218
Bacterial Cellulose
2,2,6,6-tetramethylpyperidine-1-oxyl. (TEMPO)-mediated. oxidation. and.
medium.modification.by.addition.of.amino.sugar.N-acetylglucosamine.
(GlcNAc). during. cellulose. biosynthesis.. The. carboxylate. content. of.
TEMPO-oxidized.BC.(BC-TEMPO).measured.by.conductimetric.titration.
was.0.25.mmol/g.cellulose..The.amount.of.GlcNAc.incorporated.in.BC.
determined.by.the.radiolabeling.method.was.0.03–0.36.mole%,.depending. on. the. amount. of. nonradioactive. GlcNAc. present. in. the. culture.
medium. and. the. type. of. starter. culture. used.. Attenuated. total. reflectance–Fourier. transform. infrared. spectroscopy. (ATR-FTIR). and. inductively.coupled.plasma.atomic.emission.spectroscopy.(ICP-AES).analysis.
indicated. that. the. crystalline. phase. nucleated. on. the. BC. microfibrils.
surface.was.calcium-deficient.carbonated.apatite.through.the.initial.formation.of.octacalcium.phosphate.(OCP).or.OCP-like.calcium.phosphate.
phase..From.field.emission.scanning.electron.microscopy.(FE-SEM).and.
transmission.electron.microscopy.(TEM).observations,.the.apatite.mineral. was. in. the. form. of. globules. or. clusters. of. thin. film. plates,. which.
varied.in.size.from.less.than.1.μm.to.approximately.6.μm.with.respect.to.
different.BC.templates.and.the.soaking.method..The.BC-TEMPO.having.
active.carboxyl.functional.groups.showed.a.faster.nucleation.rate.than.
native.BC.and.GlcNAc-incorporated.BC..It.was.found.that.the.ability.of.
BC.templates.to.induce.mineral.nucleation.differed.according.to.the.surface.structure.of.the.BC,.which.strongly.influenced.the.growth.behavior.
of.the.apatite.crystals.
Introduction
Bacterial.cellulose.(BC).produced.by.the.bacterium.(Hestrin.and.Schramm.
1954).Gluconacetobacter xylinus—.previously.named.Acetobacter xylinum—has.
unique.properties,.including.an.ultrafine.network.with.higher-order.architecture,. great. mechanical. strength. and. crystallinity,. high. water-holding.
capacity,.in.situ.moldability,.and.chemical.purity.(free.of.lignin.and.hemicellulose),.that.distinguish.it.from.other.forms.of.plant.cellulose.(Jonas.and.
Farah.1998;.Yamanaka.et.al..1989)..The.unique.physical.and.mechanical.properties.of.BC.as.well.as.its.purity.have.been.exploited.for.multiple.applications.
that. range. from. high-quality. audio. membranes,. electronic. paper,. and. fuel.
cells.to.biomedical.materials.(Czaja.et.al..2006;.Klemm.et.al..2001)..Moreover,.
the.in.vivo.biocompatibility.evaluation.of.BC.in.rats.has.demonstrated.that.it.
is.well.integrated.into.the.host.tissues.and.does.not.elicit.any.chronic.inflammatory.reaction,.making.it.a.potentially.interesting.scaffolding.material.for.
tissue.engineering.(Helenius.et.al..2006)..Because.of.its.high.water-holding.
capacity,.the.hydrophilic.network.of.BC.enables.particulates.to.infiltrate.into.
its. network.. This. unique. property. allows. BC. to. be. used. as. a. template. for.
Bacterial Cellulose
2,2,6,6-tetramethylpyperidine-1-oxyl. (TEMPO)-mediated. oxidation. and.
medium.modification.by.addition.of.amino.sugar.N-acetylglucosamine.
(GlcNAc). during. cellulose. biosynthesis.. The. carboxylate. content. of.
TEMPO-oxidized.BC.(BC-TEMPO).measured.by.conductimetric.titration.
was.0.25.mmol/g.cellulose..The.amount.of.GlcNAc.incorporated.in.BC.
determined.by.the.radiolabeling.method.was.0.03–0.36.mole%,.depending. on. the. amount. of. nonradioactive. GlcNAc. present. in. the. culture.
medium. and. the. type. of. starter. culture. used.. Attenuated. total. reflectance–Fourier. transform. infrared. spectroscopy. (ATR-FTIR). and. inductively.coupled.plasma.atomic.emission.spectroscopy.(ICP-AES).analysis.
indicated. that. the. crystalline. phase. nucleated. on. the. BC. microfibrils.
surface.was.calcium-deficient.carbonated.apatite.through.the.initial.formation.of.octacalcium.phosphate.(OCP).or.OCP-like.calcium.phosphate.
phase..From.field.emission.scanning.electron.microscopy.(FE-SEM).and.
transmission.electron.microscopy.(TEM).observations,.the.apatite.mineral. was. in. the. form. of. globules. or. clusters. of. thin. film. plates,. which.
varied.in.size.from.less.than.1.μm.to.approximately.6.μm.with.respect.to.
different.BC.templates.and.the.soaking.method..The.BC-TEMPO.having.
active.carboxyl.functional.groups.showed.a.faster.nucleation.rate.than.
native.BC.and.GlcNAc-incorporated.BC..It.was.found.that.the.ability.of.
BC.templates.to.induce.mineral.nucleation.differed.according.to.the.surface.structure.of.the.BC,.which.strongly.influenced.the.growth.behavior.
of.the.apatite.crystals.
Introduction
Bacterial.cellulose.(BC).produced.by.the.bacterium.(Hestrin.and.Schramm.
1954).Gluconacetobacter xylinus—.previously.named.Acetobacter xylinum—has.
unique.properties,.including.an.ultrafine.network.with.higher-order.architecture,. great. mechanical. strength. and. crystallinity,. high. water-holding.
capacity,.in.situ.moldability,.and.chemical.purity.(free.of.lignin.and.hemicellulose),.that.distinguish.it.from.other.forms.of.plant.cellulose.(Jonas.and.
Farah.1998;.Yamanaka.et.al..1989)..The.unique.physical.and.mechanical.properties.of.BC.as.well.as.its.purity.have.been.exploited.for.multiple.applications.
that. range. from. high-quality. audio. membranes,. electronic. paper,. and. fuel.
cells.to.biomedical.materials.(Czaja.et.al..2006;.Klemm.et.al..2001)..Moreover,.
the.in.vivo.biocompatibility.evaluation.of.BC.in.rats.has.demonstrated.that.it.
is.well.integrated.into.the.host.tissues.and.does.not.elicit.any.chronic.inflammatory.reaction,.making.it.a.potentially.interesting.scaffolding.material.for.
tissue.engineering.(Helenius.et.al..2006)..Because.of.its.high.water-holding.
capacity,.the.hydrophilic.network.of.BC.enables.particulates.to.infiltrate.into.
its. network.. This. unique. property. allows. BC. to. be. used. as. a. template. for.