Regulation Of Permeability Of Yeast Cells And Its Synthesis Of Glutathione

Glutathione(GSH)is the most abundant non-protein sulphydryl compound in organism.Under the action of ?-glutamy cysteine synthase(GCS)and glutathione synthase(GS),the precursor amino acid glutamate,cysteine and glycine were condensed into glutathione.Glutathione has the functions of antioxidation,maintaining cellular enzymatic activity,participating in the synthesis of DNA and protein,resisting endotoxin and free radical damage to cells,and it is widely used in the fields of food,cosmetics and healthcare.In this paper,flocculation yeast SP5,a strain with a good ability of GSH synthesis was used in GSH production.In order to accumulate and secret high concentration of GSH,the strategies of regulating the permeability of cells,changing cell culture condition,reducing GSH degradation were used.The main contents and results of the study are as follows:(1)The cell growth,GSH synthesis and glucose metabolism in the process of GSH fermentation and enzymatic synthesis of GSH were investigated,which showed that the cell culture time was 36 h,enzymatic reaction time was 6 h.The methods of freeze drying,ethanol permeabilization and tween-60 permeabilization were used to permeate cells,The results showed that Tween-60 had no significant effect on cell permeability and GSH synthesis.After freezing,cell permeability was improved and the amount of intracellular GSH secretion increased.Freeze-drying for three days,the total GSH concentration reached 330 mg/L,which was 17.8% higher than the blank.When cells were treated with 30% ethanol,the intracellular GSH can be secreted out of cells,and the cell enzymatic synthesis of GSH concentration reached321 mg/L.(2)There were some positive effects on the secretion of GSH after adding cinnamaldehyde or citral aldehyde in the initial stage of fermentation,but it was not conducive to the growth of cells,the concentration of intracellular GSH decreased,and the total amount of GSH produced by cell fermentation did not increase significantly.The collected cells were used in enzymatic synthesis of GSH.The cells were found to have the ability of secreting GSH,and the amount of intracellular accumulation increased either.After regulating cells growth by 45 ?g/mL cinnamalde-hyde or 100 ?g/mL citral,the total amount of GSH reached the relatively highervalue of 446 mg/L and 410 mg/L respectively.(3)The effects of the liquid volume,carbon source types and the initial concentration,fermentation mode and glucose supplement on the enzymatic synthesis of GSH were investigated.The result showed that glucose 45 g/L,flask liquid volume70 mL,after 24 h,static culture for 12 h,and glucose supplement 25 g/L,were more conducive to the enzymatic synthesis of GSH,the GSH yield reached 461 mg/L.Combined with the regulation of cinnamaldehyde or citral,the enzymatic synthesis of GSH reached 580 mg/L and 551 mg/L respectively.(4)The effects of L-serine and potassium borate alone and in combination on cell growth and GSH synthesis were preliminary studied,and It was found that the addition of L-serine alone was helpful for the growth of cells,but had no significant effect on the GSH synthesis ability of the cells.The addition of potassium borate alone had a strong inhibition on the growth of cells,but the ability of cells to synthesize GSH was improved and when L-serine and potassium borate were added together,the GSH synthesis ability of the cells is further improved.