The development of expression systems for recombinant proteins and recombinant protein particles which cannot be secreted and are located in specific cell locations necessitates the development of novel, more selective techniques for cell lysis and or product release. Mechanical cell disruption methods do not discriminate the release of the desired product from among a host of other contaminating molecules and cell debris, and they may also damage the protein product. In contrast, the use of lytic enzyme systems, which can provide biological specificity to the process of cell lysis and product release, shows an interesting potential for controlled lysis. In this chapter we have reviewed the enzymes presently available for cell lysis of bacteria and yeast and have described mathematical models developed to describe the process of lysis, particularly of yeast cells, including simple, structured, and population balance models. Factors affecting the kinetics of lytic enzyme reactions, enzyme recovery, and the effect on downstream operations as well as conditions for use have been discussed. Sources of lytic enzymes and latest developments on enzyme production have been reviewed. Finally, the potential for large-scale use of lytic enzyme technology has been discussed. The design and use of lytic enzyme systems for differential product release from microbial cells have been reviewed. Lytic enzyme systems are usually specific either for yeast or for different types of bacteria. The activity profile of a lytic system will have an effect on the product distribution. This profile can be manipulated at the genetic, physiological, production reactor, enzyme purification, and lysis reactor levels. Alternative process designs that will allow the sequential release of products from different cell locations are discussed. Alternatives are explored by process modeling, process simulation, and optimization techniques. These studies show that the use of lytic enzyme systems has tremendous promise as a method of controlled lysis and differential product release.