Streamlined production, purification, and comparison of recombinant extracellular polyhydroxybutyrate depolymerases

Abstract

Heterologous production of extracellular polyhydroxybutyrate (PHB) depolymerases (PhaZs) has been of interest for over 30 years, but implementation is sometimes difficult and can limit the scope of research. With the constant development of tools to improve recombinant protein production in Escherichia coli, we propose a method that takes characteristics of PhaZs from different bacterial strains into account. Recombinant His-tagged versions of PhaZs (rPhaZ) from Comamonas testosteroni 31A, Cupriavidus sp., Marinobacter algicola DG893, Pseudomonas stutzeri, and Ralstonia sp. were successfully produced with varying expression, solubility, and purity levels. PhaZs from C. testosteroni and P. stutzeri were more amenable to heterologous expression in all aspects; however, strategies were developed to circumvent low expression and purity for the other PhaZs. Degradation activity of the rPhaZs was compared using a simple PHB plate-based method, adapted to test for various pH and temperatures. rPhaZ from M. algicola presented the highest activity at 15 {degrees}C, and rPhaZs from Cupriavidus sp. and Ralstonia sp. had the highest activity at pH 5.4. The methods proposed herein can be used to test the production of soluble recombinant PhaZs, and to perform preliminary evaluation for applications that require PHB degradation.