An integrated process for conversion of Zostera marina residues to bioethanol

Zostera marina is an aquatic plant forming wide grasslands and considered as the lungs of the marine ecosystems. However, the residues reaching the coastlines create nuisance and high costs are required for their disposal. The objective was to investigate the potential of Z. marina residues as a source of secondary metabolites and feedstock in order to propose alternative solutions to the landfill. The supercritical CO2 extract had a total phenol value of 55.4 mg GAE/g extract and a radical scavenging capacity of 71.4%. Considering the raffinate phase, 3% higher hemicellulose content was reached after supercritical CO2 treatment. Enzymatic hydrolysis revealed 31.45% and the yield of simultaneous saccharification and fermentation was 8.72% corresponding to a productivity of 0.273 kg/(m3 h). An integrated process is proposed, where supercritical fluid extraction can act both as the main process to obtain solvent-free pharmaceutical compounds and a pretreatment method in order to loosen the lignin structure, thereby liberating some of the hemicellulose in the matrix.

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► Z. marina residues were extracted with supercritical CO2.
► The raffinate phase was subjected to simultaneous saccharification and fermentation to produce bioethanol.
► Supercritical CO2 extracts proved to be a rich source of phenolic compounds.
► The yield of bioethanol was 8.72%.
► The potential of Z. marina residues was presented as part of the biorefinery approach.