Kinetic, oxygen mass transfer and hydrodynamic studies in a three-phase stirred tank bioreactor for the bioconversion of (+)-valencene on Yarrowia lipolytica 2.2ab

摘要

The oxidation of (+)-valencene on Yarrowia lipolytica 2.2ab in a three-phase partitioning bioreactor using orange essential oil is a promising technology to market natural (+)-nootkatone overcoming both substrate and product inhibitions. The adequate determination and selection of thermodynamic, kinetic, deactivation, hydraulic and mass transport parameters are essential to perform a suitable strategy of scaling-up. This study is aimed at determining these parameters to identify through a regime analysis the mechanisms limiting the bioconversion process. The volumetric oxygen transfer coefficient (k(L)a) and the Sauter mean drop diameter (d(32)) values ranged from 10 to 116 h(-1) and 8 to 18 mu m, respectively. The substrate (k(S)) and product (k(P)) global interfacial mass transfer coefficients were determined from a modified Lewis cell. The k(S) and k(P) values ranged from 0.6 to 3.0 x 10(-5) and 2 to 3 x 10(-5) ms(-1), respectively. Finally, a kinetic model, considering a bi-substrate reaction and accounting for cell deactivation, was developed. The affinity constants for oxygen and (+)-valencene were K-O2 = 7.11 x 10(-2) mg(O2) L-1 and K-S = 7.865 x 10(-3) mg(S) L-1, respectively, while catalytic constant related to (+)-nootkatone formation was k(cat) =5.025 x 10(3) mgP mg(E)(-1) h(-1). Thus, the regime analysis in terms of the characteristic times suggested that kinetics, namely the consumption rate of (+)-valencene was the main mechanism limiting the bioconversion process. (C) 2016 Elsevier B.V. All rights reserved.