Method of culturing micro-organisms under a mutagenic influence

Details Method of culturing micro-organisms under a mutagenic influence Method of culturing micro-organisms under a mutagenic influence

1996-10-29

1998-08-25

Lankford, Jr., Leon B.

Chemistry: molecular biology and microbiology

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

435245, 435262, 435821, 435822, 435813, 435819, C12N 100, C12N 136, C12N 120

Patent

active

057982538

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a method of culturing micro-organisms that are suitable for the degradation of certain harmful substances, by which method existing micro-organisms are cultured in a growth-promoting nutritive solution, subjected to chemically and/or physically mutagenically acting influences, stabilized under growth-promoting conditions, and selected under the influence of the harmful substances under growth-limiting conditions, whereby said selected micro-organisms are returned to the start of the process.
2. The Prior Art
The use of micro-organisms for the biological degradation of harmful substances finds important application in the restoration of old materials, as well as in the purification of waste waters and air, in connection with which the harmful substances are decomposed by the micro-organisms, or converted into other substances, whose disposal is less problematic. Micro-organisms suitable for the efficient biological degradation of harmful substances must have, beyond the specific capability of degradation, an optimal harmful substance tolerance, the highest possible division rate, as well as genetic stability.
For culturing bacteria mutants capable of degrading harmful substances, DE 41 24 900 A1 discloses a method by which the bacteria are cultured under conditions not limiting the growth, subject to a mutation-producing UV-radiation, and the mutated bacteria are then brought together with the harmful substance under conditions limiting the growth. If necessary, the micro-organisms could be transferred from the selection stage into a first reactor, in which they are stabilized in order to be subsequently subjected in the mutation stage to UV-radiation again.
However, it has been found that the method according to the state of the art is not suitable for developing micro-organism populations that are capable of degrading organic compounds and particularly complex compounds, because one or two mutagenic treatment do not suffice for obtaining within a reasonable time the establishment of a micro-organism population suitable for degrading complex organic compounds. This is, to begin with, a basically statistic problem, which with high probability is connected with the fact that for degrading complex organic harmful substances, several degradation reactions are required, which take place sequentially, and in which intermediate products are produced which, under certain circumstances, are more toxic for the micro-organisms than the starting product. Thus the composition of the selection medium changes in the course of time, so that the micro-organism population has to adapt itself time and again with respect to degradation capability and harmful substance tolerance. Such adaptation requires some time and causes the process to take a longer time, overall, and to thus become uneconomical.
Furthermore, the method known from the state of the art requires a considerable expenditure in terms of equipment, because the culturing, mutagenic treating and stabilizing of the micro-organism population is carried out in different reactors. Moreover, following stabilization in a nutrient-rich medium, the micro-organisms are directly transferred into the selection fermenter for inoculation with the selection medium containing the harmful substance. It may occur, for example, that the biomass subjected to selection still contains considerable proportions of nutritive substances, the latter having been introduced in the selection fermenter and adversely influencing the selection, as such nutritive substances are preferably used as a nutrient source by the micro-organisms. Therefore, the selection of micro-organisms degrading the harmful substances will start only once the introduced nutritive substances have been consumed. This, firstly, leads to positive selection of micro-organisms not capable of degrading the harmful substances, which results in an additional delay of the entire selection process.


SUMMARY OF THE INVENTION

Therefore, the object of

REFERENCES:
patent: 4391887 (1983-07-01), Baumgarten et al.

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