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There are no funded Research Studentship opportunities available at present but  the following self funding projects are now on offer:

To apply for any of these projects please go to the University web site         https://www.ulster.ac.uk/doctoralcollege/find-a-phd?query=marchant

Investigation of the diversity and role of rhamnosyltransferase enzymes in rhamnolipid synthesis in bacteria.

Rhamnolipids have been identified as microbial biosurfactants with huge potential for industrial exploitation, however, the best known producer, Pseudomonas aeruginosa is a human pathogen and therefore unacceptable as an industrial organism. A number of other non-pathogenic bacterial producers of rhamnolipid have been identified and these are currently being intensively researched.  All these bacteria yield a mixture of mono-rhamnolipids and di-rhamnolipids in different proportions since the mono form provides the substrate for a second rhamnosyltransferase to add the second sugar molecule to produce the di form. It is this second rhamnosyltransferase that will form the focus for this project since it controls the proportion of mono to di-rhamnolipid in the final product.

The approach in this project will be to use our existing knowledge of the gene sequences of this enzyme from different organisms to give heterologous expression in E.coli  of a his-tagged protein which can then be purified. Having a purified enzyme will allow protein sequencing to be carried out by mass spectrometry and the development of a cell free enzyme assay to determine the kinetics of each of the rhamnosyltransferases.

Related references:

V.U. Irorere, L. Tripathi, R. Marchant, S. McClean and I. M. Banat (2017). Microbial Rhamnolipid Production: A Critical Re-evaluation of Published Data and Suggested Future Publication Criteria. Applied Microbiology & Biotechnology. 101:3941–3951. DOI 10.1007/s00253-017-8262-0

For further information Contact:

Prof. Ibrahim Banat,   email: im.banat@ulster.ac.uk

Prof. Roger Marchant   email:  r.marchant@ulster.ac.uk

The regulation of rhamnolipid biosynthesis in Burkholderia thailandensis.

Microbial biosurfactants, such as the rhamnolipids produced by Burkholderia thailandensis, have been identified as surface active agents which may have extensive application in a wide range of consumer products. Some of these biosurfactants such as sophorolipids have already found their way to the market place, however, rhamnolipids have yet to make an impact since the best producer organism is a human pathogen. B. thailandensis is an alternative non-pathogenic producer which is being investigated. The key problem to be overcome with biosurfactant production is the low yield of product and the consequent poor economics of the process. A clear knowledge of the regulation of production is therefore essential to achieve high productivity and an economic process.

The focus of this project will therefore be to examine the genetic regulation of rhamnolipid production in B. thailandensis principally through the use of knockout mutants of the key production enzymes. This organism has two identical operons containing the relevant genes but the contribution and regulation of these two operons is not known.A library of knockout mutants is available, but some of the key mutants are not contained in the library, it will therefore be necessary to produce in-house additional mutants to complete the study. The availability of a complete genome sequence will facilitate this approach.

QRT-PCR will be the initial tool to examine the expression of the two operons at different times and under different conditions during growth.

Related References:

S. Funston, K. Tsaousi, M. Rudden, TJ. Smyth, PS. Stevenson, R. Marchant and I.M. Banat (2016). Characterising rhamnolipid production in Burkholderia thailandensis E264,, a non-pathogenic producer. Appl. Microbiol & Biotechnol. 205: 1-6. 10.1007/s00253-016-7564-y

S. Funston, K. Tsaousi, T. J. Smyth, M. S. Twigg, R. Marchant and I.M. Banat (2017). Enhanced rhamnolipid production in Burkholderia thailandensis transposon knockout strains deficient in polyhydroxyalkanoate (PHA) synthesis. Applied Microbiology and Biotechnology, 101 (23), 8443-8454. DOI: 10.1007/s00253-017-8540-x

For further information Contact:

Prof. Ibrahim Banat,   email: im.banat@ulster.ac.uk

Prof. Roger Marchant   email:  r.marchant@ulster.ac.uk

The production of rhamnolipid biosurfactant by Pseudomonas aeruginosa growing in biofilms.

Rhamnolipid biosurfactants produced by Pseudomonas aeruginosa have been investigated as potential replacements for chemical surfactants in a variety of commercial applications. However, P. aeruginosa is a human pathogen and the rhamnolipids also play an important role in pathogenicity including the development of biofilms. Most of the research on production of the rhamnolipids has been carried out using planktonic cultures of the bacterium, but this project will focus on the regulation of the rhamnolipid production when the organism is growing as a biofilm.

The synthesis of rhamnolipid will be investigated in biofilms at various stages of development and production under different growth conditions. There are well established techniques for examining the expression of the relevant genes using qRT-PCR and analytical methods to quantify and characterise the biosurfactant produced all of which have been developed in our laboratory.

Related References:

M. Dίaz de Rienzo, P. Stevenson, R. Marchant and I.M.Banat (2016). P. aeruginosa biofilm disruption using microbial biosurfactants. Journal of Applied Microbiology, 120: 868—876. DOI: 10.1111/jam.13049

S.K. Satpute, A.G. Banpurkar, I.M. Banat, J.N. Sangshetti, R.R. Patil, W.N. Gade (2016).  Multiple Roles of Biosurfactants in Biofilms. Current Pharmaceutical Design 22, 1429-1448.

For further information Contact:

Prof. Ibrahim Banat,   email: im.banat@ulster.ac.uk

Prof. Roger Marchant   email:  r.marchant@ulster.ac.uk

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