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Ryan W. Davis

Ryan W. Davis

As a Principal Member, Sandia National Laboratories

Title: Cultivation and utilization of cyanobacterial exopolysaccharide for production of biobased polymers

Biography

As a Principal Member of Technical Staff at Sandia National Laboratories, Ryan’s research has focused on science and technology for production of biobased commodities from renewable feedstocks using nonarable land and non-freshwater resources. Ryan recieved his Ph.D. in Physical Chemistry from the University of New Mexico and completed post-doctoral studies at Sandia Laboratories in New Mexico and California.  Ryan has published  >25 articles in peer-reviewed journals and is director of the Sandia Algae Raceway Testbed Facility

Abstract

Development of polycultures has been identified as a potential means for overcoming several challenges facing scale-up of algae-based commodities which can displace petroleum but do not compete with food production.  In this presentation, we describe findings from our recent studies on cultivation of a marine cyanobacterial consortium in open algae raceways, and downstream conversion to bioplastic.  In the consortium, three distinct cyanobacterial cultivars were combined to provide nitrogen fixation, photoprotection, and high rates of secretion of extracellular polysaccharides in support of a long-term bioproduct ‘milking’ strategy.  Following lab-scale investigations of various combinations of the individial cultivars to identify optimal algae raceway inoculation and maintenance strategies, the best performing consortia were successfully cultivated in pilot-scale algae raceways for >120 days.  The growth trials indicated bioproduct concentrations >2 g/L consisting primarily of a variety of C5 and C6 monosugars which were recovered using a low-cost semi-continuous harvesting strategy.  In addition to the remarkable stability of the consortium in open cultivation, measurements of culture density time course indicated insignificantly different log-phase specific growth rates at different levels of nitrate or carbon dioxide addition, which should have significant techno-economic and sustainability impacts for commercialization.   Following recovery of the biomass and exopolymer, generation of cyanobacterial-derived bioplastic was demonstrated and performance characteristics were found to be similar to common biobased plastics, such as PLA.  Initial technoeconomic analysis based on the product yield and corresponding biomass production, harvesting, and conversion costs indicate an Nth-plant model finished product cost of $600/ton.