Metabolic flux analysis of glutathione biosynthesis with batch culture of Candida utilis

The metabolic network of Candida utilis WSH 02-08 for GSH biosynthesis,with glucose as the sole carbon source,was developed based on the stoichiometric balance equations to illustrate the carbon flux distribution of intermediates and metabolites.The metabolite flux distribution and alteration among pathways during diverse batch culture phases were calculated by using the metabolic flux analysis method.Subsequently,the carbon flux of glutathione biosynthesis was adjusted by two-stage temperature control of switching temperature from 30℃ to 26℃ in 8 h,or addition of 8 mmol·L -1 L-cysteine to the culture broth in 14 h.It was indicated that the production of glutathione was increased by 23% and 91%,respectively.Moreover,the mechanisms of the over-production of glutathione with the above-mentioned culture strategies were interpreted with the principles of metabolic engineering.