The specification for Jet A and Jet A-1, ASTM D1655, requires the fuel to be produced from petroleum stock. Biofuel has been used for some test programs and approved in-service demonstrations, but it is not used in the production of normally used Jet fuel.
The industry is very aware of the potential for biological contamination to build up with airplanes in storage, and has sampling, control programs, and cleaning processes defined in the aircraft maintenance manuals. In fact, there is an issue currently being worked with one of the major biocide products, Kathon FP 1.5, that is causing extra attention to this subject at this time.