Abstract: The morphology and ultra-structure of Monoraphidium were studied with the transmission electron microscope and the aqueous enzymatic method. The cell of the algae was quasi-ellipse smoothing surface without flagellum and the thickness of its cell wall was about 50 nm. The cell wall was mainly composed of cellulose and hemicelluloses. The extraction of lipid from the Monoraphidium through aqueous enzymatic process was investigated. The results showed that the combination of the alkaline pretreatment and the enzymatic treatment subsequently and then the dual solvent system extraction was the most effective process. Under the mild reaction conditions, the lipid yield of monoraphidium with cellulose enzyme reached more than 13% with the extraction rate more than 80%. In addition, it was found that the content of saponifiable lipid extracted by n-hexane was higher than that by trichloromethane. The fatty acids, containing 71.59% of saturated and Monounsaturated fatty acid, with a lower degree of unsaturation (DU) of 97.20% and the main carbon number of C16—C22 was obtained from lipid in Monoraphidium, which could be used as feed to produce biodiesel.

Key words: Monoraphidium, ultra-structure, lipid, extraction, aqueous enzyme