Reactor performance in glucose isomerization by cellulose bead immobilized actinoplanes cells

Abstract

The properties, mass transport characteristics, reactor kinetics, and the biocatalytic behavior in a packed bed glucose isomerization reactor of cellulose bead entrapped Actinoplanes missouriensis cells were investigated. Substrate and product transport in the biocatalyst particle boundary layer is closely related to reactor flow dynamics. Both film diffusion and internal mass transport resistance were found to be negligible. For a column reactor (height/ø = 6/1.1; bead porosity ϵ = 0.8; voidage ω = 0.38; 2.5 M glucose; flow rate Q = 0.8 b.v.h. −1) a mean mass transport coefficient of k = 7.3 × 10 −4 was obtained. The concentration difference between bulk liquid and particle surface was only 0.3% of feed concentration. The average effective diffusivity, as obtained from Fick's first law, was D eff = 2.6 × 10 −6 cm 2s −1. At 8% (w/w) biocatalyst cell mass (bead ø 1.4 mm; Thiele modulus ø = 1.6; V mf max = 1 × 10 −3 mol dm −3s −1) K mf = 0.8, V mf = 3 × 10 −4 mol dm −3 s −1, and the effectiveness factor η min = 0.85 were obtained. At typical process conditions at high initial substrate levels ( G 0), η → 1. About 48% conversion was reached at high initial glucose level of G 0 = 2.75 M, τ = 3 h, and nearly 60% at G 0 < 1.1 M. With 3 reactors in series, relatively high fructose levels did not affect enzyme stability, and about 42% conversion was obtained at τ = 3 × 0.4 h. Activity half-lives of T 1 2 = 150 d (50°C), 40 d (60°C), 20 d (65°C), and 9 d (70°C) were obtained, with an inactivation energy of 127 kJ mol −1 equal to 2.3 times the activation energy. Total productivity was estimated at about 1050 kg isomerized glucose per kg of biocatalyst during 60 d at biocatalyst activity of 1.3 μ Kat g −1, 60°C.