Preparation methods,biological activities,and potential applications of marine algae oligosaccharides:a review

Marine algae are valuable sources of health-promoting molecules that have been consumed by Asians for decades.Among aquatic flora,marine algae stand out in terms of high content of marine algae polysaccharides(MAP)such as carrageenan,alginate,fucoidan,laminaran,agarose,rhamnan,and ulvan.When hydrolyzed,MAP generate marine algae oligosaccharides(MAO),which have attracted interest in recent years due to their superior solubility compared with MAP.Besides,MAO have been demonstrated numerous biological activities including antioxidant,antidiabetic,anti-inflammatory,antimicrobial,and prebiotic activities.Thus,this review summarizes the main chemical classes of MAO,their sources,and the main processes used for their production(i.e.,physical,chemical,and biological methods),coupled with a discussion of the advantages and disadvantages of these methods.Highlights of the biological activities of MAO and their potential applications in food,nutraceutical,and pharmaceuticals would also be discussed and summarized.

Mutual effects of nitric oxide and iron on the growth of marine algae

Experiments on the effects of nitric oxide （NO） and iron on the growth of marine microalgae Skeletonema costatum were conducted. The results are as follows： exogenous NO could increase the growth rate of marine algae and raise the biomass remarkably under iron-deficient conditions. But it was a complicated process that the phytoplankton growth was influenced by NO and iron, which was controlled by the NO concentration, the nutrition level of the culture medium and the iron concentration, etc. Meanwhile, the iron concentration in the medium also has a direct influence on the growth and NO release capacity of the algae. Therefore, the effects of NO and iron on the growth of marine phytoplankton were mutual.

The research on the adsorption effect on metal ions by immobilized marine algae

The process of adsorption of Cu^2+ Cd^2+ by immobilized marine algae was investigated, it can be noted from the results that, the process for biosorption of heavy metals (copper, cadmium) by immobilized Laminaria japonica can be described by the Banerm model. According to the model, the adsorption rate constant calculated was 0.107 8 and 0.030 28 min^-1 for Cu^2+ and Cd^2+ respectively. The experimental biosorption equilibrium data for Cu^2+ and Cd^2+ were in good agreement with those calculated by the Langmuir model. The maximum uptake capacity calculated was 83.3 and 112.4 mg/g for Cu^2+ and Cd^2+ according to the Langmuir model, respectively. The appetency of Laminaria japonica to Cu^2+ was better than Cd^2+.

Oomycetes and fungi:important parasites on marine algae

Considering that the field is largely unexplored and its importance to aquaculture,outline of oomycetes and fungi parasiting on marine algae was provided in this paper,including 15 species of oomycetes,six species of chytrids,31 Ascomycota species and one species of mitosporic fungi.In natrue,both the oomycetes and chytrids frequently occurred and induced prevalences of disease which could destroy the populations of host plants greatly.However,the parasites in Ascomycota on algae have never occurred as epidemics so far.Some issues relating to the field were discussed such as performing tests to satisfy Koch＇s postulates,investigations of host specificity,interactions between host and parasite and the potential effects of environmental factors on occurrence of a disease,which are urgent in need of further investigations.

Brown marine algae turbinaria conoides as biosorbent for Malachite green removal:Equilibrium and kinetic modeling

In this study,the biosorption of Malachite green(MG)onto Turbinaria conoides,brown marine algae,was studied with respect to initial pH,temperature,initial dye concentration,and sorbent dosage.The optimum initial pH and temperature values for MG removal were found to be 8.0 and 30℃,respectively.Sorbent dosage was found to strongly influence the removal of MG.Equilibrium studies were carried out to test the validity of the Langmuir(q_(max)=66.6 mg/g and b=0.526 mL mol/L)and the Freundlich(n=1.826 and K=3.751 mg/g)isotherms.The kinetic studies indicated the validity of the pseudo first-order and second-order equation.

The Marine Benthic Algae Diversity of Gabon: Case of the Rocky Foreshore of Cap Estérias

This study has allowed to classify the marine macroalgae from the intertidal zone on the Atlantic side of Cap Estérias (Gabon). This area has a rich biodiversity but very few studies in the knowledge of benthic macroalgae have been done. The first study on the knowledge of the algae of the Gabonese coast was made in February 1974 by John and Lawson. This article has been revised to transcribe books and our study would aim to update the existing collection. The algae census is spread over a year from August 2020 to August 2021 and is the first detailed study carried out over a year, with regard to this part of the Gabonese coast. This study has allowed to know the specific diversity, to determine the structure of the flora and its spread out over time. The results show a significant algal diversity of thirty five (35) identified species. Three classes of macroalgae were determined and the percentage of species in the class (%EC): Floridaophyceae at 50% EC, Phaeophyceae at 30% EC and Ulvophyceae at 20% EC. The red algae are the most common in the area with sixteen (16) species determined against twelve (12) species of brown algae and seven (7) species of green algae. The Phaeophyceae class presents the Dictyotaceae family which is the most diverse with 7 species found. Some species seen appear in the collection of John et al., but others are new species encountered in Gabon such as Caulerpa sertularioides, Bryopsis plumosa (two Ulvophytes), Padina arborescens which is a Pheophyte and Galaxaura filamentosa, Digenea simplex,Hildenbrandia rubra, Asparagopsis armata and Caulacanthus ustulatus which are Rhodophytes. Some species are permanently present, they are found in all seasons but with significant abundance from July to September.

Seasonal and spatial variations of macrobenthic community in intertidal Sargassum field off Naozhou Island, South China Sea

Seasonal and spatial variations in the macrobenthic community in an intertidal gulfweed field off Naozhou Island were investigated from April 2011 to January 2012.We identified 407 macrobenthic organism species:64 macroalgae(15.72%of total species);123 Arthropoda(30.22%);107 Mollusca(26.29%);67 Annelida(16.46%);15 Cnidaria(3.69%);14 Echinodermata(3.44%);8 Porifera(1.97%);4 Chordata(0.98%);2 Urochorda(0.49%);and 1 each of Echiura,Sipunculida and Angiospermae(0.25%).Arthropods,mollusks,annelids,and macroalgae were four main groups in the benthic organism community and accounted for 88.70%of the total species.In terms of abundance of biomass,there were 15 dominant species,including 8 macroalgal,5 mollusk and 2 arthropod species.The species diversity indices ranged from 1.21 to 4.42 with an average of 2.80;the annual average of evenness was 0.47.Species richness indices varied from 2.97 to 7.24(average 4.97);and Simpson dominance indices varied from 0.20 to 0.92 in annual average of 0.75.Macroalgal distribution showed clear vertical zonation and seasonal changes.The number of macroalgal species found in the high tide zone,upper middle tide zone,middle tide zone,lower middle tide zone,low tide zone,and below low tide zone were 1,8,10,16,22,and 32,respectively.Biomass among the benthic organisms,macroalgae and crustaceans had significant positive correlation(P<0.05)with the coefficients of 0.802,0.894,and 0.592,respectively.Macroalgal biomass showed a clearly negative correlation with the concentration of dissolved inorganic nitrogen(DIN)(R=0.486,P<0.05).During the winter and spring,when macroalgae were growing vigorously,DIN reached the lowest level in seawater and displayed a clear weak correlation between macroalgal growth and the nutrient concentration.

Characteristics of major and trace elements in surface sediments of the Makran Accretionary Prism, Pakistan and their implications for natural gas hydrates

To accurately identify the natural gas hydrates(NGH)in the sea area of the Makran Accretionary Prism,Pakistan,this paper presents the testing and analysis of major and trace elements in sediment samples taken from two stations(S2 and S3)in the area by the China Geological Survey.As shown by testing results,all major elements are slightly different in content between the two stations except SiO2 and CaO.This also applies to the trace elements that include Sr and Ba primarily and Cr,Ni and Zn secondarily.It can be concluded in this study that the tectonic setting of the Makran Accretionary Prism is dominated by oceanic island arc and that provenance of the Makran Accretionary Prism is dominated by felsic igneous provenance,which is at the initial weathering stage and mainly consists of granodiorite.Besides terrigenous detritus,there are sediments possibly originating from Makran-Bela Ophiolite from the northwestern part and Murray Ridge igneous rocks from the southeastern part.The V/Cr,Ni/Co,and V/(V+Ni)ratios indicate that sediments of the two stations are in an oxidation-suboxidation environment.However,the authors infer that the sedimentary environment of the sediments 3.0 m below the seafloor tends to be gradually transformed into a reduction environment by comparison with the Qiongdongnan Basin in the South China Sea where NGH has been discovered.The sediments in the Makran Accretionary Prism are rich in organic matter,with total organic carbon(TOC)content greater than 1%.According to comprehensive research,the organic matter in the sediments mainly originates from marine algae and has high TOC content,which is favorable for the formation of NGH.

Codon Usage of Chloroplast Gene rbcL in Laurencia sensu lato(Rhodophyta)species

Recent advances in molecular biology make it possible to sequence not only genes or genomes,but also to understand codon dynamics.For the organelle genes of these organisms,a small set of preferred codons are used for encoding proteins.For the first time,this paper treats the divergence of synonymous codon usage and its bias in the rbcL gene within the Laurencia complex of red algae.We observed that the synonymous codon preference biases in rbcL are large and differ among species.A clear distinction in codon usage between genera is evident:the genera Dasya and Delesseria use a set that fluctuated between 53 and 58 codons.Whereas,in the genera Ceramium,Chondrophycus,Chlamydomonas,Chlorella,Laurencia s.s,Osmundea,and Palisada codon usage indicates a higher restriction fluctuating between 40 to 51 codons.Laurencia complex genera and other representative algae showed a defined composition pattern,with lower percentage values of NNC/G(7-24.9%).Dasya and Delesseria showed a selective pattern tendency because of high percentage values of NNC/G(54-55%).The estimated codon bias parameters were tested to infer systematic relationships and match suitable codons with the NNC/G codon percentages.Cluster analysis based on Codon Usage supports phylogenetic relationships between Chondrophycus,Palisada,Laurencia,Osmundea,and Yuzurua species.

Antibacterial activity of selected marine macro algae against vancomycin resistant Enterococcus faecalis

Objective:To evaluate the antibacterial activity of different extracts of Caulerpa chemnitzia(Epser)J.V.Lamououx,Caulerpa racemosa(Frosk.)Weber-van-Bosse(C.racemosa),Caulerpa scalpelliformis(R.Br.)Weber-van-Bosse,Ulva lactuca Lin,Ulva fasciata Dellie,Ulva reticulata Forsk,Stoechospermum marginatum(Ag.)Kutz(S.marginatum),Sargassum wightii Grev,Gracilaria verrucosa(Huds.)Papenfuss and Gracilaria edulis(S.G.Gemelin)P.C.Silva against Enterococcus faecalis(MTCC 439)(E.faecalis)and one clinical isolate of vancomycin resistant E.faecalis.Methods:The selected marine macro algae were extracted with different solvents viz.,hexane,chloroform,ethyl acetate,acetone and methanol.Antibacterial assay was carried out by using disc diffusion method,determination of minimum inhibitory concentration and minimum bactericidal concentration.Results:The maximum antibacterial activity was recorded in the ethyl acetate extracts of S.marginatum and C.racemosa than the other extracts.The mean zone of inhibition produced by the extracts in agar diffusion assays against the tested bacterial strains ranged from 7.1 to 14.5 mm.The minimum inhibitory concentration was between 250 and 500μg/mL,while the minimum bactericidal concentration was from 500 to 1000μg/mL.The ethyl acetate extracts of the seaweeds showed the presence of strong terpenoids,tannins and phenolic compounds compared with the other solvent extracts.Conclusions:These findings suggest that ethyl acetate extracts of S.marginatum and C.racemosa can be used as an antibacterial substance for the treatment of infection caused by E.faecalis.

Structure of Palisadin B,C15H24Br2O

Palisadin B,a brominated sesquiterpenoid, was isolated from the marine alga genus Laurencia Karlae Zhang et Xia collected from the Nansha Islands of the South China Sea. The structure was examined by MS and NMR spectra and confirmed by X-ray diffraction analysis.C15 H24 Br2O, Mr=380.18, tetragonal,P41212, a= 10. 812（3） ,c=27. 436（7）,V=3027. 1, Z=8, Dc= 1. 948Mg. m￣（-3） ,μ（MoKa） = 61. 81 cm￣（-1）, F（000） =1900,T=296K,final R=0. 050 for 1082 observed reflections. The molecule is composed of a cyclohexane ring fused with a seven-membered cyclic ether, and the latter exhibits a twist boat conformation.The molecules in the crystal lattice are held together by van der Waals forces （m. p.367-368K）. Bond lengths and angles are internally consistent and the van der Waals interactions are normal.

Uncommon N-Methoxyindolediketopiperazines from Acrostalagmus luteoalbus,a Marine Algal Isolate of Endophytic Fungus

Main observation and conclusion Four new N-methoxyindolediketopiperazines(acrozines D—G,1—4)and six known congeners(5—10)were purified from the organic extract of Acrostalagmus luteoalbus TK-43,which was a marine algal-derived fungus obtained from Codium fragile.Their structures were determined by interpretation of NMR and mass spectroscopic data.The structures of compounds 1,2,and 4 including their absolute configurations were confirmed by single-crystal X-ray diffraction,while the absolute configuration of compound 3 was elucidated by comparative analysis of ECD and TDDFT-ECD calculations.Compounds 1—4,with a unique methoxy substitution at N-2,were rarely discovered among indolediketopiperazine alkaloids.All these compounds were evaluated for antimicrobial activities against human-and aquatic-pathogenic bacteria and plant-related pathogenic fungi,with compounds 5 and 7 exhibiting potent activity against Edwardsiella icataluri(MIC=3 and 5μmol/L,respectively),while compound 9 displayed a broad spectrum of antibacterial activities.The four new compounds were further tested for anti-acetylcholinesterase(AChE)properties,and compound 3 exhibited inhibitory activity with IC_(50)value of 8.4μmol/L.

Metabolic relationships between marine red algae and algae‑associated bacteria

Mutualistic interactions between marine phototrophs and associated bacteria are an important strategy for their success-ful survival in the ocean,but little is known about their metabolic relationships.Here,bacterial communities in the algal sphere(AS)and bulk solution(BS)of nine marine red algal cultures were analyzed,and Roseibium and Phycisphaera were identified significantly more abundantly in AS than in BS.The metabolic features of Roseibium RMAR6-6(isolated and genome-sequenced),Phycisphaera MAG 12(obtained by metagenomic sequencing),and a marine red alga,Porphyridium purpureum CCMP1328(from GenBank),were analyzed bioinformatically.RMAR6-6 has the genetic capability to fix nitrogen and produce B vitamins(B1,B2,B5,B6,B9,and B12),bacterioferritin,dimethylsulfoniopropionate(DMSP),and phenylacetate that may enhance algal growth,whereas MAG 12 may have a limited metabolic capability,not producing vitamins B9 and B12,DMSP,phenylacetate,and siderophores,but with the ability to produce bacitracin,possibly modulating algal microbiome.P.purpureum CCMP1328 lacks the genetic capability to fix nitrogen and produce vitamin B12,DMSP,phenylacetate,and siderophore.It was shown that the nitrogen-fixing ability of RMAR6-6 promoted the growth of P.pur-pureum,and DMSP reduced the oxidative stress of P.purpureum.The metabolic interactions between strain RMAR6-6 and P.purpureum CCMP1328 were also investigated by the transcriptomic analyses of their monoculture and co-culture.Taken together,potential metabolic relationships between Roseibium and P.purpureum were proposed.This study provides a bet-ter understanding of the metabolic relationships between marine algae and algae-associated bacteria for successful growth.

A cytotoxic pyrrolidinoindoline diketopiperazine dimer from the algal fungus Eurotium herbariorum HT-2

A new cytotoxic pyrrolidinoindoline diketopiperazine dimer, cristatumin E （1）, was isolated from the fermentation broth of the algal fungus Eurotium herbariorum HT-2 associated with the marine algae, Enteromorpha prolifera. The structure was determined by spectroscopic analyses and Marfey＇s amino acid analysis. Cristatumin E （1） showed cytotoxicity against K562 tumor cell line and antibacterial activity against Enterobacter aerogenes and Escherichia coli with IC50 and MIC values of 8.3, 44.0 and 44.0 μmol/L, respectively.

Bioactive compounds from larvicidal and antibacterial Caulerpa racemosa as a potent agent

Marine algae are rich sources ofbioactive compounds capable of harboring secondary metabolites which are structurally and biologically active. In our study, the methanolic extract of marine algae Caulerpa racemosa （green algae） was employed to determine the antibacterial and larvicidal activity. The antibacterial activity showed effective inhibition against five pathogenic bacteria. A significant zone size of 16 mm was observed for Pseudomonas aeruginosa. The methanolic extract of Caulerpa racemosa showed effective larvicidal activity against Culex tritaeniorhynchus and the histopathological studies revealed the rupture in mid gut of larvae. The bioactive compounds in the crude extract were further identified as 2-（-3-bromo-1-adamantyl） acetic acid methyl ester and Chola-5, 22- dien-3-ol by GC-MS. Hence the bioactive compounds obtained from the methanolic extracts could be used for the bactericidal and larvicidal activity which will overcome the harmful impact of synthetic insecticide on environment.