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IMPROVEMENT OF LACTIC STREPTOCOCCAL STARTER CULTURES

Objective

THE RESEARCH SHOULD CONTRIBUTE TO THE IMPROVEMENT OF THE STARTER CULTURES WHICH ARE USED BY THE EUROPEAN INDUSTRIES FOR THE PRODUCTION OF CHEESE, SOUR MILK AND CREAM BUTTER.
IT IS EXPECTED, THROUGH RECOMBINANT DNA WORK, TO IMPROVE AND STABILIZE THE FUNCTIONS OF THESE STARTER CULTURES, THAT IS TO SAY ESSENTIALLY :

- PRODUCTION OF LACTIC ACID,
- PRODUCTION OF AROME COMPOUNDS,
- CONTRIBUTION TO CHEESE RIPENING, TEXTURE AND FLAVOUR.

THE EXPECTED RESULTS ARE VERY IMPORTANT FOR THE EUROPEAN COMMUNITIES WHICH PRODUCE 33% OF THE WORLD TOTAL CHEESE PRODUCTION AN A VERY SUBSTANTIAL FRACTION OF THE TOTAL AMOUNTS OF SOUR MILK AND CREAM BUTTER.
Genetic technologies have been developed for use in lactic acid bacteria and genes have been analysed for key properties that have potential for application in industry. Perfection of genetic engineering technology focussed on vectors, food compatible selection systems, chromosomal integration, gene expression and product secretion. Natural gene transfer processes including conjugation and transposition have also been studied; lactic acid bacteria proteinases are central to flavour generation in food fermentation and, accordingly, were characterized in detail.
Bacteriophage attack is a major industrial problem and the research included extensive in depth analysis of bacteriophages and their mechanisms of resistance.

Heterologous genes were expressed and secreted in Lactococcus. Integration and amplification of genes in the bacterial chromosome were achieved. Lactose catabolism, proteolysis and naturally occurring conjugation were analysed in detail. Hybrid proteinases and protein engineered proteinases were constructed and genes for a lactococcal peptidase and bacteriocin production were characterized. A molecular taxonomy for bacteriophages of lactic acid bacteria was developed and the gene for a bacteriophage lysin was characterized and exploited for a novel flavour generation technology. Bacteriophage receptors on lactococci were characterized and genes for resistance to bacteriophage attack were analysed and are being exploited in improved starter strains.
THE RESEARCH WILL BE CARRIED OUT AS PART OF AN INTEGRATED EFFORT BY A GROUP OF LIVE LABORATORIES (DEPT. DAIRY AND FOOD MICROBIOLOGY, CORK, IRL; NAT. INST. RES. DAIRYING, READING, UK; B7NDESANST. F. MILCHFORSCH. KIEL, FRG; NED. INST. RES. DAIRYING, EDE, NL, GENT. INST. UNIV. GRONINGEN, HAREN, NL).
THE MAIN FEATURES ARE THE FOLLOWING:

1. DEVELOPMENT OF CLONING VECTORS ON THE BASIS OF STREPTOCOCCAL PLASMIDS.
2. EXPRESSION OF HOMOLOGOUS AND HETEROLOGOUS GENES IN STREPTOCOCCI.
3. IMPROVEMENT OF GENE TRANSFER METHODS (E.G. TRANSFORMATION).
4. STABILIZATION OF GERMENTATION PROPERTIES BY TRANSFER OF GENES FROM PLASMIDS INTO THE CHROMOSOME.
5. CHARACTERIZATION AND CONSTRUCTION OF BACTERIOPHAGE RESISTANT BACTERIA.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSITY OF GRONINGEN
Address
Institute Of Genetics Kerklaan 30
9751 NN Haren
Netherlands

Participants (4)

FEDERAL RESEARCH CENTRE FOR NUTRITION AND FOOD
Germany
Address
Hermann-weigmann-strasse 1
24103 Kiel
INSTITUTE OF FOOD RESEARCH
United Kingdom
Address
Norwich Research Park, Colney
Norwich
NETHERLANDS INST. FOR DAIRY RESEARCH (NIZO)
Netherlands
Address

Haren
UNIVERSITY COLLEGE
Ireland
Address

Cork