Study On Liquid Fermentation Of Monascus ZH2 With High Yield Of Orange Yellow Pigment And Low Yield Of Citrinin

The fermentation products of Monascus purpureus include Monascus pigment,Monacolin K,isoflavone,γ-aminobutyric acid,dimeric acid,citrinin and other compounds.As a kind of natural pigment,Monascus pigment can be divided into three types according to color:red pigment,orange pigment and yellow pigment.The production process of Monascus red pigment is very mature and the consumer market is huge.The sensory properties of Monascus orange pigment and yellow pigment are excellent,but the output does not meet the market demand,so it has great economic development potential.Citrinin and Monascus pigment have a common way of formation,which has a strong renal toxicity.Therefore,citrinin content is reduced in the fermentation process.The purpose of this thesis is to increase the output of red yeast orange and yellow pigment while reducing the content of citrinin,study the basic properties of Monascus orange and yellow pigment,improve the safety of the production and application of Monascus products,and expand foreign markets.The main research contents are as follows:（1）At first,the single factor optimization experiment was carried out on the Monascus purpureus ZH2,and the orthogonal design experiment was carried out on the factors that have great influence on the pigment yield.Finally,the suitable medium composition and culture conditions were determined as follows:soluble starch 50 g/L,（NH₄）₂SO₄ 10 g/L,K₂HPO₄ 2.0g/L,Mg SO₄ 2.0 g/L,Zn SO₄ 0.02 g/L;at 28℃,the liquid loading amount was 50 m L/250 m L,the initial p H was 4,the rotation speed was 200 r/min and incubated for 5 days.The color value of orange and yellow increased from 17.304 U/m L and 26.404 U/m L to 154.375 U/m L and 106U/m L respectively,8.23 and 4.42 times higher.The content of citrinin decreased by 30%to5.804μg/ml.（2）By adding different external additives,it was found that 10 g/L Tween-80 and 10 g/L tralaton X-100 in the surfactant had more prominent effect on the growth of Monascus zh2.The most suitable medium for Monascus pigment growth was 20 m L olive oil/50 m L medium.Among the fatty acids,octanoic acid is the most important one to promote orange and yellow pigment,while decanoic acid is the most obvious one to inhibit citrinin.（3）The results showed that the extraction rate of Monascus and yellow pigment was the highest under the conditions of pure methanol,40℃and 30 min.The results of citrinin extraction showed that the extraction amount of citrinin was the largest when pure methanol was used,the ratio of material to liquid was 1:20,the extraction temperature was 70℃,and the extraction time was 60 min.（4）The separation,preparation and performance analysis of Monascus orange and yellow pigment were carried out.The separation of Monascus orange pigment was the best with toluene:ethyl acetate:formic acid=8:2:1（V/V/V）.The separation effect was the best with n-hexane:ethyl acetate:petroleum ether 32:16:5（V/V/V）.The thermal stability,p H stability,light stability,time stability and antioxidant activity of Monascus pigment were analyzed.The results showed that the heat stability of yellow pigment was the best,the p H and light stability of Monascus yellow pigment was the strongest,and the time stability of Monascus orange pigment was the best.