Bioplastic degradation by a polyhydroxybutyrate depolymerase from a thermophilic soil bacterium

Area of Science:

• Biochemistry
• Enzymology
• Polymer Science

Background:

• The escalating issue of single-use plastic pollution necessitates the development of biodegradable alternatives.
• Enzymatic degradation offers a promising route for managing plastic waste and promoting a circular economy.

Purpose of the Study:

• To characterize the structure and enzymatic activity of a novel polyhydroxyalkanoate (PHA) depolymerase from Lihuaxuella thermophila.
• To investigate the enzyme's substrate specificity, thermal stability, and potential applications in bioplastic degradation.

Main Methods:

• Isolation and purification of the alkaline poly[(R)-3-hydroxybutyric acid] (PHB) depolymerase from Lihuaxuella thermophila.
• Biochemical assays to determine enzyme activity against various polyhydroxyalkanoates (PHAs), polylactic acid (PLA), and polycaprolactone (PCL).
• X-ray crystallography to elucidate the enzyme's three-dimensional structure at 1.2 Å resolution.

Main Results:

• The Lihuaxuella thermophila PHB depolymerase (LtPHBase) demonstrates broad substrate specificity, degrading PHB, other PHAs, PLA, and PCL.
• LtPHBase exhibits optimal activity at 70°C and retains significant activity after prolonged incubation at elevated temperatures.
• Structural analysis revealed an α/β-hydrolase fold with a shallow active site, suggesting a mechanism for its broad substrate recognition.

Conclusions:

• LtPHBase is a highly thermostable enzyme with a unique ability to hydrolyze a wide range of bioplastics.
• Its properties make it a promising candidate for industrial applications in bioplastic recycling and waste management, particularly at high temperatures.