Abstract
This study investigated the effects of glutamic acid on production of monacolin K and expression of the monacolin K biosynthetic gene cluster. When Monascus M1 was grown in glutamic medium instead of in the original medium, monacolin K production increased from 48.4 to 215.4 mg l−1, monacolin K production increased by 3.5 times. Glutamic acid enhanced monacolin K production by upregulating the expression of mokB-mokI; on day 8, the expression level of mokA tended to decrease by Reverse Transcription-polymerase Chain Reaction. Our findings demonstrated that mokA was not a key gene responsible for the quantity of monacolin K production in the presence of glutamic acid. Observation of Monascus mycelium morphology using Scanning Electron Microscope showed glutamic acid significantly increased the content of Monascus mycelium, altered the permeability of Monascus mycelium, enhanced secretion of monacolin K from the cell, and reduced the monacolin K content in Monascus mycelium, thereby enhancing monacolin K production.
Highlights
Monascus species, which are characteristically found in East Asian countries, have been influential in local life and culture, and have received attention worldwide because of their diverse products (Cheng et al 2016) and abundant beneficial metabolites (Ming-Jen et al 2010)
Monacolin K, known as lovastatin, is able to act on cholesterol biosynthesis, which can reduce the function of HMG-CoA reductase as a competitive inhibitor
The monacolin K biosynthetic gene cluster has been identified according to the similarities with lovastatin synthetic genes (LNKS) in Aspergillus
Summary
Monascus species, which are characteristically found in East Asian countries, have been influential in local life and culture, and have received attention worldwide because of their diverse products (Cheng et al 2016) and abundant beneficial metabolites (Ming-Jen et al 2010). Monascus species are known to produce various secondary metabolites with polyketide structures, including monacolins (Ming-Tao et al 2013), pigments (Dajung et al 2014), γ-aminobutyric acid (Su et al 2003), and citrinins (Radu et al 2012a; Zhang et al 2016). Monacolin K, an inhibitor of cholesterol biosynthesis, was the first monacolin isolated from the cultures of Monascus ruber. This compound has been independently found in Aspergillus terreus, in which it is designated lovastatin (Nezami et al 2012). Monacolin K is Monacolin K can be produced by Monascus during liquid or solid fermentation (Yu et al 2013). Previous studies have shown that the secondary metabolites of Monascus fermentation are strongly influenced by the environmental factors
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