Study On Mutation Breeding Of Escherichia Coli With Low Energy Ion Implantation

Low-energy ion implantation has been considered as new kind of mutation breeding and foreign gene delivery techniques. By the means of implanting low-energy ions into organisms, the biological effects and the function mechanisms of the technique were investigated by some researchers. Although the researchers have observed some biological effects and revealed some basic mechanisms since past the decade, they do not master the roles of low-energy ion implantation, and the studies on the law of inheritance in the microorganism irradiated by low-energy metal ions has not been reported so far. In our experiments, choosing the Escherichia coli containing aspartate transminase as the target of low-energy ion implantation, we observed and counted the biological effects of the E.coli,to make the fundaments for exploring the interaction between low-energy ions and complicated organisms further. At the same time by strain breeding high-yielding E.coli.can we make an improvement the productivity of L-Phenylalanine.First of all, the best E.coli was screening from laboratory preserved bacterium after rejuvenating , culturing and determining the activity of the aspartate transminase. Then we studied its character of bearing the irradiated with UV,counted the biological effects of the E.coli, and choosed the high-yielding mutation as the beginning E.coli waiting for farther irradiated with low-energy ions.In this paper, we chiefly discussed the biological effects after implanting low-energy ions into the E.coli. We studied the interaction between low-energy ions and E.coli.by irradiating it with different energy, doses and different kinds of ions. Then we compared the different mutagenic effects of E.coli irradiated with UV and low-energy ions. The results show that the E.coli by ion implantation can achieve higher rate of mutation and wide mutational spectrum. A high yield L-phe strains has been bred from this. In the shaking flask, the L-phe productivity of strain U12-J3 increased by 22.67% than of the comparison strain with the PPA concentration of 20g/L.On the other hand, we found that it was feasible of using PPA grads culture medium to breed L-phe strains that can bear high concentration of PPA. As a result that L-phe yield was 27.5g/L with the PPA concentration of 40g/L.and increased by 17.36% than of the comparison strainThe last, we studied several chief factors that could impact on the activity of the aspartate transminase and optimized the culturing and bioconversion conditions. By doing experiments we optimized the quantity of culture medium and seed.,fermentation time, bioconversion time and the speed of the shaking flask while conversing. In the optimum condition, the L-phe productivity of strain U12-J3 could steady at about 85%. with the PPA concentration of 20g/L.