For those fermentations where there already exists a considerable body of knowledge regarding the role and activity of the relevant microflora, the challenges facing the scientists and technologists are somewhat different. Fermentations involved in the production of many cheeses, yoghurts and some fermented meats in particular, are already quite sophisticated,are generally reliable and predictable and can deliver products of excellent quality. Here, the goals are to further improve reliability and product quality through optimisation of starter culture performance and to eliminate those factors that impede the fermentation process. In this regard, it is to be anticipated that the considerable resources that have been devoted to the ‘biotechnology of lactic acid bacteria’ over the past number of years will deliver results with respect to these objectives. This is already evident in the case of the protection of cheese starter cultures of L. lactis against bacteriophage infection. This provides an excellent case study as to how a deliberate, programmed research effort, designed to provide a more complete understanding of phage-host interactions, has ultimately binant phage resistant strains for use in industrial fermentations (Allison and Klaenhammer, 1998).