Two acidic, thermophilic GH28 polygalacturonases from Talaromyces leycettanus JCM 12802 with application potentials for grape juice clarification.

Efficient hydrolysis of pectic materials to sugars requires the synergistic action of endo- and exo-polygalacturonases. Two novel polygalacturonases (exo-TePG28a and endo-TePG28b) were identified in Talaromyces leycettanus JCM12802, overexpressed in Pichia pastoris, and characterized in this report. The specific activities of TePG28a and TePG28b towards polygalacturonic acid were 280±9 and 25,900±502U/mg, respectively. Both enzymes exhibited optimal activities at pH 3.5 and retained highly stable over a broad pH range of 2.0-7.0. Distinct from most fungal polygalacturonases that have low temperature optima, TePG28a and TePG28b were optimally active at 70°C. When treated the grape juice with the enzyme combination (the unit ratio of TePG28a:TePG28b was 1:4), higher pectin-degrading efficiency (up to 140%) was achieved, and light transmittance was improved from 14% to 82%. These favorable enzymatic properties make TePG28a and TePG28b attractive for the applications in the juice industry.