A simple method to prepare magnesium oxide catalysts for biodiesel production by transesterification reaction of soybean oil with ethanol is proposed. The method was developed using a metal-chitosan complex. Compared to the commercial oxide, the proposed catalysts displayed higher surface area and basicity values, leading to higher yield in terms of fatty acid ethyl esters (biodiesel). The deactivation of the catalyst due to contact with CO(2) and H(2)O present in the ambient air was verified. It was confirmed that the active catalytic site is a hydrogenocarbonate adsorption site. (C) 2011 Elsevier B.V. All rights reserved.