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

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Monascus is a source of food colorant with high productivity of the pigment azaphilone. Monascus azaphilone (MAz) is biosynthesized through a single non-reducing polyketide pathway, the major components of which are ankaflavin (1), monascin (2), rubropunctatin (3) and monascorubrin (4); valuable biological activities have been reported for these compounds. Thus, various culture conditions were explored to reduce the cost of culture ingredients, enhance productivity and modulate compound composition. In the present study, we examined an extractive fermentation (EF) method with Diaion HP-20 resin (HP20) in direct comparison to a previously explored method involving Triton X-100 (TX100) to explore the modulated production of the major MAzs. We employed wild-type Monascus purpureus as well as two derivative recombinant strains (ΔmppG and ΔmppE) that are known to have differential MAz profiles as that of the wild-type strain. The HP20 resin was capable of modulating the MAz profile in favor of orange MAzs 3 and 4, oxidized congeners in this class, as was TX100-a phenomenon not previously observed for TX100 EF with Monascus anka. These finding substantiate that HP20 can be employed for the selective production of oxidized MAz and for diversifying the culture conditions used for Az production.