Accumulation Regularity And Strategies For Control Of Ergothioneine Biosynthesis In The Fermentation Process Bypleurotus Ostreatus

L-ergothioneine(EGT)is a physiological protective agent with high added value.It has broad applications in areas such as cosmetics,functional foods,pharmaceuticals,therapeutics,biomedicine,and so on,for it’s biology and physiology characteristics.In recent studies,mushrooms were discovered to be the primary source of EGT and therefore possessed high antioxidant ability.Relevant research such as biosynthesis and industrialize preparation of EGT was carried out mainly through submerged fermentation of mycelia.In this thesis,Pleurotus ostreatus,was used to produce mycelia with high ergothioneine content.In the process of EGT fermentation,EGT accumulate regularity and control strategies was investigated,meanwhile,the industrialized preparation process of EGT was further optimized and strategies for control of EGT biosynthesis was studied.The main research and results are as follows:Regularity of EGT accumulate was studied,it was found that majority of EGT accumulate intracellular,and contents of extracellular was affected by external factors.Based on the level of shake flask,research was performed by investigating the effects of physical,chemical and biochemical factors on EGT permeation and accumulation regularity.The results indicated that addition of non-ionic surface active agent promoted the intracellular and total EGT accumulation,contents of EGT was up to 18.72mg/L、212.70 mg/L respectively,it was increased by 114.43%and 96.29%than the control group.Based on the regularity of EGT accumulation,effect of different extract solvent and extract times on intracellular EGT extraction was studied to verify the feasibility of using water as the sole extract solvent;Subsequently Response Surface Methodology was applied to optimize the temperature and ratio of water to mycelia in the extract process.At the optimized conditions,extraction rate of intracellular EGT was up to 97.1%.Based on the level of shake flask,studies was performed with an phase control to study the influence of pH and temperature on EGT biosynthesis,it showed that after rapid growth stage of mycelia,phase control of pH and temperature could significantly improve EGT production,it was increased by 23.45%and 19.97%respectively than the control group.Based on the level of shake flask and 30L fermenter,an investigation about regularity of EGT fermentation was carried out.The results showed that biomass of mycelia has positive correlation on EGT yield;On the conditions of 25℃,inoculum rate 9.5%(V/V),10%sat,contents of total EGT was up to 240 mg/L,contents of EGT for mycelia is about 8.00 mg/g DW.Based on the level of 75 L fermenter,factors that have significant effect on EGT biosynthesis was investigated,it reveals that high EGT contents was achieved in the high concentration of nitrogenous source,addition of precursors,proper control of dissolved oxygen.On the conditions of 25℃,glycerol 75.0 g/L,peptone from casein 35 g/L,methionine 2.1 g/L,cysteine 0.9 g/L,inoculum rate 6.6%(V/V),dissolve oxygen 30%sat,contents of total EGT was up to 352.83 mg/L,contents of EGT for mycelia is about 13.00 mg/g DW.