A bioprocess is a specific process that uses complete living cells or their components (e.g., bacteria, enzymes, chloroplasts) to obtain desired products.Transport of energy and mass is fundamental to many biological and environmental processes. Areas, from food processing (including brewing beer[1]) to thermal design of buildings to biomedical devices to pollution control and global warming, require knowledge of how energy and mass can be transported through materials (momentum, heat transfer, etc.). Therapeutic cell manufacturing processes can be separated into upstream processes and downstream processes. The upstream process is defined as the entire process from early cell isolation and cultivation, to cell banking and culture expansion of the cells until final harvest (termination of the culture and collection of the live cell batch).Aside from technology challenges, concerning the scalability of culture apparatus, a number of raw material supply risks have emerged in recent years[when?], including the availability of GMP grade fetal bovine serum[citation needed].The upstream part of a bioprocess refers to the first step in which microbes/cells are grown, e.g. bacterial or mammalian cell lines (see cell culture), in bioreactors. Upstream processing involves all the steps related to inoculum development, media development, improvement of inoculum by genetic engineering process, optimization of growth kinetics so that product development can improve tremendously. Fermentation has two parts: upstream and downstream. After product development, the next step is the purification of product for desired quality. When they reach the desired density (for batch and fed-batch cultures) they are harvested and moved to the downstream section of the bioprocess.