A newly isolated alkaliphilic cyanobacterium for biomass production with direct air CO2 capture
Song Gao, Kyle Pittman, Scott Edmundson, Michael H. Huesemann, Mattias Greer, William Louie, Peter Chen, David R. Nobles, John R. Benemann, Braden Crowe
Abstract
Large-scale microalgal biomass production usually relies on concentrated CO 2 as the carbon source which is a major logistical and economic challenge because of the required infrastructure and geospatial constraints of siting large algal production facilities close to concentrated CO 2 sources. By taking advantage of enhanced CO 2 mass transfer within alkaline media due to the reaction between CO 2 and OH - , carbon can be directly captured from the ambient air and used by the algae. Achieving such goal requires algal strains that can grow fast under alkaline conditions. In this study, a newly isolated alkaliphilic cyanobacterial strain Cyanobacterium sp. PNNL-SSL1 was characterized for its temperature, pH, and salinity tolerance. The result shows that PNNL-SSL1 could sustain grow at pH above 11.2 but exhibited the highest growth rates at pH below 10.5. The strain is a warm season strain and grows the best at 10 PSU (practical salinity unit). The strain was then evaluated in indoor climate simulation ponds under outdoor-relevant pond cultivation conditions with carbon supplied only through direct air CO 2 capture at the culture surface. Two batch culture runs, at slightly different initial pH, exhibited average biomass productivity of 15.2 g m -2 day -1 on ash-free dry weight basis. CO 2 was directly captured from the air at an average rate of 21.6 g CO 2 m -2 day -1 (78.8 tons ha -1 yr -1 ), contributing 74% of the carbon fixed in the biomass. The results demonstrated that PNNL-SSL1 is a promising strain for biomass production using air CO 2 as the carbon source.