Micro Algea for Oil Strain Selection, Induction of Lipid Synthesis and Outdoor Mass Cultivation in a Low-Cost Photobioreactor Yariv Shamash

The rational  Checking if nutrient deprivation raises the fatty acid production rate.  After finding that species and the best growth method, how much fatty acid could be produced per area?  Could these yields compete with fossil fuel prices?

Introduction  Microalgae have high lipid content.  up to 40% of dry weight under nutrient sufficient conditions and up to 85% of dry weight under nutrient deprivation.  Various growth conditions can alter microalgae’s lipid content and composition.

target  Maximizing areal lipid productivity with a biomass containing about 50% of the fixed energy as the form of lipids. 1.Finding a micro algae species from 30 screened species that would have the largest fatty acid yields. 2.Finding the suitable growing strategy to produce the most Triacylglycerol TAG

Strategies  Nutrient sufficient  High biomass productivity  Low lipids  Nutrient limited  Lower biomass productivity  High lipid content  Two phase strategy  First growing culture in nutrient sufficient then limiting the nutrient concentration

The screen  30 strains of microalgae were grown in 250 ml flasks in nutrient replete medium. Air and CO 2 were delivered in various fashions making sure no CO 2 insufficiency for 2 weeks.  Promising strains were cultivated in lab in a 600 ml bubbled tube to investigate nitrogen deprivation. 50% harvested after 4 days, subtracted volume was refilled with Nitrogen depleted medium to achieve Nitrogen deprivation.  Only Nannochloropsis sp. F&M-M24 made it to the next step.

Scale up  Nannochloropsis was grown in 20 liter Flat Alveolar Panel under artificial illumination to evaluate light intensity, nitrogen deprivation and phosphorus deprivation on culture productivity.  Light intensity was checked in two irradiance levels 115 and 230 μmol PAR photons/m 2 /s and two illumination methods, one sided and two sided.  Nutrient (N/P) deprivation experiments were done with one sided illumination only.

Outdoor experiments  Nannochloropsis was cultivated in 110 liter Green Wall Panels out door in the Italian summer of to check nutrient deprivation and outdoor growth.  4 mediums with various nutrient treatments:  Nutrient sufficient (Control).  Nutrient sufficient where N and P deficient was added to substitute for the daily harvested volume (-N and –P).  Nutrient sufficient where P deficient was added to substitute for the daily harvested volume (-P).  Nutrient sufficient where N deficient was added to substitute for the daily harvested volume (-N).

Studying nitrogen deprivation  On the same green wall panel system 4 different nitrogen levels were tested.