Chemistry: molecular biology and microbiology – Vector – per se
Patent
1992-08-13
1996-12-03
LeGuyader, John L.
Chemistry: molecular biology and microbiology
Vector, per se
435 691, 435139, 4351723, 4352523, 424 9345, C12N 1509, C12N 1563, C12N 1574, C12P 756
Patent
active
055807879
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the provision of improved lactic acid bacteria useful as food starter cultures. In particular, the invention relates to a recombinant plasmid useful as a cloning vector which is easily selectable in transformed lactic acid bacteria and a method for the construction of such a vector. Furthermore, the invention relates to the construction of improved food starter cultures comprising lactic acid bacteria into which desired genes have been introduced by means of the cloning vector and to such improved starter cultures.
GENERAL BACKGROUND OF THE INVENTION
For centuries, lactic acid bacterial cultures have been used in food production due to their ability to convert sugars by fermentation into preserving organic acids, predominantly lactic acid and various metabolic products associated with the development in the food product of a desirable taste and flavour. Some lactic acid bacteria produce hydrolytic enzymes including peptidases, proteases and lipolytic enzymes. The production of such enzymes contribute e.g. to flavour development in cheeses.
An interesting characteristic of certain lactic acid bacterial strains is their ability to produce antimicrobial compounds or bacteriocins having an inhibitory effect on closely related bacterial species. Certain lactic acid bacterial bacteriocins are applied in the food industry as preservatives.
However, for industrial production of a wide range of desired fermented food products such as all the well-known traditional dairy products including yoghurt, acidophilus milk, butter and cheeses; fermented vegetables; fermented meat products and animal feed a large range of lactic acid bacterial cultures, each of which are adapted to particular types of food products are required. Such cultures are presently being selected from naturally occurring strains of lactic acid bacteria on the basis of characteristics such as their ability to ferment sugars in the food product to be fermented, specific growth temperature requirements, production of desired flavouring compounds, the specific combination of which characteristics renders an individually selected culture useful for the production of a particular food product but normally less useful for production of others.
Obviously, this presently used procedure for developing useful lactic acid cultures by selection of naturally occurring strains is cumbersome and costly. Furthermore, it has proven difficult to provide starter culture strains which combine all the required characteristics at an optimal level. Presently, this problem is usually solved by the use of starter cultures comprising a multiplicity of selected lactic acid bacterial strains each having one or several of the characteristics desirable for a particular food product. The necessity to use such mixed cultures will of course also add to the costs in the manufacture of starter cultures.
Based on their traditional and long term application in food manufacturing and the fact that they are considered as non-pathogenic the lactic acid bacteria are generally recognized as safe food ingredients even if they are present in a fermented food product as live bacteria in a very high number.
Currently, it is widely recognized that a substantial industrial need exists to find economically and technically more feasible ways of developing starter cultures. It is obvious that gene technology may provide the means to meet this need. In the present context it is crucial that lactic acid bacteria for food starter cultures which are developed by introduction of desired genes by use of gene technology can still be recognized as safe for consumption. It is therefore essential that recombinant plasmids in order to be useful as cloning vectors in this development of lactic acid bacteria meet all the safety criteria as defined hereinbefore including the feature that such vectors only contains DNA originating from lactic acid bacteria including wild-type plasmids isolated from lactic acid bacteria. It is assumed that recombined lactic
REFERENCES:
von Wright et al. "Isolation of a Replication Region of a Large Lactoccocal Plasmid and Use in Cloning of a Nisin Resistance Determinate" Appl. Environ. Microbiol. vol. 56, No. 7, pp. 2029-2035. Jul. 1990.
von Wright et al. 1990. Applied and Env. Microbiology vol. 56 (7): 2029-2035.
Gasson et al. 1985, FEMS Microbio. Letters 30:193-196.
Balbas et al. 1988, The Plasmid pBR322, pp. 5-8IN: Vectors; A Survey of Molecular Cloning Vectors and their Use. ed: R. Rodriguez and D. Denhardt. Butterworths, Boston.
Josephsen Jytte
Nielsen Egil W.
Tynkkynen Soile
Vogensen Finn
von Wright Atte
Josephsen Jytte
Larson Thomas G.
LeGuyader John L.
Nielsen Egil W.
Valio Finnish Cooperative Dairies Association
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