乙酸钠、烟酸对红曲菌白色变种产Monacolin K的影响

Effect of sodium acetate and niacin on monacolin K production by Monascus sp. var. white

【背景】红曲是由红曲菌寄生在大米发酵而成的一种食用米曲,含有胆固醇抑制剂Monacolin K,但市售红曲中酸式Monacolin K含量低且普遍呈红色,其应用存在局限性。红曲菌白色变种3001-18具有不产色素和桔霉素而高产酸式Monacolin K的优点。【目的】研究微量营养物对红曲菌固态发酵Monacolin K产量及酸式结构占比的作用,并分析其对相关基因表达的影响。【方法】将不同微量营养物添加到固态发酵培养基中以提高红曲菌生物量、Monacolin K产量及酸式结构的含量,并对Monacolin K合成相关基因进行分析。【结果】添加质量分数为0.1%的乙酸钠后红曲Monacolin K总产量提高10.63%,可达17.90 mg/g;添加0.015%的烟酸后可以使红曲产品中MonacolinK酸式结构的比例由76.08%提升至90.51%;乙酸钠能促进MonacolinK合成相关基因mokA、mokB和mokC的表达,提高Monacolin K产量;烟酸则通过上调mokF、mokH和mokI的表达,使酸式Monacolin K迅速合成并外排且产物Monacolin K中酸式结构占比提升。【结论】微量营养物能通过增加红曲菌Monacolin K合成相关基因的表达量来促进其合成,为高产酸式Monacolin K的研究提供了一定的理论依据。

[Background] Red yeast rice is an edible rice koji fermented by Monascus on rice, and possess the cholesterol inhibitor monacolin K. However, commercially available red yeast rice has low levels of acid form monacolin K and generally exhibits red color, which limit its application. Monascus sp. var. white 3001-18 has the advantages of not producing pigments and citrinin, but producing high levels of acid form monacolin K. [Objective] To study the effect of micronutrients on the production of monacolin K and the proportion of acid form, and also their effects on synthesis-related genes expression. [Methods]Adding different micronutrients to the solid-state fermentation medium to increase the biomass of Monascus, monacolin K production and the content of acid form. We analyzed the expression of genes related to monacolin K synthesis. [Results] The production of monacolin K improved by 10.63%, reached up to 17.90 mg/g by adding 0.1% sodium acetate. Moreover, the proportion of acid form monacolin K increased from 76.08% to 90.51% by adding 0.015% niacin. RT-qPCR analysis showed that sodium acetate increased the production of monacolin K by promoting the expression of mokA, mokB and mokC genes related to the synthesis of monacolin K. Niacin up-regulated the transcription of mokF, mokH and mokI genes, resulting in faster transport and higher proportion of acid form monacolin K. [Conclusion] Micronutrients can promote the synthesis of monacolin K by increasing the expression of synthesis-related genes. The study provides a certain theoretical basis for the application research of high producing acid form monacolin K.