A BIOPROCESSING COMPARISON OF HIGH DENSITY BOTRYOCOCCUS BRAUNII AND CHLORELLA VULGARIS VERIFYING LIGHT LIMITED GROWTH

Open Access
Author:
Grady, Lisa Kathleen
Graduate Program:
Chemical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 17, 2010
Committee Members:
  • Wayne Roger Curtis, Thesis Advisor
  • Patrick Cirino, Thesis Advisor
  • Andrew Zydney, Thesis Advisor
Keywords:
  • High Density
  • Photobioreacor
  • Chlorella vulgaris
  • Botryococcus braunii
  • Thin Film
  • Light limited growth
Abstract:
High density cultures of Chlorella vulgaris and Botryococcus braunii were achieved in a trickle screen thin film photobioreactor. Both algae were grown under high light (525 µE/m2/s measured perpendicular to the screen and 280 µE/m2/s measured parallel to the screen), photoautrophic growth conditions in a semi-continuous reactor system where the dilution rate was set at 7.5% per day. Even though the doubling times of Botryococcus, 4-7 days, and Chlorella, 2-3 hours, are drastically different, essentially the same steady state Biomass Dry Weights, 20 gDW/L and 19 gDW/L respectively, and Biomass Productivities, 0.1 gDW/L/Photo-hr and 0.09 gDW/L/Photo-hr respectively, were achieved verifying light limited growth. Oil productivities between Botryococcus and Chlorella were quite different: 16.6 mg-oil/L/Photo-hr and 5.2 mg-oil/L/Photo-hr respectively. This difference in lipid accumulation is likely due to differences in the physiological roles of these lipids. Isoprene hydrocarbons are a structural component of the Botryococcus matrix that is inherent to the survival of the algae and fatty acids/triglycerides are a storage form of energy for Chlorella.