Food, nutraceutical, cosmeceutical, pharmaceutical and biomedical industries are putting significant effort into looking for new natural ingredients [1,2]. Microalgae have been recognised as potential sources of high-value chemicals, with most attention focused on antioxidants, pigments and specialty oils [3]. An under-exploited group of biochemicals produced by microalgae are extracellular polymeric substances (EPS) with hyaluronan (HA) representing one of them. Current industrial production methodologies for HA leave opportunities for the establishment of improved routes with higher molecular mass, enhanced biophysical properties, lower production costs and non-bacterial nor animal origins as key unique selling points. At present, incumbent platforms are either based upon Streptococcus spp. (pathogen) bacterial fermentation, modified (GM) Bacillus subtilis or derived from animal tissues.
Furthermore, the extraction of various economically exploitable cell components from microalgal biomass is at the core of a successful microalgal biorefinery approach, and it remains a current bottleneck for the economic feasibility of microalgal biotechnological processes [4]. Cell disruption is often required to break down the hard and complicated microalgal cell walls in order to retrieve microalgal constituents such as proteins, lipids, and polysaccharides. Viral enzymes may play a beneficial role in this scenario and might be used to facilitate genetic engineering by overcoming the cell wall barrier or for biorefinery purposes.
This project's hypothesis was that it was feasible for microalgae to produce HA. The objectives included investigating a stress-induced platform for the possible production of HA, learning how Chlorovirus/C. varibilis infection leads to HA formation, improving the HA production for the latter platform and looking into intriguing enzymes that can break down polysaccharides.
This PhD project focused on exploring, characterizing and developing new platforms in order to achieve profitable industrial production of valuable compounds from microalgae and identify viral enzymes that could help with the processing of Chlorella cells for multiple applications. Two platforms were successfully explored for the production of valuable polysaccharides, and multiple enzymes were identified, produced, characterised and evaluated for Chlorella cell wall digestion to enable possible biorefinery approaches of a non-domesticated Chlorella vulgaris strain.