DNA typing continues to evolve into the food arena.

DNA techniques have provided reliable, reproducible and indisputable characterizations of microorganisms used in food fermentations. In fermentations, for example, it's crucial to use the proper microbes since contamination is costly and possibly even dangerous. Because the microorganisms used for these processes are usually proprietary to the companies that use them, it is important to use extremely precise tools to identify them. Genetically fingerprinting microorganisms does this.

A variety of DNA-based techniques have evolved over the last ten years or so that are able to identify and type microorganisms. The advantage of DNA technologies: they can generate a DNA profile of every individual human, animal or microorganism. Researchers at Keygene NV have developed and patented a process known as selective amplification of restriction enzyme fragments (AFLP). We're told it is one of the more precise DNA typing techniques available for use in detecting and characterizing microbes.

AFLP is able to distinguish among closely related subspecies of microorganisms, including bacteria, yeast and fungi. It has found extensive use in plant breeding, but demand is growing to apply such technology to foods and beverages. A nearly ten-fold increase in AFLP citations in the scientific literature in the past five years is an indication of its wide acceptance as a useful DNA fingerprinting technique in the plant science area and its growing use for identifying microorganisms in other areas.

With this technology it is possible to analyze simple and complex DNA. No prior sequence or other data are required to fingerprint a microorganism. In an AFLP reaction, subsets of genomic DNA fragments are amplified. The key here is to use selective nucleotides, which will make possible a complete scan of a target genome. AFLP displays fragments that are gathered from the entire genome.

Different enzyme or primer combinations produce AFLP patterns of different complexity. In the process, genomic DNA is digested with two restriction enzymes. Amplification reactions occur. The generated amplified products are separated by gel electrophoresis, using radioactive, fluorescent or infrared labels. Software converts the AFLP patterns into digital images.

AFLP is highly reproducible and is able to discriminate microbial strains. Its use does not require any previous knowledge of the genome sequence, and the technology is amenable to high-throughput applications.

Patent. 6,045,994--Selective restriction fragment amplification: fingerprinting. Issued April 4, 2000. Inventors: Marc Zabeau and Pieter Vos. Assigned to Keygene N.V. The technology involves a process for the controlled amplification of at least one part of a starting DNA containing a plurality of restriction sites for a determined specific restriction endonuclease, and of which at least part of its nucleic acid is unknown.

Further information. Max van Min, Keygene NV, P.O. Box 216, 6700 AE Wageningen, The Netherlands; phone: [phone]; fax: [phone]; URL: www.keygene.com.