From Bioblast
Description
IUPAC distinguishes three definitions of 'substrate': (1) The chemical entity whose conversion to a product or products is catalysed by one or several enzymes . A solution or dry mixture containing all ingredients which are necessary for the growth of a microbial culture or for product formation. Component in the nutrient medium, supplying the organisms with carbon (C-substrate), nitrogen (N-substrate), etc.
Reference: https://goldbook.iupac.org/terms/view/S06083
MitoPedia topics: Substrate and metabolite