Glucose Production Profile from Sugarcane Pulp in a Fluidized-Bed Reactor

Large amounts of lignocellulosic "waste" can potentially be converted into various important products including biofuels, chemicals, cheap energy sources for fermentation, and etc. Particularly important is the production of second generation ethanol. This commodity can be produced by enzymatic degradation of the cellulose using the cellulase enzyme complex followed by glucose fermentation.  This work studied the immobilization of the enzyme cellobiase on solid supports by reversible linkage using the commercial supports octyl-agarose and DEAE-Sephacel, and irreversible linkage using agarose and silica activated with glutaraldehyde. The immobilization conditions were 25 ^oC, pH 7.0 and low ionic strength (5 mM sodium phosphate buffer). Cellobiase was quickly immobilized on all supports with immobilization yields of 98, 99, 90 and 99% using octyl-agarose, DEAE-Sephacel, silica-glutaraldehyde and agarose-glutaraldehyde, respectively. Moreover, the recovered activities were very satisfactory, i.e., over 50%. The attachment strength on DEAE-Sephacel and octyl-agarose was very strong; at least 150 and 300 mM were necessary, respectively, for the enzyme to be desorbed from the supports. The immobilization on these supports provided good thermal stabilization values. All derivatives were more stable than the soluble enzyme. Cellobiase immobilized on glutaraldehyde-agarose was ca. 8-fold more stable than the soluble enzyme. A bath reactor containing sugarcane pretreated by steam explosion and cellulase enzyme was coupled to a fluidized bed reactor containing cellobiase immobilized on Glutaraldehyde-silica. The system was used for at least 13 days in a recycling fluidized bed reactor and still sustained average conversions values of around 80%.