A novel enzyme from a halophilic marine Antarctic strain, with potential in recalcitrant biomasses degradation

As a part of the "National Antarctic Research Program" (PNRA16_00105 - A1) and of the Biotechnological Inter-university Consortium (CIB) project "A glocal approach to third generation biorefinery", we recently isolated a Halomonas sp. M68 strain from a polyvinyl-chloride panel submerged for three months at -20 meters in Terra Nova Bay (Antarctica). When grown in the presence of sodium chloride and copper sulphate, M68 produces an enzyme able to oxidize the lignin-like substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and 2,6-dimethoxyphenol, both in solid and in liquid spectrophotometric assays. The enzyme activity was found intracellularly and biochemically characterized: kinetic parameters were Vmax 13.99 mU/mg and Km 2.43 mM for ABTS and Vmax 1.37 mU/mg and Km 5.87 mM for 2,6-dimethoxyphenol. Furthermore, more than 80% of the activity measured in standard conditions was maintained even at 10 °C or in the presence of 1M NaCl, and it was stable over a broad range of temperatures, from -20 °C up to 37 °C. Therefore, it could prove its activity as a promising biocatalyst in processes dealing with the degradation of recalcitrant lignocellulosic biomasses or wastewaters treatment.