Thesis
Investigation of lipid production by oleaginous yeast Cryptococcus curvatus from effluents of food wastes hydrogen fermentation
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/102363
Abstract
Lipid produced from oleaginous yeast can be a potential feedstock for biodiesel production if low cost raw material is available. Combining hydrogen and lipid production from waste streams could have significant economic advantages. In this study, volatile fatty acids (VFA) produced from a dark fermentation process for hydrogen production was tested as a feedstock for oleaginous yeast culture. Suitable culture conditions for oleaginous yeast Cryptococcus curvatus were identified when acetate was used as carbon source. Hydrogen production effluent from food waste was used as the feedstock in continuous culture of the yeast. The biomass productivity in the continuous culture was 0.34 g/L/hour and the lipid productivity was 0.046 g/L/hour. However, the food waste hydrogen production effluent was rich in ammonia (2.4 g N/L), which was found to inhibit yeast cell growth and lipid production. So, the inhibitory effect of ammonia on C. curvatus growth and its possible mechanism of action were studied. The results showed that ammonia significantly inhibited yeast growth when VFA were the growth carbon sources, but it did not affect cell growth when pyruvate generating substances (PGS) were the carbon sources. The presence of ammonia suppressed lipid production when the yeast was grown on either VFA or PGS. The mechanism of ammonia inhibition was suggested to be the suppression of acyl-CoA synthetase as its assay showed 40.5 ± 1.2% inhibition at 3.1 g N/L ammonia. These results suggest that food waste alone is not a good feedstock for yeast culture, but a combination with nitrogen-deficient waste streams from cellulosic materials to maintain an initial C/N ratio between 30/1 and 80/1 could be applied to this two-step process. This study provides preliminary evidence for integrating lipid and biodiesel production with hydrogen fermentation, which would benefit both waste treatment and biofuel production. Moreover, the demonstrated mechanism for ammonia inhibition may lead to practical solutions for this perplexing problem, which affects anaerobic digestion and other processes that use VFA as growth substrate.
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Details
- Title
- Investigation of lipid production by oleaginous yeast Cryptococcus curvatus from effluents of food wastes hydrogen fermentation
- Creators
- Yubin Zheng
- Contributors
- Shulin Chen (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Systems Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525136901842
- Language
- English
- Resource Type
- Thesis