Self funded students who are interested in researching for a PhD within the group are encouraged to contact either Lydia or Steve to discuss this.
We will shortly (after the New Year) be advertising a James Watt PhD Scholarship in the area of separation of galactolipid biosurfactants from green plant waste. The James Watt studentships cover UK/EU fees and a stipend for three years. These are competition studentships and applicants will be assessed against other students applying for a range of topics within the Institute of Mechanical, Process and Energy Engineering. Further details are given below. Informal inquiries can be made to Steve Euston on 0131 451 3640 during office hours or by email at S.R.Euston@hw.ac.uk.
Extraction and Physicochemical Characterisation of Galactolipid Biosurfactants from Plant Green Waste
Supervisors: Professor Stephen R. Euston, Professor Derek Stewart, Professor Nik Willoughby.
Surfactants are organic compounds used to mix two immiscible substances, such as oil and water. The importance of SAs to industry is evidenced from the enormous volumes that are used and the diversity of applications that include, but not limited to, food, healthcare, agriculture, public health, textiles, and in environmental pollution control (e.g. bio-remediation). The global emulsifier market alone, in for e.g., foodstuffs is worth ca. US $1 billion/pa. Although a significant fraction of the market demand for surfactants is met by organo-chemical synthesis using petrochemicals as precursors, an important trend in the food and healthcare industries is the adoption of ‘natural’ ingredients with perceived benefits for the consumers’ health. Bio-surfactants are produced by biological systems (plants, animals or microorganisms). They are commercially promising alternatives to those derived from petrochemical feedstock as they have been shown to offer improved properties such as foaming and stabilisation, as well as better tolerance to wider extremes of temperature, pH and salinity. They are also associated with lower toxicities, higher bio-degradability, and perceived consumer-friendliness as a natural ingredient.
Microbial derived biosurfactants such as rhamnolipids and sophorolipids are being produced commercially through biofermentation. Despite the potential advantage, commercial production is often hindered because of typically low yields and high production costs. A further limitation for the consumer product industries is the relative lack of toxicological data for biosurfactants. For glycolipids, this is exacerbated because the rhamnolipids, are produced by Pseudomonas aeruginosa which is a known opportunistic pathogen. This limits the glycolipids available to the consumer product industries, and combined with the higher production costs likely explains the lack of take-up by mass consumer product sectors. Thus, there is a definite commercial need to expand the available range of biosurfactants, and to find ways to lower the cost barrier by introducing surfactants that either have enhanced surface activity or have additional, non-surfactant activities (e.g. biological properties) that are also desired by end-users. There is sufficient evidence in the literature that plant based glycolipids have the potential to circumvent these barriers for uptake into the consumer product industries.
One potential source of glycolipids is from green plants. Galactolipids are found in all plant tissue, and in particular are found in the thylakoid membrane of the chloroplast. A method to extract these from green plant waste, could open up an important new source of glycolipid surfactants. This has the potential to reduce the cost of biosurfactant production, as this source would not require the time consuming and expensive process of large scale fermentation, and would use a very cheap source material (green plant waste) as the starting point.
There is also sufficient evidence to suggest that galactolipids may find certain niche and mass applications within the consumer product industries. Galactolipids are a component of wheat flour used in baking. Research has shown that the galactolipids in flour act as surfactants and improve the volume, texture, and reduce staling of bread. Therefore, galactolipids are a very interesting surfactant group for bread, making them a potential replacer of palm derived mono and diglycerides currently added for these functions.
The project would involve the student developing skills in a number of areas. Initially, a method for the separation and purification of galactolipids from green waste will be developed. A number of techniques will be investigated, possibly including solvent extraction, chromatography, supercritical CO2 extraction amongst others. Methods for pre-treatment of the green waste to facilitate the extraction of the galactolipids will also be explored. Although this is principally a proof of principle project, consideration will be given to yield, sustainability, and potential for scaling and cost effectiveness of these methods. Once a method is found that gives sufficient yield and purity, the physicochemical properties of the extracted surfactants will be assessed for their application in foaming, emulsification and gel enhancement. Finally, if time allows the galactolipids will be assessed in model food systems possibly in collaboration with some of our industrial collaborators.