Novel Bioreactors for Culturing Marine Organisms 12.2 Photobioreactors (PBR)-Tubular, Plate/Panel and Stirred Tank Configurations 331
Part B | 12.2
tion – peak antibiotic activity (PAA) and peak activity attainment rate (PAAR) simultaneously attaining
their highest values at this operating condition – 50%
disk submergence. Both PAA and PAAR are observed
to increase with increasing aeration at all operating
conditions examined. At the niche-mimic condition,
a threefold increase in the aeration rate causes PAA
to increase by 33%, whereas PAAR increases by 2:5
times, underlining the strong aeration dependence of
this actinomycin-D producer. Again, compared to the
highest values obtained for antimicrobial production in
flask (500 mL) experiments, the corresponding RDBR
values were 16% higher for PAA and more than five
times higher for PAAR – strong evidence for employing
these novel bioreactors for cultivation of antibioticproducing marine microbes.
It follows from the above discussion that for microorganisms which synthesize metabolites/enzymes at
the highest rates only when growing in surface-attached
condition, i. e., as biofilms anchored to solid surfaces,
special culture conditions are necessary that are conducive to surface attachment and biofilm formation.
For this purpose, several typical niche-mimic bioreactors have been developed (e.g., modified roller bottle
cultures, AMS-BR, ULS-RDBR, etc.) as described earlier in this section. However, a lack of small-scale
shaken vessels with high surface/volume ratio and surface properties favoring attachment of biofilm-forming
microbes was noted by Sarkar et al. [12.6]. They developed a novel small scale, extended surface shaken
vessel (ESSV) in the form of a PMMA acrylic made
conico-cylindrical flask (CCF) (volume 500 mL) in
which enhanced surface for microbial attachment and
biofilm formation was provided by eight equidistantly
located vertical rectangular strips radially mounted on
the base of the vessel with the base diameter close
to that of a 500 mL Erlenmeyer flask (EF) for easy
placement in a rotary shaker. The small-scale vessel
was designed to allow the use of different internal
surface materials – hydrophilic (glass) or hydrophobic (acrylic). Furthermore, protease production by two
strains in the ESSV were examined, of which one
was marine – an intertidal gamma – Proteobacterium
(DG II). Relative to a standard EF with no additional
surface, growth and protease synthesis by the marine
isolate DG II were 20 and 30% higher, respectively.
Again, compared to glass, the use of acrylic surface
(hydrophobic) resulted in more than 200% increase in
protease production and a dramatic increase (i. e., by
19; 275%) in microbial growth.
Mitra et al. [12.7] cultivated two biofilm-forming
marine bacteria in the novel ESSV described above,
viz. Shewanella colwelliana for melanin production and
Pseudoalteromonas rubra for antibiotic synthesis. The
design allowed comparison of production between (1)
CCF with hydrophobic surface (PMMA), (2) ESSV
with hydrophilic glass surface, and (3) standard unbaffled EF. Growth and melanin production by S. colwelliana were highest in the ESSV with (hydrophilic)
acrylic surface, further melanin synthesis increased
with increase in surface (for attachment) and increase
in biofilm formation and increase in planktonic growth.
Growth of P. rubra was also highest in the acrylic ESSV
but not antibiotic synthesis – it was maximum in the EF
without any extended surfaces. Thus antibiotic production was favored by a hydrophilic vessel surface (glass).
Mitra et al. [12.8] examined cellulase and xylanase
production in relation to biofilm formation by two intertidal filamentous fungi, viz. Chaetomium crispatum
and Gliocladium viride, respectively, in the novel ESSV
(described above) with either hydrophobic (acrylic) or
hydrophilic (glass) surface and compared with that in an
ordinary EF. Mixed results were obtained with regard to
suitability of the EF or the ESSVs for enzyme production by the two filamentous fungi – surface properties
as well as surface area of attachment of the cultivation vessel affected biofilm formation and enzyme
production.
12.2 Photobioreactors (PBR)-Tubular, Plate/Panel
and Stirred Tank Configurations
Photobioreactors, as the name indicates, are specialized bioreactors (Table 12.2) for phototrophic growth of
microorganisms – mainly alga but also photosynthetic
bacteria; as well as macroorganisms, i. e., macroalgae
(seaweed). Application of PBRs for microalgal growth
has been extensively reviewed [12.19, 20]. PBRs originated as open-air cultivation systems with natural sunlight as the source of illumination that are easy to
build and operate – these include natural or artificial
ponds/tanks, raceway-shaped culture ponds (which are
basically closed-loop recirculation channels) and socalled inclined surface ponds driven by paddle wheels.
However, open-air PBR systems are prone to evaporative losses and contamination problems and most im-
Part B | 12.2
tion – peak antibiotic activity (PAA) and peak activity attainment rate (PAAR) simultaneously attaining
their highest values at this operating condition – 50%
disk submergence. Both PAA and PAAR are observed
to increase with increasing aeration at all operating
conditions examined. At the niche-mimic condition,
a threefold increase in the aeration rate causes PAA
to increase by 33%, whereas PAAR increases by 2:5
times, underlining the strong aeration dependence of
this actinomycin-D producer. Again, compared to the
highest values obtained for antimicrobial production in
flask (500 mL) experiments, the corresponding RDBR
values were 16% higher for PAA and more than five
times higher for PAAR – strong evidence for employing
these novel bioreactors for cultivation of antibioticproducing marine microbes.
It follows from the above discussion that for microorganisms which synthesize metabolites/enzymes at
the highest rates only when growing in surface-attached
condition, i. e., as biofilms anchored to solid surfaces,
special culture conditions are necessary that are conducive to surface attachment and biofilm formation.
For this purpose, several typical niche-mimic bioreactors have been developed (e.g., modified roller bottle
cultures, AMS-BR, ULS-RDBR, etc.) as described earlier in this section. However, a lack of small-scale
shaken vessels with high surface/volume ratio and surface properties favoring attachment of biofilm-forming
microbes was noted by Sarkar et al. [12.6]. They developed a novel small scale, extended surface shaken
vessel (ESSV) in the form of a PMMA acrylic made
conico-cylindrical flask (CCF) (volume 500 mL) in
which enhanced surface for microbial attachment and
biofilm formation was provided by eight equidistantly
located vertical rectangular strips radially mounted on
the base of the vessel with the base diameter close
to that of a 500 mL Erlenmeyer flask (EF) for easy
placement in a rotary shaker. The small-scale vessel
was designed to allow the use of different internal
surface materials – hydrophilic (glass) or hydrophobic (acrylic). Furthermore, protease production by two
strains in the ESSV were examined, of which one
was marine – an intertidal gamma – Proteobacterium
(DG II). Relative to a standard EF with no additional
surface, growth and protease synthesis by the marine
isolate DG II were 20 and 30% higher, respectively.
Again, compared to glass, the use of acrylic surface
(hydrophobic) resulted in more than 200% increase in
protease production and a dramatic increase (i. e., by
19; 275%) in microbial growth.
Mitra et al. [12.7] cultivated two biofilm-forming
marine bacteria in the novel ESSV described above,
viz. Shewanella colwelliana for melanin production and
Pseudoalteromonas rubra for antibiotic synthesis. The
design allowed comparison of production between (1)
CCF with hydrophobic surface (PMMA), (2) ESSV
with hydrophilic glass surface, and (3) standard unbaffled EF. Growth and melanin production by S. colwelliana were highest in the ESSV with (hydrophilic)
acrylic surface, further melanin synthesis increased
with increase in surface (for attachment) and increase
in biofilm formation and increase in planktonic growth.
Growth of P. rubra was also highest in the acrylic ESSV
but not antibiotic synthesis – it was maximum in the EF
without any extended surfaces. Thus antibiotic production was favored by a hydrophilic vessel surface (glass).
Mitra et al. [12.8] examined cellulase and xylanase
production in relation to biofilm formation by two intertidal filamentous fungi, viz. Chaetomium crispatum
and Gliocladium viride, respectively, in the novel ESSV
(described above) with either hydrophobic (acrylic) or
hydrophilic (glass) surface and compared with that in an
ordinary EF. Mixed results were obtained with regard to
suitability of the EF or the ESSVs for enzyme production by the two filamentous fungi – surface properties
as well as surface area of attachment of the cultivation vessel affected biofilm formation and enzyme
production.
12.2 Photobioreactors (PBR)-Tubular, Plate/Panel
and Stirred Tank Configurations
Photobioreactors, as the name indicates, are specialized bioreactors (Table 12.2) for phototrophic growth of
microorganisms – mainly alga but also photosynthetic
bacteria; as well as macroorganisms, i. e., macroalgae
(seaweed). Application of PBRs for microalgal growth
has been extensively reviewed [12.19, 20]. PBRs originated as open-air cultivation systems with natural sunlight as the source of illumination that are easy to
build and operate – these include natural or artificial
ponds/tanks, raceway-shaped culture ponds (which are
basically closed-loop recirculation channels) and socalled inclined surface ponds driven by paddle wheels.
However, open-air PBR systems are prone to evaporative losses and contamination problems and most im-