Cultivation conditions affect the monosaccharide composition in Ulva fenestrata

In recent years, the interest in using seaweed for the sustainable production of commodities has been increasing as seaweeds contain many potentially worthwhile compounds. Thus, the extraction and refining processes of interesting compounds from seaweeds is a hot research topic but has been found to have problems with profitability for novel applications. To increase the economic potential of refining seaweed biomass, the content of the compounds of interest should be maximized, which can potentially be achieved through optimization of cultivation conditions. In this study, we studied how the monosaccharide composition of the green seaweed species Ulva fenestrata is influenced by the abiotic factors; irradiance, temperature, nitrate, phosphate, and pCO2. It was evident that lower nitrate concentration and cultivation at elevated temperature increased monosaccharide contents. A 70% increase in iduronic acid and a 26% increase in rhamnose content were seen under elevated irradiance and temperature conditions, though the absolute differences in monosaccharide concentration were small. Irradiance and nitrate impacted the ratio between iduronic and rhamnose, which is an indicator of the ulvan structure. These results could potentially be utilized to coax the ulvan towards specific bioactivities, and thus have a considerable impact on a potential biorefinery centered around Ulva.\ua0\ua9 2020, The Author(s)

Influence of preservation methods on biochemical composition and downstream processing of cultivated Saccharina latissima biomass

Saccharina latissima biomass cultivated along the Swedish west coast was subjectedto four different scalable preservation methods after harvest; freezing, sun-drying,oven-drying and ensiling. Freeze-drying and freezing at -80 °C were also included toprovide dry and wet references. The effects of the different preservation methods onthe composition of Saccharina biomass (on dry weight, DW, basis), and the recoveryas well as properties of high-quality protein, alginate and biogas were evaluated. Sundrying significantly reduced protein, alginate and fatty acid content of the seaweeds and thereby concentrated ash in the biomass compared to the other methods.Protein/amino acids and fatty acids were significantly concentrated in ensiled biomass,while mannitol and laminarin were reduced compared to the other biomasses. Ovendryingand -20 °C freezing affected the composition the least, with lower ash content and alterations in some specific amino and fatty acids. Sun-drying and ensiling resulted in significantly lower protein solubility at high pH compared to the other biomasseswhich translated into the lowest total seaweed protein recovery using the pH-shiftprocess. Highest protein yield was obtained with the freeze-dried reference. Ensilinglead to a significant decrease in the molecular weight of alginate, while sun-dryingcaused a negative effect on alginate by inducing a shift in the guluronic and mannuronic acids composition of alginate. Sun-drying gave the lowest methane yield inthe anaerobic digestion experiments while freezing at -80 °C gave the highest yield,closely followed by freezing at -20 °C and ensiling. To conclude, preservation methods must be carefully chosen to protect the valuable component in Saccharina latissima ,and to achieve an efficient downstream processing ultimately yielding high quality products as part of a seaweed biorefinery.Seafar