Currently, the production of palm oil leads to the destruction of rainforest. A more sustainable source of lipids could be obtained using abundant lignocellulosic waste (e.g. wheat straw) as a source of carbon in the form of polysaccharides. Some species of oleaginous yeast, grown on sugars, can be made to accumulate between 20-80% of their biomass as oil and so offer a promising alternative to terrestrial crops. In this thesis, the yeast Metschnikowia pulcherrima was selected for its resilience to contamination. Although not previously classified as oleaginous, a combination of low temperature and restricted nutrient availability prevented sporulation and consequently triggered levels of oil production in M. pulcherrima cultures of up to 47%. The potential of this yeast to produce lipids inexpensively on waste resources was investigated. This yeast was grown under non-sterile conditions at pilot scale with minimal temperature control. The possibility of growing M. pulcherrima on lignocellulose was studied on models and showed that it was tolerant to a range of sugars and inhibitors commonly found in hydrolysed lignocellulose. The yeast produced 6.04 g L-1 lipid when cultivated on a mixture of hexoses and pentoses. This was corroborated by demonstrating that the yeast could be cultured on oligomers and sugars produced by hydrolysing wheat straw. Evidence of cellulase production was observed, and this was utilised in a process involving mildly pretreated wheat straw, using a range of pretreatment processes and culture conditions to yield a maximum of 1.12 g L-1 lipid. The usefulness of the products of this cultivation in forming oil in water emulsions was evaluated, and some evidence of surface-active effects was found. Overall, M. pulcherrima was found to have phenotypes that would be highly beneficial in reducing the capital and running costs of a putative lipid production process.
|Date of Award||15 Feb 2016|
|Supervisor||Chris Chuck (Supervisor)|