Culture and preservation of microorganisms within a concentrated

Details Culture and preservation of microorganisms within a concentrated Culture and preservation of microorganisms within a concentrated

1988-09-27

1991-03-12

Naff, David M.

Chemistry: molecular biology and microbiology

Micro-organism, per se ; compositions thereof; proces of...

Bacteria or actinomycetales; media therefor

4352529, 4352536, 435260, 435839, 435857, C12N 120, C12N 104, C12N 100

Patent

active

049993011

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the culture of microorganisms. More particularly it relates to the preservation of viable microorganisms and a method of producing a quantity of such microorganisms for industrial use. A good example of this is the treatment of grass for ensilage.
Microorganisms are cultured in nutrient media typically composed of water, carbon sources, nitrogen sources and mineral salts, which provide for growth under favourable conditions of temperature, pressure, pH etc. In such a medium microorganisms proceed through a typical growth cycle, which is a consequence of the relative balance between the growth and death rates of the microorganisms, and which may be described as consisting of a lag phase or delayed growth phase, during which the microorganisms become acclimated to the environment of the nutrient medium; an exponential growth phase, during which numbers increase logarithmically with time; an apparently stationary phase, during which an equilibrium culture density is reached; and finally a phase of accelerating death. The stationary phase arises from a number of factors, such as the accumulation of toxic substances and the depletion of nutrients, which inhibit the growth of the microorganisms. The rate of growth decreases and the death of cells commences, the balance between cell growth and cell death determining the population of viable microorganisms. In their natural environment a slow rate of cell death can prolong the stationary phase of the growth cycle, so effecting a strategy for maintaining viability between the intermittent occurrence of nutrients. This prolonged stationary phase of the growth cycle is the natural condition of many non-spore forming microorganisms between short spells of active growth, when nutrients once again become available.
Microorganisms are useful industrially, for example, for cheese manufacture, silage fermentation, effluent treatment, and deposit removal. The present method of producing microorganisms for such use is to grow them under optimum conditions (using the optimum growth
utrient medium), harvest them, then preserve them by drying, freezing or freeze drying until ready for use. However all these methods of producing an industrially useful quantity of microorganisms are costly.
It is an object of the present invention to provide a means of preserving microorganisms in a viable condition without the need for drying and the like.
According to a first aspect of the invention there is provided a microorganism culture kit comprising a quantity of viable microorganisms, and a concentrated growth medium containing the microorganisms, the degree of concentration of the growth medium being such that the normal death phase is delayed and that on subsequent dilution of said growth medium, the number of microorganisms increase.
The length of the growth cycle of the microorganisms in the concentrated growth medium will increase with concentration. Generally, they will go through in sequence, a growth phase in which the rate of growth of the microorganisms is greater than the rate of death thereof, at the top end of this growth phase the number of microorganisms will be at a maximum; a stationary phase in which the growth and death rates are approximately equal; and a death phase in which the death rate of the microorganisms is greater than the growth rate thereof.
A microorganism culture in a medium designed for optimum growth of the microorganism will be taken as standard or normal.
As can be seen, whereas previous methods of supplying microorganisms all involve firstly growing the microorganisms in a normal/optimum growth medium, the present invention is contrary to this in that the growth medium purposely is not at optimum conditions: it is more concentrated.
The advantage of such a concentrated medium is that the shelf life of the microorganisms is sufficiently increased. That is, it has been found that under optimum growth conditions the limiting factor terminating the logarithmic growth phase is dominantly, depletion of one or more essential nutri

REFERENCES:
Klaar, "Reproduction and Preservation of Lactobacillus plantarum, Lactobacillus acidophilus and Propionibacterium shermanii Cells in Concentrated Media," Eesti Pollumajanduse Akad. Tead. Toode Kogumik, 1967, No. 55, 125-42.
G. Bryan-Jones, "II.5 Lactic Acid Bacteria in Distillery Fermentations," in Fourth Long Ashton Symposium 1973 Lactic Acid Bacteria in Beverages and Food, proceedings of a Symposium held at Long Ashton Research Station University of Bristol, 19-21 Sep. 1973, Ed. Carr, J. G., Cutting, C. U. and Whiting, G. C., Academic Press, N. Y. (1975), pp. 165-175.

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