Addressing natural product supply: Gram scale production of spliceostatins by Burkholderia sp

The top two challenges in natural product drug discovery are adequate supply and ease of structure diversification. Hundreds of grams to kilograms of pure material are commonly necessary to advance a hit to pre-clinical and clinical trials (1). Spliceostatins are bacterial metabolites that bind to the spliceosome, an emerging target in cancer therapy (2). Spliceostatin biosynthesis is encoded in a hybrid nonribosomal peptide synthetase (NRPS), polyketide synthase (PKS) gene cluster of the trans-acyltransferase (AT) type (3, 4). Burkholderia sp. strains FERM BP-3421 and MSMB43 produce a suite of spliceostatin analogs. The major compounds detected in fermentation bear either a terminal carboxylic acid or a hemiketal function. We were particularly interested in the carboxyl series due to its improved stability. Our objectives were to attain 1) sustainable compound production in gram scale; and 2) virtually one-component fermentation to facilitate downstream processing and purification. Our approach was to combine classical fermentation media development to improve overall titers and biosynthetic engineering to block production of hemiketals and increase biosynthesis of the desired carboxyl analog (also referred to as thailanstatin A). This presentation will describe how we attained production of thailanstatin A at 2.5 g/L from the starting 50 mg/L titers and how a strain was obtained that produces nearly exclusively thailanstatin A.

References
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