ENHANCEMENT OF CANDIDA-RUGOSA LIPASE PRODUCTION BY USING DIFFERENT CONTROL FED-BATCH OPERATIONAL STRATEGIES

Simulation studies have predicted that maximum lipase activity is reac hed with fed-batch operation strategies. In this work, two different f ed-batch operational strategies have been studied: constant substrate feeding rate and specific growth rate control. A constant substrate fe eding rate strategy showed that maximum aqueous lipolytic activity (55 U/mL) was reached at low substrate feeding rates, whereas lipase tend s to accumulate inside the cell at higher rates of substrate addition. In the second fed-batch strategy studied, a feed back control strateg y has been developed based on the estimation of state variables (X and mu) from the measurement of indirect variables such as CER by means o f mass spectrometry techniques. An on-off controller was then used to maintain the specific growth rate at the desired value by adjusting th e substrate feeding rate. A constant specific growth rate strategy gav e higher final levels of aqueous lipolytic activity (117 U/mL) at low specific growth rates. At higher specific growth rates the enzyme rema ined accumulated inside the cell, as was observed with a constant feed ing fed-batch strategy. With a constant specific growth rate strategy, lipase production by Candida rugosa was enhanced 10-fold compared to a batch operation. Purification studies have demonstrated that lipolyt ic and esterasic specific activity ratios of Candida rugosa isoenzymes can be modified by using different operational conditions. These stud ies have also showed that the isoenzymes obtained in a controlled grow th rate strategy are around three- to four-fold more active than those obtained in a constant feeding rate strategy. (C) 1998 John Wiley & S ons, Inc.