Selective production of red azaphilone pigments in a Monascus purpureus mppDEG deletion mutant

Abstract

The Monascus azaphilone (MAz) pigment is a wellknown food colorant that has yellow, orange and red components. The structures of the yellow and orange MAz differ by two hydride reductions, with yellow MAz being the reduced form. Orange MAz can be non-enzymatically converted to red MAz in the presence of amine derivatives. It was previously demonstrated that mppE and mppG are involved in the biosynthesis of yellow and orange MAz, respectively. However, ΔmppE and ΔmppG knockout mutants maintained residual production of yellow and orange MAz, respectively. In this study, we deleted the region encompassing mppD, mppE and mppG in M. purpureus and compared the phenotype of the resulting mutant (ΔmppDEG) with that of an mppD knockout mutant (ΔmppD). It was previously reported that the ΔmppD strain retained the ability to produce MAz but at approximately 10% of the level observed in the wildtype strain. A chemical analysis demonstrated that the ΔmppDEG strain was still capable of producing both yellow and orange MAz, suggesting the presence of minor MAz route(s) not involving mppE or mppG. Unexpectedly, the ΔmppDEG strain was observed to accumulate fast-eluting pigments in a reverse phase high-performance liquid chromatography analysis. A LC-MS analysis identified these pigments as ethanolamine derivatives of red MAz, which had been previously identified in an mppE knockout mutant that produces high amounts of orange MAz.Although the underlying mechanism is largely unknown, this study has yielded an M. purpureus strain that selectively accumulates red MAz.

Extractive fermentation of Monascus purpureus promotes the production of oxidized congeners of the pigment azaphilone

“…The HP20 sample contained R-1 and R-2, the ethanolamine derivatives of red MAz 5 and 6, respectively. These compounds were previously identified in the M. purpureus ΔmppE and ΔmppDEG mutants [29]. Low yields of 3 and 4 might make R-1 and R-2 noticeable in the chromatograms.…”

“…This finding could be due to the immediate export of 3 and 4, which minimizes the formation of red MAzs. The red MAzs were previously suggested to form that red MAz is formed inside the cell through the reaction of intracellular amine derivatives [29]. Under these LC conditions, the peaks for 1 and 3 overlapped; thus, UV-visible absorption and mass spectra were used to deduce the relative compositions of 1 and 3.…”

Diversifying of Chemical Structure of Native Monascus Pigments

“…On the other hand, feeding of yellow Monascus pigment ( 17 ) to ΔMpPKS5 mutant also excludes the possibility of conversion of yellow Monascus pigment into the corresponding orange one ( 1 ) (Balakrishnan et al, 2017b). Similarly, a reductase, encoded by mpp E gene (corresponding to Mrpig H in Figure 2A), controls the conversion of the intermediate 14 into yellow Monascus pigments ( 17/18 ) (Balakrishnan et al, 2017a). The key role of intermediate 14 to the biosynthesis of Monascus pigments is also confirmed via analysis of Mrpig E by gene disruption, complementation and overexpression in Monascus ruber (Liu et al, 2014).…”

“…The results demonstrate that the Mrpig E deletion strain failes to produce orange Monascus pigments and the Mrpig E complementation strain recovers the ability to production of orange Monascus pigments. However, there are still detectable yellow Monascus pigments in the broth after culture of Δmpp E mutant (Balakrishnan et al, 2017a). Further experiment indicates the Δmpp DEG (mpp D corresponding to Mrpig G in Figure 2A) mutant remains the ability for production of orange Monascus pigments as well as yellow ones (Balakrishnan et al, 2017a).…”

Inactivation of the genes involved in histone H3-lysine 4 methylation abates the biosynthesis of pigment azaphilone in Monascus purpureus

“…MAz is biosynthesized by a nonreducing polyketide pathway, which is associated with a special fatty acid synthase [15,16]. Extensive characterization of MAz biosynthetic genes established the biosynthetic mechanism [17][18][19][20][21], firmly establishing that MAz biosynthesis is the sole factor responsible for pigmentation of Monascus under general culture conditions. Monascus is highly productive of MAz, implying that the cognate biosynthetic genes are highly active in transcription.…”