Journal of Biotechnology & Biomaterials
Open Access

Abstract

The association of two bioreactors, photoautotrophic and heterotrophic, connected by the gas phase, allowing an exchange of O2/CO2 gases between them, benefiting from a symbiotic effect, is described. The O2-rich outlet gas flow from the autotrophic bioreactor was used as the inlet gas flow for the heterotrophic bioreactor. In parallel, the CO2-rich outlet gas flow from another heterotrophic bioreactor was used as the inlet gas flow for the autotrophic bioreactor. One mixotrophic bioreactor was also used as a model, for its claimed advantage of CO2 and organic carbon being simultaneously assimilated. Chlorella protothecoides was chosen as a model due to its ability to grow under auto, hetero, and mixotrophic nutritional modes, yielding high biomass productivity and lipid content, suitable for biodiesel production. Heterotrophic growth achieved the highest biomass productivity and lipid content (>22%), as well as the most suitable fatty acid profile in order to produce high quality biodiesel. Both associations showed higher biomass productivity (10�20%), compared to the sum of the two separately operated bioreactors (controls). A more remarkable result would have been obtained if the two bioreactors had been inter-connected in a closed loop. The biomass and lipid productivity gain would have been 30% and 100%, respectively, by comparing the productivities of the symbiotic assemblage with the sum of the two non-connected control bioreactors. These results show an advantage of the symbiotic bioreactors association towards a cost-effective microalgal biodiesel production. The concept can be extended to any single-cell-oil rich heterotroph, such as the yeast Rodotorula glutinis.

Biography

Alberto Reis, chemical engineer, Ph.D. degree (biochemical engineering) from the Technical University of Lisbon in 2001. In 2001, he was appointed as a Researcher at the National Institute of Engineering, Technology, and Innovation (INETI) in Lisbon, now the National Laboratory for Energy and Geology (LNEG). He was awarded as a postdoc at the Birmingham University (UK) for one year. He currently conducts research at the Bioenergy Unit of LNEG being a Coordinator of the Bioengineering Program at the same institute. He authored over 40 international peer-review scientific publications. He is the Editorial board member of Journal of Biomedicine and Biotechnology.