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| − | <h3>Our fun project!</h3> | + | <h3>This autumn, we're coming!</h3> |
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| − | <h4>Project Description</h4> | + | <h4> This is our team!</h4> |
| − | <p> | + | <p>Team Nankai 2015 is consist of ? junior students, ? senior students and 3 instructors. With our team established in March 2015, we are more than excited to join the big community of iGEM. Our team is organized within the College of Life Science of Nankai University, where all of the team members have spent two or three years studying and conducting researches. </p> |
| − | Poly-γ-glutamic acid (γ-PGA) is an important, naturally occurring polyamide consisting of D/L-glutamate monomers. Unlike typical peptide linkages, the amide linkages inγ-PGA are formed between the α-amino group and the γ-carboxyl group. γ-PGA exhibits many favorable features such as biodegradable, water soluble, edible and non-toxic to humans and the environment. Therefore, it has been widely used in fields of foods, medicines, cosmetics and agriculture and many unique applications, such as a sustained release material and drug carrier, curable biological adhesive, biodegradable fibres, and highly water absorbable hydrogels.<br>
| + | <p>The idea of synthetic biology attracted us in a way that other fields of study never could, and our passion about science is the engine that has led us all the way through obstacles and setbacks. We are persevering and capable as a research team. However, at spare times, we are just a group of fun-loving young college students. There is always an atmosphere of anticipation that we could blend into iGEM community. So we are looking forward to seeing you at the Giant Jamboree!</p> |
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| − | Strains capable for producing γ-PGA are divided into two categories based on their requirement for glutamate acid: glutamate-dependent strains and glutamate-independent strains. Glutamate-independent strains are preferable for industrial production because of their low cost and simplified fermentation process. However, compared with glutamate-dependent strains, their lower γ-PGA productivity limits their industrial application. Therefore, the construction of a glutamate-independent strain with high γ-PGA yield is important for industrial applications. <br>
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| − | <em>Bacillusamyloliquefaciens</em> LL3, isolated from fermented food, is a glutamate-independent strain, which can produce 3-4 g/L γ-PGA with sucrose as its carbon source and ammonium sulfate as its nitrogen source. The <em>B. amyloliquefaciens</em> LL3 strain was deposited in the China Center for Type Culture Collection (CCTCC) with accession number CCTCC M 208109 and its whole genome has been sequenced in 2011. In this study, we aimed to improve the γ-PGA production based on the <em>B. amyloliquefaciens </em>NK-1 strain (a derivative of LL3 strain with its endogenous plasmid and <em>upp</em> gene deleted).<br>
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| − | In order to improve γ-PGA production, we employed two strategies to fine-tune the synthetic pathways and balance the metabolism in the glutamate-independent <em>B. amyloliquefaciens </em>NK-1 strain. Firstly, we constructed a metabolic toggle switch in the NK-1 strain to inhibit the expression of ODHC (2-oxoglutarate dehydrogenase complex) by adding IPTG in the stationary stage and distribute the metabolic flux more frequently to be used for γ-PGA precursor-glutamate synthesis. As scientists had found that the activity of ODHC was rather low when glutamate was highly produced in a <em>Corynebacterium glutamicum</em> strain. Second, to balance the increase of endogenous glutamate production, we optimized the expression level of <em>pgsBCA</em> genes (responsible for γ-PGA synthesis) by replacing its native promoter to seven different strength of promoters. Through these two strategies, we aimed to obtain a γ-PGA production improved mutant strain. </p>
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