Team:CityU HK/Description
Overview
What is lactose intolerance and
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For most people, indulging in sweet food like ice-cream, cheesecake and chocolate is as natural as breathing. However, the same kind of food could remind some people of the discomfort and annoyance brought on by lactose intolerance. Should they avoid all these delicacies altogether or resort to taking lactase pills every time after eating food containing lactose? Here, we offer you a new choice.
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How we are going to tackle it |
We aim to design and construct a probiotic E. coli strain that (1) produces high level of the beta-galactosidase enzyme (a type of lactase) constitutively, and (2) autolyses to release the beta-galactosidase enzyme upon detecting lactose in the external environment. For process (1), we will construct a lacZ (beta-galactosidase) -lacY (lactose permease) biobrick that is driven by a strong constitutive promoter to enable high expression of the beta-galactosidase enzyme. For process (2), we will construct a lysis cassette consisting of the S (holin)-R (endolysin) -Rz (spannin) genes driven by a lacI promoter to facilitate lactose-induced cell lysis.
To optimize the efficiency of E. coli cell lysis, we will carry out the following modifications to certain genes in the lysis cassette: 1. Genes in the lysis cassette will be codon optimized for optimal expression in E. coli; 2. The anti-holin component will be deleted to speed up cell lysis; 3. Specific mutations will be introduced into the lysis gene cassette to facilitate shorter lysis time. In this project, we will also prepare and compare the lysis efficiency of two different lysis cassettes – (1) Cassette 1 will be constructed using the Sλ , Rλ and Rzλ genes derived from E. coli lambda phage, and (2) Cassette 2 will be constructed using the S21, R21 and Rz21 genes derived from E. coli phage 21. |
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