Safety Assessment of Genetically Modified Microorganisms Applied in Meat Fermentations

Abstract

The use of genetically modified microorganisms (GMMs) in food processing requires a thorough assessment of potential risks which may arise from their application. To follow a science based vertical approach, a strategy for experimental design of strains and the investigation of their effects on food was developed permitting a safety assessment of GMMs. As a realistic model genetically modified lactic acid bacteria were studied in meat fermentation. Model organisms were constructed by cloning into the competitive meat starter organismus Lactobacillus curvatus LTH1432 the lysostaphin gene lys of Staphylococcus simulans (model I) and the catalase gene katA of Lactobacillus sake LTH677 (model II). Based on the concept of employing a food grade system pJK356 was used as cloning vector. Investigation of the stability of the recombinant plasmids in the host revealed that the constructs were structurally stable but the segregational stability was decreased, however, not beyond 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, conjugal transfer of pAMβ1 between strains of L. curvatus was detected, however, without mobilisation of the recombinant plasmids. It is remarkable that under optimal laboratory conditions no transfer of pAMβ1 between L. curvatus and Staphylococcus carnosus was observed, whereas, the conditions prevailing in the meat matrix permitted an efficient 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 bv case saferv assessment is the appropriate procedure which is facilitated by applying the concept of constructing food grade organisms.