Sugarcane by-products within the biodiesel production chain: Vinasse and molasses as feedstock for oleaginous fungi and conversion to ethyl esters

Oleaginous microorganisms pose a number of technical advantages when compared to first generation oil crops, but a common drawback to their utilization is often linked to the high operational costs involved in media preparation, using mostly industrial-grade sugars as carbon sources. Considering the abundance of by-products generated by the sugarcane industry, the combined use of molasses and vinasse is suggested in this work as culture medium for the fungal strain Mucor circinelloides URM 4182. Results demonstrate that a 3:1 vol% medium (vinasse to diluted molasses ratio) with minor supplementation of organic nitrogen can provide values within the range of 5 g L−1 of oil-rich biomass with 25 wt% of lipids. The microbial oil was then analyzed in terms of fatty acid profile, demonstrating a favorable composition for biodiesel production, and was subjected to simultaneous esterification and transesterification assays using ethanol and heterogeneous catalyst (H3PMo/Al2O3) in a pressurized reactor, demonstrating satisfactory conversions (>95%). The purified ethyl esters possessed viscosity and density values within the regulating standards and lack of triacylglycerols, suggesting a potential biodiesel production system that could be coupled within sugarcane ethanol facilities.