Most of the polymers incorporated a fair amount of lactic acid, which can also form ester bonds. There’s normally lots of lactic acid in the cell since it’s one of the potential products of glucose metabolism. But the researchers knocked out the gene that encodes the primary enzyme that produces with lactic acid, dramatically cutting down the amount incorporated into the polymer.
The researchers also tried a variety of conditions, showing that they could create polymers that were a mixture of two different amino acid monomers, and incorporating non-amino acids into the mixture. By adding a few additional enzymes to the E. coli strain, they managed to boost the
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