Revealing a novel natural bioflocculant resource from Ruditapes philippinarum: Effective polysaccharides and synergistic flocculation

Filamentous cyanobacteria and hydrophobic protein in extracellular polymeric substances facilitate algae-bacteria aggregation during partial nitrification

In algae-bacteria symbiotic wastewater treatment, the excellent settling performance of algae-bacteria aggregates is critical for biomass separation and recovery. Here, the composition of extracellular polymeric substances (EPS), microbial profiles, and functional genes of algae-bacteria aggregates were investigated at different solid retention times (SRTs) (10, 20, and 40 d) during partial nitrification in photo sequencing bioreactors (PSBRs). Results showed that SRTs greatly influenced the nitrogen transformation and the formation and morphological structure of algae-bacteria aggregates. The highest nitrite accumulation, the largest particle size (~1.54 mm) and the best settling performance were observed for the algae-bacteria aggregates in the PSBR with an SRT of 10 d, where the abundant occurrence of filamentous cyanobacteria with the highest ratio of chlorophyll a/b and the lowest EPS amount with the highest protein-to-polysaccharide ratio were observed. In particular, the EPS at 10 d of SRT contained a higher amount of protein-related hydrophobic groups and a lower ratio of α-helix/(β-sheet + random coil), indicating a looser protein structure, which might facilitate the formation and stabilization of algae-bacteria aggregates. Moreover, algal-bacterial aggregation greatly depended on the composition and evolution of filamentous cyanobacteria (unclassified _o__Oscillatoriales and Phormidium accounted for 56.29 % of the identified algae at SRT 10 d). The metagenomic analysis further revealed that functional genes related to amino acid metabolism (e.g., genes of phenylalanine, tyrosine, and tryptophan biosynthesis) were expressed at high levels within 10 d of SRT. Overall, this study demonstrates the influence of EPS structures and filamentous cyanobacteria on algae-bacteria aggregation and reveals the biological mechanisms driving photogranule structure and function.

Structural diversity, functional versatility and applications in industrial, environmental and biomedical sciences of polysaccharides and its derivatives - A review

Recent efforts on the expansion of sustainable and commercial primal matters are essential to enhance the knowledge of their hazards and noxiousness to humans and their environments. For example, polysaccharide materials are widely utilized in food, wound dressing, tissue engineering, industry, targeted drug delivery, environmental, and bioremediation due to their attractive degradability, nontoxicity and biocompatibility. There are numerous easy, quick, and efficient ways to manufacture these materials that include cellulose, starch, chitosan, chitin, dextran, pectin, gums, and pullulan. Further, they exhibit distinctive properties when combined favourably with raw materials from other sources. This review discusses the synthesis and novel applications of these carbohydrate polymers in industrial, environmental and biomedical sciences.

Characteristics of exopolysaccharides produced by isolates from natural bioflocculant of Ruditapes philippinarum conglutination mud

Three novel types of exopolysaccharides (EPS) EPS-S8, EPS-S5, and EPS-F10 were extracted and purified from bacterial isolates Bacillus sp. GHS8, Pseudoalteromonas sp. GHS5 and Psychrobacter sp. GHF10, which were originated from natural bioflocculant of Ruditapes philippinarum conglutination mud (RPM), respectively. The EPS had similar function groups C-H, N-H, C-O, and C = O. The EPS were composed of different monosaccharides (EPS-F10, Man: GlcN: GlcUA: GalUA = 1:0.66:5.75:0.51; EPS-S5, Man: Gal: GlcN: Rib = 1: 0.50: 2.94: 0.26; EPS-S8, Man: Gal: GlcN = 1:1.54:7.69). The molecular weights (Mw) of EPS were ordered as 51.4 kDa (EPS-S5) > 9.15 kDa (EPS-S8) > 4.41 kDa (EPS-F10). Three types of EPS all showed higher peak flocculation activities than the reported crude EPS from the RPM. Besides, the EPS also exhibited efficient decoloration and antioxidation activities, especially for EPS-S8, which might be due to the low Mw and specific monosaccharide composition.

Bio-flocculation of Microcystis aeruginosa by using fungal pellets of Aspergillus oryzae: Performance and mechanism

Algal blooms caused by eutrophication are global phenomena that seriously threaten the sustainable use of freshwater resources. Traditional water treatment chemicals often typically lead to high levels of residue and cause damage to the morphology of algal cells. This study investigated an eco-friendly fungal bio-flocculant, Aspergillus oryzae, to remove the representative microalgae (Microcystis aeruginosa). Furthermore, it explored crucial flocculation parameters, adsorption kinetics, and thermodynamics of microalgae using A. oryzae. Accordingly, a flocculation efficiency of >95% was achieved when the fungus was cultured for six days, flocculant dosage was 11 g/L, rotation speed was 100 rpm, temperature was 25 °C, flocculation time was 5 h, and pH ranged between 4.0 and 9.0. KEGG analysis based on the genomic data, and chemical composition analysis revealed that proteins and polysaccharides were the major components of metabolites. Zeta potential analysis, scanning electron microscopy, three-dimensional fluorescence, X-ray spectroscopy, and infrared spectroscopy, electrostatic attraction revealed that electrostatic attraction promoted the destabilization and aggregation of microalgae. Additionally, hyphal surface adsorption and chemisorption from extracellular proteins and exopolysaccharides aided in the removal of microalgae. Therefore, fungi-based bio-flocculants have the potential to remove microalgae in a simple, effective, and eco-friendly manner without the complex extraction of extracellular metabolites.

Wastewater Treatment in Mineral Processing of Non-Ferrous Metal Resources: A Review

Water used by mining enterprises needs to be comprehensively recovered and utilized to achieve clean production. This requires the effective treatment of mineral processing wastewater. Wastewater produced during non-ferrous metal mineral processing contains a complex mixture of pollutants at high concentrations, making comprehensive treatment difficult. Here, the sources of and hazards posed by wastewater produced during non-ferrous metal mineral processing are introduced and the techniques for removing heavy metal ions and organic chemicals are reviewed. Chemical precipitation and adsorption methods are often used to remove heavy metal ions. Chemical precipitation methods can be divided into hydroxide and sulfide precipitation methods. Organic chemicals are mainly removed using oxidation methods, including electrochemical oxidation, photocatalytic oxidation, and ultrasonic synergistic oxidation. External and internal cyclic utilization methods for treating wastewater produced by mineral processing plants are introduced, and a feasibility analysis is performed.

Isolation, Identification and Characterization of Bioflocculant-Producing Bacteria from Activated Sludge of Vulindlela Wastewater Treatment Plant

The low microbial flocculant yields and efficiencies limit their industrial applications. There is a need to identify bacteria with high bioflocculant production. The aim of this study was to isolate and identify a bioflocculant-producing bacterium from activated sludge wastewater and characterise its bioflocculant activity. The identification of the isolated bacterium was performed by 16S rRNA gene sequencing analysis. The optimal medium composition (carbon and nitrogen sources, cations and inoculum size) and culture conditions (temperature, pH, shaking speed and time) were evaluated by the one-factor-at-a-time method. The morphology, functional groups, crystallinity and pyrolysis profile of the bioflocculant were analysed using scanning electron microscope (SEM), Fourier transform infrared (FTIR) and thermogravimetric (TGA) analysis. The bacterium was identified as Proteus mirabilis AB 932526.1. Its optimal medium and culture conditions were: sucrose (20 g/L), yeast extract (1.2 g/L), MnCl2 (1 g/L), pH 6, 30 °C, inoculation volume (3%), shaking speed (120 rpm) for 72 h of cultivation. SEM micrograph revealed the bioflocculant to be amorphous. FTIR analysis indicated the presence of hydroxyl, carboxyl and amino groups. The bioflocculant was completely pyrolyzed at temperatures above 800 °C. The bacterium has potential to produce bioflocculant of industrial importance.

Ubiquitous flocculation activity and flocculation production basis of the conglutination mud from Ruditapes philippinarum along the coast of China

Ruditapes philippinarum conglutination mud (RPM) is a typical waste by-product from manila clam R. philippinarum aquaculture. However, RPM from the clam at an aquaculture farm in Zhoushan, China, has been newly reported as a promising natural bioflocculant resource that contains effective flocculating polysaccharides from the clam associated bacteria. With an intent to figure out whether RPM flocculation activity is ubiquitous to the manila clam across a wide geographical range or only the Zhoushan location, and to explore the flocculation production basis and ultimately widen its exploitation scope, in this study, an extensive survey of RPMs from four representative locations along the coast of China was performed to determine their flocculation activity, polysaccharide constitution and bacterial community composition. Frozen preserved RPM samples from Zhoushan, Dalian, Weihai and Zhanjiang exhibited comparable flocculation activities (FRs) ranging from 61.9±2.4% to 73.2±0.9% at dosage of 8 g·L-1; while fresh RPMs from Zhoushan exhibited a much higher flocculation activity of 91.34±1.18% than its frozen counterpart. Polysaccharide extracts from the four locations showed similar monosaccharide constitutions to some extent. The geographical distribution led to certain variation in bacterial community structures. The similarity clustering of the polysaccharide compositions coincided with that of bacterial community structures from RPMs, suggesting that polysaccharides and respective bacterial communities might be the foundation of the flocculation activity for all RPMs. The overlapping OTUs across all the RPMs accounted for 44.6-62.22% of the overall sequences in each sample and contained the vast majority of the most abundant OTUs (Operational Taxonomic Units), forming a common "core microbiome" that is probably responsible for polysaccharide production and flocculation activity development.

Novel Cellulose Derivatives Containing Metal (Cu, Fe, Ni) Oxide Nanoparticles as Eco-Friendly Corrosion Inhibitors for C-Steel in Acidic Chloride Solutions

Novel environmentally-friendly corrosion inhibitors based on primary aminated modified cellulose (PAC) containing nano-oxide of some metals (MONPs), for instance iron oxide nanoparticles (Fe₃O₄NPs), copper oxide nanoparticles (CuONPs), and nickel oxide nanoparticles (NiONPs), were successfully synthesized. The as-prepared PAC/MONPs nanocomposites were categorized using Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and selected area diffraction pattern (SAED) techniques. The data from spectroscopy indicated that successful formation of PAC/MONPs nanocomposites, as well as the TEM images, declared the synthesized PAC/Fe₃O₄NPs, PAC/CuONPs, and PAC/NiONPs with regular distribution with particle size diameters of 10, 23 and 43 nm, respectively. The protection performance of the as-prepared PAC and PAC/MONPs nanocomposites on the corrosion of C-steel in molar HCl was studied by the electrochemical and weight-loss approaches. The outcomes confirmed that the protection power increased with a rise in the [inhibitor]. The protection efficiency reached 88.1, 93.2, 96.1 and 98.6% with 250 ppm of PAC/CuONP, PAC/Fe₃O₄NPs, and PAC/NiONPs, respectively. PAC and all PAC/MONPs nanocomposites worked as mixed-kind inhibitors and their adsorption on the C-steel interface followed the isotherm Langmuir model. The findings were reinforced by FT-IR, FE-SEM and EDX analyses.

Adsorption characteristics of methylene blue by a dye-degrading and extracellular polymeric substance -producing strain

Biosorption of dye by microbes and the extracellular polymeric substances (EPS) were of great environmental significance, especially for the dye-degrading and EPS-producing strain. Previous studies were mainly focused on the adsorption capacities and regeneration properties of pure culture, few were on the biosorption of dyes by the dye-degraders and the contributions of EPS on adsorption. In this study, a dye-degrading and EPS-producing strain i.e., Klebsiella oxytoca was used to evaluate its removal capacity to methylene blue. The maximum adsorption capacity (q_e) by the strain was calculated as 145 mg g^-1, which is superior to many reported bio-adsorbents and some synthetic materials. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results suggested that CO, -NH₂ and P-OH groups were involved in the adsorption. High pressure steam sterilization (HPSS) increased the hydrophilicity of cell wall but did not significantly change the cell structure. Compared with the dead resting cell (DRC), the relative higher q_e obtained by live resting cell (LRC) possibly due to the loss of some cell structure during the HPSS process. Adsorption experiments by EPS-free LRC, confocal laser microscope and three-dimensional excitation-emission matrix fluorescence spectroscopy results confirmed that the EPS played a role in the adsorption of MB dye. The adsorption characteristics of the dye-degrader and the contributions of EPS on adsorption were investigated in detail in this study. The results were benefit for better understanding of the interaction mechanisms between the dye molecules and cells that before the biodegradation process, which were of great significance for the practical usage of residual sludge on removal of dyes.

Recent advances and perspectives in efforts to reduce the production and application cost of microbial flocculants

Microbial flocculants are macromolecular substances produced by microorganisms. Due to its non-toxic, harmless, and biodegradable advantages, microbial flocculants have been widely used in various industrial fields, such as wastewater treatment, microalgae harvest, activated sludge dewatering, heavy metal ion adsorption, and nanoparticle synthesis, especially in the post-treatment process of fermentation with high safety requirement. However, compared with the traditional inorganic flocculants and organic polymeric flocculants, the high production cost is the main bottleneck that restricts the large-scale production and application of microbial flocculants. To reduce the production cost of microbial flocculant, a series of efforts have been carried out and some exciting research progresses have been achieved. This paper summarized the research advances in the last decade, including the screening of high-yield strains and the construction of genetically engineered strains, search of cheap alternative medium, the extraction and preservation methods, microbial flocculants production as an incidental product of other biological processes, combined use of traditional flocculant and microbial flocculant, and the production of microbial flocculant promoted by inducer. Moreover, this paper prospects the future research directions to further reduce the production cost of microbial flocculants, thereby promoting the industrial production and large-scale application of microbial flocculants.

Wastewater treatment using plant-derived bioflocculants: green chemistry approach for safe environment

The rapid expansion of global trade and human activities has resulted in a massive increase in wastewater pollution into the atmosphere. Suspended solids, organic and inorganic particles, dissolved solids, heavy metals, dyes, and other impurities contained in wastewater from various sources are toxic to the atmosphere and pose serious health risks to humans and animals. Coagulation-flocculation technology is commonly used in wastewater treatment to remove cell debris, colloids, and contaminants in a comfortable and effective manner. Flocculants, both organic and inorganic, have long been used in wastewater treatment. However, because of their low performance, non-biodegradability, and associated health risks, their use has been limited. The use of eco-friendly bioflocculants in wastewater treatment has become essential due to the health implications of chemical flocculants. Because of their availability, biodegradability, and protection, plant-derived coagulants/flocculants and plant-based grafted bioflocculants have recently made significant progress in wastewater treatment. This study will undoubtedly provide a clearer understanding of the current state, challenges, and solutions for bioflocculation in wastewater remediation using green materials for the sake of a cleaner climate.

Marine Actinobacteria Bioflocculant: A Storehouse of Unique Biotechnological Resources for Wastewater Treatment and Other Applications

The bioactive compounds produced by actinobacteria have played a major role in antimicrobials, bioremediation, biofuels, enzymes, and anti-cancer activities. Biodegradable microbial flocculants have been produced by bacteria, algae, and fungi. Microbial bioflocculants have also attracted biotechnology importance over chemical flocculants as a result of degradability and environmentally friendly attributes they possess. Though, freshwater actinobacteria flocculants have been explored in bioflocculation. Yet, there is a paucity of information on the application of actinobacteria flocculants isolated from the marine environment. Similarly, marine habitats that supported the biodiversity of actinobacteria strains in the field of biotechnology have been underexplored in bioflocculation. Hence, this review reiterates the need to optimize culture conditions and other parameters that affect bioflocculant production by using a response surface model or artificial neural network.

Evaluation of Fresh Water Actinomycete Bioflocculant and Its Biotechnological Applications in Wastewaters Treatment and Removal of Heavy Metals

This study evaluated the potential of a biopolymeric flocculant produced by Terrabacter sp. isolated from Sterkfontein Dam, South Africa. Microbial flocculants aid the aggregation of suspended solutes in solutions, thus, suggesting its alternative application to inorganic and synthetic organic flocculants, which are associated with health-related problems. The 16S rDNA analysis revealed the bacteria to have 98% similarity to Terrabacter sp. MUSC78T and the sequence was deposited in the Genbank as Terrabacter sp. with accession number KF682157.1. A series of experimental parameters such as bioflocculant dosage, cations concentrations, pH, and application of the purified bioflocculant in wastewaters treatment were investigated. In the presence of glucose as a sole carbon source, Ca²⁺ as cation at pH 8, the optimal flocculating activity attained was 85%. Optimum bioflocculant dosage of 0.5 mg/mL was able to remove chemical oxygen demand (COD), biological oxygen demand (BOD), suspended solids (SS), nitrate, and turbidity in dairy wastewater. In addition, the tested bioflocculant exhibited higher flocculating efficiency as compared to polyaluminum chloride, polyethylenime, and alum. Inductible coupled plasma optical emission spectroscopy (ICP-OES) analyses confirmed significant removal of 77.7% Fe, 74.8% Al, 61.9% Mn, and 57.6% Zn as representatives of heavy metals from treated dairy wastewater. Fourier transform infrared spectroscopy (FTIR) indicated the presence of carboxyl, hydroxyl, and amino groups in the purified bioflocculant which could be responsible for flocculation. Findings from this study showed the prospect of the studied bioflocculant as an alternative candidate in wastewater treatment and remediating of heavy metals.

Microbial origin of bioflocculation components within a promising natural bioflocculant resource of Ruditapes philippinarum conglutination mud from an aquaculture farm in Zhoushan, China

Ruditapes philippinarum conglutination mud (RPM) is a byproduct from the aquiculture of an important commercially bivalve mollusk R. philippinarum and has been recently reported as a promising natural bioflocculant resource. However the origin of bioflocculation components within RPM is still a pending doubt and impedes its effective exploitation. This study investigated the probability that RPM bioflocculation components originate from its associated microbes. RPM samples from an aquaculture farm in Zhoushan of China were applied to characterize its microbial community structure, screen associated bioflocculant-producing strains, and explore the homology between extracellular polysaccharides (EPS) from bioflocculant-producing isolates and RPM flocculation components. Results showed that RPM exhibited high bacterial biodiversity, with Proteobacteria, Bacteroidetes and Actinobacteria as the most abundant phyla; hgcI_clade, CL500_29_marine_group, Fusibacter, MWH_UniP1_aquatic_group and Arcobacter as the dominant genera. Fourteen highly efficient bioflocculant-producing strains were screened and phylogenetically identified as Pseudoalteromonas sp. (5), Psychrobacter sp. (3), Halomonas sp. (2), Albirhodobacter sp. (1), Celeribacter sp. (1), Kocuria sp. (1) and Bacillus sp. (1), all of which except Bacillus sp. were reported for the first time for their excellent flocculation capability. Furthermore, EPS from the bioflocculant-producing strains exhibited highly similar monosaccharide composition to the reported flocculation-effective RPM polysaccharides. On the other hand, the existence of fungi in RPM was rare and showed no flocculation functionality. Findings from Zhoushan RPM strongly supported that RPM flocculation components were of bacterial origin and make RPM reproduction possible by fermentation approach.

Preparation and characterization of a substitute for Ruditapes philippinarum conglutination mud as a natural bioflocculant

In this study a preparation strategy was attempted to produce a substitute (BBF) for the Ruditapes philippinarum conglutination mud (RPM), which was newly discovered to be a promising natural bioflocculant resource. A stable yield of 73.77 ± 1.79 g L^-1 BBF was established by a sequential batch fermentation under optimized conditions via single factor experiments. BBF attained similar flocculation performance as RPM, showing a maximum flocculation rate of 87.92 ± 0.65%. BBF had significant decolorization efficiency on methylene blue, crystal violet and malachite green by 98.78 ± 0.46%, 89.37 ± 0.35% and 99.11 ± 0.17%, respectively. BBF could harvest microalgae Chlorella salina by 84.38 ± 0.57%. High throughput sequencing revealed that Vibrio and Bacillus might be the extracellular polysaccharides producers. The successful preparation will enable a potential industrial production of BBF thus avoid scattered collection of RPM.