Potential assessment of some micro- and macroalgal species for bioethanol and biodiesel production
Mona M. Ismail, Gehan A. Ismail, Mostafa M. El‐Sheekh
Abstract
In this study, five macroalgae and four microalgae in addition to seven Cyanophycean, blue-green algae, were isolated from different environmental habitats. The ability of these species for bioethanol and biodiesel production was assessed. Five techniques were examined for cell wall disruption, namely thermic shock, manual grinding, acid, base, and enzymatic digestion. Among these methods, sulfuric acid (3%) achieved the highest reducing sugar yield (%) followed by the enzymatic then the base hydrolysis methods. For each species, the resulted yield of reducing sugars (%) was dependent on the hydrolysis method rather than on the quantity of the total sugars (as mg/100 mg dr weight). After 48 hours of fermentation, Arthrospira platensis, Chlorella marina, and Ulva linza proved to be promising for bioethanol production estimating 45.49%, 23.24%, and 12.01% as ethanol yield, respectively. For all the tested species, grinding followed by enzymatic hydrolysis methods recovered maximum protein amounts (as mg/100 mg dry weight). On the other hand, Caulerpa prolifera, Anabaena variabilis, and Scenedesmus obliquus produced elevated biodiesel quantities of 13.55%, 21.63%, and 28.44% of dry weight, respectively. For each tested species, the quantity of the obtained biodiesel (%) was proportional to the extracted amount of lipids. Gas chromatography–mass spectroscopy (GC-MS) analysis of the produced oil showed dominant composition of saturated fatty acids implying a suitable oil quality. The results of this study recommended large-scale cultivation of A. platensis, C. marina, and U. linza as costless candidates for bioethanol production. The study also validated S. obliquus, A. variabilis, and Caulerpa prolifera as reliable biodiesel producers with an encouraging oil composition ratio for probable commercial applications.