柠檬酸对紫色红曲菌液态发酵产Monacolin K能力的影响

为了提高红曲菌液态发酵产Monacolin K的能力,本文以实验室保藏的Monacolin K产量稳定的紫色红曲菌(Monascus purpureus)M1为试验菌株,拟在培养红曲菌的过程中添加不同浓度的柠檬酸,以分析其对红曲菌次级代谢产物合成的影响。通过扫描电镜对实验组与对照组的红曲菌菌丝体的超微结构进行观察、荧光定量PCR检测红曲菌Monacolin K合成关键基因的表达量的方法,进而探究提高Monacolin K产量的机理。结果表明:当添加的柠檬酸浓度在0.1%左右时,对Monacolin K产量促进效果最为明显,与原始培养基相比提高了2.71倍。扫描电镜的观察结果显示,实验组表面出现更多的褶皱,因此推测柠檬酸可能是通过提高红曲菌细胞膜通透性,将细胞合成的Monacolin K及时分泌到细胞外,细胞质中的Monacolin K浓度降低,进而分泌出细胞外的Monacolin K积累量增加。荧光定量PCR检测发现,添加柠檬酸的培养基中,红曲菌MonacolinK合成关键基因(mokA~mokI和LaeA)的表达量呈现一定的上升趋势,进而提高Monacolin K的产量。综上,Monacolin K在添加柠檬酸浓度为0.1%左右的培养基中产量最高,推测机理是柠檬酸改变了红曲菌细胞膜的通透性并提高了相关基因的表达量。

Effect of Citric Acid on the Production of Monacolin K by Liquid State Fermentation of Monascus purpureus

In order to improve the ability of Monacolin K produced by liquid fermentation of Monascus,this study used laboratory preservation Monacolin K output stable Monascus purpureus M1 as the test strain,intending to add different concentrations of citric acid in the process of cultivation of Monascus purpureus to analyze its effect on the synthesis of secondary metabolites of Monascus purpureus. The ultrastructure of the mycelium of Monacolin K in the experimental group and the control group was observed by scanning electron microscope. The expression of the key gene of Monacolin K was detected by fluorescence quantitative PCR,and the mechanism of increasing the production of Monacolin K was studied. The results showed that when citric acid concentration was 0.1%,the production of Monacolin K increased by 2.71 times than the original medium. The results of scanning electron microscope showed that the experimental group surface appeared more fold,thus speculated that citric acid might be through improving Monascus cell membrane permeability,timely secreted the Monacolin K synthesized by cells to the outside of cells,the cytoplasm Monacolin K concentration was reduced,and then increased the accumulation of extracellular Monacolin K.The expression of Monacolin K biosynthesis related key genes of Monacolin K in M.purpureus mycelium was determined by RT-qPCR determination,and it was found that citric acid could promote the expression of key genes(mokA~mokI and LaeA)of Monacolin K synthesis and thus improved the production of Monacolin K in M.purpureus. Therefore,it was concluded that the production of Monacolin K was the highest in the medium with citric acid concentration of about 0.1%. The possible mechanism was that citric acid changed the permeability of Monascus cell membrane and increased the expression of related genes.