PHYSICAL AND CHEMICAL PARAMETERS

PHYSICAL Temperature Pressure Agitator shaft power Rpm Foam Weight Flow rate

TEMPERTURE Vessel and pipe is important parameters to control in any process It measured by Mercury in glass thermometers Pressure blub thermometers Thermometers

Mercury in glass thermometers Small bench fermenters Insert it into a thermometer pocket in vessel introduces a time lag in registering the vessel temperature Used solely for indication not for automatic control

Thermomistors Semiconductors made from specific mixtures of pure oxides of iron, nickel and others metals Main characteristic is large change, in resistance with a small temperature change It a relatively cheap and have proved to be very stable Dis adv; is the marked non-linear temperature versus resistance curve.

Pressure measurement Its needed for several reasons most important is safety The measurement of pressure is also so important in media sterilization. In fermenter, pressure will influence the solubility of gases and contribute to the maintenance of sterility when a positive pressure is present.

Pressure control Different working pressure required in different parts of a fermentation. Normal operation pressure of 1.2 atmospheres is maintained in a fermenter to assist in the maintenance of aseptic condition Correct pressure in different components maintained by regulatory valves.

Agitator shaft power Large scale, watt meter attached to the agitator motor will give a fairly good indication of power uptake. Less accurate as there is a decrease in scale to pilot scale and finally to laboratory fermenters Torsion dynamometers can be used in small scale application.

Chemical parameters pH REDOX OXYGEN EXIT-GAS ANALYSIS MEDIUM ANALYSIS

PH control In batch culture,PHoften changes To maintain a steady state Ph the following has to be monitored 1.careful design of media-particularly in choice of carbon and nitrogen sources 2.further controlled by addition of appropriate quantities of NaOH and ammonium hydroxide if it is too acidic. 3. sulphuric acid is used to change to alkaline condition.

Con…. PH measurement is carried out using A. 1.glass reference electrode –this withstand sterilization temperature of 121 degree celsius 2.It is made up of silver /silver chloride with potassium chloride as a electrolyte. B.1.calomel/mercury electrodes are used 2.this is connected to Ph meter/controller. If the electrode and fermentor has to be sterilized together means The electrode should be in such a way that it should withstand the temperature and must retain the electrical resistance.

Con… ON/OFF controller: The controller is set with a predetermined PH. When the Ph fluctuates the pinch valve opens and acid or alkali is added for a short time period of (0 to 5 sec). The addition cycle is followed by mixing cycle for a period of (0 to 60) at that time no acid or alkali should take place.

REDOX It is the measure of oxidation-reduction potential of biological system. The measuring electrode consists of gold, platinum or iridium which is welded to a copper lead. The redox potential may be controlled by sparging with oxygen or nitrogen or by adding cysteine, ascorbic acid

DISSOLVED OXGEN In aerobic fermentations it is essential to note the dissolved oxygen concentration In 1970 sterilizable oxygen electroes are used for monitoring This measure the partial pressure of the dissolved oxygen and not the dissolved oxygen concentration Thus at equilibrium,the probe signal of an electrode is determined by p(02)=c(02)*PT

Con… P(o2)-is the partial pressure of dissolve o2 gas sensed by probe. C(O2 )-Is The Volume Or Mole Fraction Of Oxygen In The Gas Phase PT –Is the total pressure Dissolved oxygen concentration may also be determined by tubing method.