Seaweed polysaccharide is an important active substance in seaweed with good gel property, stability, and film-forming properties. It possesses various biological activities such as anti-virus, anti-tumor, immune regulation, anti-oxidation, and is widely used in food, health care and cosmetics. This article reviews recent advances on biological activities of seaweed polysaccharides, with a view to better development and utilization of seaweed polysaccharides, and promoting the sustainable and healthy development of the seaweed polysaccharide industry.

Bioactive components of marine species have received great attention in recent years, especially phlorotannins isolated from brown algae. This paper summarized progress in the structures and bioactivities of phlorotannins including antibacterial, antioxidant, anticoagulant, anti-diabetic, anti-hypertensive, inhibiting HIV, anti-tumor, anti-allergic, anti-inflammatory, defense activity, and deodorant activities.

Biotoxins are a group of significant biogenicactive compounds that are usually present in trace amounts in a matrix, and they become the focus of attention in the fields of food safety and medicine research for their toxicities and bioactivities. The biotoxins in food are mainly mycotoxins and marine biotoxins. This review introduced mainly the source, structures and toxicities of aflatoxins (AFs), fumonisins (FBs), trichothecenes (TCTs), zearalenone (ZON), ochratoxin and patulin (PAT) of mycotoxins, which are highly toxic and common in foods. In addition, the classification of marine toxins has also been introduced. Moreover, the detection methods of biotoxins were also introduced including immunological methods, enzyme activity inhibition assay methods, high performance liquid chromatography (HPLC), mass spectrometry (MS), biosensor methods, and aptamer methods, which are intended to provide reference for the study of biotoxins in food. The detection of food biotoxins can prevent food poisoning and control food quality.

In recent years, marine natural products isolated from associated microorganisms have become a hot topic in medicine. It has been reported that secondary metabolites produced by sponge-associated fungi are of great importance for the discovery of active substances with novel structures and they own broad prospects for clinical medicine and the development of drugs. Herein, we summarize the structures of marine sponge-associated fungi including lactones, anthraquinones, pyrenes, chromones and others, as well as the bioactivities of polyketides from marine sponge-associated fungi.

Bletilla striata (Thunb.) Reichb.f. is a species of genus Bletilla (Family Orchidaceae) and it is a commonly used traditional Chinese medicine. Bletilla striata polysaccharides (BSPs) were extracted from the tuber of Bletilla striata. Herein, we reviewed the extraction and purification methods of BSPs, compared the advantages and disadvantages of different methods comprehensively, and analyzed molecular weights and structural characterization of BSPs systematically. In addition, we analyzed hemostasis, anti-oxidation, anti-aging and other functional activities of BSPs to provide scientific basis for further study of BSPs.

Sponge is the simplest type of multicellular animal, but it has a huge family. Marine sponge is a low-pitched filter animal containing many microorganisms. Therefore, the enormous diversity and abundance of sponge associated bacteria envisages sponges as hot spots of microbial diversity and dynamics. Many researchers have extracted compounds and secondary metabolites with anti-inflammatory, anti-tumor and anti-fatigue activities from sponges. However, there are few reports on the mechanism of sponges and their symbionts. This paper focuses on the interactions between sponges and bacteria, cyanobacteria, fungi, mangroves and illustrates the mechanism of their interaction. The symbiotic relationship between sponge and bacteria/cyanobacteria was analyzed from the genetic level. Sponge has always been a hot issue and will be worthy of further research.

Iron (Fe), an essential micro-nutrient for marine organisms, is a necessary element for many biochemical processes such as photosynthesis, respiration, synthesis of DNA and chlorophyll, and reduction of nitrate. However, the iron for life is in water under natural pH conditions in the main form of Fe(OH)₃. The concentration of soluble iron is very low in seawater due to its insolubility. While iron is the fourth most abundant transition metal in the Earth's crust, the insolubility of iron(III) [K_Sp of Fe(OH)₃ = 10^-39] at physiological pH in aerobic environments limits the availability of this essential nutrient severely. Marine microbes face similar challenges for obtaining iron because they live in the environments with very low iron concentrations. In this paper, we summarize the detection methods of siderophores from marine microbials and their structures.

Chitosan is a kind of amino polysaccharide biopolymer with good film-forming, biocompatibility, biodegradability, bacteriostasis and nontoxic, obtained from the deacetylation of chitin, which contains abundant active amino and hydroxyl groups. With creative properties, functions and various applications especially in the biomedical field, chitosan is mainly used as pharmaceutical membrane, gel, microsphere (microcapsule), nanoparticle, drug and gene delivery, etc. This minireview provides an overview on the structure and properties of chitosan, the applications of chitosan biomaterials is introduced, and its research and development in the biomedical field are prospected.

As the main species in the marine environment, Rhodotorula benthica contains abundant nutritions including proteins, vitamins and astaxanthin, which can improve the body's immune function and prevent disease and cure diseases. It would possess a wide range of applications and broad market prospects due to the particularity of its nutrition and metabolites and be commonly used in medicine, food, chemical, agricultural and environmental protection industries. Microbial cultivation of Rhodotorula benthica, an excellent strain to produce astaxanthin, was investigated to produce astaxanthin. The diversity, main characteristics, strains, the optimization of culture conditions, progress in fermentation and application to industry of Rhodotorula benthica were summarized.

The protective effect of the polysaccharides on ethylene glycol induced kidney impairment has been explored. Polysaccharides have been extracted from Sargassum graminifolium, which belongs to brown algae. Three different doses of polysaccharides were used for rats with kidney stones by ethylene glycol feeding. Then, urinary biochemistry parameters, renal function factors including blood urea nitrogen (BUN) and serum creatinine (Scr) levels were detected. Besides, interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) in kidney tissue were elevated, which belong to proinflammatory cytokines. Moreover, kidney histopathological sections were examined. The results illustrated that polysaccharides not only increased calcium level but also decreased oxalate, Scr, and BUN levels. In addition, the levels of IL-6 and TNF-α were reduced. Moreover, renal micro-scopic analysis showed polysaccharides treatment alleviated observably calcium oxalate deposits in the kidney tissue. The results indicated that the renoprotective mechanism of SGP may be attributed to suppression of inflammation, reducing the growth of urinary stones and improving kidney function in vivo, which explained SGP through multiple ways to protect kidney cells from damaging of hyperoxaluria rats.