Those that produce microbial cells e.g.Baker's yeast or mycoprotein.

Those that produce microbial enzymes e.g. alpha amylase for starch processing, glucose isomerase for the production of high fructose corn syrups, proteases and lipases for use in biological washing powders.

Those that produce a microbial metabolite e.g. ethanol or butanol as biofuels, citric acid as a food additive, benzyl penicillin and other human human antibiotics.

Those that perform the specific chemical transform (bioconversion) of a compound e.g. asymmetric oxidation, reduction, hydroxylation, resolution. Those that produce therapeutic proteins (biologics) for human use e.g. interferon, insulin, therapeutic antibodies (i.e. Herceptin, Rituximab, etc), tissue plasminogen activator etc.