Study On Microecological Mechanism Of Natural Bioflocculant From Ruditapes Philippinarum Conglutination Mud

Ruditapes philippinarum conglutination mud(RPM)has been reported as a natural bioflocculant resource recently with the good flocculation capability,decoloration and heavy metal removal activity.RPM can precipitate naturally and is suitable for fresh water and seawater treatment.Some researches has contributed to the hypothesis of this article,the flocculation activity of RPM may derive from its associated microbes.For this reason,this study has conducted in-depth research on the microbial ecological composition of RPM,biodiversity of bioflocculant-producing bacteria and chemical diversity of its extracellular polysaccharides,and antibiotic-resistant bioflocculant-producing bacteria in RPM cultured under antibiotic-inhibiting bacterial growth conditions,in order to prove that the adhesion of microorganisms in the sludge is the source of its flocculating activity.In addition,an attempt was made to eco-biomimetic preparation of RPM based on the strategy of ecological recombination.However,the microbial community profile of RPM,the biodiversity and chemical characteristics of extracellular polysaccharide of bioflocculant-producing bacteria in RPM have not yet been explored.This study will focus on the in-depth study of functional microorganisms in RPM.Through biological research,microorganisms in RPM were artificially isolated and cultured by using different types of medium,a total of 14 cultivable high efficient bioflocculant-producing bacterial strains were screened out from 32 diverse clone phenotypes,followed by phylogenetic identification as Pseudoalteromonas sp.(5),Psychrobacter sp.(3),Halomonas sp.(2),Albirhodobacter sp.(1),Celeribacter sp.(1),Kocuria sp.(1)and Bacillus sp.(1).At the same time,high-throughput 16 S rDNA / 18 S rDNA / ITS sequencing method was used to study the bacterial / fungal community structure in RPM which showed a high biodiversity with 16 phyla,32 classes,78 orders,132 families and 140 genera after species classification analysis,while the fungal community has a low abundance.6 isolates could find OTU with same taxonomic status in the bacterial community.Through chemical research,the results of the physicochemical analysis of the extract of the fermentation broth which came from bioflocculant-producing bacteria showed that the main constituent of flocculating active ingredients were small amount of protein and more than 93%(w/w)polysaccharides.The extract had the flocculant activity of more than 50% at a fixed dosage.The monosaccharide composition of polysaccharides in each bioflocculant-producing bacterial strain was analyzed by HPLC and the results indicated that these polysaccharides were mostly composed by 9-10 of mannose,glucosamine,rhamnose,glucuronic acid,galacturonic acid,galactosamine,glucose,galactose,xylose,arabinose,fucose,etc.Comparing the results of this study with the analysis results of the chemical properties of flocculent components from RPM in previous researches,we found that both showed a high degree of similarity in terms of quantitative analysis and monosaccharide composition.Based on the study of the flocculation and decolorization performance of RPM which came from the aquacultural system of adding antibiotics to regulate the influence of bacteria,the microorganisms in RPM collected under this condition were separated and screened.Then,the diversity and abundance of microorganisms in RPM was examined by high-throughput sequencing.The results showed that there were some drug-resistant bacteria with flocculating activity in RPM and the main taxa of drug-resistant bacteria was the genus Glaciecola sp.with the abundance of 99.3%.This study has demonstrated the existence of a wealth of microorganisms in sludge through biological and chemical means.The bioflocculant-producing microbial community was one of the key factors of flocculating activity in RPM.At the same time,the new bioflocculant-producing bacteria obtained from RPM can be used as a new bioflocculant development and utilization.The disclosed microbial diversity can be used as the basis for research on the complex ecological environment for RPM.In the later studies,although the ecological bionic compound of bioflocculant-producing bacteria was not realized,the theoretical basis for the industrial production of bio-flocculants using the natural RPM as a biological source was identified in the future.