Fluidized-bed immobilized-enzyme reactor for the hydrolysis of cornstarch to glucose

We have developed an economical fluidized‐bed immobilized‐enzyme cornstarch hydrolysis reactor employing an inexpensive glucoamylase‐on‐alumina (covalently bonded) catalyst having a high initial activity (130 units/g) and excellent long term stability (t1/2 = 6450 hr at 50°C). The reactor can give higher yields of dextrose from streams containing ∼30% (wt) low dextrose equivalent (DE) cornstarch than can a comparable fixed‐bed reactor because its design exploits the fact that fluidixation permits the use of very small catalyst particles (down to 50μm in our case) which overcomes the yield‐limiting diffusion‐associated problems encountered in the use of conventional fixed‐bed cornstarch hydrolysis reactors. Furthermore, even when small catalyst particles are used the fluidized‐bed reactor does not suffer from plugging and high pressure drop problems typical of fixed‐bed reactors. The results of an initial economic analysis based on bench‐scale results indicate that the processing cost for a plant using this new technology to produce 100 × 106lb dextrose/year from low DE cornstarch would be as much as 33% lower than for a comparable plant employing conventional soluble‐enzyme technology.