Monday, April 30, 2007

Lignin peroxidase from Streptomyces viridosporus T7A: concentration via membrane processes and effect of pH on enzyme stability

Leda M. F. Gottschalk, Elba P.S. Bon, and Ronaldo Nobrega. Chemistry Institute, Federal University of Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 539, Ilha do Fundão, Rio de Janeiro, Brazil

Lignin peroxidase (LiP) production, separation and concentration cost must be low to justify its use in the control of environmental pollution. LiP concentration by ultrafiltration using polysulfone (PS) and cellulose acetate (CA) membranes with molecular weight cut off (MWCO) 10, 20 and 50 KDa were studied. The yield and the best process conditions were evaluated using a laboratory stirred cell. Increasing transmembrane pressure (TMP) from 1 to 3 bar increased initial permeate flux although LiP activity losses were greater. The best results were obtained using PS membrane with 10 KDa MWCO where retention of 90% of enzyme activity in the concentrate, suggesting that LiP must have a molecular weight around 10 KDa.  The enzyme thermal stability was evaluated on pH 7,0 and 8,0. The LiP stability was superior in pH near to neutrality with 60% of residual activity after 4 hours at 40°C.