Figure 2.10
Oxygen Level in Medium with Bacteria in Tube Bioreactor
400
350
300
250
200
150
100
50
0
0
5
10
Time (hours)
15
20
O
2 Level (% air saturated)
37
Effect of Cultivation on BNC Biomaterials
Figure 2.10
Oxygen.level.measurements.during.BNC.tube.culture.using.the.tube.bioreactor.with.100%.O 2 .
supply.(70.mL/min)..Since.pure.oxygen.is.used,.the.oxygen.level.in.the.cultivation.medium.
is saturated.
Close. to. the. silicone. surface,. the. bacteria. have. access. to. oxygen. during.
cultivation;.in.the.cultivation.medium,.however,.the.level.of.oxygen.is.very.
low,.which.might.be.due.to.the.fact.that.a.thin.layer.of.cellulose.was.produced. on. the. silicone. surface. and. that. this. may. act. as. an. oxygen. barrier..
Thus.the.. oxygen.cannot.diffuse.out.into.the.media..The.oxygen.limitation.
in.the.tube.bioreactor.may.affect.the.metabolism,.since.the.bacterium.is.an.
ob . ligate.. aerobe..To.avoid.oxygen.limitations.and.to.get.more.evenly.distributed.. oxygen.in.the.cultivation.medium,.it.would.be.preferable.to.use.a.continuous.bioreactor..In.a.continuous.bioreactor,.an.inflow.of.new.cultivation.
medium,.which.is.saturated.with.oxygen,.can.be.used.
Properties and Components of CSL
The. composition. of. CSL. is. not. fully. known. and. varies. between. different.
batches.. This. is. most. challenging,. as. it. results. in. varying. growth. conditions. and. therefore. a. varying. quality. of. the. tubes. produced.. The. pH. of.
CSL.is.3.5–4.5.(Liggett.and.Koffler.1948).and.the.variation.depends.on.the.
composition.of.the.CSL.batch..Common.for.all.the.batches.is.that.the.color.
of. CSL. is. light. brown. to. brown. and. has. a. characteristic. odor.. The. major.
components. of. CSL. are. crude. proteins. (47%). and. lactic. acid. (26%). (White.
and.Johnson.2003).
The.amino.acid.composition.of.CSL.has.been.analyzed.and.16–20.different.
amino.acids.have.been.found..Saha.and.Racine.(2010).compared.the.amino.
acid.content.of.three.different.batches.(see.Table 2.2)..In.this.table,.it.can.be.
seen.that.the.total.amount.of.amino.acids.differs.quite.a.lot.between.different.
batches.(from.39.38.to.76.11.mg/g)..The.highest.amounts.of.amino.acids.are.
represented.by.glutamic.acid,.proline,.alanine,.leucine,.and.arginine.(Saha.
Oxygen Level in Medium with Bacteria in Tube Bioreactor
400
350
300
250
200
150
100
50
0
0
5
10
Time (hours)
15
20
O
2 Level (% air saturated)
37
Effect of Cultivation on BNC Biomaterials
Figure 2.10
Oxygen.level.measurements.during.BNC.tube.culture.using.the.tube.bioreactor.with.100%.O 2 .
supply.(70.mL/min)..Since.pure.oxygen.is.used,.the.oxygen.level.in.the.cultivation.medium.
is saturated.
Close. to. the. silicone. surface,. the. bacteria. have. access. to. oxygen. during.
cultivation;.in.the.cultivation.medium,.however,.the.level.of.oxygen.is.very.
low,.which.might.be.due.to.the.fact.that.a.thin.layer.of.cellulose.was.produced. on. the. silicone. surface. and. that. this. may. act. as. an. oxygen. barrier..
Thus.the.. oxygen.cannot.diffuse.out.into.the.media..The.oxygen.limitation.
in.the.tube.bioreactor.may.affect.the.metabolism,.since.the.bacterium.is.an.
ob . ligate.. aerobe..To.avoid.oxygen.limitations.and.to.get.more.evenly.distributed.. oxygen.in.the.cultivation.medium,.it.would.be.preferable.to.use.a.continuous.bioreactor..In.a.continuous.bioreactor,.an.inflow.of.new.cultivation.
medium,.which.is.saturated.with.oxygen,.can.be.used.
Properties and Components of CSL
The. composition. of. CSL. is. not. fully. known. and. varies. between. different.
batches.. This. is. most. challenging,. as. it. results. in. varying. growth. conditions. and. therefore. a. varying. quality. of. the. tubes. produced.. The. pH. of.
CSL.is.3.5–4.5.(Liggett.and.Koffler.1948).and.the.variation.depends.on.the.
composition.of.the.CSL.batch..Common.for.all.the.batches.is.that.the.color.
of. CSL. is. light. brown. to. brown. and. has. a. characteristic. odor.. The. major.
components. of. CSL. are. crude. proteins. (47%). and. lactic. acid. (26%). (White.
and.Johnson.2003).
The.amino.acid.composition.of.CSL.has.been.analyzed.and.16–20.different.
amino.acids.have.been.found..Saha.and.Racine.(2010).compared.the.amino.
acid.content.of.three.different.batches.(see.Table 2.2)..In.this.table,.it.can.be.
seen.that.the.total.amount.of.amino.acids.differs.quite.a.lot.between.different.
batches.(from.39.38.to.76.11.mg/g)..The.highest.amounts.of.amino.acids.are.
represented.by.glutamic.acid,.proline,.alanine,.leucine,.and.arginine.(Saha.