Effect Of Several Flavonoids On The Yield Of Citrinin From Monascus Aurantiacus AS3.4384

Monascus sp.is a kind of traditional fermented edible fungus in China and belongs to filamentous fungi.It has been used in China for many years.Its main metabolites include monascus pigments,y-aminobutyric acid,Monacolin K and ergosterol,which have a variety of activities,not only food value,but also have medicinal functions.However,Monascus also produces citrinin,which greatly limits the wide application of Monascus.In order to reduce the ability of erythromycin-producing citrinin,it can be achieved by improving the fermentation process or using genetic engineering methods to knock-out citrinin synthesis related gene.In this study,Monascus aurantiacus AS3.4384 was used as the research object,and several flavonoids were mainly used to inhibit the synthesis of citrinin by adding exogenous flavonoids in the liquid fermentation medium.The production of beneficial secondary metabolites gave the fermentation product more abundant activity.The main results were as follows:(1)Monascus aurantiacus AS3.4384 was used as the fermentation strain and liquid fermentation was carried out in rice powder inorganic salt,starch inorganic salt,amylase,sucrose yeast soaking(YES)mediums,and citrinin was detected by high performance liquid chromatography(HPLC).The yield of pigments were detected by ultraviolet spectrophotometry,and the biomass was measured by cell weighing method.The results showed that:Monascus aurantiacus AS3.4384 could produce different amounts of citrinin in several of the above-mentioned culture mediums.Among them,the production of citrinin reached 41.00 μg/ml in a liquid shake flask for 16 days in rice powder inorganic salt mediums.Fermentation in liquid shake flask for 12 days in starch inorganic nitrogen source inorganic salt mediums,the yield of citrinin was 11.59 μg/mL Fermentation in liquid shake flasks for 24 days in high-starch amyloid mediums,the yields of citrinin was 95.09 μg/mL.In the YES mediums for 15 days,the yield of citrinin was as high as 671.98 μg/mL.(2)Monascus aurantiacus AS3.4384 strain was used as fermentation strain,starch inorganic salt mediums were used as fermentation mediums,and 3 different sources of rutins were used as exogenous additives.After the addition of 3 kinds of rutins,the contents of citrinin,pigments and biomass in the liquid culture broth of Monascus aurantiacus AS3.4384 were measured.The results showed that α-glucosylrutin and troxerutine significantly inhibited the production of citrinin,and the yield of citrinin decreased by 54.66%and 40.56%after adding 5.00 g/L of α-glucosylrutin and troxerutine respectively.Rutin’s ability to inhibit citrinin was weak,only a decrease of 29.23%with 5 g/L added dose.(3)Adding 5.00 g/L rutin to the starch inorganic salt fermentation mediums increased the content of yellow pigments from 5.19 U/mL to 10.25 U/mL.Added 5.00 g/L α-glucosylrutin,yellow pigments also increased to 10.08 U/mL.with 5.00 g/L of troxerutine,yellow pigments production increased to 10.06 U/mL,and red pigments and orange pigments decreased slightly.The addition of α-glucosylrutin and troxerutine had no effect on the dry cell weight for the strain.The addition of rutin changed the color of the fermentation broth,didn’t reduce the biomass,and affect the growth of the fungal cell.(4)The above-mentioned culture mediums which producing citrinin were used as fermentation mediums,Monascus aurantiacus AS3.4384 was used a fermentation strain,and troxerutine was used as an exogenous additive,and it was subjected to liquid shake flask fermentation.The content of citrinin in the fermentation broth and the biomass were determined.The results showed that:in the starch inorganic liquid culture mediums,after 20.00 g/L of troxerutine was added and fermented for 12 days,the yield of citrinin was reduced by 75.26%.In rice powder inorganic salt liquid mediums,the addition of 15.00 g/L troxerutine for 12 days resulted in a decrease in citrinin production by approximately 64.96%.In high starch content peptone liquid mediums,20.00 g/L troxerutine was added for 20 days and the yield of citrinin was reduced by 59.30%.Adding 15.00 g/L troxerutine to the low-starch amylase liquid fermentation mediums resulted in an 87.94%reduction in citrinin production after 14 days fermentation.When 30.00 g/L of troxerutine was added to YES liquid mediums for 12 days,the yield of extracellular citrinin was reduced by 53.73%,after adding 20.00 g/L troxerutine for 12 days static fermentation,the intracellular citrinin production decreased by 47.86%.(5)Soybean isoflavones was used as an exogenous additive.The strain Monascus aurantiacus AS3.4384 was used as a fermentative strain.The culture mediums which producing citrinin mentioned above were as fermentation mediums for liquid shake flask cultures.The citrinin production in the fermentation broth was determined by HPLC.The results showed that 20.00 g/L soybean isoflavones was added in rice powder inorganic liquid mediums,after 16 days fermentation,the yield of citrinin was reduced by 95.98%compared with the control group.In starch inorganic liquid mediums,10.00 g/L soybean isoflavones was added for 12 days fermentation,the yield of citrinin was reduced by 97.24%.In the high starch content amylase liquid culture mediums,20.00 g/L soybean isoflavones was added for 20 days fermentation,and the yield of citrinin was reduced by 82.52%.Adding 5.00 g/L soybean isoflavones in a low starch content amylase liquid culture mediums for 14 days fermentation,reduced the yield of citrinin by 45.07%.Adding 20.00 g/L soybean isoflavones in the YES(1%+0.25%)liquid mediums,and after static fermentation for 14 days,the yield of citrinin decreased by 82.21%.