disease caused by the intake of trans fattyacids, a method to eliminate trans fattyacids from foods has become a critical issue. Herein, we engineered fattyacid photo-decarboxylase from Chlorella variabilis (CvFAP) to selectively catalyze the decarboxylation of trans fattyacids to yield readily-removed hydrocarbons and carbon dioxide, while cis fattyacids remained unchanged. An efficient protein