Genomics-guided discovery of a new and significantly better source of anticancer natural drug FK228

FK228 is an FDA-approved anticancer drug naturally produced by Chromobacterium violaceum No.968 up to 19 mg/L in a pilot industry-scale batch fermentation.Here we report a genomics-guided discovery of Burkholderia thailandensis MSMB43 as a new and significantly better source of FK228.The genome of B.thailandensis MSMB43 was found to contain a functional biosynthetic gene cluster highly homologous to that of FK228 in C.violaceum No.968,and the bacterium indeed produces authentic FK228.By simple fermentation in shaking flasks in a preferred M8 medium,B.thailandensis MSMB43 produced FK228 up to 67.7 mg/L;by fedbatch fermentation in a 20-L fermentor in M8 medium,B.thailandensis MSMB43 produced FK228 up to 115.9 mg/L,which is 95 fold higher than that of C.violaceum No.968 under the same laboratory fermentation conditions.RT-PCR analysis indicated that the high FK228 yield of B.thailandensis MSMB43 was due to high expression of biosynthetic genes,represented by Bth_depA,during the fermentation process.Further genetic manipulation resulted in a recombinant strain,B.thailandensis MSMB43/pBMTL3-tdpR,which harbors a broad host-range vector expressing the thailandepsin biosynthetic pathway regulatory gene tdpR.This engineered strain produced up to 168.5 mg/L of FK228 in fed-batch fermentation in a 20-L fermentor in M8 medium.Therefore,the wild-type B.thailandensis MSMB43 or its engineered derivative could potentially be a good starting point for an industrial process to improve FK228 production for its expanding use in therapy.