Algae fermentation
Fermentation is a bacterial-based process designed to increase the nutritional value of algae through enzymatic decomposition. In this method, bacteria grow directly on algae, using it as both an energy and carbon source. The process typically takes place in a bioreactor, where controlled conditions optimize the breakdown of algal components. The primary goal is to improve the digestibility and nutritional quality of algae — such as ulvan, laminarin, and starch — by degrading cell-wall polysaccharides and hydrolyzing proteins. This unlocks essential amino acids and bioactive compounds, making them more accessible for both human and animal consumption, including applications in aquafeeds.
The fermentation process focuses on degrading cell-wall structures and increasing protein hydrolysis, which enhances the bioavailability of nutrients in algae. Cell-wall polysaccharides, which provide structural integrity and protection against pathogens, are broken down using specialized enzymes called carbohydrases. These include agarases, alginate lyases, and carrageenases, which target complex polysaccharides like agar, alginates, and carrageenan. Bacteria such as Saccharophagus degradans and Microbulbifer naturally produce these enzymes to metabolize polysaccharides as an energy source. By leveraging these microbial processes, fermentation effectively modifies algal compounds for easier extraction and improved nutritional use.
Recent research has shed light on the metabolic pathways of bacteria capable of degrading algal polysaccharides. For example, the marine flavobacterium Formosa agariphila employs a cascade of 12 carbohydrate-active enzymes, including polysaccharide lyases, to break down ulvan into simpler oligo- and monosaccharides. This enzymatic process not only enhances the digestibility of algae but also unlocks their potential for applications in human nutrition and animal feed. Studies, such as those by Reisky et al. (2019), provide detailed insights into these pathways, demonstrating how bacterial fermentation can be harnessed to maximize the value of algal biomass.