Co‐Expression of ORFCma with PHB Depolymerase (PhaZCma) in Escherichia coli Induces Efficient Whole‐Cell Biodegradation of Polyesters

Whole‐cell degradation of polyesters not only avoids the tedious process of enzyme separation, but also allows the degraded product to be reused as a carbon source. In this study, Escherichia coli BL21(DE3) harboring phaZ Cma , a gene encoding poly(3‐hydroxybutyrate) (PHB) depolymerase from Caldimonas manganoxidans , is constructed. The extra‐cellular fraction of E. coli /pPHAZ exhibits a fast PHB degradation rate where it only took 35 h to completely degrade PHB films, while C. manganoxidans takes 81 h to do the same. The co‐expression of ORF Cma (a putative periplasmic substrate binding protein that is within the same operon of phaZ Cma ) further improves the PHB degradation. While 28 h is needed for E. coli /pPHAZ to cause an 80% weight loss in PHB films, E. coli /pORFPHAZ needs only 21 h. Furthermore, it is able to degrade at‐least four different polyesters, PHB, poly(lactic acid) (PLA), polycaprolactone (PCL), and poly(butylene succinate‐co‐adipate) (PBSA). Testing of the time course of 3‐hydroxybutyrate concentration and the turbidity of the degradation solutions over time shows that PhaZ Cma has both exo‐ and endo‐enzymatic activity. The whole‐cell E. coli /pORFPHAZ can be used for recycling various polyesters while ORF Cma can potentially be a universal element for enhancing the secretion of recombinant protein.