日光下生长时，增加的最终糖原效价。GlgC的过表达导致糖原含量的暂时增加，但最终滴度或含量没有整体增加。生长，收获最好的菌株，并用于配制培养基来生长大肠杆菌。蓝细菌培养基能够支持工程菌的生长大肠杆菌 并以与普通实验室培养基相同的滴度生产辛酸。