Study On Fermentation, Extraction Technology And In Vitro Antioxiant Activities Of A Higher Monascus Exopolysaccharides Producing Strain

Monascus belongs to Ascomycetes, Euascomycetes, Plectascales, Eurotiaceae, is a nutritional and medicinal mushroom with refreshing fragrance. Its secondary metabolites such as Monascus pigment, Monacolin K and y-aminobutyric acid (GABA) had been widely studied for their chemical properties and biological activities. The polysaccharides from Monascus had also attracted great attention in recent years, due to their various biological functions such as antitumor, antibacterial and antioxidant activity.In this study, a Monascus strain with higher yield expolysaccharides production was isolated from different market-sold red fermented rice and red preserved beancurd; liquid fermentation conditions and medium composition optimization of a high-yield of expolysaccharides Monascus strain Mr-70was studied; the extraction conditions for exopolysaccharides and mycelium polysaccharides in submerged culture were optimized on the basis of single-factor test and response surface methodology (RSM). The in vitro antioxiant activities of exopolysaccharides and mycelium polysaccharides were evaluated.(1) Two hundred and fifty-six Monascus strains were isolated and purified from different red yeast rice and red preserved beancurd. Through shake flask test, the strain Mr-70with the highest-yield exopolysaccharides (EPS) of5.35g/1was screened out. The strain Mr-70was identified as Monascus rubber based on morphological, physiological characters and ITS region sequence comparisons.(2) To maximize the exopolysaccharides productivity of the strain Mr-70, various parameters were studied through single-factor experiments in liquid-fermentations. The fermentation conditions were optimized as follows:glucose60.0g/1, peptone20.0g/1, KH2PO410.0g/1, MgSO4·7H2O1.1g/1, pH6.5, rotation speeds200r/min, culture tEPSerature32℃, and fermentation lasted for96h. Under these conditions, the yield of exopolysaccharides for the strain Mr-70could reach10.15g/1in shaking-flask.(3) The extraction conditions for producing exopolysaccharides by the strain Mr-70were optimized in order to enhance the extraction yield. Single-factor experiments were carried to investigate the influences of the extraction time, the alcohol concentration, and the pH value of fermentation broth on extraction yield of Monascus exopolysaccharides. On the basis of single-factor experiments, a quadratic polynomial regression equation of the forecasting model was set up by using Box-Behnken central composite design of three factors and three levels and the method of response surface analysis. The optimized extraction conditions were obtained:alcohol concentration80%, extraction time16.5h, the pH value of fermentation broth8.05. Based on these conditions, the yield of exopolysaccharides for the strain Mr-70could reach7.40g/1.(4) In the present work, alkali extraction technology was used to optimize the extraction of the strain Mr-70mycelium polysaccharides for the first time. Single-factor experiments were carried to investigate the influences of extraction temperature, alkali concentration, solvent/material ratio and extraction time on the extraction yield of the strain Mr-70mycelium polysaccharides. On the basis of single-factor experiments, a quadratic polynomial regression equation of the forecasting model was set up by using Box-Behnken central composite design of four factors and three levels and the method of response surface analysis.The optimum conditions were extraction temperature49℃, alkali concentration7%, solvent/material ratio23:1(ml/g) and extraction time2.3h with an enhanced yield of10.1%for the strain Mr-70.(5) The in vitro antioxidant activities of the strain Mr-70exopolysaccharides (EPS), alkali extracted Monascus mycelium polysaccharides (AMP) with hot water extracted Monascus mycelium polysaccharides (HMP) were investigated including superoxide radical (02-·), hydroxyl radical (OH-) and2,2-diphenyl-l-picrylhydrazyl (DPPH) radical. The results showed that three kinds of Monascus polysaccharides have a certain extent antioxidant effect in vitro, but EPS exhibited stronger scavenging activities than mycelium polysaccharides. The result also demonstrated that AMP have the similar capability of scavenging superoxide radical, hydroxyl radical and DPPH radical with HMP in vitro. Compared with the extracting yield4.76%of HMP, alkali extraction technology is not only a high-efficiency way to extract the strain Mr-70mycelium polysaccharides, but also can retain the natural antioxidant activities of AMP, which can be used in pharmaceutical and food industries.