Food-Grade Corynebacteria for Enzyme Production

The expression of genes coding for heterologous extracellular enzymes or proteins in corynebacteria has provided new capacities to these industrially important microorganisms, such as the use of the culture media as sources of essential amino acids and hydrolytic enzymes that can be used as complements in animal food or for the production of enzymes with industrial, clinical, or pharmaceutical applications. Using genetic manipulation techniques, several corynebacteria strains expressing genes coding for hydrolytic enzymes or proteins have been constructed in different laboratories. Such strains carry antibiotic resistance genes and consequently they cannot be used in the food industry due to the stringent regulations on genetically manipulated microorganisms. To solve this problem, here we describe a general method for the construction of engineered corynebacteria bearing a single copy of a gene coding for a hydrolytic enzyme or a desired protein in its chromosome where it is stably maintained with no selective pressure and lacking any antibiotic resistance gene.