Abstract
Barley beta-amylase was immobilized using different techniques. The highest global yield was obtained using the cross-linked enzyme aggregates (CLEA) technique, employing bovine serum albumin (BSA) or soy protein isolate (SPI) as feeder proteins to reduce diffusion problems. The CLEAs produced using BSA or SPI showed 82.7 +/- 5.8 and 53.3 +/- 2.4% global yield, respectively, and a stabilization effect was observed upon immobilization at neutral pH value, e.g., after 12 h at 55 degrees C, the free beta-amylase is fully inactivated, while CLEAs retained 25 and 15% of activity (using BSA and SPI, respectively). CLEA using SPI was selected because of its easier recovery, being chosen to convert the residual starch contained in cassava bagasse into maltose. This biocatalyst permitted to reach almost 70% of maltose conversion in 4 h using 30.0 g/L bagasse starch solution (Dextrose Equivalent of 15.88) and 1.2 U of biocatalyst per gram of starch at pH 7.0 and 40 degrees C. After 4 reuses (batches of 12 h) the CLEA using SPI maintained 25.50 +/- 0.01% of conversion due to the difficulty of recovering.