Gold Award For International Genetically Modified Machines Competition In 2008

I worked in Chris French's lab in Darwin Building at Kings' Buildings from June to September in 2008 summer. I was a main member of the iGEM 08' team and worked on a project, which was about the production of starch and beta-carotene from cellulosic biomass. Basically, we were trying to build five different genetic devices, which together give rise to the production of three different products: starch, beta-carotene and limonene. These five different devices are: the degradation of cellulose into glucose, the production of glycogen from glucose, the production of starch from glycogen, the production of beta-carotene from glucose and the production of limonene from glucose. We used E.coli as the host to carry out those five different pathways. So, in order to encourage E.coli to do so, we genetically modified this commonly used organism according to the needs of different genes in each pathway. For the degradation of cellulose into glucose, we employed Cex, CenA and beta-glucosidase. CenA encodes an endoglucanase, which makes nicks on the cellulose backbone; Cex encodes an exoglucanase, which degrades the exposed ends to release cellobioses. The cellobiose is further degraded into glucose by beta-glucosidase. Moreover, the glgc encodes a rate-limiting enzyme, which is involved in the process of converting glucose into glycogen. So, we mutated this gene into glgc16 by changing the glycine into aspartic acid at position 336. As a result, the yield of glycogen production increased. Finally, we used two genes (su1 and iso2) isolated from maize to convert glycogen into starch. For the production of beta-carotene, we cloned dxs, Appy, CrtEBIY into a BABEL vector. In contrast, a gene, LIMS1 isolated from limon citrus, was used to produce limonene from glucose. In the lab, most of our lab works were genetic cloning. We made each gene as a biobrick by adding the same prefix and suffix on each end of the gene using PCR, and then combined them in order according to each pathway. Finally, we cloned the combined biobricks into a vector, and added promoter and ribosome binding site in the front of each device; finally we tested the productions by using different assays. What we have achieved was that we managed to increase the yield of glycogen by mutating glgc. This result was tested by a glycogen assay. We also produced the lycopene, which is the last precursor of beta-carotene. In 8 & 9 November 2008, we went to the Jamboree MIT in US and presented our summer work to all the teams from the whole world. We were awarded a gold medal for what we did in the end.