2045 Bainer Hall
Characterization of Algal Cell Walls for Biofuels Development
The cell wall compositions of green microalgae species were studied under different growth conditions including autotrophic growth, mixotrophic growth using acetate, glycerol, and glucose as carbon sources, and nitrogen replete and deplete. Algae were cultivated under different growth conditions, harvested, and fractionated. Two fractionation methods were used to improve cell wall monosaccharide yields. One method removed lipids and starches from cell wall material. The other method was a modified metabolomics approach, aimed at a gentle handling of the cell wall to improve chemical accessibility for methanolysis. Two classes of analyses were also compared in this thesis: wet chemistry methods that included acid hydrolysis, colorimetric assays, and high performance liquid chromatography (HPLC) and organic chemical methods of Trimethylsilyl Methylglycosides (TMS) derivatization that used gas chromatography/mass spectrometry (GC/MS) for quantification. The rationale for the selected TMS method and the modifications made to the TMS method will be presented. The modifications made to the TMS method are aimed at reduction of side reactions with water and the decreased evaporation of derivatives to maintain high yields. Under mixotrophic growth conditions, the cell wall of A. protothecoides is composed of fucose, mannose, and galactose. When glucose was the source of organic carbon, A. protothecoides cell wall also has rhamnose and galacturonic acid constituents. Under nitrogen deplete conditions, a higher percentage of the cell wall was identified by TMS derivatization, indicating Chlorella may use structural protein in the cell wall when nitrogen is readily available. Future studies should investigate the role of nitrogen in the cell wall and determine the linkages between the cell wall monomers to improve deconstruction for biofuels production.
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2045 Bainer Hall University of California Davis