The successful commercialization of therapeutic proteins and industrial enzymes expressed in mammalian cell culture and microbial hosts has inspired plant and animal scientists to develop a variety of new protein production systems. Improvements in expression technology have resulted in the accumulation of high levels of recombinant proteins in tissues of numerous plant hosts, including corn and rice seed, tobacco chloroplast, and in entire organisms such as the aquatic plant lemna. Improvements in transgenic animal production have also enabled the production of recombinant proteins in milk, urine, and eggs. As advances continue to increase expression levels of recombinant proteins in transgenic systems, the development of efficient bioprocesses becomes essential for successful product commercialization. Since each transgenic host and tissue presents a unique environment for protein production, there are a number of factors that may influence the choice of downstream processing steps. This entry describes the commonly used strategies to recover and purify recombinant proteins from transgenic plant and animal hosts.
