Assimilation is the process of absorption of vitamins, minerals, and other chemicals from food as part of the nutrition of an organism.
Most foods are composed of largely indigestible components depending on the enzymes and effectiveness of an animal's digestive tract.
The most well-known of these indigestible compounds is cellulose; the basic chemical polymer in the makeup of plant cell walls.
However, some animals and species have developed symbiotic relationships with cellulase-producing bacteria (see termites and metamonads.)
Because of the use of bacterial derivatives, enzymatic dietary supplements now contain such enzymes as amylase, glucoamylase, protease, invertase, peptidase, lipase, lactase, phytase, and cellulase.