Steven Baldassano

AMOPs in BiofuelsAMOP = Aquatic Microbial Oxygenic

PhotoautotrophIncludes cyanobacteria, algae, diatomsHigh neutral lipid yield (20-50% of dry weight)

Potentially more useful for biofuels than current sources such as corn grain ethanolMore efficient conversion of solar energyUse of little or no landEasier conversion of lipids to useful biofuelsUseful byproducts such as protein for animal feed

PurposeDetermination of the effects of nitrogen

deprivation on Phaeodactylum tricornutumInability to create proteins will change carbon

compositionMeasurement of carbohydrate/protein/lipid

composition

Use of C13 labeling to determine source and distribution of carbon

Experimental Setup

•Cultures of Phaeodactylum tricornutum grown for 4 days in F/2 media with sufficient N and C12

•On day 4, cells were pelleted and resuspended in C13 labeled bicarbonate in sealed flasks

•3 in F/2 media•3 in F/2 media without NO3-

•N2 bubbling used to evacuate flasks

•Assays performed on day 4 (t=0 timepoint) and day 7 (t=3 days after resuspension).

MethodspHCell count by microscopyOptical density at 625 nmChlorophyll contentβ-1,3-glucan (carbohydrate storage)

C13 content by mass spectroscopyMembrane carbohydratesProtein contentLipid Content

Fractionation and C13 content using LCMSAsh weight percent

ResultsN- cells became much larger and more ovoidSignificantly lower cell count in N- samples

due to arrested cell divisionDecreased chlorophyll content in N- samples

Decrease in pH relative to N+ samples

Optical density readings correlate well with cell count and dry weight for N+ samples only

ResultsN-, ash-free dry weight %

N+, ash-free dry weight %

ResultsOverall lipid increase after resuspension:

Ongoing ResearchCompletion of lipid content analysis

FractionationC13 labeling

Mass spectroscopy for carbohydrate C13

content

C13 content will provide information as to the source of carbon for glucan and lipid increaserearrangement vs de novo synthesis

SummaryNitrogen deprivation resulted in changes in

compositionIncrease in cell size and massIncrease in glucan contentIncrease in lipid content (per cell and dry weight)Slight decrease in overall lipids per mlDecrease in membrane carbohydrate contentDecrease in protein content

Source of carbon for lipid and glucan increase to be determined soon