Preface
Bacterial. nanocellulose. (BNC). is. an. emerging. nanomaterial. with. unique.
properties. produced. by. several. species. of. bacteria.. The. most. important. of.
these.is.Acetobacter xylinum,.now.renamed.Gluconacetobacter xylinus,.discovered.in.1886.by.A..J..Brown. These.bacteria.are.highly.ubiquitous..They.are.
found. wherever. the. fermentation. of. sugars. and. plant. carbohydrates. takes.
place;.for.example,.on.the.surfaces.of.rotting.fruits.and.in.unpasteurized.or.
unsterilized.juice,.beer,.and.wine.
Although. the. molecular. formula. and. morphology. of. BNC. is. similar. to.
nanocellulose.produced.from.wood,.the.former.present.several.advantages..
Bacteria. produce. pure. cellulose,. free. from. other. plant. components. such.
as. hemicelluloses. and. lignin,. and. form. a. three-dimensional. network. that.
provides.unique.mechanical.properties..Due.to.their.large.surface.area.and.
hydrophilic.nature,.cellulose.nanofibrils.produced.by.bacteria.hold.a.large.
amount.of.water.making.them.a.very.strong.hydrogel..BNC.has.been.used.
for. a. variety. of. commercial. applications. including. textiles,. cosmetics,. and.
food.products,.and.has.a.high.potential.for.medical.applications..This.book.
provides.state-of-art.scientific.knowledge.about.the.mechanism.of.cellulose.
production. by. bacteria. and. points. out. the. challenges. in. the. expansion. of.
BNC.production.to.a.large.scale..It.also.provides.the.latest.information.on.
BNC.structure.and.its.modification,.as.well.as.comprehensive.information.
concerning.current.and.future.applications.of.BNC.
Since. the. first. identification. of. genes. for. cellulose. biosynthesis. in.
Gluconacetobacter xylinus.more.than.twenty.years.ago,.homologous.sequences.
have.been.identified.in.the.genomes.of.a.large.number.of.bacterial.species..
The.genes.for.cellulose.biosynthesis.are.organized.in.an.operon.consisting.
of.three.to.four.genes.and.this.organization.is.conserved.in.most.bacteria..
The.first.gene.in.the.operon.encodes.the.enzyme.cellulose.synthase.and,.so.
far,.this.is.the.only.protein.with.a.known.function.in.cellulose.biosynthesis..
Although.genetic.analysis.demonstrated.a.role.in.cellulose.biosynthesis.for.
the. other. genes. in. the. operon,. the. exact. function. of. the. proteins. encoded.
by.these.genes.remains.to.be.determined..Chapter.1.introduces.the.field.of.
biosynthesis.of.BNC.
BNC. is. a. unique,. nontoxic. hydrogel. with. good. mechanical. properties.. It. has. been. shown. to. be. biocompatible. and,. therefore,. it. has. found.
. several.applications.in.the.medical.field.as.wound.and.burn.dressings.and.
has. high. potential. for. development. as. medical. implants. and. scaffolds. for.
. tissue.engineering..Another.unique.property.is.its.ability.to.be.shaped.into.
three-dimensional.structures.during.biosynthesis..For.instance,.in.the.case.of.
vascular.grafts,.the.material.synthesis.and.tubular.product.formation.takes.
ix
Bacterial. nanocellulose. (BNC). is. an. emerging. nanomaterial. with. unique.
properties. produced. by. several. species. of. bacteria.. The. most. important. of.
these.is.Acetobacter xylinum,.now.renamed.Gluconacetobacter xylinus,.discovered.in.1886.by.A..J..Brown. These.bacteria.are.highly.ubiquitous..They.are.
found. wherever. the. fermentation. of. sugars. and. plant. carbohydrates. takes.
place;.for.example,.on.the.surfaces.of.rotting.fruits.and.in.unpasteurized.or.
unsterilized.juice,.beer,.and.wine.
Although. the. molecular. formula. and. morphology. of. BNC. is. similar. to.
nanocellulose.produced.from.wood,.the.former.present.several.advantages..
Bacteria. produce. pure. cellulose,. free. from. other. plant. components. such.
as. hemicelluloses. and. lignin,. and. form. a. three-dimensional. network. that.
provides.unique.mechanical.properties..Due.to.their.large.surface.area.and.
hydrophilic.nature,.cellulose.nanofibrils.produced.by.bacteria.hold.a.large.
amount.of.water.making.them.a.very.strong.hydrogel..BNC.has.been.used.
for. a. variety. of. commercial. applications. including. textiles,. cosmetics,. and.
food.products,.and.has.a.high.potential.for.medical.applications..This.book.
provides.state-of-art.scientific.knowledge.about.the.mechanism.of.cellulose.
production. by. bacteria. and. points. out. the. challenges. in. the. expansion. of.
BNC.production.to.a.large.scale..It.also.provides.the.latest.information.on.
BNC.structure.and.its.modification,.as.well.as.comprehensive.information.
concerning.current.and.future.applications.of.BNC.
Since. the. first. identification. of. genes. for. cellulose. biosynthesis. in.
Gluconacetobacter xylinus.more.than.twenty.years.ago,.homologous.sequences.
have.been.identified.in.the.genomes.of.a.large.number.of.bacterial.species..
The.genes.for.cellulose.biosynthesis.are.organized.in.an.operon.consisting.
of.three.to.four.genes.and.this.organization.is.conserved.in.most.bacteria..
The.first.gene.in.the.operon.encodes.the.enzyme.cellulose.synthase.and,.so.
far,.this.is.the.only.protein.with.a.known.function.in.cellulose.biosynthesis..
Although.genetic.analysis.demonstrated.a.role.in.cellulose.biosynthesis.for.
the. other. genes. in. the. operon,. the. exact. function. of. the. proteins. encoded.
by.these.genes.remains.to.be.determined..Chapter.1.introduces.the.field.of.
biosynthesis.of.BNC.
BNC. is. a. unique,. nontoxic. hydrogel. with. good. mechanical. properties.. It. has. been. shown. to. be. biocompatible. and,. therefore,. it. has. found.
. several.applications.in.the.medical.field.as.wound.and.burn.dressings.and.
has. high. potential. for. development. as. medical. implants. and. scaffolds. for.
. tissue.engineering..Another.unique.property.is.its.ability.to.be.shaped.into.
three-dimensional.structures.during.biosynthesis..For.instance,.in.the.case.of.
vascular.grafts,.the.material.synthesis.and.tubular.product.formation.takes.
ix