Abstract
A new approach to process Saccharina latissima algal biomass was developed using sodium citrate and a polyvalent cation-specific resin to sequentially extract the alginate into several usable fractions. The fractionation was performed in a cyclic manner, utilizing a stepwise removal of the native polyvalent ions present in the algae to isolate fractions of alginate with different solubility in the presence of these ions. Sodium citrate was used in different concentrations in the extraction solution to remove polyvalent cations to adjust the alginate liberation while AMBERLITE IRC718 resin was added to further remove these ions and regenerate the extraction solution. Alginate was recovered by acid precipitation and analyzed for its uronic acid composition and molecular weight, and the carbohydrate compositions of the insoluble and soluble parts of the algal biomass residue were determined. Finally, the fractionation method was assessed with a life cycle analysis to determine the energy and water efficiency as well as the greenhouse gas emissions and the results were compared to conventional alkaline extraction. The results indicate that the energy and water use as well as the emissions are considerably lower for the cyclic extraction in comparison with the conventional methods.
Highlights
The prospect of a large-scale aquaculture expansion at sea has a potential to generate large volumes of new biomass on so far unutilized spaces
We have previously studied the role of chelation in alginate extraction and discovered that if a strong chelating salt was used in the extraction solution, it interacted with the polyvalent cations and liberated more alginate (Sterner and Edlund 2016)
We previously showed that sodium citrate is a potent agent for extraction of alginate at neutral pH due to its high chelation strength at neutral conditions (Sterner and Edlund 2016)
Summary
The prospect of a large-scale aquaculture expansion at sea has a potential to generate large volumes of new biomass on so far unutilized spaces. New techniques to automatize the cultivation of fast-growing algae are developed to convert it to an industrial scale business, but to further pave the way for an algae-based industry, it is beneficial to optimize and broaden the use of the crops. The search for a more complete utilization of biomass with fractionation techniques and valorization of the recovered components is referred to as biorefining (Kamm and Kamm 2004). The fermentable fraction with little other commercial value can be converted to biogas or ethanol, while more valuable components can be utilized for food, feed, and advanced material purposes
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