Methane production from glycolate excreting algae as a new concept in the production of biofuels

Abstract

It is the aim of the present work to introduce a new concept for methane production by the interaction of a glycolate-excreting alga (Chlamydomonas reinhardtii) and methanogenic microbes operating in separate compartments within one photobioreactor. This approach requires a minimum number of metabolic steps to convert light energy to methane thereby reducing the energetic and financial costs of biomass formation, harvest and refinement. In this feasibility study it is shown that the physiological limitations for sustained glycolate production can be circumvented by the use of C. reinhardtii mutants whose carbon concentrating mechanisms or glycolate dehydrogenase are suppressed. The results also demonstrate that methanogenic microbes are able to thrive on glycolate as single carbon source for a long time period, delivering biogas composed of CO2/methane with only very minor contamination.