School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China.
School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China.
Enzyme Microb Technol. 2020 Jun;137:109533. doi: 10.1016/j.enzmictec.2020.109533. Epub 2020 Feb 7.
Phytate is the major storage form of phosphorus in plants. It is present in cereals and raw materials of vegetable origin used in animal and human diets. However, non-ruminant animals have little phytase activity in their guts and, therefore, cannot digest phytate. As a result, almost all dietary phytate is discharged into the environment, causing phosphorus pollution. Phytate is also considered as an "antinutrient" for its ability to form insoluble and stable complexes with metal ions, thus reducing dietary absorption of essential minerals. It is a dire need to develop sustainable approaches for environmentally-friendly utilization for this valuable and abundant natural resource. To this end, we engineered Pichia pastoris to express and secrete phytase in a "made-to-order" fashion in response to external level of inorganic phosphate (Pi). Responsiveness to external Pi level was achieved by generating a Pi-responsive promoter library using directed evolution. The resultant yeast strains were proven to liberate Pi from wheat-based meal in a simulated in vitro digestion model. These yeast-based whole cell biocatalysts may serve as platform hosts with potential applications in food processing industry and animal waste treatment.
植酸是植物中磷的主要储存形式。它存在于谷物和蔬菜原料中，这些原料被用于动物和人类的饮食。然而，非反刍动物的肠道中几乎没有植酸酶活性，因此无法消化植酸。结果，几乎所有的膳食植酸都被排放到环境中，造成了磷污染。植酸还被认为是一种“抗营养物质”，因为它能够与金属离子形成不溶性和稳定的复合物，从而降低膳食中必需矿物质的吸收。因此，迫切需要开发可持续的方法，以环保的方式利用这种有价值且丰富的自然资源。为此，我们通过定向进化生成了一个磷响应启动子文库，从而使毕赤酵母能够以“定制”的方式表达和分泌植酸，以响应外部无机磷（Pi）水平。通过这种方式，酵母菌株被证明可以在模拟体外消化模型中从基于小麦的膳食中释放 Pi。这些基于酵母的全细胞生物催化剂可以作为平台宿主，在食品加工行业和动物废物处理中有潜在的应用。
