Aldehyde functionalised poly(acryloyl hydrazide) polymers for modulating E. coli K-12 biofilm formation and subsequent biofilm functionality in the biocatalysis arena

Adoni, Pavan (2021). Aldehyde functionalised poly(acryloyl hydrazide) polymers for modulating E. coli K-12 biofilm formation and subsequent biofilm functionality in the biocatalysis arena. University of Birmingham. Ph.D.

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Abstract

The use of bacterial biofilms in industry has emerged as an alternative to whole cell biotransformations, where they can use many of their resilient properties to overcome some of the environmental, physical and chemical stresses required for many industrial reactions, e.g. substrate/product or solvent toxicity. As such, a host of research can now be found to optimise biofilm mediated process by optimising biofilm properties, either through genetic regulation or through bacterial interaction with soft materials enabling a level control over biofilm structure. Recently, synthetic polymers have been used to interact and aggregate bacteria with interesting changes in phenotype, including the expression of biofilm factors. In this project, poly(acryloyl hydrazide) was used as the polymer scaffold onto which biologically relevant functional groups could be easily introduced post polymerisation, resulting in a library of functional poly(acryloyl hydrazide) polymers that could be used to aggregate bacteria to potentially induce and control biofilm levels. Firstly however, we describe the optimisation of poly(acryloyl hydrazide) synthesis via RAFT polymerisation, resulting in greater control over polymer chain lengths and dispersities. Then, the ability of aldehyde functionalised poly(acryloyl hydrazide) polymers to interact and aggregate the E. coli K-12 overproducing mutant PHL644 (which contains an ompR234 mutation, leading to overexpression of the biofilm adhesin curli) and its parental MC4100 strain was investigated. In general, polymer induced cell aggregation and overall induced biofilm quantities were found to be directly modulated by polymer hydrophobicity, with the most hydrophobic polymers enabling MC4100 biofilm quantities (as measured by crystal violet) to exceed that of the overproducing PHL644. Importantly, the expression of curli within MC4100 polymer induced biofilms was influenced greatly by the addition of different polymers, with curli expression levels being highly linked to the physiochemical properties of the aggregating polymer (hydrophobicity and heteroaromaticity) so much so that MC4100 curli expression levels were made to match and exceed that of the overproducing PHL644. The functionality of these polymer induced biofilms were then assessed in the biocatalytic arena, again with polymer induced biofilm properties being linked to the ability of the recombinant biofilms to convert 5-fluoroindole to 5-fluorotryptophan. We also harnessed the natural metabolic esterase generation of the polymer induced E. coli biofilms to catalyse the lipid ester 4-Nitrophenyl dodecanoate into 4-Nitrophenol in toxic reaction conditions.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):