BIOTEC Bioresource Technology Unit, National Center for Genetic Engineering and Biotechnology, Pathumthani, Thailand.
FEMS Microbiol Lett. 2010 Jan;302(1):8-14. doi: 10.1111/j.1574-6968.2009.01811.x. Epub 2009 Oct 5.
Cell-surface expression of phytase allows the enzyme to be expressed and anchored on the cell surface of Pichia pastoris. This avoids tedious downstream processes such as purification and separation involved with extracellular expression. In addition, yeast cells with anchored proteins can be used as a whole-cell biocatalyst with high value added. In this work, the phytase was expressed on the cell surface of P. pastoris with a glycosylphosphatidylinositol anchoring system. The recombinant phytase was shown to be located at the cell surface. The cell-surface phytase exhibited high activity with an optimal temperature at 50-55 degrees C and two optimal pH peaks of 3 and 5.5. The surface-displayed phytase also exhibited similar pH stability and pepsin resistance to the native and secreted phytase. In vitro digestibility test showed that P. pastoris containing cell-surface phytase released phosphorus from feedstuff at a level similar to secreted phytase. Yeast cells expressing phytase also provide additional nutrients, especially biotin and niacin. Thus, P. pastoris with phytase displayed on its surface has a great potential as a whole-cell supplement to animal feed.
植酸酶在细胞表面的表达使该酶能够在毕赤酵母的细胞表面表达和锚定。这避免了繁琐的下游处理过程，如与胞外表达相关的纯化和分离。此外，带有锚定蛋白的酵母细胞可以作为具有高附加值的全细胞生物催化剂使用。在这项工作中，植酸酶通过糖基磷脂酰肌醇锚定系统在毕赤酵母的细胞表面表达。结果表明，重组植酸酶位于细胞表面。该细胞表面植酸酶表现出较高的活性，最佳温度为 50-55°C，有两个最佳 pH 峰，分别为 3 和 5.5。与天然分泌型植酸酶相比，表面展示的植酸酶也表现出相似的 pH 稳定性和胃蛋白酶抗性。体外消化试验表明，含有细胞表面植酸酶的毕赤酵母从饲料中释放的磷与分泌型植酸酶相当。表达植酸酶的酵母细胞还提供了额外的营养物质，特别是生物素和烟酸。因此，表面展示植酸酶的毕赤酵母作为动物饲料的全细胞补充剂具有巨大的潜力。
