Boosting extracellular FastPETase production in E. coli: A combined approach of cognate chaperones co-expression and vesicle nucleating peptide tag fusion.

Enzymatic PET recycling has emerged as a promising green solution in addition to mechanical recycling, but low soluble expression levels of the inherently hydrophobic PET hydrolases hinder large-scale applications. Here, we propose a novel strategy for enhanced production of FastPETase in Escherichia coli using co-expression of molecular chaperones from Ideonella sakaiensis. Co-expression of cognate DnaK and DnaJ chaperones significantly increased soluble FastPETase expression (up to 2.5-fold), surpassing commercial chaperone plasmids. Furthermore, a combinatorial approach employing co-expression of DnaK/DnaJ chaperones and fusion of FastPETase with the VNp6-tag significantly boosted FastPETase secretion, yielding over 2 g/L of target protein in a 5-l bioreactor. Notably, the crude FastPETase in fermentation broth displayed comparable PET hydrolysis effects to the purified enzyme. This work not only provides new insights into the process of chaperones in protein folding but also suggests a novel and efficient strategy for producing recombinant proteins.