| Monascus is a filamentous fungus of the monascaceae,and used for a traditional dual-purpose microbe more than 1000 years in China.Monascus pigments(MPs)is a general term for a series of polyketides produced by Monascus during growth and metabolism.With the advantages of "natural,nutrition and multi-function",MPs has a variety of functions such as lipid lowering,antibacterial antiseptic,anti-cancer and anti-tumor.Therefore,it has been widely used in food,medicine,feed and textile industries.In this paper,a strain of Monascus purpureus with high yield of MPs was isolated and identified from commercial red yeast rice.The technology of liquid and solid state fermentation of the M.purpureus was studied.The technology of extraction and concentrate of MPs from liquid fermentation broth was established by using ethanol-ammonium sulfate aqueous two-phase extraction method.The stability of MPs was investigated in order to provide a reference for the further development and utilization.There are the main research results of this paper:1.Screening and identification of MPs-producing strainsUsing the method of plate dilution coating,a Monascus strain YY1-3 with good growth and fermentation performance and high potential for MPs production was screened from commercially available red yeast rice.It was identified as Monascus purpureus by morphological observation and 18S rDNA sequence analysis.2.Study on the production of MPs by liquid fermentation of M.purpureusSingle factor experiments were used to investigate the effects of carbon sources,nitrogen sources,inorganic salt types and concentrations on the production of MPs by liquid fermentation with YY 1-3.The results showed that nitrogen sources and glycerol concentrations had significant effects on MPs production.By optimizing the medium composition of MPs produced of YY 1-3,The optimum medium composition as follows:12.1 g/L for peptone,61 g/L for glycerol,0.10 g/L for FeSO4·7H2O,and 4.2 g/L for KNO3.The model prediction of highest yield of MPs was 5.22 mg/mL,the verification value was 5.93 ± 0.13 mg/mL higher than former,the closeness of two values was 88.03%.The amount of MPs in optimized medium was improved by 275%than initial medium.On this basis,after fermentation of 6 days at 30? pH 4.5,and 100 mL/250mL of liquid,the maximum yield of MPs could up to 6.02 ± 0.11 mg/mL.3.Study on the process of solid-state fermentation of MPs with M.purpureusTake the yield of MPs produced by YY 1-3 as the evaluation index,soybeans residue was the best solid-state fermentation matrix compared with rice,peeled soybeans,soybeans and wheat bran.On this condition,by the single factor method,the optimal values of glycerol,NaNO3,KH2PO4,MgSO4,ascorbic acid,initial water content,inoculum size,and fermentation time were selected.Then the orthogonal test of L16(45)was designed to further screen the optimal combination of glycerol,NaNO3,KH2PO4,MgSO4,and ascorbic acid.After analysis and verification experiments,the optimal combination of MPs was 6%of glycerol,NaNO3 0.04%,KH2PO4 0.3%,MgSO4 0.2%,ascorbic acid 22 g/kg,under this condition,the amount of MPs could reach to 6.03±0.11 mg/g.4.Extraction,purification and stability of MPsIn this experiment,the ethanol-ammonium sulfate two aqueous phase extraction method was used to extract and concentrate MPs from the fermentation broth by M.purpureus.The extraction and concentration of MPs was ideal when the mass concentration of ammonium sulfate was 28%and the mass concentration of ethanol was 16%in a 50-mL scale-out extraction system,the ratio R was 0.36,the distribution coefficient K and the recovery rate Y were 173.07 and 98.43%,respectively.About stability of MPs produced by YY 1-3,the research showed that MPs was more stable in condition of low temperature(65 ?),partial acid of pH value(5 and 6)and away from light.Food additives had little effects on their stability. |
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