Xu, Y;
(2014)
Exploring the potential of microalgae as a source for bioenergy production.
Doctoral thesis , UCL (University College London).
Abstract
Microalgae are playing an increasingly important role in biotechnology because of their natural abundance of valuable products such as proteins, pigments and bioactive compounds. Intensive research is also being applied to biofuel production from algal biomass owing to their fast reproduction rates and high lipid content. This thesis explored several main steps in algal biotechnology including screening suitable algal strains; optimizing algal growth either by controlling cultivation conditions or using non-motile mutants instead of motile wild type strains; algal biomass harvesting through flocculation using chitosan as the flocculant; and the use of algal biomass for engine combustion. The effect of algal cell motility on growth rate and biomass productivity was explored using Chlamydomonas reinhardtii as the model species. The motility of a non-motile mutant bld1 was recovered by expressing the BLD1 cDNA in the nuclear genome, and the growth of these two strains with equivalent genetic backgrounds was compared. The superior cell growth of the bld1 mutant indicates that the use of non-motile mutants instead of their motile wild types for algal biomass production may help improve the productivity while using the same energy input. Flocculation with chitosan to harvest algal biomass of several algal species was explored in this study. Chitosan proved to be highly efficient in the induction of cell flocculation of green alga Chlorella sorokiniana with the clarification efficiency reaching above 99% below pH 7 at optimal dosage. Influencing factors of flocculation efficiency were explored in detail. Finally, to reduce the complicated and costive processes of algal biofuel production, this work explored an alternative way of utilizing energy from algal cells by blending algal slurry into fossil diesel using specific combinations of surfactants: the aim being to reduce the consumption of fossil diesel, and at the same time improve engine performance compared with standard diesel/water emulsions.
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