Abstract：
Microalgal biomass for biofuel production, integration into functional food, and feed supplementation has generated substantial interest worldwide due to its high growth rate, non-competitiveness for agronomic land, ease of cultivation in containments, and presence of several bioactive molecules. In this study, genetic engineering tools were employed to develop transgenic lines of freshwater microalga Chlorella vulgaris with a higher starch content, by up-regulating ADP-glucose pyrophosphorylase (AGPase), which is a rate-limiting enzyme in starch biosynthesis. Expression of the Escherichia coli glgC (AGPase homolog) gene in C. vulgaris led to an increase in total carbohydrate content up to 45.1% (dry cell weight, DCW) in the transgenic line as compared to 34.2% (DCW) in the untransformed control. The starch content improved up to 16% (DCW) in the transgenic alga compared to 10% (DCW) in the control. However, the content of total lipid, carotenoid, and chlorophyll decreased differentially in the transgenic lines. The carbohydrate-rich biomass from the transgenic algal line was used to produce bioethanol via yeast fermentation, which resulted in a higher ethanol yield of 82.82 mg/L as compared to 54.41 mg/L from the untransformed control. The in vitro digestibility of the transgenic algal starch revealed a resistant starch content of up to 7% of total starch. Faster growth of four probiotic bacterial species along with a lowering of the pH of the growth medium indicated transgenic alga to exert a positive prebiotic effect. Taken together, the study documents the utilization of genetically engineered C. vulgaris with enriched carbohydrates as bioethanol feedstock and functional food ingredients.
摘要：
用于生物燃料生产的微藻生物质，融入功能性食品，饲料补充由于其高增长率而在全球范围内引起了极大的兴趣，农艺用地的非竞争性，易于在容器中种植，以及几种生物活性分子的存在。在这项研究中,基因工程工具被用来开发具有较高淀粉含量的淡水微藻小球藻的转基因系，通过上调ADP-葡萄糖焦磷酸化酶（AGPase），这是淀粉生物合成中的限速酶。大肠杆菌glgC（AGPase同源物）基因在普通梭菌中的表达导致总碳水化合物含量增加至45.1％（干细胞重量，转基因品系中的DCW）与未转化对照中的34.2％（DCW）相比。与对照中的10%(DCW)相比,转基因藻类中的淀粉含量提高到高达16%(DCW)。然而,总脂质的含量，类胡萝卜素，和叶绿素在转基因品系中差异降低。来自转基因藻类系的富含碳水化合物的生物质用于通过酵母发酵生产生物乙醇，与未转化对照的54.41mg/L相比,这导致82.82mg/L的更高的乙醇产量。转基因藻类淀粉的体外消化率显示抗性淀粉含量高达总淀粉的7％。四种益生菌物种的更快生长以及生长培养基pH的降低表明转基因藻类发挥了积极的益生元作用。一起来看,该研究记录了利用基因工程的C.vulgaris富含碳水化合物作为生物乙醇原料和功能性食品成分。
