Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants (BS) because of their many potential applications. Despite all the advantages, BS and MELs in particular, are merely fermented on a limited scale. The main reasons for this are: (1) a limitation in structural variation of naturally occurring BS and (2) the cost, which is often not competitive with that of the chemically synthesized surfactants.
The high cost is to a large extent determined by the cost of the feedstock. MELs are currently produced from soybean oil, a valuable substrate that increases the load on fertile land use. A possible alternative to vegetable oil could be oil from oleaginous yeasts. For several of these yeasts it has been shown that they are able to produce oil from volatile fatty acids, a very inexpensive substrate which can be obtained through acidogenesis of wastewater, an abundant waste stream.
The objective of this project can be comprised in the research components below, each responding to a limiting factor of MEL-production:
- Cost of the substrate: The development and optimization of a multi-stage production system where MELs are produced from oil fermented by the oleaginous yeast Cryptococcus curvatus. For the production of oil by C. curvatus, volatile fatty acids (VFA) and / or glycerol will be used as feedstock. Finally, we designed a case study to obtain VFA from industrial wastewater.
- Limited structural variation: In order to obtain a structural variety of MEL-derivatives, alternative feeding of fatty acids and derivatives, such as hydroxylated and bifunctional fatty acids, are fed instead of (vegetable) oil. Hereby we will identify what the most promising varieties are, and their production will be optimized.
- Limitations in fermentation yield: Elucidation of the trigger effect of a hydrophobic carbon source in MEL production by Pseudozyma aphidis. To achieve this, the expression of MEL biosynthesis genes will be analyzed under various conditions, with the aid of RT-qPCR. This is also a support towards the other research components.
For the production of MELs and oil, fermentation technology is used. Analyses will be carried out with the aid of chromatography. The conversion of industrial wastewater to VFA is done by means of acidogenesis in a sequencing batch reactor (SBR).
For exploring the trigger effect of a hydrophobic carbon source on MEL production by P. aphidis, an RT-qPCR assay is first developed.
This project forms a bridge between different areas of research within the research group Bio-Chemical Green Engineering & Materials (BioGEM) at the Faculty of Applied Engineering (FTI). These are water technology, industrial biotechnology and green and renewable materials.