The production and evaluation of microcapsules from biological sources

The outer walls of pollen and spores are formed from sporopollenin: a strong, chemically inert biopolymer. In this thesis, several methods were applied to a range of pollen and spore species with the primary aim of removing all non-sporopollenin material, which may elicit an allergic response in some humans. The ultimate goal was to produce hollow, sporopollenin microcapsules from both pollen and spores and subsequently evaluate their properties and potential uses. Microcapsules were prepared from Lycopodium clavatum spores according to a published base and acid treatment. The base step of this treatment caused notable damage to the pollen species investigated. Acetolysis was evaluated as an alternative method. It successfully removed most non-sporopollenin material, but turned all pollen and spore species investigated dark brown. As lighter-coloured microcapsules are usually desirable, acetolysed pollen and spores could not be used as microcapsules without bleaching. A published enzyme treatment applied to pollen failed to remove most non-sporopollenin material and caused pollen from one species to crack. This method was therefore not considered suitable to produce microcapsules from the pollen species studied. Attempts were made to encapsulate Lactobacillus bacteria inside enzyme-treated Betula fontinalis pollen. Light microscopy indicated that although encapsulation possibly took place, further analysis, as well as optimisation of the encapsulation method, would be desirable. Pollen and spores from a range of species were successfully differentiated according to their fluorescence emission spectra. All contained several similar, intense emission peaks, attributed to sporopollenin. Rhodamine B’s emission shifted to longer wavelength after binding to pollen and spores, and also quenched emission from sporopollenin. Rhodamine B bound preferentially to pollen walls rather than their protoplasts. Fluorescence studies confirmed p-coumaric acid and ferulic acid as potential sporopollenin proxies