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A model system for increasing the intensity of whole‐cell biocatalysis: Investigation of the rate of oxidation of D ‐sorbitol to L ‐sorbose by thin bi‐layer latex coatings of non‐growing Gluconobacter oxydans
Author(s) -
Fidaleo M.,
Charaniya S.,
Solheid C.,
Diel U.,
Laudon M.,
Ge H.,
Scriven L.E.,
Flickinger M.C.
Publication year - 2006
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21051
Subject(s) - sorbitol , sorbose , coating , materials science , chemical engineering , biocatalysis , nuclear chemistry , chemistry , catalysis , fructose , composite material , organic chemistry , reaction mechanism , engineering
We developed a novel <50‐µm thick nano‐porous bi‐layer latex coating for preserving Gluconobacter oxydans , a strict aerobe, as a whole cell biocatalyst. G. oxydans was entrapped in an acrylate/vinyl acetate co‐polymer matrix ( T g ∼10°C) and cast into 12.7‐mm diameter patch coatings (cellcoat) containing ∼10 9 CFU covered by a nano‐porous topcoat. The oxidation of D ‐sorbitol to L ‐sorbose was used to investigate the coating catalytic properties. Intrinsic kinetics was studied in microbioreactors using a pH 6.0 D ‐sorbitol, phosphate, pyruvate (SPP) non‐growth medium at 30°C, and the Michaelis–Menten constants determined. By using a diffusion cell, cellcoat and topcoat diffusivities, optimized by arresting polymer particle coalescence by glycerol and/or sucrose addition, were determined. Cryo‐FESEM images revealed a two‐layer structure with G. oxydans surrounded by <40‐nm pores. Viable cell density, cell leakage, and oxidation kinetics in SPP medium for >150 h were investigated. Even though the coatings were optimized for permeability, ∼50% of G. oxydans viability was lost during cellcoat drying and further reduction was observed as the topcoat was added. High reaction rates per unit volume of coating (80–100 g/L · h) were observed which agreed with predictions of a diffusion‐reaction model using parameters estimated by independent experiments. Cellcoat effectiveness factors of 0.22–0.49 were observed which are 20‐fold greater than any previously reported for this G. oxydans oxidation. These nano‐structured coatings and the possibility of improving their ability to preserve G. oxydans viability may be useful for engineering highly reactive adhesive coatings for multi‐phase micro‐channel and membrane bioreactors to dramatically increase the intensity of whole‐cell oxidations. © 2006 Wiley Periodicals, Inc.