Low impact methods for microbial lipids production for third generation biofuels and biobased polyurethanes

Single cell oils (SCOs) have recently attracted attention as possible candidates to replace vegetable oils in several industrial applications. Efficient and sustainable recovery of SCOs is required for their widespread application in oil-based sectors. In this work, SCOs were produced by the oleaginous yeast Lipomyces tetrasporus grown in a 50 L bioreactor, fed with the enzymatic hydrolysates of steam pretreated wheat straw. The process was carried out in fed-batch mode and yielded 28.0 g/L of cell biomass and 18.4 g/L microbial lipids. An innovative solvents mixture, made of methyl ethyl ketone (MeK) and ethanol (EtOH) was tested for the extraction of SCOs. The optimal extraction mixture contained 5:1 MeK/EtOH which corresponded to a SCOs yield of 68.8 %, comparable to that obtained with the reference procedure based on the Blight and Dyer method. The extracted oil displayed a high content of oleic (56 %) and palmitic (26 %) acids and was successfully tested in the production of some biobased products, namely diesel-like hydrocarbons and polyurethanes. Diesel-like hydrocarbons were produced with a conversion yield of 79 %. Polyurethanes were synthetized through the preliminary conversion of the microbial oils in epoxide and bio-polyols that were reacted with diisocyanate to produce bio-polyurethanes. Process intermediates and final products were extensively characterized by FTIR, TGA, HPIC and GC-MS. Synopsis Single-cell oils are the future resource for green and sustainable oleochemical applications to replace fossil-based products. Therefore, it is very significant to develop innovative and green extraction methodologies.