103
Bacterial Cellulose Surface Modifications
and.temperature..The.relative.activity.of.the.immobilized.glucoamylase.was.
still.greater.than.77%.at.pH.2.0,.the.highest.value.reported.in.the.literature.
Recently.Hu.and.Catchmark.(2011a).developed.a.bioresorbable.BNC.material.integrating.one.or.more.cellulose.degrading.enzymes.(cellulases).in.order.
tions..A.double.lyophilization.process.was.used.to.preserve.the.BNC.microstructure,.as.well.as.the.activity.of.embedded.enzymes,.allowing.for.long-term.
storage.of.the.material..For.the.immobilization.of.cellulases,.enzyme.solution.
was.added.to.small.pieces.of.lyophilized.BC.pellicles..In.vitro.studies.showed.
that.acidic.cellulases.from.T. viride.presented.reasonable.activity.for.pH.values.
between.4.5.and.6..This.bioresorbable.BNC.could.be.ideal.for.many.wound.
care.and.tissue.engineering.applications..Nevertheless,.changes.in.wound.or.
tissue.pH.may.occur,.thus.decreasing.the.activity.of.some.enzymes..So.the.
same.authors,.in.a.later.work.(Hu.and.Catchmark.2011b).also.incorporated.
buffer.ingredients.into.the.BC.along.with.the.cellulases.in.order.to.provide.
an. optimal. pH. microenvironment. for. the. preferred. acid. cellulases,. whose.
. activity.is.significantly.decreased.at.physiological.pH.
Also. in. a. recent. work,. Wang. et. al.. (2011). developed. a. novel. matrix. for.
enzyme. immobilization. and. biosensor. manufacturing. consisting. of. a.
gold. nano. particles-BC. nanofibers. (Au-BNC). nanocomposite,. prepared.
through. a. one-step. biotemplated. method. in. aqueous. suspension. using.
poly(ethyleneimine).as.a.reducing.and.linking.agent..The.authors.were.able.
to. successfully. immobilize. heme. proteins. with. different. sizes,. like. horseradish.peroxidase,.hemoglobin,.and.myoglobin,.by.embedding.them.on.the.
surface.of.the.Au-BNC.nanocomposite,.while.maintaining.the.bioactivity.of.
the. protein.. In. this. way,. this. nanocomposite. material. proved. to. have. vast.
applications.in.the.field.of.biosensors.and.biocatalysis.
Immobilization of Cells
The.investigation.of.immobilized.microbial.cells.with.applications.in.wastewater.treatment.has.gained.great.interest..This.technique.accounts.for.high.
cell.concentration.in.the.bioreactor.tank,.and.thus.increased.efficiency,.as.
well.as.it.facilitates.the.separation.of.liquids.and.solids.in.the.. settling.tank..
In.addition,.biological.denitrification.has.proved.to.be.one.of.the.most.feasible,.advanced,.selective,.and.cost-effective.processes.for.nitrate.removal.
via. dissimilatory. reduction.. Exploiting. this. concept,. Rezaee. et. al.. (2008b).
investigated.the.use.of.BNC.as.a.matrix.for.the.immobilization.of.denitrifying.bacteria,.namely.Pseudomonas stutzeri..After.BNC.production,.small.
pieces.(5–10.mm).were.shaken.together.with.a.cell.suspension.of.P. stutzeri.
for.96.h.on.a.rotating.shaker.(to.promote.physical.surface.immobilization.
of.the.bacterium).and.subsequently.washed.twice.to.remove.free.cells..The.
Bacterial Cellulose Surface Modifications
and.temperature..The.relative.activity.of.the.immobilized.glucoamylase.was.
still.greater.than.77%.at.pH.2.0,.the.highest.value.reported.in.the.literature.
Recently.Hu.and.Catchmark.(2011a).developed.a.bioresorbable.BNC.material.integrating.one.or.more.cellulose.degrading.enzymes.(cellulases).in.order.
tions..A.double.lyophilization.process.was.used.to.preserve.the.BNC.microstructure,.as.well.as.the.activity.of.embedded.enzymes,.allowing.for.long-term.
storage.of.the.material..For.the.immobilization.of.cellulases,.enzyme.solution.
was.added.to.small.pieces.of.lyophilized.BC.pellicles..In.vitro.studies.showed.
that.acidic.cellulases.from.T. viride.presented.reasonable.activity.for.pH.values.
between.4.5.and.6..This.bioresorbable.BNC.could.be.ideal.for.many.wound.
care.and.tissue.engineering.applications..Nevertheless,.changes.in.wound.or.
tissue.pH.may.occur,.thus.decreasing.the.activity.of.some.enzymes..So.the.
same.authors,.in.a.later.work.(Hu.and.Catchmark.2011b).also.incorporated.
buffer.ingredients.into.the.BC.along.with.the.cellulases.in.order.to.provide.
an. optimal. pH. microenvironment. for. the. preferred. acid. cellulases,. whose.
. activity.is.significantly.decreased.at.physiological.pH.
Also. in. a. recent. work,. Wang. et. al.. (2011). developed. a. novel. matrix. for.
enzyme. immobilization. and. biosensor. manufacturing. consisting. of. a.
gold. nano. particles-BC. nanofibers. (Au-BNC). nanocomposite,. prepared.
through. a. one-step. biotemplated. method. in. aqueous. suspension. using.
poly(ethyleneimine).as.a.reducing.and.linking.agent..The.authors.were.able.
to. successfully. immobilize. heme. proteins. with. different. sizes,. like. horseradish.peroxidase,.hemoglobin,.and.myoglobin,.by.embedding.them.on.the.
surface.of.the.Au-BNC.nanocomposite,.while.maintaining.the.bioactivity.of.
the. protein.. In. this. way,. this. nanocomposite. material. proved. to. have. vast.
applications.in.the.field.of.biosensors.and.biocatalysis.
Immobilization of Cells
The.investigation.of.immobilized.microbial.cells.with.applications.in.wastewater.treatment.has.gained.great.interest..This.technique.accounts.for.high.
cell.concentration.in.the.bioreactor.tank,.and.thus.increased.efficiency,.as.
well.as.it.facilitates.the.separation.of.liquids.and.solids.in.the.. settling.tank..
In.addition,.biological.denitrification.has.proved.to.be.one.of.the.most.feasible,.advanced,.selective,.and.cost-effective.processes.for.nitrate.removal.
via. dissimilatory. reduction.. Exploiting. this. concept,. Rezaee. et. al.. (2008b).
investigated.the.use.of.BNC.as.a.matrix.for.the.immobilization.of.denitrifying.bacteria,.namely.Pseudomonas stutzeri..After.BNC.production,.small.
pieces.(5–10.mm).were.shaken.together.with.a.cell.suspension.of.P. stutzeri.
for.96.h.on.a.rotating.shaker.(to.promote.physical.surface.immobilization.
of.the.bacterium).and.subsequently.washed.twice.to.remove.free.cells..The.