Production Technology Of Yeast Mannan

Saccharomyces cerevisiae mannan was a layer of biologically active polysaccharide polymer coating the yeast cell walls, and its backbone was composed of sugar chain of mannose formed by α-(1,6) glycosidic bonds, linked with abundant branched chains through α-1,2 or α-1,3 glycosidic bonds. Yeast mannan was found to be the cell wall polysaccharide with the strongest immune function so far. It can significantly increase body immunity, stimulate the growth of intestinal probiotics, inhibit and reduce the breeding of pathogens, coupled with antiviral, antitumor, and antioxidant activities,making it a potential functional food and feed additive. Considering its remarkable biological activity and wide application prospect, the research and development of yeast mannan become a research hotspot. The process conditions for the formation and release of yeast mannan were studied in this paper, and on this basis, extraction process of yeast mannan was preliminarily constructed.With yeast mannan content as an indicator, the yeast culture technology was optimized by using the single factor and the response surface method. Through single factor experiment on culture medium composition, significant factors were selected, and the optimized culture medium compositions determined by the response surface method were 4.62% glucose, 5% peptone, 3.23% yeast extract powder, and 0.06% MgSO4. The content of the yeast mannan after optimization reached 1.69 g/L, increased by 122.37%.On this basis, optomal culture conditions optimized by further response surface method were as followed: temperature 29.73℃, shaking speed 212.66 rpm, initial pH 5.45, and liquid volume in flask 40 ml. The optimal culture process was verified, and the content of yeast mannan was 1.94 g/L, increased by 15.48% to that before optimization.Using yeast-Bacillus subtilis mixed stage fermentation system, yeast mannan from the fermentation system was released into fermentation broth. Firstly, the mode of yeast-Bacillus subtilis mixed fermentation was established: Yeast was initially inoculated in the fermentation system, then yeast was inactivated after culture, followed by the inoculation of Bacillus subtilis. Using the complex enzymatic system secreted by Bacillus subtilis, yeast cell walls were degraded and destroyed, releasing mannan into the fermentation liquid. Secondly, the medium fed-batch mode for the yeast-Bacillus subtilis mixed fermentation was optimized. Using exponential fed-batch feeding mode,concentration of yeast mannan in the supernatant of the fermentation system reached up to5.89 g / L, with a yeast mannan release rate of 96.56% in the fermentation system.Yeast mannan extraction process and condition was studied, and the optimal condition for alcohol precipitation of mannan was established: fermentation broth enrichment factor was 5, processing temperature was 4 ℃, pH 7, alcohol precipitation duration was 5h, first alcohol precipitation concentration was 90%, and second one was70%. Through the process optimization, the crude yield was 39.05% with a purity of 39.57%.