Substrate-Limiting Microbial Fermentation

If we assume a constant fractional yield and no slowing of the rate as a result of product poisoning or increase in cell crowding in the broth, then the general rate equation of the previous chapter, Eq. 28.8, reduces to the well-known Mo-nod equation 

Let us examine ideal reactors processing feed which is reacting away according to these kinetics. 

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Chapter 28 Microbial Fermentation—Introduction and Overall Picture 1623 Chapter 29 Substrate Limiting Microbial Fermentation /630 Chapter 30 Product Limiting Microbial Fermentation /645... 

Chapter 29 Substrate-Limiting Microbial Fermentation Replacing r from Eq. 1 into Eq. 6 then gives... 

Chapter 29 Substrate-Limiting Microbial Fermentation SOLUTION... 

In biosensor systems employing this type of mediator, the natural substrate for GOD (molecular oxygen) is replaced by a compound which is carefully chosen to be capable of carrying out the same role. The mediator serves to re-oxidise the reduced form of GOD (Eq. (23.2)), following its interaction with glucose (Eq. (23.1)). Consequently, these systems can be operated at the potential of the mediator couple (Eq. (23.3)) and 02 concentration at the electrode/solution interface does not become a limiting factor in the analysis this is particularly important in samples where 02 concentrations are low, such as neonatal blood or microbial fermentations. 

Odour will return in treated slurry as a result of post treatment fermentation. The concentration of readily fermentable substrates, measured as BOD5, provide an indicator of this problem. In continuous culture without oxygen limitation the BOD5 can be described by a model derived from the Monod (13) model of microbial growth (14). The supernatant BOD5 (g/1) from treatment at 15 to 45°C, was described by equation 3 and the whole BOD5 by equations 4 and 5(15). 

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