Biosynthesis of tyrosine-incorporated aromatic Biopolyesters via engineered Escherichia coli

Aromatic biopolyesters, known for their enhanced thermal stability and mechanical strength, provide a sustainable alternative to petroleum-based plastics. However, their large-scale production is still limited by dependence on fossil fuels and inefficient biosynthetic pathways. This study introduces a metabolic engineering approach to synthesize tyrosine-incorporated aromatic biopolyesters using an engineered strain of Escherichia coli . Key modifications included site-directed mutagenesis of PHA synthase (PHA Ps6-19 ) and the heterologous expression of the acetyl-CoA transferase gene (HadA), which were integrated into the plasmid pACY-HadA-PHA. Shake-flask fermentation resulted in a yield of 0.66 g/L of crude product, accounting for 32.29 wt% of cell dry weight, with 1 H NMR confirming the formation of aromatic polyesters. However, the low product purity (3.11 wt%) and weak signal intensity revealed challenges related to enzymatic efficiency and substrate tolerance. Critical barriers, such as insufficient catalytic activity of polymerases and microbial toxicity, were identified. Proposed solutions include enzyme engineering to optimize substrate-binding pockets and fermentation strategies to enhance chain elongation. This work highlights the potential of biocatalytic pathways for the synthesis of aromatic biopolyesters while emphasizing the necessity for interdisciplinary efforts to address existing limitations in yield and scalability.