Solid byproducts of Aurantiochytrium sp. oil made into the biodiesel

Abstract

Microalgae have rich oil production under full photosynthesis, which reaches over 50 mass%. In addition, microalgae oil contains the prolific cis-4,7,10,13,16,19-docosahexaenoic acid that is usually refined for making health food or food additives. This study investigated Aurantiochytrium sp., which is a kind of microalgae, the oil of which is also refined for use in health food or food additives. The solid byproducts of Aurantiochytrium sp. oil are more than 20 mass%, discarded as rubbish. Fortunately, the solid byproducts have been found to contain a large amount of palmitic acid that exceeds more than 67 mass%, but it is difficult to transesterify from the solid byproducts of Aurantiochytrium sp. oil, such as the waste cooking oil or waste engine oil, which contain many impurities. Thus, the impurities, the free fatty acids, and the microalgae cell wall of solid byproducts interfere with transesterification. Sequences of saponification, reduction reaction, and acid-catalyzed reactions were conducted for the full process of transesterification in this study. Gas chromatography analysis, differential scanning calorimetry thermal analysis, and Fourier transform infrared spectroscopy repeatedly corroborated the results of the transesterification, which proved that the solid byproducts of Aurantiochytrium sp. oil form a high-yield and high-quality biodiesel. Overall, we have successfully obtained more than 92 mass% transesterification rates from the solid byproducts of Aurantiochytrium sp. oil. The solid byproducts are waste turned into gold.