A common problem associated with continuous bioprocesses are the risks of cell washout at high dilution rates, a problem which microbial immobilisation offers a solution for. Previously developed Polyvinyl alcohol-based hydrogels formed at ambient conditions provide suitable physical characteristics to be employed as an immobilisation material. In this study, the long-term cell viability of Rhodopseudomonas palustris immobilised in these hydrogels was investigated, as well as the effects which the gelation process has on the cell viability. The robustness of R. palustris allows for a lenient time frame for gelation and bead removal to occur. Approximately 48 hours is required before the beads can be easily removed from the molds, with cell viability starting to decrease around the 10-day point. Interestingly, the viable application period of the immobilised cells is not limited by cell degradation as previously suspected, but rather by the slow dissolution process of the PVA-based hydrogels. After an investigation period of just short of one year, the cells continued to exhibit a relative cell viability of 90 ± 11 % viable. However, after this period, the beads had lost approximately 50 – 60 % of their initial volume.

A common problem associated with continuous bioprocesses are the risks of cell washout at high dilution rates, a problem which microbial immobilisation offers a solution for. Previously developed Polyvinyl alcohol-based hydrogels formed at ambient conditions provide suitable physical characteristics to be employed as an immobilisation material. In this study, the long-term cell viability of Rhodopseudomonas palustris immobilised in these hydrogels was investigated, as well as the effects which the gelation process has on the cell viability. The robustness of R. palustris allows for a lenient time frame for gelation and bead removal to occur. Approximately 48 hours is required before the beads can be easily removed from the molds, with cell viability starting to decrease around the 10-day point. Interestingly, the viable application period of the immobilised cells is not limited by cell degradation as previously suspected, but rather by the slow dissolution process of the PVA-based hydrogels. After an investigation period of just short of one year, the cells continued to exhibit a relative cell viability of 90 ± 11 % viable. However, after this period, the beads had lost approximately 50 – 60 % of their initial volume.

Hydrogel materials have a variety of applications, ranging from biomedical materials tissues and drug delivery systems, to their employment as immobilisation matrices in bioprocessing applications. Polyvinyl alcohol (PVA) is a synthetic, water-soluble and biocompatible polymer denoted by the general formula [CH2CH(OH)]n. Due to its physical properties when gelled, this polymer has been highlighted itself as a suitable candidate for application in the bioprocessing industry as an immobilisation matrix for microorganisms. This study aims to investigates the effects which of using various polyols as co-solvent have on the gelation of PVA-based hydrogels formed at ambient conditions, and their resulting properties. In addition to glycerol, previously known for its capabilities to induce improve gelation when used as co-solvent, polyols including erythritol (C4H10O4), xylitol (C5H12O5) and sorbitol (C6H14O6) were investigated. The key physical properties of these the resulting PVA-based hydrogels were investigated, including: transparency; tensile and compressive strengths; diffusion coefficients; rates of gelation; and method of gelation. It was determined that these hydrogels are formed through physical crosslinking rather than chemical crosslinking. The glycerol-PVA hydrogels tended to exhibit more suitable properties for application in the immobilisation of photosynthetic organisms, although the difference in properties between the glycerol-PVA, xylitol-PVA and sorbitol-PVA hydrogels were comparable and often not significantly different after rehydration. This investigation showed that through the addition of simple polyols, solid PVA-based hydrogels could be formed at ambient conditions without the requirement of toxic cytotoxic chemicals, harsh gelation conditions or unfavourable intermediate chemicals.

Hydrogel materials have a variety of applications, ranging from biomedical materials tissues and drug delivery systems, to their employment as immobilisation matrices in bioprocessing applications. Polyvinyl alcohol (PVA) is a synthetic, water-soluble and biocompatible polymer denoted by the general formula [CH2CH(OH)]n. Due to its physical properties when gelled, this polymer has been highlighted itself as a suitable candidate for application in the bioprocessing industry as an immobilisation matrix for microorganisms. This study aims to investigates the effects which of using various polyols as co-solvent have on the gelation of PVA-based hydrogels formed at ambient conditions, and their resulting properties. In addition to glycerol, previously known for its capabilities to induce improve gelation when used as co-solvent, polyols including erythritol (C4H10O4), xylitol (C5H12O5) and sorbitol (C6H14O6) were investigated. The key physical properties of these the resulting PVA-based hydrogels were investigated, including: transparency; tensile and compressive strengths; diffusion coefficients; rates of gelation; and method of gelation. It was determined that these hydrogels are formed through physical crosslinking rather than chemical crosslinking. The glycerol-PVA hydrogels tended to exhibit more suitable properties for application in the immobilisation of photosynthetic organisms, although the difference in properties between the glycerol-PVA, xylitol-PVA and sorbitol-PVA hydrogels were comparable and often not significantly different after rehydration. This investigation showed that through the addition of simple polyols, solid PVA-based hydrogels could be formed at ambient conditions without the requirement of toxic cytotoxic chemicals, harsh gelation conditions or unfavourable intermediate chemicals.