Enhancing Photosynthetic Production of Glycogen-Rich Biomass for Use as a Fermentation Feedstock
Enhancing Photosynthetic Production of Glycogen-Rich Biomass for Use as a Fermentation Feedstock
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DOI：
10.3389/fenrg.2020.00093
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发表时间：
2020-05-29
影响因子：
3.4
通讯作者：
Pfleger, Brian F.
中科院分区：
文献类型：
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作者：
Comer, Austin D.;Abraham, Joshua P.;Pfleger, Brian F.
目前发酵原料的来源，如玉米、甘蔗或植物生物质，不足以满足美国对液体运输燃料和商品化学品的需求。包括蓝藻在内的水生光养生物有可能补充当前可发酵原料的供应。在这种策略中，细胞被改造成积累储存分子，包括糖原、纤维素和/或脂质油，这些分子可以从收获的生物质中提取出来，并喂给异养生物，以生产所需的化学产品。在这篇手稿中，我们研究了糖原的生产模式蓝藻，聚球菌。菌株pcc7002，以及随后通过工程大肠杆菌将蓝藻生物量转化为辛酸作为模型产品。为了最大限度地提高糖原的产量，我们探索了分解代谢酶的缺失和GlgC的过度表达，GlgC是催化糖原合成的第一步。我们发现，当细胞在日光下生长时，glgp2的缺失增加了最终糖原滴度。GlgC的过表达导致糖原含量的暂时增加，但最终滴度或含量的总体增加不明显。对最佳菌株进行了培养、收获，并用于配制培养基以培养e。杆菌。蓝藻培养基能够支持工程ede的生长。大肠杆菌产生的辛酸滴度与普通实验室培养基相同。
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,Synechococcussp. strain PCC 7002, and subsequent conversion of cyanobacterial biomass by an engineeredEscherichia colito 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 ofglgPincreased 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 ofE. coli. The cyanobacterial media was able to support the growth of an engineeredE. coliand produce octanoic acid at the same titer as common laboratory media.