Biosynthesis Of Glutathione And Its Kinetices Model

Biosynthesis of Glutathione and its Kinetices ModelThe analytical method of glutathione were studied by iodimetry, visible spectroscopy and ultraviolet spectroscopy. The analytical results obtained by ultraviolet spectroscopy gave the best method, which was very fit the assay of glutathione. The ultraviolet spectroscopy is steady and sensitive. The average relative error of the ultraviolet spectroscopy was no more than 3%.A zinc chloride- and ethionine- resistant mutant 0.5Eth400-5 was obtained from its parent strain Saccharomyces cerevisiae 346 by UV and 60Co r-ray treatment and rational screening. The glutathione productivity of the mutant reached 165.96mg/L by flask culture, which was 350% higher than the parent strain, and the glutathione content in the dried cells reached 19.76mg/g, which was 320% higher than the parent strain. A desecend of only 10.7% in the glutathione yield of the mutant was observed after ten times of subculture. Therefore, the obtained mutant is stable strain that is worthwhile to be studied further.Systematic studies were carried out on the optimization of composition of medium which accumulated the largest amount of glutathione in the mutant 0.5Eth400-5. This optimizing medium was formulated vas Plackett-Burman design and response surface analysis(RSA).The glutathione yield was235.7mg/L under the optimum condition, which was 45.4% higher than that of non-optimized medium.In a 5 -liter scale batch bioreactor, the rules of glutathione fermentation were studied by fed-batch operation. The maximum glutathione yield was obtained as well after 36 hours' fermentation, which was 638.91mg/L.The fermentation kinetics of glutathione with Saccharomyces cerevisiad).5Eth4QQ-5 were studied. The kinetic models were obtained. A simple model was proposed using the Logistic equation for growth, the Luedeking-Piret equation for glutathione and the Luedeking-Piret-like equation for glucose consumption. The cell growth modelwas the glutathione biosynthesis model was ln(0.9927 + 0.007329 the glucose consumption model was Cs(t)=32.52359coefficients of the three models were no less than 0.979. The kinetic model provideda reasonable description for biomass, product and substrate variation along with thefermentation process.