Identification,Characterization,and Production Potential Study Of Bioactive Compounds In Seaweed

Objective: Wild seaweeds were collected from China’s coastal areas.firstly,the specific species and genera of seaweed can be revealed by morphological and molecular biological identification,which is conducive to the subsequent studies on the biological active components of seaweed.Secondly,the comprehensive characterization of the biochemical components and physicochemical properties of seaweed is helpful to understand the potential of each seaweed in the production of bioactive compounds.Finally,the physicochemical properties of seawater where seaweed grow were clarified,and the correlation between seawater factors and seaweed growth/active substances was explored,so as to provide parameter guidance for large-scale artificial culture of seaweed.Methods: Seaweed samples were collected from Shandong,Hainan,and Liaoning provinces,while seawater samples from three sampling sites were collected.The species and genus of seaweed were identified by morphological and molecular identification,and the biochemical composition(carbohydrate,protein,lipid,moisture,total solids,volatile solids,ash)of seaweed was determined.The proportion of carbon,nitrogen,hydrogen,oxygen,and sulfur in seaweed biomass was determined by the elemental analyzer.Fourier infrared spectroscopy(FTIR)and thermogravimetric analysis(TGA)were used to determine the important functional groups,potential bioactive compounds and their relative proportions in seaweed biomass.p H meter,multifunctional water quality detector,portable dissolved oxygen meter,total organic carbon analyzer,total nitrogen meter,and multi-parameter water quality meter were used to determine the p H,electrical conductivity,total dissolved solids and salinity,total organic carbon,total nitrogen,total phosphorus and chemical oxygen demand of seawater samples.Total polyphenols,phlorotannin,and flavonoids were extracted and measured from S.thunbergii GEEL-15 and P.australis GEEL-18 by ultrasonic-assisted extraction,and the extraction methods and yields were compared with those of previous studies.Results:(1)Six species of seaweed were collected from Qingdao in Shandong province,Sanya in Hainan province,and Dalian in Liaoning province.They were identified by sequencing as Sargassum thunbergii GEEL-15,Mastocarpus stellatus GEEL-16,Ulva sp.GEEL-17,Padina australis GEEL-18,Chondrus sp.GEEL-19,and Betaphycus gelatinae GEEL-20.(2)Based on the analysis of biochemical components in seaweed biomass,the proportions of carbohydrate,protein,and lipid in six kinds of seaweed were compared,which provided guidance for the selection of bioactive compounds extracted from each seaweed.In addition,the biochemical composition of the seaweed in this study was determined in the corresponding seaweed by comparison with the biochemical composition of the seaweed in the same genus in previous studies,which is helpful to determine which kind of bioactive compounds the seaweed in this study is a better choice for extraction at the level of the same genus.(3)Volatile solids in seaweed represent a wide range of secondary metabolites.The high volatile solids in seaweed in this study indicate that they are rich in bioactive compounds.The high ash content in the biomass of M.stellatus GEEL-16,P.australis GEEL-18 and Chondrus sp.GEEL-19 suggested that these seaweeds were the dominant species for extraction of sulphate polysaccharides.(4)FTIR spectra showed the important functional groups of seaweed biomass and predicted the compounds that may be present in seaweed,such as polysaccharides,glycoprotein,amino acid,alginate,β-manuronic acid,and sulfate polysaccharides.In addition,FTIR spectroscopy can distinguish the structure of important compounds in seaweed to a certain extent,such as the position of sulfate groups in polysaccharides.(5)TGA curves showed the main compounds present in seaweed and their relative proportions,such as ulvan,alginic acid,fucoidan,alginate,laminarin,as well as the pyrolytic properties of these compounds,through the percentage of weight loss presented in different temperature ranges.(6)Among the physicochemical properties of seawater,p H,total nitrogen,total phosphorus,salinity,and temperature are the key parameters affecting the growth and active components of seaweed.(7)The contents of total polyphenols,phlorotannin,and flavonoids of S.thunbergii GEEL-15 were higher than those of P.australis GEEL-18,which showed that S.thunbergii GEEL-15 had more potential to extract bioactive compounds of polyphenols.In addition,compared with traditional solvent extraction,ultrasonic assisted extraction can significantly increase the yield of polyphenols.Conclusions: In this study,the identification of seaweed species,as well as the measurement of biochemical components and physicochemical properties,clarified the potential of these seaweeds in the production of bioactive compounds,which is conducive to the selection of the extraction of bioactive compounds and the study of biological activities.Understanding the physical and chemical properties of the seawater where seaweeds grow can provide guidance for setting parameters for the laboratory and large-scale cultivation of these seaweeds in the future.In addition,on the basis of known culture conditions,the content of some biochemical components and bioactive compounds can be controlled by adjusting some or some parameters,so as to improve the synthesis and maximum production of valuable biological compounds in seaweed culture,so as to better serve human health.