Enzyme transmission during crossflow filtration of yeast suspensions using gas/liquid two-phase flows.

The optimal conditions for recovery of an enzyme were determined using gas/liquid two-phase flows. When filtering the enzyme-only solution under single-phase flow conditions, severe fouling occurred. This fouling was manifest as a decline in flux to less than 2% of the initial water flux and a decline in protein concentration in the permeate to 30% of its initial value, during a five-hour filtration period. When yeast cells were added under the same experimental conditions, enzyme transmission was maintained at 100% for the five-hour period and the enzyme mass flux was twofold higher. During gas-sparged microfiltration of the enzyme/yeast mixture in a permeate-recycling mode at the same liquid flow rate, gas/liquid slug flow strongly decreased the transmission of the enzyme (70% decrease), even though the permeate flux was improved (140% improvement). As a result, the mass flux of the enzyme was significantly reduced. However, with a bubble flow pattern, the permeate flux was 1.5 times higher and the transmission was maintained at a high level. The enzyme mass flux was then 25% higher when compared to single-phase flow filtration conditions. During diafiltration experiments with a bubble flow pattern, a 13% higher enzyme recovery was achieved.