Sun Angela, Hasan Mafruha Tasnin, Hobba Graham, Nevalainen Helena, Te'o Junior
Department of Molecular Sciences, Macquarie University, Sydney, New South Wales, Australia.
Biomolecular Discovery and Design Research Centre, Macquarie University, Sydney, New South Wales, Australia.
J Phycol. 2018 Aug;54(4):529-538. doi: 10.1111/jpy.12758. Epub 2018 Jul 19.
Euglena gracilis Z and a "sugar loving" variant strain E. gracilis var. saccharophila were investigated as producers of paramylon, a β-1,3-glucan polysaccharide with potential medicinal and industrial applications. The strains were grown under diurnal or dark growth conditions on a glucose-yeast extract medium supporting high-level paramylon production. Both strains produced the highest paramylon yields (7.4-8 g · L , respectively) while grown in the dark, but the maximum yield was achieved faster by E. gracilis var. saccharophila (48 h vs. 72 h). The glucose-to-paramylon yield coefficient Y = 0.46 ± 0.03 in the E. gracilis var. saccharophila cultivation, obtained in this study, is the highest reported to date. Proteomic analysis of the metabolic pathways provided molecular clues for the strain behavior observed during cultivation. For example, overexpression of enzymes in the gluconeogenesis/glycolysis pathways including fructokinase-1 and chloroplastic fructose-1,6-bisphosphatase (FBP) may have contributed to the faster rate of paramylon accumulation in E. gracilis var. saccharophila. Differentially expressed proteins in the early steps of chloroplastogenesis pathway including plastid uroporphyrinogen decarboxylases, photoreceptors, and a highly abundant (68-fold increase) plastid transketolase may have provided the E. gracilis var. saccharophila strain an advantage in paramylon production during diurnal cultivations. In conclusion, the variant strain E. gracilis var. saccharophila seems to be well suited for producing large amounts of paramylon. This work has also resulted in the identification of molecular targets for future improvement of paramylon production in E. gracilis, including the FBP and phosophofructokinase 1, the latter being a key regulator of glycolysis.
纤细裸藻（Euglena gracilis Z）和一个“嗜糖”变种菌株——嗜糖纤细裸藻（E. gracilis var. saccharophila）被作为副淀粉的生产菌株进行了研究。副淀粉是一种β-1,3-葡聚糖多糖，具有潜在的医药和工业应用价值。这些菌株在昼夜或黑暗生长条件下，于支持高水平副淀粉生产的葡萄糖-酵母提取物培养基上生长。两种菌株在黑暗中生长时都产生了最高的副淀粉产量（分别为7.4 - 8 g·L），但嗜糖纤细裸藻变种达到最大产量的速度更快（48小时对72小时）。本研究中在嗜糖纤细裸藻变种培养过程中获得的葡萄糖到副淀粉的产量系数Y = 0.46 ± 0.03，是迄今为止报道的最高值。对代谢途径的蛋白质组学分析为培养过程中观察到的菌株行为提供了分子线索。例如，包括果糖激酶-1和叶绿体果糖-1,6-二磷酸酶（FBP）在内的糖异生/糖酵解途径中的酶的过表达，可能有助于嗜糖纤细裸藻变种中副淀粉积累速度更快。叶绿体生成途径早期步骤中差异表达的蛋白质，包括质体尿卟啉原脱羧酶、光感受器和一种高度丰富（增加68倍）的质体转酮醇酶，可能使嗜糖纤细裸藻变种菌株在昼夜培养过程中在副淀粉生产方面具有优势。总之，嗜糖纤细裸藻变种似乎非常适合大量生产副淀粉。这项工作还导致确定了未来提高纤细裸藻中副淀粉产量的分子靶点，包括FBP和磷酸果糖激酶1，后者是糖酵解的关键调节因子。
