Monday, May 4, 2009
9-15
Oil accumulation from waste via heterotrophic/mixotrophic Chlorella vulgaris and Chlorella protothecoides
Tamarys Heredia, Department of Chemical Engineering, University of Puerto Rico, PO Box 9000, Mayagüez, PR 00681-9000 and Bo Hu, Department of Chemical Engineering, University of Puerto Rico Mayaguez, Rd 108 Km 1.0, Mayaguez, PR 00681-9046.
One of the global issues acquiring significant attention these days is related to energy supply and demand. The irreversible decrease of fossil fuels left to supply energy and the greenhouse gases increase in the atmosphere have led to the utilization of alternate sources of energy, such as oil from microalgae. The aim of this study is to optimize the oil accumulations of Chlorella protothecoides and Chlorella vulgaris by using carbon sources from waste instead of glucose as the organic carbon source in heterotrophic and mixotrophic culture media. Carbon source concentrations, pH values, temperatures, dissolved oxygen and rotational speeds are studied as factors controlling the growth rate of the microalgae and accumulation of oil. High cell densities achieved from Chlorella protothecoides and Chlorella vulgaris under heterotrophic-glucose carbon source conditions, 19.7 g L-1 and 19.4 g L-1, respectively, are significantly greater than those obtained under autotrophic conditions, 2.07g L-1 and 2.15 g L-1, correspondingly. Studies showed superior behavior of the mixotrophic culture of these algae species for the industrial production of liquid fuel than autotrophic culture. Waste materials are applied in this study to partly replace the glucose in order to lower the cost of carbon sources; heterotrophic and mixotrophic microalgae cultures with waste show almost the same cell densities and oil contents as the cultures with glucose.