Approaches to convert Mucor circinelloides lipid into biodiesel by enzymatic synthesis assisted by microwave irradiations

Abstract

Abstract This work aimed to study the enzymatic production of biodiesel from lipids produced by Mucor circinelloides URM 4182 using Novozym 435® as catalyst under different conditions, in which microwave irradiations were used to perform both the lipids extraction and transesterification heating. Sequential or simultaneous approaches were also investigated. In direct transesterification, ethanol serves as a solvent for lipid extraction and a reactant for the reaction, simultaneously. Cell growth and the lipids accumulation were carried out in a bioreactor containing glucose and corn steep liquor as carbon and nutrients sources, respectively. Corn steep liquor (CSL) can be a good replacement for synthetic nutrients allowing higher volumetric biomass production (3.1 ± 0.01 gL−1day−1). M. circinelloides oil revealed as main fatty acids: palmitic acid C16:0 (18.9%), oleic C18:1 (25.3%), linoleic C18:2 (19.3%) and linoleic acid C18:3 (18.3%). With regards to biodiesel synthesis, the two steps technology, which combined the lipids extraction from microbial biomass followed by enzymatic transesterification reaction both carried out under microwave irradiation, allowing for the attainment of 98.5% ethyl esters in 10 h, compared to 30 h under conventional heating. The simultaneous extraction and transesterification also shows promising results, although the ester content was slight lower (90.1%).