Enzymatic Transesterification using Immobilized Lipase in Production of Biodiesel from Nannochloropsis Oculata

Abstract

The microalgae have higher photosynthetic efficiency, higher biomass production and faster growth compared to other energy crops. The growth of Nannochloropsis oculata was enhanced in 300mg/l of nitrogen concentration and the optimum temperature for growth is 25^â—¦C. 38% of microalgal oil was extracted and then converted to biodiesel by enzymatic transesterification using an immobilized lipase (triacyl glycerol acylhydrolase, EC 3.1.1.3). In this study, expensive to produce biodiesel because of the cost of enzyme could be reduced by using immobilized lipase. Immobilization of lipase is expected to provide the hydrophobic microenvironment, reusability and thermo stability of lipase. The lipase was entrapped in sodium alginate substrate to produce 3.2 mm diameter beads with the high lipase activity of about 8.84 U/mg. The reaction rate with alginate-immobilized lipase was lower than with the free enzyme but the immobilized lipase could be used for up to three reaction cycles with little loss of activity. The optimun pH of immobilized lipase was found as 8, while the optimum temperature was 45^ºC. Then the enzymatic transesterification between free fatty acid and methanol was carried out using immobilized lipase enzyme at 45^â—¦C with shaking 200 rpm. This reaction was performed in presence of hexane and the sample was analyzed by GC-MS.