Terminal carboxylation of branched carbon chain contributing to acidic stability of azaphilone pigments from a new isolate of Talaromyces amestolkiae

Red Monascus pigments, a series of natural azaphilone alkaloids, have been utilized in China as a traditional food colorant for over 1000 years. However, instability under an acidic condition is its drawback. A new strain of Talaromyces amestolkiae was isolated in the present work, which produced the azaphilone talaromycorubrin and the corresponding azaphilone alkaloid (N-MSG-talaromycorubramine) exhibiting good stability even at pH below 3. The azaphilone alkaloid with acidic stability, an alternative of Chinese traditional red Monascus pigments, is potential for application as natural food colorant in acidic foods. The acidic stability of azaphilone alkaloid also benefits for direct fermentation of N-MSG-talaromycorubramine under a low pH condition. More importantly, correlation relationship between the terminal carboxylation of branched carbon chain of azaphilone and the stability of azaphilone alkaloids under an acidic condition is set up for the first time, which makes designing other acidic stable azaphilone alkaloids via genetic engineering become possible.

Azaphilone alkaloids: prospective source of natural food pigments

Azaphilone, biosynthesized by polyketide synthase, is a class of fungal metabolites. In this review, after brief introduction of the natural azaphilone diversity, we in detail discussed azaphilic addition reaction involving conversion of natural azaphilone into the corresponding azaphilone alkaloid. Then, setting red Monascus pigments (a traditional food colorant in China) as example, we presented a new strategy, i.e., interfacing azaphilic addition reaction with living microbial metabolism in a one-pot process, to produce azaphilone alkaloid with a specified amine residue (red Monascus pigments) during submerged culture. Benefit from the red Monascus pigments with a specified amine residue, the influence of primary amine on characteristics of the food colorant was highlighted. Finally, the progress for screening of alternative azaphilone alkaloids (production from interfacing azaphilic addition reaction with submerged culture of Talaromyces sp. or Penicillium sp.) as natural food colorant was reviewed. KEY POINTS: • Azaphilic addition reaction of natural azaphilone is biocompatible • Red Monascus pigment is a classic example of azaphilone alkaloids • Azaphilone alkaloids are alterative natural food colorant.

Interfacing non-enzymatic catalysis with living microorganisms

Interfacing non-enzymatic catalysis with cellular metabolism is emerging as a powerful approach to produce a range of high value small molecules and polymers. In this review, we highlight recent examples from this promising young field. Specifically, we discuss demonstrations of living cells mediating redox processes for biopolymer production, interfacing solar-light driven chemistry with microbial metabolism, and intra- and extracellular non-enzymatic catalysis to generate high value molecules. This review highlights the vast potential of this nascent field to bridge the two disciplines of synthetic chemistry and synthetic biology for a sustainable chemical industry.

Alkaloids in Contemporary Drug Discovery to Meet Global Disease Needs

An overview is presented of the well-established role of alkaloids in drug discovery, the application of more sustainable chemicals, and biological approaches, and the implementation of information systems to address the current challenges faced in meeting global disease needs. The necessity for a new international paradigm for natural product discovery and development for the treatment of multidrug resistant organisms, and rare and neglected tropical diseases in the era of the Fourth Industrial Revolution and the Quintuple Helix is discussed.