COMPARISON OF RECOMBINANT ESCHERICHIA-COLI STRAINS FOR SYNTHESIS AND ACCUMULATION OF POLY-(3-HYDROXYBUTYRIC ACID) AND MORPHOLOGICAL-CHANGES

A stable high-copy-number plasmid pSYL105 containing the Alcaligenes e utrophus polyhydroxyalkanoic acid (PHA) biosynthesis genes was constru cted. This plasmid was transferred to seven Escherichia coli strains ( K12, B, W, XL1-Blue, JM109, DH5 alpha, and HB101), which were subseque ntly compared for their ability to synthesize and accumulate poly-(3-h ydroxybutyric acid) (PH B). Growth of recombinant cells and PHB synthe sis were investigated in detail in Luria-Bertani (LB) medium containin g 20 g/L glucose. Cell growth, the rate of PHB synthesis, the extent o f PHB accumulation, the amount of glucose utilized, and the amount of acetate formed varied from one strain to another. XL1-Blue (pSYL105) a nd B (pSYL105) synthesized PHB at the fastest rate, which was ca. 0.2 g PHB/g true cell mass-h, and produced PHB up to 6-7 g/L. The yields o f cell mass, true cell mass, and PHB varied considerably among the str ains. The PHB yield of XL1-Blue (pSYL105) in LB plus 20 g/L glucose wa s as high as 0.369 g PHB/g glucose. Strains W (pSYL105) and K12 (pSYL1 05) accumulated the least amount of PHB with the lowest PHB yield at t he lowest synthesis rate. JM109 (pSYL105) accumulated PHB to the highe st extent (85.6%) with relatively low true cell mass (0.77 g/L). Consi derable filamentation of cells accumulating PHB was observed for all s trains except for K12 and W, which seemed to be due either to the over expression of the foreign PHA biosynthesis enzymes or to the accumulat ion of PHB. (C) 1994 John Wiley & Sons, Inc.