Academic and industrial research efforts over the last quarter century have generated a solid appreciation for the physiology and genetics of dairy LAB. Most recent and significant advances in LAB physiology are derived from studies made possible by recombinant DNA technology. The great advantage of this technology in analysis of cellular and industrial processes of LAB is that it facilitates construction of isogenic mutants that differ only by the action (knockout mutants) or relative activity (overexpression mutants) of one or more defined polypeptides. By contrasting the phenotype of the wild-type culture to its isogenic derivative, the role of that polypeptide in a given process can often be explicitly defined. The knowledge that is accumulated from this work can then be used to isolate or construct, by several different mechanisms, new strains with enhanced industrial utility. This approach has already provided industry with strains that are better able to resist bacteriophage infection or produce higher levels of diacetyl. With the advent of food-grade recombinant DNA technologies, the potential for commercialization of value-added LAB that have been developed through gene additions, modifications, or deletions, is truly great. With this knowledge base, it is anticipated that the dairy industry will soon see more widespread application of genetic technologies in ways that provide innovation and vitality to the fermented milk industry for years to come.
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