Seawater-Based Biorefining for Bioethanol Production

Bioethanol production traditionally relies on large volumes of freshwater and terrestrial yeasts, resulting in significant water footprints and competition with agricultural water resources. Seawater-based biorefining offers a sustainable alternative by utilising abundant marine resources—namely seawater, marine-adapted microbes and saline-tolerant enzymes—to process lignocellulosic and other biomass feedstocks. Key stages include pretreatment, enzymatic hydrolysis of cellulose and fermentation in seawater media, thereby reducing freshwater demand and enabling coastal biorefinery locations. Marine yeasts with high osmotic tolerance can ferment sugars in high-salt environments, while halotolerant enzymes maintain catalytic efficiency in ionic solutions. Integrating seawater into each processing step not only alleviates pressure on freshwater supplies but also opens new opportunities for the valorisation of coastal biomass and renewable energy production. Life cycle assessments indicate that coastal biorefineries can significantly lower water depletion, land use and carbon emissions compared with conventional inland systems. The global significance of this approach lies in its potential to decouple bioethanol production from freshwater scarcity and to support circular bioeconomy models in marine settings.

Research from Nature Portfolio

Recent studies have demonstrated the feasibility of replacing freshwater with seawater throughout the bioethanol production chain. A foundational investigation established a marine-focused biorefinery using a novel marine yeast strain, achieving ethanol concentrations exceeding 90 g L–1 with seawater-based media and industrial substrates such as sugarcane molasses. The marine yeast exhibited superior osmotic tolerance, matching freshwater benchmarks in yield and productivity while drastically reducing the water footprint. More recently, a halophilic cellobiohydrolase (SMECel6A) was characterised from a salt-marsh metaproteome. This enzyme retained over 80 per cent activity in full-strength seawater and demonstrated partial reversible denaturation under thermocycling, thereby offering a robust biocatalyst for saline hydrolysis of crystalline and amorphous cellulose.

Seawater-Based Biorefining for Bioethanol Production publication trend

The graph below shows the total number of articles in seawater-based biorefining for bioethanol production across all publications each year (not limited to Nature Index journals).

Technical terms

Biorefinery: Facility that integrates biomass conversion processes to produce fuels, power and value-added products.

Halotolerant enzyme: Protein catalyst capable of maintaining activity in high-salt environments such as seawater.

Marine yeast: Yeast strain isolated from marine environments, often exhibiting salt tolerance and unique metabolic traits.

Life cycle assessment (LCA): Systematic analysis of environmental impacts of a product or process over its entire life cycle.

Lignocellulosic biomass: Plant biomass composed of cellulose, hemicellulose and lignin, used as a renewable feedstock for biofuel production.

References

1. Functional characterisation of a new halotolerant seawater active glycoside hydrolase family 6 cellobiohydrolase from a salt marsh. Scientific Reports (2024).
2. Kinetic modeling and optimization of ethanol fermentation by the marine yeast Wickerhamomyces subpelliculosus ZE75. World Journal of Microbiology and Biotechnology (2024).
3. The establishment of a marine focused biorefinery for bioethanol production using seawater and a novel marine yeast strain. Scientific Reports (2018).
4. Exploring the tolerance of marine yeast to inhibitory compounds for improving bioethanol production. Sustainable Energy & Fuels (2019).
5. A Preliminary Life Cycle Analysis of Bioethanol Production Using Seawater in a Coastal Biorefinery Setting. Processes (2021).