title: Growth optimization of algae for biodiesel production.
abstract: OBJECTIVE
  Algae are favourable as a biofuel source because of the potential high oil content and fast generation of biomass. However, one of the challenges for this technology is achieving high oil content while maintaining exponential or high growth of the organism. Introducing a two-stage reactor to optimize both growth and oil content of the algae could be a solution to this hurdle. The aim of this study was to determine the reactor design parameters of the first-stage reactor, which would optimize growth of two algal strains, Oocystis sp. and Amphora sp.
  
  
  RESULTS
  Growth kinetics were monitored by in vivo fluorescence and correlated to dry mass for both cultures under several environmental conditions during exponential growth. Temperatures of 25 and 30°C and light intensities of 150 and 80 μmol m(-2) s(-1) provided the most robust growth for Oocystis sp. and Amphora sp., respectively. Both strains showed optimized growth at a light : dark cycle of 16 : 08. At these conditions, the doubling rate for Oocystis sp. was 0·333 d(-1) and for Amphora sp. was 0·179 d(-1) .
  
  
  CONCLUSIONS
  For both cultures, growth rate was more dependent on light : dark cycle and temperature than light intensity. Both strains grew slower in this work than data reported in the literature, however agitation and air/CO(2) sparging were not incorporated in the system under study. The highest doubling rate for Amphora sp. was observed near the maximum tolerable temperature, and it is suggested to grow this strain at 30°C for a consistent high growth rate.
  
  
  CONCLUSIONS
  Optimized growth conditions were determined for two lipid producing strains identified in the Aquatic Species Program summary report. An optimized, first-stage growth reactor operating at these conditions would thus offer the maximum productivity for an algal biomass feed stream into a lipid-optimized second-stage reactor.
authors.affiliation: Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Csavina
authors.forename: B J
authors.initials: BJ
authors.lastname: Stuart
authors.forename: R Guy
authors.initials: RG
authors.lastname: Riefler
authors.forename: M L
authors.initials: ML
authors.lastname: Vis
mesh_terms: D056804:Biofuels; D018533:Biomass; D019149:Bioreactors; D000460:Chlorophyta / Q000254:growth & development* / Q000378:metabolism; D017377:Diatoms / Q000254:growth & development* / Q000378:metabolism; D008027:Light; D008055:Lipids / Q000096:biosynthesis; D013696:Temperature
chemical_list: D056804:Biofuels; D008055:Lipids