A New Esterase from Thermobifida halotolerans Hydrolyses Polyethylene Terephthalate (PET) and Polylactic Acid (PLA)

• Published in: Polymers Vol. 4; no. 1; pp. 617 - 629
• Main Authors: Ribitsch, Doris, Herrero Acero, Enrique, Greimel, Katrin, Dellacher, Anita, Zitzenbacher, Sabine, Marold, Annemarie, Rodriguez, Rosario Diaz, Steinkellner, Georg, Gruber, Karl, Schwab, Helmut, Guebitz, Georg M.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.03.2012
• Subjects: enzymatic polyester functionalization; Thermobifida halotolerans esterase
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym4010617

A new esterase from Thermobifida halotolerans (Thh_Est) was cloned and expressed in E. coli and investigated for surface hydrolysis of polylactic acid (PLA) and polyethylene terephthalate (PET). Thh_Est is a member of the serine hydrolases superfamily containing the -GxSxG- motif with 85–87% homology to an esterase from T. alba, to an acetylxylan esterase from T. fusca and to various Thermobifida cutinases. Thh_Est hydrolyzed the PET model substrate bis(benzoyloxyethyl)terephthalate and PET releasing terephthalic acid and mono-(2-hydroxyethyl) terephthalate in comparable amounts (19.8 and 21.5 mmol/mol of enzyme) while no higher oligomers like bis-(2-hydroxyethyl) terephthalate were detected. Similarly, PLA was hydrolyzed as indicated by the release of lactic acid. Enzymatic surface hydrolysis of PET and PLA led to a strong hydrophilicity increase, as quantified with a WCA decrease from 90.8° and 75.5° to 50.4° and to a complete spread of the water drop on the surface, respectively.