Species variation in the effects of dewatering treatment on macroalgae

Abstract

Seaweeds can be a valuable resource for biorefinery and biotechnology applications, but their high water content is a recurrent problem and one of the key bottlenecks for their sustainable use. Treatments to increase dry matter content of the kelp Laminaria digitata were recently described by the authors. However macroalgae are an extremely diverse group of organisms and compositional variation between species may influence the effects of particular treatments. In this study, potential dewatering treatments including drying, osmotic media, and the application of both organic and mineral acids all followed by screw-pressing have been tested on two other species of kelp (Laminaria hyperborea and Saccharina latissima) and a red seaweed (Palmaria palmata). Conditions that dewatered these species were identified and the data have been combined with the previous results for L. digitata. There were significant differences between species across all the traits of interest. However dewatering was highly dependent on specific interactions with both treatment and season of collection. Nevertheless, the dry matter content of brown seaweeds was widely and successfully increased by air drying or acid treatment followed by screw-pressing. The results for P. palmata were quite different, particularly with regard to juice production. For this species, acid treatment did not result in dewatering, but dry matter content could be increased by screw-pressing immediately after harvest. Together the data presented here demonstrate that dewatering pre-treatments need to be specific for the type of seaweed to be processed; important knowledge for the future use of this sustainable biomass resource.

Bio-processing of macroalgae Palmaria palmata: metabolite fractionation from pressed fresh material and ensiling considerations for long-term storage

“…Whilst it may be possible to increase the volume and/or the concentration of the juice produced during screw-pressing by adjusting the back pressure, surface water present on the feedstock would also have played a part as the material tested at bench top scale was dried more thoroughly before screw-pressing. Recovery of pressed product was higher in the current study at 84% rather than 68% at bench top scale (Gallagher et al 2018) but partitioning of the utilized products into juice lower at 26% juice and 74% residue rather than 37% and 63%, respectively. The major proportions of the original biomass metabolites measured in this study remained in the screw-pressed residue.…”

“…Interest is growing in the use of marine algae as feedstocks, as they have high productivity and do not compete with food production for land use and fresh water (Loureiro et al 2015;Suutari et al 2015) or require fertilizers (Adams et al 2017). However, their high water content has energy cost implications that may be inhibitory during biomass preparation processes when working at scale (Suutari et al 2015;Soomro et al 2016), as does macroalgae's rapid decomposition once harvested with ensiling one route to longer-term preservation (Gallagher et al 2018). Therefore, it is appropriate to investigate both rapid processing and longer-term products from preserved macroalgae.…”

Integral Utilization of Red Seaweed for Bioactive Production

“…Postharvest treatment with acid, alkali or formaldehyde is necessary to prevent enzymatic and microbial degradation [32,37,40,47,50,53]. Another factor requiring attention after harvesting algae is correct drying under 20% moisture and packing, and avoid wetting during the transporting and storage period, but dewatering pre-treatments have to be defined according to the species and to collection season [54].…”

A Review of Seaweed Pre-Treatment Methods for Enhanced Biofuel Production by Anaerobic Digestion or Fermentation

“…The suitability of different types of pre-treatment for processing seaweed is likely to vary with differences in seaweed chemical composition [57,58]. Chemical profiling of 107 seaweed types showed many similarities between different seaweed groups [59], with red and green seaweed having more similar characteristics in their water-soluble and insoluble components compared to brown seaweed, which held more unique characteristics [59].…”

“…Screw-pressing itself has been found to increase ethanol yields of Laminaria digitata [83]. However, these methods will also need to be selectively chosen for different types of seaweeds as it was found that red and brown seaweeds required different dewatering methods [57].…”