Integrating the Carboxylate Platform into a Red Seaweed Biorefinery

Area of Science:

• Biotechnology
• Chemical Engineering
• Sustainable Chemistry

Background:

• Macroalgae are a sustainable resource for food, biofuels, and chemicals.
• Carrageenan extraction from red seaweed generates significant waste streams.
• Valorizing algal waste is crucial for developing circular biorefinery processes.

Purpose of the Study:

• To investigate the conversion of red seaweed carrageenan extraction waste into carboxylic acids and ketones.
• To evaluate the efficiency of acidogenic digestion for waste valorization.
• To explore the potential of producing higher-value chemicals and biofuels from algal waste.

Main Methods:

• Acidogenic digestion of carrageenan extraction waste using an open microbial culture.
• Batch fermentations at 35°C and 55°C with calcium carbonate or ammonium bicarbonate buffer.
• Solid-liquid counter-current percolation fermentation in a four-stage system at 35°C.
• Thermal decomposition of carboxylate salts to produce ketones.

Main Results:

• Mixed carboxylic acids (C1-C7) were produced, with higher yields and longer chains at mesophilic temperatures (35°C).
• The highest carboxylic acid titer reached 18 g L⁻¹.
• Thermal decomposition yielded a mixture of ketones, including acetone, 3-pentanone, 2-hexanone, 2-heptanone, 3-heptanone, and 4-octanone.
• The produced ketones can be used as chemicals or hydrogenated to secondary alcohols with higher energy density.

Conclusions:

• Acidogenic digestion is an effective method for converting red seaweed waste into carboxylic acids.
• The resulting ketones represent valuable co-products for chemical or biofuel applications.
• This biorefinery process enhances the economic viability of seaweed-based industries.