In the late 20th century, Energy Bi

In the late 20th century, Energy BioSystems Corporation filedtwo patents (Xu et al., 1997; Xu et al., 1998) on the demetallizationof liquid fossil fuels (e.g. petroleum) by the biocatalytical degra-dation of porphyrine molecules (incl. metalloporphyrines). It isclaimed that the patented method is able to remove nickel, vana-dium, cobalt, copper, iron, magnesium, and zinc. The biocatalystcan be an enzyme from heme oxygenase and cytochrome Creductase, such as cytochrome C reductase from Bacillus mega-terium, Catharanthus roseuse, Escherichia coli, animal cells (such asliver or kidney cells), plant cells (e.g. Arabidopsis thaliana) or yeastcells (e.g. Candida tropicalis). Mogollon et al. (1998) reported thebiocatalytic removal of nickel and vanadium from petroporphyrins and asphaltenes. Garcia-Arellano et al. (2004) demonstrated thesuccessful modification of Cytochrome C, which not only showedimproved activities in a ternary solvent mixture (solvo-tolerance isan important criteria for use in process line), but also the ability totransform the highly recalcitrant asphaltenes.Earlier research by Fedorak et al. (1993) on demetallation hasshown that the enzyme chloroperoxidase from Caldariomyces fumago was able to remove 93% of Ni and 53% of V contained inporphyrins and asphaltenes. However, the catalyzed destruction ofthe porphyrinic ring also resulted in the formation of undesirablechlorinated byproducts.