Effect of increased PHA synthase activity on polyhydroxyalkanoates biosynthesis in Synechocystis sp PCC6803

Polyhdroxyalkanoate (PHA) synthase activity in Synechocystis sp. PCC6803 was increased two-fold by introducing the PHA biosynthetic genes of Ralstonia eutropha. The resulting recombinant Synechocystis sp. PCC6803 strain was subjected to conditions that favor PHA accumulation and the effects, of carious carbon sources were studied. In addition. the fine structure of both wild-type and recombinant Synechocystis sp. PCC6803 was examined using freeze-fracture electron microscopy technique. The PHA granules in the recombinant Synechocystis sp. PCC6803 were localised near the thylakoid membranes. Maximum amount of PHA accumulation vas obtained in the presence of acetate, where the number of granules in the recombinant cells ranged from 4 to 6 and their sizes were in the range of 70 - 240 nm. In comparison to wild-type Synechocystis sp. PCC6803. recombinant cells kith increased PHA synthase activity showed only a marginal increase in PHA content suggesting that PHA synthase is not the rate limiting enzyme of PHA biosynthesis in Synechocystis sp. PCC6803. (C) 2002 Elsevier Science B.V. All rights reserved.