Bubble Column Systems for Algal Biomass Production and their Application to Environmental Virology and Biofuel Research

As a highly specialised and diverse group of organisms, algae play a vital role as primary producers within the world’s oceans. They are studied extensively in order to identify their functional roles at the base of global ecosystems. However, research into their exploitation for commercial purposes is a relatively recent development, in particular the use of algal biomass for biofuel production. The mass culture of phytoplankton strains as a method of sustainably producing biofuel whilst offsetting carbon emissions is an attractive prospect. This study aims to investigate the physiology and dynamics of the mass culture of algal strains within a newly developed photo bioreactor: the PML bubble column system. A secondary aim to investigate the use of viral infection and mechanical disruption as a method of improving the efficiency of harvesting oil as cells lyse. Cultures of Isochrysis galbana, Rhinomonus reticulata, Emiliania huxleyi, Tetraselmis sueica, Nannochloropsis salina, and Dunaliella salina were grown in batch culture within bubble columns and compared to flask cultures using cell counts, flow cytometry, optical density and Fluorescence induction and relaxation. The growth and density of cultures within the columns exceeded that of flask cultures in most cases, with the exception of R. reticulata. It was determined that light limitation and reduced contact with nutrients was experienced within flask cultures due to minimal turbulence. The continual mixing of column cultures reduced these limitations. Cultures of Chlorella variabilis NC64A and Emiliania huxleyi were then infected with Paramecium bursaria Chlorella virus-1 (PBCV-1) and EhV-18 respectively and subjected to disruption within a vortex reactor. After an hour cycle within the vortex reactor, uninfected cultures remained relatively stable throughout, whereas infected cultures experienced accelerated lysation due to the compromised cellular integrity. Within Emiliania huxleyi cultures, lysis is at its most prominent two days post infection. As infected cells lyse within the reactor, viruses are released which may then be available to infect any uninfected cells present. Virally infected C. NC64A showed rapid lysis within 15 minutes of the induction of turbulent flow, associated with a subsequent increase of virus particles. More work is required to determine the optimum incubation period between viral infection, the compromisation of cellular structural integrity and lipid harvesting.In collaboration with Plymouth Marine Laborator