MIXED CULTURE VERSUS PURE CULTURE FERMENTATIONS: WHICH IS EASIER?

Traditionally in microbiology and biotechnology lectures and practicals, there seemed to be a slant towards pure culture practicals. In real life, microorganisms in nature do not often occur in pure culture communities. Microbial ecology generally involves the interactions of mixed cultures and their environment.
No amount of pure culture data studies will give the accurate picture what really happened to microorganisms in nature! At best, pure culture will perhaps help in giving understanding as to what really happened in nature
Mixed culture studies seem to be avoided by most microbiologists especially those involved in the studying of microbial physiology and biochemistry of microorganisms. Don’t believe me? Just read a few popular microbiological or biochemical textbooks!
Although the study of pure culture has its own strength especially in the production of fermentation products by single pure microorganism, its success is more attributed to the ability of microbiologists to generate pure cultures or aseptic techniques. To these microbiologists the presence of other microorganisms in the industrial process is more a minus minus factor and regarded as a microbial contaminant which will complicate the fermentation process and affect its productivity
In my personal experience it is far more difficult to understand and control a mixed culture fermentation compared to doing a pure culture fermentation!
There are many parameters which affect the mixed culture fermentation process and slight change in one operating parameter will result in the change in the components of the mixed culture population dynamics….. To put it simply, the process may easily run out of control.
In pure culture fermentation this is not the problem. Pure culture fermentation are more stable and the only goal is to obtain the optimum fermentation process to produce the best yield possible!
The principles of mixed culture fermentation are often complicated by:
1 Selection of steady environment
2 Ensuring stable substrate composition and delivery
Most that involve complex substrate will often see the formation of microbial succession which could be good or bad depending on the purpose of fermentation
Mixed culture metabolism too tend to change the environment that lead to microbial succession
This is one of the main reason in traditional mixed culture fermentation becomes further complicated when the scaling up is exercised!
Merry Christmas!


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