A method for treating petroleum, petroleum fraction, or natural gas, the process comprising:
adding




a) a first component which is selected from material, particularly roots, of a plant of the genus Glycyrrhiza, and/or an arbuscular mycorrhizal fungi, and
b) a second component which is selected from a plant material or -ingredient comprising plastids, algae and/or cyanobacteria,

to the petroleum, petroleum fraction, or natural gas.