Team:Caltech/BBa K338003


iGEM 2010



Project Details


Completed Systems



Human Impact



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PHA Synthase Composite, Part 1/2

This is half of a planned part which would contain all three PHA synthase genes required to produce polyhydroxybutyrate (PHB) in cells: phaA, phaB1, phaC1. This half contains only phaA: BBa_K156012. It was designed to be ligated upstream of part BBa_K338004.

Usage and Biology


When ligated upstream of BBa_K338004, the completed construct was designed to express all three PHA synthase genes required to make PHB oligomers from soybean oil. The three genes would be transcribed polycistronically on a single mRNA transcript under the IPTG-inducible control of the BBa_K215000 promoter. Naturally, each gene is preceded by a standard RBS (BBa_B0034) and the transcript finishes with a strong terminator (BBa_B0015), for a total size of about 3500bp.

Note that these three genes should only cause the production of PHB oligomers in cells, not hardened plastic. A crosslinking agent is required to link the oligomers and form the final plastic product. Over-expression of the phaC1 gene could cause some crosslinking, but this has not been experimentally verified.


Lee describes how a similar gene construct (pSYL105) was used to produce very large amounts of PHB, up to 80-90% of the dry cell weight, under certain conditions. Synthesis of PHB is related to the amount of acetyl-CoA available - synthesis was bolstered in the presence of complex nitrogen sources, amino acids, or oleic acid. He also mentions that PHB production was highly dependent on the particular bacterial strain used. [10]

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