Comparison of free and immobilized Pichia pastoris cells for conversion of ethanol to acetaldehyde.

Free and immobilized cells of Pichia pastoris were used to convert ethanol to acetaldehyde in small-scale batch reactors. Immobilized cells were less active than free cells (V(max) free = 7.81 g/L h, V(max) immobilized = 3.17 g/L h) due to a number of factors including end product inhibition and diffusional limitations. Immobilized cells were more resistant to heat denaturation both in the presence and absence of ethanol. Immobilized cells retained more of their activity during repeated batch cycles than did free cells.