Transcript MICROBIAL CULTURES Group : Cysteine Tiah

MICROBIAL
CULTURES
Group : Cysteine
Tiah Chai Ching
Norilyana Ramli
Mohd Akhmam Yusof
Nurul Maisyarah binti Samsudin
Types of Microbes
Microbial Growth
Requirement
for microbial
growth
Physical
Requirement
Chemical
Requirement
Physical requirement
• Temperature
– Microbes grow in a small range of
temperature.
– Their maximum temperature is 50oC
– Their minimum temperature is 20oC
– Growth best at 20oC-30oC
• pH
– pH most bacteria grow best near neutral
6.57.5.
– For yeast is at 4.5-6.5
Chemical Requirement
• Sources of carbon
• Source of nitrogen
• Source of oxygen
• Source of hydrogen
• Source of sulphur
• Source of phosphorous
• Source of trace elements
• Nitrogen, Sulfur and
Phosphorus
–DNA synthesis needs
nitrogen and phosphorus.
–Protein synthesis need
nitrogen and some sulphur
–ATP need phosphorus
–Trace element (example:
iron. Copper, zinc)
Remember !!
•Microbes that
Innoculum
introduced into a
culture
Culture
•Microbes that grow
in/on a culture
•
•
•
•
•
Simple Fungi
Most yeast are aerobes
Grow best on 20oC to 30oC
Maximum operating temperature- 50oC
Need water in high concentration for
growth and metabolism
• Operating pH 4.5 – 6.5
• Media acidified with organic acid(acetic)
are more inhibitory to yeast grow than
media acidified with mineral
acid(hydrochloric)
Characteristic of yeast
Yeast refers to the unicellular phase of the life
cycles of many different fungi, but it is used
more commonly as a generic term for fungi that
have only a unicellular phase.
Yeast has simple nutritional needs.
Unable to carry out photosynthesis, they
require a reduced carbon source which can be as
simple compound as acetate and nitrogen source
such as ammonium sulfate.
• Yeasts can use a variety of organic nitrogen
compounds (including urea and various amino
acids)
• The only other complex compound that they
require is the vitamin, biotin. they also require a
variety of salts and trace elements.
• One of the more well known characteristics is the
ability to ferment sugars for the production of
ethanol.
• The most well-known and commercially
significant yeasts are the related species and
strains of Saccharomyces cerevisiae.
• These organisms have long been utilized to
ferment the sugars of rice, wheat, barley, and
corn to produce alcoholic beverages and in the
baking industry to expand, or raise dough.
• The yeast's function in baking is to ferment
sugars present in the flour or added to the
dough. This fermentation gives off carbon dioxide
and ethanol. The carbon dioxide is trapped within
tiny bubbles and results in the dough expanding,
or rising.
• Saccharomyces cerevisiae is commonly used as
baker's yeast and for some types of
fermentation.
• One yeast cell can ferment approximately its own
weight of glucose per hour.
• Under optimal conditions S. cerevisiae can
produce up to 18 percent, by volume, ethanol
with 15 to 16 percent being the norm.
Requirement of
Microbial Bioreactor
Bioreactor
Bioreactor used in the industry
• Bioreactor used for yeast is stirred tank
bioreactor.
• Conventional mixing vessel has low capital and
low operating costs.
• Vessel with volume up to 20 litres is made from
glass
• Larger volumes, used stainless steel.
• Height: Diameter ratio of the vessel is between
2:1 and 6:1, depending on the amount of heat to
be removed.
• Stirrer may be on top or bottom
Baffles
 Tank is fitted with baffles to prevent
central vortex and improve mixing.
 D<3m, 4 baffles of 6-8 inches are used.
 Larger vessel needed 6-8 baffles.
 The width of the baffle is usually between
T/10 and T/12. ( T = tank diameter)
Baffled tank with six-blade turbine agitator with
disk showing flow patterns: (a) side view, (b)
bottom view, (c) dimensions of turbine and tank.
Volumes
• 75% of the designed volume is used as
working volume.
• Eg.: In fermentation vessel about 75% of
the total CSTR volume is filled with liquid,
the remaining 25% is used for gas space.
• If foaming takes place, no chance for
immediate contamination.
Agitators
• Controls the operation of the bioreactor,
so careful consideration has to be given
when designing the agitator
• Vessel with H=D, one agitator is sufficient.
• If H=2D or more, additional sets of
agitators should be mounted on the shaft,
separated by a distance, φ.
• Multi-sets of impellers improves mixing
and enhances mass transfer
types of agitators: (a) high-efficiency, threeblade impeller (b) double-helical-ribbon, (c)
helical-screw.
types of agitators: (a) four-blade
paddle, (b) gate or anchor paddle, (c)
six-blade open turbine, (d) pitchedblade (45 ) turbine.
• Common type used four-blade disk
turbine
• In shear-sensitive system where
solids present, advantages in using
inclined bladed turbine
• No. of agitator mounted on the shaft
depend on the height of liquid in
vessel
Impellers
• Installed to improve mixing and
mass transfer

Spargers
• Located near the bottom of the vessel with
a distance Di/2 below the agitator.
(Di = diameter of the impellers)
• For efficient mass transfer, multiple-orifice
ring sparger is used with gas outflow
diameter of 3 Di/4
• for more better, used single open-pipe
sparging; located centrally beneath the
disk.
Power Input
• Power input per unit volume of
fermentation vessel for a normal
fermenter should be greater than
100 W/m3.
• Impeller tip speed (πNDi) > 1.5 m/s
or a Froude number (N2Di/g) > 0.1
Troubleshooting
• High agitation and aeration cause foaming
• Foaming may lead to contamination
• Antifoaming can’t always be used, why?
• Because it may have inhibitory effect to
microorganism growth
• So, the simplest device have rakes mounted on
stirrer shaft, located on the surface of fluid
• More sophisticated device is the
‘Funda-foam system’; foam is
destroyed by centrifugal forces
• If heat removal is a problem, in
bioreactor > 100m3, 12 baffles can
be used through which coolant
passes
• High turbulence is required for
efficient mixing; created by vortex
field
• Centrifugal force will draw the gas
into the system, which ensures that
sufficient turbulence
• To maintain the sterility, bioreactor
must have minimum number of
openings
• For Small opening made with Oring(leak-proof),for larger opening
fitted with gaskets
• Most difficult areas to seal effectively
is where the agitator shaft passes
into the vessel; used double
mechanical shaft seal
• Avoid any direct connection between
the non-sterile and sterile area; that
is sampling devices and injection
port must be accommodated in
steam-sterilisation closures.