Screening And Identification Of High-quality Monascus Strains And Carbon/nitrogen Metabolism Differences

Monascus is also known as "Red Rice" "Hong Qu","Dan Qu" and so on in ancient times,and is widely used in Fujian,Zhejiang,Jiangxi,Guangdong and Taiwan,in China.It is mainly used in wine,medicine and food additive etc.Fujian abounds in Monascus and has much species diversity.It is the local characteristic resources in Fujian province.In this paper,the Monascus strains of high pigment,Monacolin K and low citrinin were screened systematically.What's more,the medium of Monascus strains was optimized and the carbon/nitrogen sources regulation was studiedFifty-three strains of Monascus were firstly isolated from the red yeast rice in Fujian,seventeen of which were selected through morphological classification and identification.Then the seventeen strains were classified and identified by molecular biological method with physiological and biochemical method to determine its biological status.Comprehensive analysis of morphological,physiological and biochemical tests and molecular biological identification revealed that seven strains were Monascus serorubescens Sato,six strains were Monascus kaoliang,and three strains were Monascus albidulus and one strain was Monascus purpureus.Through liquid and solid fermentation,the production ability of pigment,Monacolin K and citrinin was detected.A kind of good quality strain of Monascus kaoliang,which was named T3,was creened because of its good producing ability of pigment,Monacolin K,and weak ability to produce citrinin.Through the comparison of pigment yield of Monascus strains in nine different fennentation substrates,the most suitable substrate was selected.The research results showed that the brown rice was the best substrate to get the highest pigment yield in solid state fermentation system.What's more,carbon,nitrogen sources and inorganic salts were added to compare the effects of different types of carbon,nitrogen sources and inorganic salts on the stain's pigment-producting capacity.The results showed that the optimal conditions were 0.6%fructose,0.05%NH4Cl,initial moisture content of 50%,0.30%KH2PO4 and 0.20%MgSO4.The results of response surface method showed that the fructose additive amount,NH4C1 additive amount and initial moisture content had significant effect on pigment production,and the interaction between NH4Cl additive amount and initial moisture content was found.The optimal process conditions optimized were 0.54%fructose,0.06%NH4Cl and initial moisture content of 46%.The maximum pigment production predicted in the model in was 6693.99 U�g-1.Under the optimal conditions optimized by response surface analysis method,5 parallel experiments were conducted,and the actual measured monascus pigment color value was 6684.16 U�g-1,which was very close to the predicted value of 6693.99 U�g-1.The liquid fermentation conditions of T3 were optimized.Glycerol,sucrose,rice powder,soluble starch,lactose,maltose,glucose,mannitol and fructose was used as carbon source,and peptone,soybean meal,yeast powder,sodium nitrate,beef extract,corn syrup,(NH4)2SO4,sodium glutamate were selected as nitrogen source.The results indicated that glycerol and beef extract were the most suitable carbon and nitrogen source for T3 in liquid fermentation.Carbon and nitrogen sources with large pigment production differences were selected to study the metabolite characteristics.The results showed that the large differences in pigment production began at the 9th day in the fermentation.After the detection of other metabolites,we found that different carbon and nitrogen sources had obvious effects on pigment,Monacolin K and citrinin production in the liquid fermentation of Monascus.Finally,RNA libraries were construsted by differential analysis of transcriptomes.The numbers of differentially expressed genes in pairwise samples of soluble strach and glycerol,peptone and beef extract,ammonium sulfate and peptone,ammonium sulfate and beef extract were 865,495,659 and 53 1.The differentially expressed genes mainly belong to carbohydrate transport and metabolism,amino cid trasport and metabolism,inorganic icon transport and metabolism,posttranslational modification,and protein turnover,chaperones by COG functional annotation methods.What's more,many genes classified to secondary metabolites biosynthesis,trasport and catabolism were identified.This paper provides reference information and theoretical basis for the systematical classification of Monascus strains in Fujian Province,the culture medium optimization of Monascus,and the carbon and nitrogen sources regulation.