Abstract：
Currently, levan is attracting attention due to its promising applications in the food and biomedical fields. Levansucrase synthesizes levan by polymerizing the fructosyl unit in sucrose. However, a large amount of the byproduct glucose is produced during this process. In this paper, an engineered oleaginous yeast (Yarrowia lipolytica) strain was constructed using a surface display plasmid containing the LevS gene of Gluconobacter sp. MP2116. The levansucrase activity of the engineered yeast strain reached 327.8 U/g of cell dry weight. The maximal levan concentration (58.9 g/l) was achieved within 156 h in the 5-liter fermentation. Over 81.2 % of the sucrose was enzymolyzed by the levansucrase, and the byproduct glucose was converted to 21.8 g/l biomass with an intracellular oil content of 25.5 % (w/w). The obtained oil was comprised of 91.3 % long-chain fatty acids (C16-C18). This study provides new insight for levan production and comprehensive utilization of the byproduct in levan biosynthesis.
摘要：
目前,由于其在食品和生物医学领域的应用前景广阔，levan引起了人们的关注。蔗糖酶通过在蔗糖中聚合果糖基来合成果聚糖。然而,在此过程中会产生大量的副产物葡萄糖。在本文中,使用包含葡糖杆菌属的LevS基因的表面展示质粒构建了工程化的产油酵母（Yarrowialipolytica）菌株。MP2116工程酵母菌株的蔗糖酶活性达到327.8U/g细胞干重。在5升发酵中，在156小时内达到了最大的果聚糖浓度（58.9g/l）。超过81.2%的蔗糖被左旋蔗糖酶酶解，并且将副产物葡萄糖转化为21.8g/l生物质,细胞内油含量为25.5%(w/w)。获得的油包含91.3%的长链脂肪酸(C16-C18)。该研究为果聚糖生物合成中果聚糖的生产和副产品的综合利用提供了新的见解。
