Pelletization of micro-algae by induced lichen formation through co-culture with filamentous fungi

The use of micro-algae within industrial applications, such as biofuel production, has several limitations with regard to cost and therefore sustainability. Micro-algae biomass consists of small single cells that stay in suspension making them difficult to harvest, requiring filtration or pelletization methods which contribute to a significant cost of the total biomass production. Recent studies have investigated the use of co-cultivation of fungi and algae to form symbiotic lichen communities as a mechanism of harvesting the micro-algae biomass. Lichens are symbiotic community structures comprised of fungal mycobionts and algal photobionts. Algae, inoculated with fungal biomass are rapidly absorbed from suspension by the mycobiont to form a pellet structure. Pelletization has several beneficial effects for industrial application due with regard to biomass and efficient harvesting by size exclusion. Additional benefits include the application towards agricultural and hydrothermal waste water, where both algal and fungal cultures are have been used for bio-remediation of waste water. The application of the lichen formation in would be to increase biomass, bio-remediate wastewater as well as potentially extract valuable by-products such as carotenoids. In this study, three commercially interesting algal species Chlorella vulgaris, Chlorella sorokiniana and Scenedesmus vacuolatus were investigated for their compatibility with a previously uncharacterized Sordariomycete to form a symbiotic lichen structure. Optimal culture conditions, photobiont-mycobiont interaction and biomass composition were investigated for application in industry.