色素生物合成相关PigE基因的缺失对紫色红曲霉Mp-21黄色素种类和产量的影响

Deletion of PigE, a pigment biosynthesis-related gene, upregulates the varieties and yields of yellow pigments in Monascus purpureus Mp-21

摘要:

红曲色素（MPs）是红曲霉次生代谢过程中产生的具有多种生物活性的天然色素，广泛应用于食品、化妆品和保健品行业。[目的]本研究从紫色红曲霉Mp-21中克隆了一个红曲色素产生相关PigE基因，并对其功能进行了鉴定。[方法]利用同源重组原理对PigE基因进行敲除，从表型、显微结构、生长速率、红曲色素、桔霉素等方面分析基因缺失前后的生物学特征变化。[结果]PigE基因的缺失主要导致黄色素产量的提高和种类的增多。与野生型Mp-21菌株以产生红色素为主的色素混合物相比，△PigE丧失了产生红色素的能力，并且新产生了至少5种新的黄色素。△PigE液体发酵13 d后，红曲色素的总色价达到了3548.2 U/g，约为野生型Mp-21菌株的4.82倍；而△PigE桔霉素的产量没有显著变化，但产生的时间延迟。[结论]PigE基因的缺失可能阻断了黄色素向橙色素的转化途径，使△PigE更趋向于黄色素的形成。由于红色素的形成需要较复杂的条件，如培养基中的氨基酸和适宜的pH值等，△PigE更倾向于先合成黄色素，丧失了产生红色素的能力。本研究为高产黄色素基因工程红曲霉菌株的构建提供了一种可能的途径。

Abstract:

Monascus pigments (MPs), a kind of natural pigments with diverse biological activities produced in the secondary metabolism of filamentous Monascus, are widely used as colorants in food, cosmetics and health-care products in East Asia. [Objective] In this study, a PigE gene related to MPs biosynthesis in Monascus purpureus Mp-21 (strain Mp-21) was cloned and characterized.[Methods] The PigE gene (one of MPs genes) was knocked out by homologous recombination in strain Mp-21 and the biological characteristics before and after the gene deletion were analyzed with regard to phenotypes, microstructures, growth rates, MPs and citrinin.[Results] The resulting data demonstrated that the disruption of PigE mainly led to the upregulation of yellow pigments in varieties and yields. In comparison to an MPs complex mixture in which the red pigments were dominant in the wild-type strain Mp-21, the △PigE (a PigE gene deletion mutant) lost the ability to produce red pigments and produced at least five new yellow pigments. The MPs production was up to 3548.2 U/g and about 4.82-fold as that in the wild type strain Mp-21 after liquid-state fermentation for 13 d. Additionally, the citrinin production had no significant change, while the productive period was delayed on account of a longer period to adapt to the growing condition. The deletion of PigE blocked the transformation pathway of the yellow pigments to orange pigments, which made the △PigE more favorable to form yellow pigments. As the formation of red pigments required more complex conditions such as amino acids and suitable pH in culture medium, the △PigE prefers to synthesize yellow pigments first and lost the ability to produce red pigments. [Conclusion] This study provides a possible way for the construction of genetic engineering Monascus strains with high yield of yellow pigments.