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Environmental effects on growth, neutral lipid and taurine biosynthesis in microalgae
Microalgae are photosynthetic, fast growing microorganisms that are found in a wide variety of environments including harsh conditions, and have been commonly exploited for producing food, biofuel and bioproducts. This research focuses on using microalgae for increasing neutral lipid and taurine biosynthesis in biodiesel production and as a supplement in aquaculture feedstock industry, respectively. The major issue with batch cultivation of microalgae for biodiesel production is the inverse relationship between biomass and neutral lipid accumulation under nitrogen deprivation. In the present study, the problem is addressed by continuous addition of the precise limited amount of nitrogen source, which not only was found to produce neutral lipid in growing microaglae, but also led to oscillatory patterns in lipid productivity. Further, the physiological significance of these lipid synthesis oscillations is presented. The kinetic modeling along with the stability analysis provided physiologically significant parameters in lipid biosynthesis. A nonequilibrium thermodynamic coupling approach was used to formulate the reaction-diffusion process in microalgae growth and lipid accumulation. Taurine is a free amino acid commonly present in almost all animals and has shown its nutritional significance. Using the high sensitivity of LC-MS/MS methodology, selected microalgae from marine as well as fresh water were found to synthesize taurine, but at very low levels and varying with lineage. An attempt at creating a synthetic pathway for taurine synthesis in the chloroplast of Chlamydomonas reinhardtii was pursued by trying to integrate the fused codon optimized cysteine dioxygenase and cysteine sulfinic acid decarboxylase genes designed using animal sequences. Genotyping combined with northern, western and analytical analysis concluded that the first step (cysteine to cysteine sulfinic acid) was functionally present. Further, based on bioinformatic analysis and supplementation experiments, a new pathway for taurine synthesis termed the serine/sulfate or Animal II pathway was proposed in microalgae. The overall study concluded that the influence of environmental factors and thermodynamic coupling have a high impact on the growth, lipid accumulation and taurine production in microalgae.
Tevatia, Rahul, "Environmental effects on growth, neutral lipid and taurine biosynthesis in microalgae" (2014). ETD collection for University of Nebraska - Lincoln. AAI3626336.