SAFETY ASSESSMENT OF GENETICALLY-MODIFIED MICROORGANISMS APPLIED IN MEAT FERMENTATIONS

The use of genetically modified microorganisms (GMMs) in food processi ng requires a thorough assessment of potential risks which may arise f rom their application. To follow a science based vertical approach, a strategy for experimental design of strains and the investigation of t heir effects on food was developed permitting a safety assessment of G MMs. As a realistic model genetically modified lactic acid bacteria we re studied in meat fermentation. Model organisms were constructed by c loning into the competitive meat starter organismus Lactobacillus curv atus LTH1432 the lysostaphin gene lys of Staphylococcus simulans (mode l I) and the catalase gene katA of Lactobacillus sake LTH677 (model II ). Based on the concept of employing a food grade system pJK356 was us ed as cloning vector. Investigation of the stability of the recombinan t plasmids in the host revealed that the constructs were structurally stable but the segregational stability was decreased, however, not bey ond those numbers of generations required to ensure maintenance of the new property during the fermentation process. In fermenting sausages the constructs retained their full activity. Horizontal gene transfer was studied in vitro and during fermentation of sausages. No transfer of the recombinant marker genes was observed. On the other hand, conju gal transfer of pAM beta 1 between strains of L. curvatus was detected , however, without mobilisation of the recombinant plasmids. It is rem arkable that under optimal laboratory conditions no transfer of pAM be ta 1 between L. curvatus and Staphylococcus carnosus was observed, whe reas, the conditions prevailing in the meat matrix permitted an effici ent transfer. The models used provide realistic examples of GMMs with the potential to improve food safety and/or quality. Furthermore, they show that a case by case safety assessment is the appropriate procedu re which is facilitated by applying the concept of constructing food g rade organisms.