Fermenter operations, liquid level

There several DO probes available. Some well-known branded fermenters, like New Brunswick, Bioflo series and the B. Braun Biotstat B fermenters are equipped with a DO meter. This unit has a 2 litre fermentation vessel equipped with DO meter and pH probe, antifoam sensor and level controllers for harvesting culture. The concentration of DO in the media is a function of temperature. The higher operating temperature would decrease the level of DO. A micro-sparger is used to provide sufficient small air bubbles. The air bubbles are stabilized in the media and the liquid phase is saturated with air. The availability of oxygen is major parameter to be considered in effective microbial cell growth rate. 

Gas hold-up is one of the most important parameters characterizing the hydrodynamics in a fermenter. Gas hold-up depends mainly on the superficial gas velocity and the power consumption, and often is very sensitive to the physical properties of the liquid. Gas hold-up can be determined easily by measuring level of the aerated liquid during operation ZF and that of clear liquid ZL. Thus, the average fractional gas hold-up H is given as... 

The fermentation department should monitor and control the COD/ BOD of its liquid waste to the sewer. Procedures for cleaning up spills and reporting should be Standard Operating Procedure. A primary aeration basin will reduce the COD to 80-90 ppm. Secondary aeration lagoons will reduce the BOD to acceptible levels which have no odor. 

A 1000-litre fermenter has been used to produce a continuous feed of Escherichia coli containing a high level of j3-D alactosidase. Investigation of the individual unit operations for the isolation of the enzyme, cell disruption, nucleic acid removal, protein precipitation and solid-liquid separation after each stage, permitted operation of a semi-continuous process which would yield 130 g protein hr comprising 23% j3-D-galactosidase. 

Batch reactors are often used for liquid phase reactions, particularly when the required level of production is low. They are seldom employed on a commercial scale for gas phase reactions because the quantity of product that can be produced in reasonably sized reactors is small. Batch reactors are well suited for producing small quantities of material, for producing several different products from one piece of equipment, and for situations in which sanitation considerations are paramount. Consequently, they find extensive use in the food, pharmaceutical, dyestuff, and polymer industries and in the production of certain specialty chemicals where such flexibility is desired. When rapid fouling is encountered or contamination of fermentation cultures is to be avoided (e.g., in brewing beer), batch operation is preferable to continuous processing... 

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