Lipid profiling, carbon partitioning, and inorganic carbon optimization to enhance growth and lipid accumulation in microalgae

Abstract

Microalgae are capable of accumulating high concentrations of lipids and other metabolites which can be used as precursor compounds for energy and valuable co-products. In order to fully exploit this resource, robust methods are needed to properly quantify and analyze the metabolites of interest. Additionally, understanding how and why these organisms synthesize these metabolites and developing optimized strategies for enhancing their metabolism is of paramount importance if algal biofuels and co-product development are to become commercially feasible. This dissertation represents the summary of work completed to develop analytical methods for quantifying lipid compounds synthesized by two Chlorophytes, Chlamydomonas reinhardtii sp. CC124 and Chlorella vulgaris UTEX 395, and the marine diatom Phaeodactylum tricornutum Pt-1. Additionally, C.reinhardtii was evaluated for factors that control and stimulate triacylglycerol (TAG) accumulation in microalgae by monitoring changes in lipid precursor compounds such as free fatty acids, mono- di- and tri-acylglycerides as well as fatty acids which were transesterified into fatty acid methyl ester (FAME); the bio-synthesized equivalent of diesel fuel. C. vulgaris was evaluated for optimized growth and lipid accumulation on various inorganic carbon substrates. This work resulted in a commercially applicable, two-phase growth/lipid accumulation regime which uses low grade sodium bicarbonate as the inorganic carbon substrate to enhance both growth and lipid accumulation and reduce the cost and resource overhead associated with using only carbon dioxide as the sole inorganic carbon source.