Applied Microbiology and Biotechnology, Vol.104, No.3, 1055-1062, 2020
Chemoenzymatic synthesis of the pH responsive surfactant octyl beta-D-glucopyranoside uronic acid
Methodology was developed to expand the range of benign alkyl glycoside surfactants to include also anionic types. This was demonstrated possible through conversion of the glycoside to its carboxyl derivative. Specifically, octyl beta-D-glucopyranoside (OG) was oxidised to the corresponding uronic acid (octyl beta-D-glucopyranoside uronic acid, OG-COOH) using the catalyst system T. versicolor laccase/2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and oxygen from air as oxidant. The effects of oxygen supply methodology, concentrations of laccase, TEMPO and OG as well as reaction temperature were evaluated. At 10 mM substrate concentration, the substrate was almost quantitatively converted into product, and even at a substrate concentration of 60 mM, 85% conversion was reached within 24 h. The surfactant properties of OG-COOH were markedly dependent on pH. Foaming was only observed at low pH, while no foam was formed at pH values above 5.0. Thus, OG-COOH can be an attractive low-foaming surfactant, for example for cleaning applications and emulsification, in a wide pH range (pH 1.5-10.0).
Keywords:Oxidation;Octyl beta-D-glucopyranoside;Octyl beta-D-glucopyranoside uronic acid;Laccase from Trametes versicolor;TEMPO and foam