Microbial lipid production using aqueous by-product stream from a lipid pyrolysis technology

  • Author / Creator
    Mameeva, Olga G
  • Currently, non-food carbon sources are making a valuable contribution to development of the next generation of hydrocarbon-based renewable fuels and value-added products. As non-food carbon feedstocks with low or negative value, yellow and brown greases, as well as biosolids, can potentially be processed through pyrolysis technologies to produce renewable fuels. Aqueous by-product streams are generated in these processes after hydrolysis, as well as after pyrolysis, and can potentially be used as a carbon and nutrient source to grow oleaginous microorganisms and to facilitate lipid production. In this study, volatile fatty acids and other compounds were quantified in pyrolysis aqueous by-product streams. It was shown that volatile fatty acids, such as acetic, propionic and butyric acids, could be used as single or mixed carbon sources for fermentation of Cryptococcus curvatus and Chlorella protothecoides. Model media mimicked the volatile fatty acid levels in the original aqueous pyrolysis by-product stream, which needed to be diluted to enable growth and lipid accumulation in microbial cells. To avoid potential inhibition caused by low pH, neutralization of the original waste streams and model media was performed to allow high biomass and lipid production. The best growth and lipid productivity of C. curvatus along with C. protothecoides biomass were observed in three-times diluted model media. It was shown that volatile fatty acid consumption by C. curvatus and C. protothecoides is time- and concentration-dependent. Moreover, the lipid production of C. curvatus and C. protothecoides using acetic acid, propionic acid, and butyric acid as a single and mixed carbon source were comparable, in some cases, with glucose. The fatty acid profiles of C. curvatus grown in the volatile fatty acids in the model media showed a higher amount of unsaturation in comparison to C. protothecoides fatty acid profiles. The aqueous by-product streams after hydrolysis of 4 % biosolids, brown grease, and their mixtures, were characterized for their ability to promote C. curvatus and C. protothecoides growth and lipid accumulation. It was established that the aqueous by-product streams after hydrolysis of 4 % biosolids or a biosolids/brown grease mix cannot be used for fermentation and lipid production by oleaginous microorganisms unless supplemented with the essential minerals to stimulate oleaginous microorganisms growth as well as glycerol to increase the carbon to nitrogen ratio to force lipid production, respectively. In supplemented conditions, a significant rise in biomass production was detected compared to low amounts of total lipids production for both C. curvatus and C. protothecoides. Moreover, substantial changes in fatty acids profiles of yeast and microalgae were detected. To summarize, the value-added application of the aqueous by-product streams after hydrolysis and pyrolysis of different lipid-containing feedstocks as a carbon and nutrient source to grow and produce lipids by oleaginous microorganisms is a promising approach. Both oleaginous microorganisms, C. curvatus and C. protothecoides, are suitable for high-concentration volatile fatty acids fermentations as well as for lipid production under the lipid-stimulated conditions.

  • Subjects / Keywords
  • Graduation date
    Fall 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.