The half-life of immobilized amyloglucosidase was determined in a fluidized-bed reactor operating continuously with a 30% w/v liquefied cassava starch solution at pH 4.5 and temperatures from 50 to 70 degrees C. For the higher temperatures : 60, 65, and 70 degrees C, thermal deactivation gives half-lives of 127, 38 and 7.3 h, respectively, in close agreement with corn starch data. For the lower temperatures : 55 and 60 degrees C, the deposition of impurities over the immobilized enzyme particle contributes significantly to deactivation, lowering expected half-lives to 32.6 and 13.2 d, respectively. Commercial exploitation of this process would then require low temperature of operation, thorough purification of the substrate solution, and control of microbial contamination to achieve sufficiently long half-lives.