| Monascus pigment is a kind of natural pigment with a variety of bioactive functions,and has a wide application in food industry due to the good characteristics of safety,nutrition,and strong protein coloring ability.With the in-depth research on monascus pigments in recent years,the advantages of water-soluble monascus yellow pigment have become increasingly prominent in terms of high economic efficiency and wide application range.In this paper,some research has been carried out as following:screening and breeding Monascus strains with high yield of water-soluble yellow pigment,the metabolic regulation of nitrogen sources on high-yielding strains,and the effect of cell membrane permeability on the mechanism of pigment transmembrane secretion.These studies provide theoretical support for the development of industrial Monascus with high water-soluble yellow pigment production.1.A Monascus mutant BWY-5 with high production of extracellular water-soluble yellow pigment has been obtained by 12C6+ heavy ion beam radiation mutation breeding.The yield of extracellular water-soluble yellow pigment of BWY-5 was 80.93 U370/mL,and the production of total yellow pigment was 105.56 U370/mL,which was 8.4 and 2.62 times higher than that of LQ-6,respectively.However,the total yields of red and orange pigments of BWY-5 were only 0.18 U510/mL and 0.27 U470/mL.The organic nitrogen source was more favorable for the extracellular water-soluble yellow pigment production by BWY-5,which was 1.27 times higher than that of ammonium chloride,and more stable in the pH range of 1-14.2.The activity of mitochondrial respiratory chain-related enzymes was inhibited by peptone compared to ammonium chloride,and the activity of mitochondrial complex Ⅰ,mitochondrial complex Ⅱ,and mitochondrial complex Ⅳ was 0.16,0.4,and 0.32 times higher than that of ammonium chloride,respectively.Meantime,ROS was 1.5 times higher than that of ammonium chloride,the peroxidase(POD)and superoxide dismutase(SOD)was 1.58 and 1.11 times higher than that of ammonium chloride culture.The arginine deiminase activity as well as the content of arginine,citrulline and ornithine in the arginine decarboxylase pathway increased when peptone was the nitrogen source,which were 2,9.49,29.67 and 23.06 times higher than that of ammonium chloride,respectively.Peptones can enhance the resistance of BWY-5 by affecting the arginine decarboxylase pathway and increasing the activity of antioxidant enzymes,and cause a certain degree of membrane lipid peroxidation in the cell membrane by inhibiting the accumulation of ROS caused by the mitochondrial respiratory chain.These changes led to increased cell membrane permeability,which promoted the transmembrane secretion of erythrocyte pigments.3.The combined multi-omics analysis revealed that the level of fatty acid degradation pathway expression was up-regulated and fatty acid biosynthesis pathway expression was down-regulated in BWY-5.The expression levels of cyclopropane fatty acid synthase,thioesterase,fatty acid desaturase and phospholipid biosynthetase,which are related to the synthesis of cell membrane components,were down-regulated to 0.57,0.21,0.23 and 0.98 times of LQ-6,respectively.The ergosterol synthesis was inhibited and that genes ERG4A,ERG4B and ERG6 were up-regulated to 7.5,4.66 and 2.11-fold of LQ-6,respectively.The total lipid molecular content was reduced to 0.1 times of 1q6,in which the relative contents of LPS,LPG and we were all reduced to 0,and the relative contents of PC,PE and PIP3 were reduced to 0.11,0.27 and 0.06 times of 1q-6 respectively.The neutral lipid TG(223 species,66.57%)was the largest in the lipid composition.The double bond saturation index(DBI)of lipid molecules PIP,DG,MG,PC and WE of BWY-5 increased to 1.96,1.23,1.09,1.1 and 1.11 times of LQ-6,respectively,and the average carbon chain length(ACL)of PE and ST all decreased by 3 carbon atoms.The synthesis of cell membrane components(membrane lipids and membrane proteins)was inhibited as well as the composition and content of lipids were altered of BWY-5,causing an increase in cell membrane fluidity and permeability and promoting the extracellular secretion of pigments. |
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