Genetic modification of the thraustochytrid Aurantiochytrium sp. 18W-13a for cellobiose utilization by secretory expression of β-glucosidase from Aspergillus aculeatus
Genetic modification of the thraustochytrid Aurantiochytrium sp. 18W-13a for cellobiose utilization by secretory expression of β-glucosidase from Aspergillus aculeatus
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DOI：
10.1016/j.algal.2019.101503
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发表时间：
2019-06-01
影响因子：
5.1
通讯作者：
Suzuki, Iwane
中科院分区：
文献类型：
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作者：
Juntila, Darryl Joy;Yoneda, Kohei;Suzuki, Iwane
破囊壶菌是一类异养原生生物，由于其高产DHA、EPA和棕榈酸而成为一类很有前途的产油微生物。角鲨烯是一种三萜烃，具有抗氧化、抗肿瘤和润肤的特性，在一些破囊壶菌菌株中积累，特别是在橙壶菌属中。破囊壶菌能产生胞外酶降解有机物作为其营养手段。许多研究试图在具有成本效益的基质如木质纤维素生物质中生长破囊壶菌。作为纤维素利用的第一步，我们遗传修饰了Aurantiochytrium sp.菌株18 W-13 a，以表达和分泌来自棘孢曲霉（Aspergillus aculeatus，AaBgl）的高活性纤维素酶β-葡萄糖苷酶。该菌株AaBgl（+）以纤维二糖为唯一碳源时，生长量和酶活均有所增加。非变性PAGE酶谱显示AaBgl（+）菌株的上清液中存在活性β-葡糖苷酶。野生型和AaBgl（+）菌株都可以产生角鲨烯和脂肪酸DHA和DPA。这项工作是在破囊壶菌的功能酶的靶向分泌的第一个报告之一。此外，在破囊壶菌中从未进行过纤维素酶的增强表达。希望本研究能为建立强化生物处理的破囊壶菌菌株奠定基础。
Thraustochytrids are osmoheterotrophic protists that are emerging as a promising group of oleaginous microorganisms due to their high DHA, EPA and palmitic acid production. Squalene, a triterpene hydrocarbon known for its antioxidant, antitumorigenic and emollient properties, is accumulated in some strains of thraustochytrids especially in the genus Aurantiochytrium. Thraustochytrids can produce extracellular enzymes to degrade organic matter as their means of nutrition. Many studies attempt to grow thraustochytrids in cost-effective substrates such as lignocellulosic biomass. As the first step towards cellulose utilization, we genetically modified Aurantiochytrium sp. strain 18W-13a to express and secrete a highly active cellulase, beta-glucosidase from Aspergillus aculeatus (AaBgl). The transformant strain, AaBgl(+), exhibited increasing growth and enzyme activity under cellobiose as the sole carbon source. Native PAGE zymogram showed an active beta-glucosidase enzyme in the supernatant of the AaBgl(+) strain. Both wild-type and AaBgl(+) strains can produce squalene and fatty acids DHA and DPA. This work is one of the first reports in targeted secretion of a functional enzyme in thraustochytrids. Moreover, enhanced expression of cellulases has never been done in thraustochytrids. We hope that this study could pave way for establishing consolidated bioprocessing thraustochytrid strains.