A Novel Stepwise Recovery Strategy of Cellulase Adsorbed to the Residual Substrate after Hydrolysis of Steam Exploded Wheat Straw

Abstract

Cellulase distribution between residual substrate and supernatant in the process of enzymatic hydrolysis of steam-exploded wheat straw was investigated. Subsequently, a novel stepwise recovery strategy with three successive steps was adopted to recover cellulase adsorbed to the residual substrate. The results showed that cellulase protein in the supernatant increased as the hydrolysis time increased. When hydrolysis ended, the cellulase remaining on the residual substrate accounted for 33–42% of the original added cellulase according to the different cellulase loading. To obtain the maximum cellulase recovery rate, the residual substrate was dealt with in three successive steps: washed with sodium acetate buffer (step 1), shaken with sodium acetate buffer (step 2), and then treated with 0.0015 mol/L, pH 10 Ca(OH)₂ (step 3). The total cellulase protein recovered by the three steps reached 96.70–98.14%. The enzyme activity of cellulase recovered by the first two steps was kept well. The ratios of the specific activity between the recovered cellulase and the original were 89–96%, which was by far higher than that using step 3 (the value was 48% ∼ 56%).