Extractive fermentation for improved production of endoglucanase by an intergeneric fusant of Trichoderma reesei/Saccharomyces cerevisiae using aqueous two-phase system

Extractive aqueous two-phase fermentation of endoglucanase, a key enzyme fo r the conversion of cellulosic substances to fermentable sugars, from an in tergeneric fusant of Trichoderma reesei/Saccharomyces cerevisiae is a meani ngful approach for better production and simple recovery of this enzyme. A phase composition of 6.5% (w/w) dextran and 7.5% (w/w) polyethylene glycol 6000, having a partition coefficient of 2.89 and 1.31 for endoglucanase fro m an intergeneric fusant of T. reesei/S. cerevisiae and T. reesei (WT) (bei ng a control in this study), respectively, was chosen for extractive fermen tation of the enzyme. Endoglucanase production is higher in medium containi ng polyethylene glycol (PEC) 6000 than in medium without PEG 6000. Comparat ive analysis of endoglucanase fermentation by fusant and T. reesei was carr ied out in shake culture and environment-controlled bioreactor conditions. The fusant produced 0.43 U of endoglucanase (overall production: 0.34 U) in the top phase of an aqueous two-phase system (ATPS), compared to 0.3 U in medium without the phase system in shake culture. In a batch reactor, the e ndoglucanase level for the fusant in the top phase of ATPS was 0.49 U (over all production: 0.40 U), compared to 0.38 U produced in medium without aque ous two-phase components. To corroborate this study, T. reesei produced 8.4 1 U of endoglucanase (overall production: 5.96 U) in the top phase of ATPS, compared to 7.18 U in the medium without the phase system in shake culture . On the other hand, in a batch bioreactor, T. reesei produced 10.13 U of e ndoglucanase (overall production: 6.90 U) in the top phase of ATPS, compare d to 8.56 U of the enzyme in medium without aqueous two-phase components. T he lower overall enzyme production by T: reesei in the two-phase system mig ht be doe to limitation in oxygen transfer to the dispersed phase where the enzyme is produced. A higher cell concentration and a reduced lag phase wa s obtained in ATPS, compared to a similar medium without phase forming poly mers for both the intergeneric fusant of T. reesei/S.. cerevisiae and T. re esei. (C) 2000 Elsevier Science S.A. All rights reserved.