Marine Polysaccharides: Occurrence, Enzymatic Degradation and Utilization

Abstract

Macroalgae species are fast growing and their polysaccharides are already used as food ingredient due to their properties as hydrocolloids or they have potential high value bioactivity. The degradation of these valuable polysaccharides to access the sugar components has remained mostly unexplored so far. One reason is the high structural complexity of algal polysaccharides, but also the need for suitable enzyme cocktails to obtain oligo‐ and monosaccharides. Among them, there are several rare sugars with high value. Recently, considerable progress was made in the discovery of highly specific carbohydrate‐active enzymes able to decompose complex marine carbohydrates such as carrageenan, laminarin, agar, porphyran and ulvan. This minireview summarizes these achievements and highlights potential applications of the now accessible abundant renewable resource of marine polysaccharides.

Laminarin, a Major Polysaccharide in Stramenopiles

“…The content of β-1,3-glucans can be extracted or measured by different procedures, such as hot water extraction [ 10 ], alkali extraction [ 36 ], phenol sulfuric acid assay [ 37 ], 3-methyl-2-benzothiazolinone hydrazone (MBTH) reducing sugar assay [ 25 ], enzymatic hydrolysis [ 7 , 8 ], and high-performance size-exclusion chromatography (HPSEC) method [ 38 ]. Among these methods, hot water extraction could achieve the highest amount of β-glucans with high purity and low cost [ 10 ].…”

“…In diatoms, the fixed carbon is mainly used to synthesize polysaccharide, storing it in the vacuole. The vacuolar polysaccharide is a central energy metabolite and accounts for up to 50% of organic carbon in sinking diatom-containing particles; it will be released extracellularly and degraded by bacterium directly in the ocean [ 7 ]. Therefore, it is important for the carbon export from the surface ocean and carbon cycle [ 8 ].…”

Functional gene analysis and cultivation experiments predict the degradation of diverse extracellular polysaccharides by ubiquitous taxa in pustular microbial mats from Shark Bay, Western Australia

“…Our comprehensive assessment of CAZymes and their potential substrates in the metagenome of a carbonate-precipitating marine mat cannot illuminate the relative "importance" of microbial groups to gene expression or substrate turnover. Additionally, there are comparably few characterized CAZymes acting on marine-specific substrates such as algal and cyanobacterial polysaccharides that can be used to inform sequence-based functional annotation (52,75,76), and our results indicate that some genes could be acting on substrates that are yet to be linked to their CAZyme families. Further, many GH and PL had no known predicted substrate at all.…”

Connecting Algal Polysaccharide Degradation to Formaldehyde Detoxification

“…[3] Compared to their terrestrial counterparts, marine polysaccharides differ in the backbone structure and side-group modifications. [4] One bacterial phylum considered to be specialist in the degradation of high molecular weight organic matter such as marine carbohydrates are the Bacteroidetes. [5][6][7] Marine Bacteroidetes harbor gene clusters which are referred to as polysaccharide utilization loci (PULs) encoding carbohydrate-active enzymes (CAZymes) as well as specific proteins for the binding and uptake of sugar units.…”

“…[5,8] Their tremendous repertoire of CAZymes allows them to depolymerize complex marine carbohydrates and utilize the imported monosaccharides as a carbon and energy source. [4,8] Observations that Bacteriodetes are among the first responders after micro-and macroalgal blooms are related to their abilities of rapid growth on colonizable surfaces such as macroalgae as well as their CAZymes production. [9,10] A model bacterium for the bioconversion of algal biomass is the marine Flavobacterium Zobellia galactanivorans Dsij T , which was originally isolated from the red alga Delesseria sanguinea near the coast of Roscoff (Brittany, France).…”