5-02: Integrated Algal Biorefinery Taking Advantages of Mixtrophic Growth

The Bioprocessing and Bioproduct Engineering Laboratory at Washington State University has been concentrating on developing a technology platform aiming at overcoming some key technical barriers through novel integration between biology and engineering.  This platform builds on two principal biological features of selected algae species. The first one is mixotroph with which the algae can be cultured either separately under heterotrophic or phototrophic conditions or cultured mixotrophically in the same reactor. The second one is the extremophile feature that allows the algae to be cultured under conditions detrimental to most other microorganisms. The first feature can be used to increase productivity according to a two-stage culture strategy. The same strategy can  help contamination control.  The second feature has also two main benefits, one being contamination control the other being efficient use of CO₂ from concentrated sources.  We were able to isolate green algae from local alkaline waters that have both features.  We have also cultured the isolated algae using organic carbon from crop residues and nutrients from wastes.  The cultured algae are harvested with electrocoagulation using solar power, the wet algal biomass is converted thorugh a sequential hydrothermal liquefaction process to separate protein and polysaccharides first then upgrade the remaining algal biomass to bio-oil.  Other discoveries are also embedded in this technical platform.  For example, we found that lipid accumulation occurred without nitrogen deprivation under mixotrophic culture conditions. The neutral lipid accumulated can also be measured live with the NMR technology.   This presentation highlights progress and results in these critical processes.