Investigation On Production Technology Of Mannan From Saccharomyces Cerevisiae

Yeast mannan presents in the outer layer of the yeast cell wall that accounts for about40% of dry weight,and it is a kind of microbial polysaccharide which has a significant physiological activity.It has been reported that mannan has a strong immune function,adsorption of mycotoxins,moreover,mannan have the founctions of anti-tumor,anti-oxidation,and it have functions of lowring blood lipids,anti-radiation and other bioactive functions.Mannan is widely used in health food,pharmaceutical and feed industries.In this work,the fermentation conditions of Saccharomyces cerevisiae with high content of mannan were studied,in addition,the pretreatment methods of the yeast cell wall and the extraction and refining process of yeast mannan were investigated.The main results are as follows:Culture conditions of Saccharomyces cerevisiae with a high content of mannan were studied.It was founded in the experiment that the mannan content varies greatly in different strains of Saccharomyces cerevisiae and KD10 had the highest content of mannan in this 10 screened strains.The content of mannan of the yeast in the stable growth phase was higher than which in the logarithmic growth phase.Compared with glucose,the mannan content was improved when glucose and lactose were used as carbon source.Compared with yeast extract,the mannan content was improved slightly and cells grew much better when yeast extract and peptone were used as nitrogen source.It was indicated that synthesis of mannan improved when C/N was set relatively low.The synthesis of the mannan content of KD10 was significantly promoted when folic acid was added.It was also been founded that stress made the mannan content of cell increased.The optimal medium for KD10 were determined as: 37.5 g/L glucose,12.5 g/L lactose,37.5 g/L yeast extract,37.5 g/L peptone,0.3 g/L KH₂PO₄,0.3 g/L K2HPO₄,0.5 g/L MgSO₄.Study on yeast cell wall pretreatment methods.The KD10's release rate of mannan was detected with 15.85% under optimum autolysis conditions?pH 6.0,bath temperature55?,holding time 40 h?.Mannan release rate was very low?0.31%?when yeast cells were dealed with snailase.Mannan was released so much when yeast cells were processed under a high temperature of 121?.Compared with the treatment of high-temperature with a short-time?121?,30 min?,the release rate of mannan was significantly increased withautolysis + high temperature processing and mechanical broken + high temperature treatment.It was determined that the suitable conditions for heat treatment of Saccharomyces cerevisiae were: bacterial suspension concentration of 15%,pH 7.0,treatment temperature 121?,treating for 10 h,which mannan release rate was 95.89%.Extraction and purification of mannan.Extraction of mannan was significantly affected by the supernatant of concentration and the concentration of ethanol.The mannan raw yield decreased with temperature of alcohol precipitation increasing.The extraction of mannan was not effected significantly by the pH of alcohol precipitation.Almost no difference in the yield and purity of mannan raw sugar when the alcohol precipitation time was 0.25¹0 h.While mannan yield decreased significantly when more than 10 h.Suitable mannan alcohol precipitation conditions were: supernatant was concentrated in multiples of 6,pH 7.0,and alcohol precipitation temperature was 4?,ethanol concentration was90%,1 h.The purity and yield of mannan were 22.24% and 92.60 mg/g.Different purity mannan were produced by the method of grade alcohol precipitation.The purity of mannan raw sugar was improved significantly after separation membrane of dialysis bag of 3500,7500,14000 Da.The mannan purity reached 36.89% with the processed of dialysis bag with MWCO of 3500 Da,which increased 65.87%.