1
Attaining a suitable conversion of organic wastes into SCFAs by means of AF
2
Development of an economic, energy efficient, and effective separation
3
Identification of the metabolic routes involved in lipid production from SCFAs in yeast
4
Optimization of fermentation to favor lipids accumulation in yeasts
5
Quantification of the potential environmental, economic and social impacts of the new microbial lipids, compared to current technologies
Attaining maximum suitable conversion of organic wastes into SCFAs by means of anaerobic fermentation
Anaerobic digestion is a biological process driven by bacteria and consisting in the breakdown of the macromolecular organic components contained in the substrate. The first steps of the process, hydrolysis and acidogenesis, convert proteins, lipids and carbohydrates of biomass into SCFAs, among other by-products. By inhibiting methanogenesis, anaerobic digestion would not produce biogas but organic matter will be converted to SCFAs. In this sense, the recovery of carbon contained in the substrate (wastes) can be maximized in the form of SCFAs. The optimization of the conversion of organic wastes into SCFAs can be achieved by appropriately tuning operational parameters in the fermentation system. Next generation sequencing will be used to identify both archaeal and bacterial communities in the anaerobic reactor and the anaerobic microbiome in digesters will be linked with the SCFAs profile and production.
Development of an economic, energy efficient, and effective separation process for the separation and concentration of SCFAs in an appropriate stream for yeast fermentation
After anaerobic fermentation, the produced SCFAs are in a diluted suspension. This suspension also contains residues of anaerobic microorganisms and non-organic components (unfermented waste). To separate the SCFAs from the fermentation broth, a mild and energy efficient membrane separation process coupled to the bioreactor will be developed through an external submerged membrane bioreactor technology.
Identification of the metabolic routes involved in lipid production from SCFAs in oleaginous yeast
Efficient metabolic engineering to increase lipid production capacity in oleaginous yeasts requires sufficient knowledge of the lipid metabolic pathways. However, the lipid production routes from SCFAs are still not completely understood. Improving lipid biosynthesis capacity will require identification of metabolic pathways and their regulation in the selected oleaginous yeasts. Genomes of the selected strains after screening will be sequenced. A model of the molecular mechanism leading to microbial oil production will be produced by means of -omics analysis, i.e. through genome sequencing and annotation as well as transcriptome analysis at different conditions.
Optimization of the fermentation process to produce high amount of lipids by oleaginous yeasts
When using SCFAs as carbon source, the C/N ratio may affect not only carbon flow within yeast cells but also substrate utilization. A suitable C/N ratio during fermentation should be determined to optimize the lipid accumulation in yeast. Agitation, temperature, pH and nutrients or oxygen concentrations are other culture conditions that can strongly influence microbial lipid accumulation. The operation of the upstream processes (anaerobic fermentation and membrane separation) will be tailored for ensuring the production of yeast biomass with a high content of oil, i.e. lipids. In this manner, yeast biomass containing a large percentage of lipids will be generated using SCFAs-rich permeates.
Quantification of the potential environmental, economic and social impacts of the new microbial lipids, compared to current technologies
Different metrics will be applied for the quantification of the life-cycle sustainability impacts of the new oleochemicals produced from microbial oils, compared to current technologies. The life-cycle approach will also address key issues such as social materiality of the new value chain and social and customer´s acceptance.