Abstract
A synthetic promoter library was developed to substitute the native promoter of phaCAB from Ralstonia eutropha in order to produce poly(3-hydroxybutyrate)(P3HB) in Escherichia coli. The library yielded over 141 successfully characterized clones, from which 35 unique promoters were identified by Sanger sequencing. The synthetic promoter P1 was shown to be particularly effective in driving the expression of downstream genes, including sfGFP and phCAB gene clusters. The performance of P1 exceeded that of the native promoter, achieving P3HB production levels of up to 79.78 ± 3.13% under aerobic conditions. Statistical analysis revealed that P1 significantly outperformed the native promoter of phCAB under aerobic conditions (P < 0.05), while displaying comparable activity under microaerobic conditions (P > 0.05).