Engineering the Microstructure and Permeability of Thin Multilayer Latex Biocatalytic Coatings Containing E. coli

Abstract

The microstructure and permeability of rehydrated 20-100 microm thick partially coalesced (vinyl-actetate acrylic copolymer) SF091 latex coatings and a 118 microm thick model trilayer biocatalytic coating consisting of two sealant SF091 layers containing a middle layer of viable E. coli HB101 + latex were studied as delaminated films in a diffusion apparatus with KNO(3) as the diffussant. The permeability of the hydrated coatings is due to diffusive transport through the pore space between the partially coalesced SF091 latex particles. Coating microstructure was visualized by fast freeze cryogenic scanning electron microscopy (cryo-SEM). The effective diffusion coefficient of SF091 latex coatings (diffusive permeability/film thickness) was determined as the ratio of the effective diffusivity of KNO(3) to its diffusivity in water (D(eff)/D). Polymer particle coalescence was arrested by two methods to increase coating permeability. The first used glycerol with coating drying at 4 degrees C, near the glass transition temperature (T(g)). The second method used sucrose or trehalose as a filler to arrest coalescence; the filler was then dissolved away. D(eff)/D was measured as a function of film thickness; content of glycerol, sucrose, and trehalose; drying time; and rehydration time. D(eff)/D varied from 3 x 10(-4) for unmodified SF091 coatings to 6.8 x 10(-2) for coatings containing sucrose. D(eff)/D was reduced by the flattening of latex particles against the surface of the solid substrate, as well as by the presence of the colloid stabilizer hydroxyethylcellulose (HEC). When corrected for the flattened particle layer, D(eff)/D of HEC-free coatings was as high as 0.20, which agreed with the value predicted from analysis of cryo-SEM images of the coat surface. D(eff)/D decreased by one-half in approximately 5 days in rehydrated SF091 coatings, indicating that significant wet coalescence occurs after glycerol, sucrose, or trehalose are leached from the films. D(eff)/D of SF091 latex trilayer coatings containing viable E. coli HB101 cells decreased as cell loading was increased from 2.2 x 10(-2) for 64 g dry cell weight per liter of coat volume to 5 x 10(-3) for 151 g DCW/L of coat volume. The reduction in coating permeability with increasing cell loading is predicted by Maxwell's equation for D(eff)/D in periodic composites.

Blind and naïve classification of toxicity by fish chromatophores

“…Researchers from The University of Turku, Finland, whose technology was presented at the workshop, developed a whole-cell bacterial sensor for the detection of heavy metals (specifically mercury and arsenite) by measuring luciferase-catalyzed bioluminescence (Tauriainen et al, 1999;Ivask et al, 2001;Hakkila et al, 2003). A similar concept was utilized for designing a fibre-optic biosensor for mercury detection, based on genetically engineered E.coli MC 1061 containing the mercury-responding promoter to control the expression of luxCDABE from Photorhabdus luminescens (Green et al, 2002), as well as for developing a latex-coated mercury sensor using E.coli-harboring pRB28 with a mer-lux constract (Lyngberg et al, 1999(Lyngberg et al, , 2001). However, the use of bioluminescence-based techniques is not limited only to mercury and arsenite testing.…”

Immobilization of Photosynthetic Microorganisms for Efficient Hydrogen Production

“…Although photosynthetic microbes were first immobilized in latex coatings nearly 20 years ago (Martens and Hall 1994), the latex polymers have been applied mainly for entrapping heterotrophic bacteria (Lyngberg et al 2001;Flickinger et al 2007). The entrapment of photosynthetic microorganisms into latex matrices has attracted more attention only recently with increasing demands of immobilizing H 2 -photoproducing cultures.…”

“…Trying to improve the light absorption properties of immobilized microalgae, Kosourov and Seibert (2009) entrapped C. reinhardtii cells within thin alginate films. The technique was based on the idea of thin layer cell immobilization into the thin nanoporous latex coatings Lyngberg et al 2001). The entrapment of phototrophic cells into the polymer allows a very precise control of the cell density inside the coatings and their thicknesses that, in the ideal case, must provide the immobilized cells with the best environment for light distribution.…”

Ink-Jet Printing of Gluconobacter oxydans: Micropatterned Coatings As High Surface-to-Volume Ratio Bio-Reactive Coatings

“…Nanoporous, adhesive latex biocatalytic coatings offer the possibility of concentrating and entrapping viable microorganisms (such as bacteria, yeast or fungi) in very thin (five to <75 µm ), partially-coalesced polymer coatings [9][10][11][12][13][14][15][16][17][18][19][20]. Their thinness, engineered adhesion, nanoporous microstructure, mass-transfer properties [21][22][23], high-entrapped cell density and ability to be stored partially desiccated at ambient temperature differ significantly from the entrapment of viable microorganisms in crosslinked micro-porous carbohydrate gels, ceramic matrices, monoliths, soft synthetic polymer matrices (such as alginate or polyacrylamide) or behind membranes.…”