The Gram-negative bacterium Escherichia coli B-3996 represents an interesting host organism for the production of the essential amino acid L-threonine. Microbial processes - especially those of aerobic cultivation - lead to the generation of considerable amounts of biomass, thus lowering the product yield. These are the reasons for studying methods for the recycling of biomass from E. coli. It will be shown that it is possible to disintegrate the microbial biomass - preferably by means of high pressure homogenisation followed by a protease treatment of the resulting slurry of debris - in an efficient way and to recycle at least different amounts of the soluble part as cultivation medium component. By studying the growth and product formation of E. coli no adverse effects have been observed.