Optimização da produção de açucares por microalgas para a produção de bioetanol

• Author(s): Paulo, Vanessa Patrícia Faria
• Date: 2011
• Persistent ID: http://hdl.handle.net/10400.5/4100
• Origin: Repositório da UTL
• Subject(s): microalgae; Spirogyra sp.; cellular disruption; sugars; yeast; bioethanol
• Document Type: Master thesis
• Language: Portuguese
• Advisor(s): Passarinho, Paula Cristina Varela; Silva, Maria Luísa Gouveia da; Martins, Maria Luísa Louro
• Contributor(s): Repositório da Universidade de Lisboa

Description

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia

Nowadays, the world energy crisis and environmental issues are in order. So, the use of biofuels has gained an extraordinary importance and microalgae seem to be a promising feedstock, as they do not compete with food either for arable land or for potable water. Also, they produce several interesting compounds such as sugars and lipids. The aim of this dissertation was the study of sugar production by Spirogyra sp. regarding the production of bioethanol. So, the first step was the cultivation of this chlorophyte under continuous lighting and day-night cycles (14 h/10 h), to evaluate the effect of light regime on the growth and sugar accumulation. Methods for cell rupture and sugars extraction were also studied and optimized. A yeast screening towards the production of ethanol from microalgae hidrolysates was the final step of this work. The highest biomass concentration was attained under day-night cycles (0,34±0,05 vs. 0,29±0,02 gL-1) but the greatest sugar accumulation occurred in the presence of continuous illumination (27 vs. 24 % g eqglu.g biomass-1). From all the tested methods for cellular disruption of Spyrogira sp., the most appropriate was acid hydrolysis by sulfuric acid 2 N in autoclave for 30 min (78 % extracted sugars). S. carlsbergensis showed to be the most promising microorganism with conversion yields of 82 % for glucose and mannose. This yeast presented also the ability to use in some extent arabinose, a pentose found in algae hydrolysates.