High Flocculating Activity Research Articles

Assessment of the bioflocculant production and safety properties of Metabacillus hrfriensis sp. nov. based on phenotypic and whole-genome sequencing analysis

Bioflocculant is considered to have broad application prospect in multi fields for the nontoxic and biodegradation properties. Screening new bioflocculant-producing bacteria with high flocculating activity, stress resistance characteristics, and application security is a significant action in the development of the biofloc technique. A novel bioflocculant-producing species, Metabacillus hrfriensis CT-WN-B3, was isolated from alkali-tolerant strains distributing in Daqing, Heilongjiang Province, China. A strong activity flocculant was detected in the extracellular polymeric substance (EPS) of CT-WN-B3, which could form biofloc more effectively under alkali conditions, with a flocculating rate of more than 70 %. The principal component of the bioflocculant was identified as the polysaccharide of extracellular polymeric substance (EPS) because of its 75.183 ± 2.268 % flocculation contribution, which was very significantly higher than that of the protein and the lipid (p < 0.01). Basing on the whole-genome sequencing analysis of CT-WN-B3, none gene encodes a known virulence factor, but two genes correspond to antibiotic resistance. Antibiotic resistance tests showed CT-WN-B3 was resistant to clindamycin. In the assessment of the antimicrobial spectrum, no antibacterial active substance was detected in the supernatant of CT-WN-B3 culture. Totally, the results of the safety assessment had eliminated the doubts about the application risk of CT-WN-B3. These results indicated that CT-WN-B3 is an alkali-suitable flocculant-producing bacterium for application in multiple fields, under alkali conditions especially.

Functional characterization and biotechnological applications of exopolysaccharides produced by newly isolated Enterococcus hirae MLG3-25-1.

This study investigated the potential applications of Enterococcus hirae MLG3-25-1 exopolysaccharides (EPS), with a focus on their isolation, identification, production, and functional characteristics. After the bacterial strain was cultured in De Man-Rogosa-Sharpe (MRS) medium containing 1% glucose at 37°C, the EPS was refined, and the highest yield of 0.85mg/mL was achieved at the 24-h incubation period. Enterococcus hirae MLG3-25-1 was found to be able to produce EPS. The study explored the microstructure of the EPS, which resembles polysaccharide sheets with smooth surfaces, through scanning electron microscope (SEM) analysis. Through Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance(NMR) analysis, the chemical composition, aligning with glycosidic bond characteristics, has been deciphered. Furthermore, the antimicrobial and antibiofilm activities against pathogenic bacteria, particularly Bacillus sp., demonstrated potential applications in combating antibiotic resistance. The EPS exhibited notable antioxidant activity (89.36% DPPH scavenging), along with high water-holding capacity (575%), emulsifying activity, and flocculation activity, suggesting its potential as a stabilizing agent in the food industry. Overall, this study provides a comprehensive characterization of Enterococcus hirae MLG3-25-1 EPS, emphasizing its diverse applications in antimicrobial, antioxidant, and food-related industries. These findings lay the groundwork for further exploration and utilization of this EPS in various sectors.

Insights into the rapid granulation for treating refractory wastewater under salt stress: Variation of sludge property, treatment performance and microbial community

Industrial effluents often contain high total dissolved solids, which exhibit negative effects on microorganisms. In this study, the granulation process under salt stress in the presence of aniline (a common organic pollutant in several types of industrial wastewaters) was evaluated. The sludge properties, removal performance of pollutants and microbial community structure were investigated. Two reactors, namely R1 and R2 were set up, and influent in R1 contained 15 g L−1 of NaCl while R2 was in the absence of salt as contrast. Results showed that aerobic granules appeared within 20 d under saline conditions with 30 min sludge volume index (SVI30) below 36 mL g−1. High salinity led to larger granule size and extracellular polymeric substances was 1.3 times higher than those in R2. However, part of Ca2+ ions in the bio-aggregate matrix of granules were replaced by Na+ ions in the saline environment, resulting in the modestly higher SVI30. Regarding the treatment performance, high removal efficiencies of aniline and COD were observed (~100% and 93.7%, respectively) after 4-h treatment under saline condition while both nitrification and denitrification were slightly retarded. The average concentration of NH4+-N and TN in the effluent of R1 after formation of granules were 1.2 ± 0.4 and 17.3 ± 1.7 mg L−1, respectively. Microbial community analysis indicated that saline condition could facilitate microorganisms with high flocculation activity and high tolerance to salinity such as Paraclostridium, Citrobacter, and Flavobacterium, which contributed to simultaneous removal of organics and nitrogen in AGS process for treating saline refractory wastewater.

Parametric and kinetic studies of activated sludge dewatering by cationic chitosan-like bioflocculant BF01314 produced from Citrobacter youngae

Bacterial strains belonging to Citrobacter spp. were reported to produce polysaccharides consisting of N-acetylglucosamine and glucosamine like chitosan, with high flocculation activity. In this work, the flocculation dewatering performance of activated sludge conditioned by a novel cationic chitosan-like bioflocculant (BF) named BF01314, produced from Citrobacter youngae GTC 01314, was evaluated under the influences of flocculant dosage, pH, and temperature. At BF dosage as low as 0.5 kg/t DS, the sludge dewaterability was significantly enhanced in comparison to the raw (untreated) sludge, featuring well-flocculated characteristic (reduction in CST from 22.0 s to 9.4 s) and good sludge filterability with reduced resistance (reduction in SRF by one order from 7.42 × 1011 to 9.59 × 1010 m/kg) and increased compactness of sludge (increase in CSC from 15.2 to 23.2%). Besides, the BF demonstrated comparable high sludge dewatering performance within the pH range between 2 and 8, and temperature range between 25 °C and 80 °C. Comparison between the BF, the pristine chitosan and the commercial cationic copolymer MF 7861 demonstrated equivalent performance with enhanced dewaterability at the dosage between 2.0 and 3.0 kg/t DS. Besides, the BF demonstrated strong flocculation activity (>99%) when added to the sludge suspension using moderate to high flocculation speeds (100–200 rpm) with at least 3-min mixing time. The BF's reaction in sludge flocculation was best fitted with a pseudo first-order kinetic model. Electrostatic charge patching and polymer bridging mechanisms are believed to be the dominant mechanistic phenomena during the BF's sludge conditioning process (coagulation-flocculation).

Natural Flocculant from a Combination of Moringa oleifera Seeds and Cactus Cladodes (Opuntia ficus-indica) to Optimize Flocculation Properties

The lack of access to clean water worldwide and organic, inorganic as well as biological contamination of existing freshwater sources are a major problem for around 2 billion people, especially in the countries of the global south. One sign of polluted water is turbidity. It is generally caused by colloidal and particulate suspended solids. Chemical flocculants are often used to reduce turbidity and thus eliminate the mostly harmful substances that cause it. However, these have some disadvantages, such as cost and availability, so increasingly natural plant-based flocculants are coming into focus and are considered as an alternative option. In this study, Moringa seeds (Moringa oleifera) and cactus cladodes (Opuntia ficus-indica) were investigated as innovative and environmentally friendly flocculants for water treatment. The parameters investigated included absolute turbidity reduction and flocculation activity, as well as shear strength of the resulting flocs. The flocculation experiments were conducted as simultaneous tests in beakers. Experiments were conducted using both a laboratory-prepared model suspension with an initial turbidity of approximately 139 NTU and natural surface water with an initial turbidity of approximately 136 NTU. The flocculant dosages used ranged from 100 to 300 mg/L. The results show that although Moringa seeds had the highest flocculation activity (up to 93%), the flocs were very fragile and were destroyed again even at low induced shear forces. Flocculants from cactus yielded stable flocs, but the flocculation activity (maximum at 54%) was not as high as that of Moringa. The combination of the two materials resulted in a flocculant with sufficiently high flocculation activity (76%) and stable flocs, which could withstand higher shear forces potentially induced in further treatment steps.

Enhanced remediation of fracturing flowback fluids by the combined application of a bioflocculant/biosurfactant-producing Bacillus sp. SS15 and its metabolites.

Fracturing flowback fluids (FFFs), which is generated from the process of oil and gas exploitation, is one of the major environmental concerns. In this study, a bacterial strain, Bacillus sp. SS15, capable of producing both bioflocculant (BF) and biosurfactant (BS), was isolated from oil-contaminated mudflat sediment. The BS produced by SS15 was identified as lipopeptide, which could reduce the surface tension of water from 74.2mN/m to 36.6mN/m with a critical micelle concentration of 44.4mg/L. It also exhibited strong tolerance against a wide range of pH (2-12), temperature (4-60°C), and salinity (0-100g/L). Meanwhile, the BF produced by SS15 exhibited high flocculating activity (84.9%) for kaolin suspension, and was confirmed to be thermostable, salt-tolerant, and alkaliphilic. The combined treatment of bioremediation (introducing SS15 and BS) followed by flocculation (introducing BF) greatly promoted the removal of chroma (85.7% reduction), suspended solids (94.4% reduction), chemical oxygen demand (84.9% reduction), n-alkanes (50.0% reduction), and polycyclic aromatic hydrocarbons (66.5% reduction), respectively. The genome analysis showed that strain SS15 possessed abundant genes related to the synthesis of carbohydrate, protein, and lipid, which might play an important role in BF and BS synthesis. The findings in this study demonstrated that Bacillus sp. SS15 has promising prospect in the remediation of FFFs.

Properties of bioflocculant-producing bacteria for high flocculating activity efficiency

A good bioflocculant-producing bacteria (BPB) was isolated from water sample collected from river sediment. This BPB was identified as Bacillus velezensis isolate JB7 based on 16S rDNA gene sequence and demonstrated maximum flocculating activity of 92.3% toward kaolin suspension compared to other 34 isolates. This isolate JB7 had a circular shape with an undulate colony edge, a smooth surface and creamy colour and it showed catalase-positive and oxidase-positive for biochemical characteristic. Scanning electron microscopy revealed morphological surface of isolated JB7 was rod-shaped structures. Energy dispersion X-ray indicated isolate JB7 contained higher contents of C (50.3 wt%) and O (29 wt%), lower levels of P (12.1 wt%) and Na (8.6 wt%). The effective BPB obtained from this study might play a significant role in increasing the flocculation performance and would be an alternative to the use of chemical flocculants for water and wastewater treatment.

Promotion effect of bacteria in phycosphere on flocculation activity of Aspergillus niger on Synechocystis biomass

The cyanobacterium Synechocystis with high scientific research value and application potential to aquaculture is hard to harvest its biomass. Bioflocculation is an economical and efficient method for harvesting microalgal biomass. In this study, Aspergillus niger 7806F3, a fungus that showed high flocculation activity on Synechocystis cells, was selected to assess its potential for the harvest of microalgal biomass. The analyses of flocculation activity and flocculation mechanism indicated that mycelial pellets of Aspergillus niger 7806F3 exhibited high flocculation activity on Synechocystis biomass through charge neutralization mechanism, and proteins of mycelial pellets participated in the flocculation activity. The flocculation activity of strain 7806F3 on aseptic algal culture indicated that bacteria in the phycosphere can promote the flocculation effect of strain 7806F3 on algal cells. Bacterial community analysis indicated that the addition of mycelial pellets changed the bacterial community diversity in the Synechocystis phycosphere, increasing the abundance of genus Pseudomonas in the phycosphere. Finally, Pseudomonas sp. Algal4 was isolated from the Synechocystis phycosphere and confirmed with the ability to promote the flocculation activity of strain 7806F3 on Synechocystis cells. This study not only provides a method to harvest Synechocystis biomass, but also confirms the promotion effect of bacteria in phycosphere on flocculation activity, which provided a new understanding for the interaction between the algae and bacteria in the phycosphere.

Algicidal activity of Aspergillus niger induced by calcium ion as signal molecule on Microcystis aeruginosa

Cyanobacterial blooms pose great threats to water environment safety and human health due to the release of microcystins, and flocculation is an effective way to control cyanobacterial blooms. In this study, Aspergillus niger 7806F3 exhibited high flocculation activity on Microcystis aeruginosa species, and the addition of calcium ion could cause lysis of algal cells. Meanwhile, the combined effect of strain 7806F3 and calcium ion was conducive to reducing extracellular microcystins. The supernatant of strain 7806F3 induced by calcium ion possessed algicidal activity, which could be inhibited by calcium/calmodulin dependent protein kinase (CaMK) inhibitor, suggesting that calcium ion, as signal molecules, can activate CaMK activity, thus regulating a series of algicidal activities. The disturbance induced by 7806F3 and calcium ion on the bacterial community was not obvious, which indicated that the algicidal activity of Aspergillus niger induced by calcium ion cannot significantly affect the bacterial community dynamics. All these results confirm for the first time that calcium ion, as signal molecules, induce the algicidal activity of Aspergillus niger, which can provide a novel choice for controlling cyanobacterial blooms.

Soluble microbial products from the white-rot fungus Phanerochaete chrysosporium as the bioflocculant for municipal wastewater treatment.

Soluble microbial products (SMP), a type of polymers released from microbial metabolism and decay, show great potential for wastewater treatment as bioflocculants; however, biogenic flocculant utilization is currently limited to bacterial SMP. In this study, SMP produced by Phanerochaete chrysosporium BKMF-1767 (SMP-P) was investigated to determine the application potential of fungal SMP. SMP-P exhibited high flocculation activity in kaolin suspension at a dosage range of 0.67-0.84mg/L with Ca2+ assistance, comparable to that of commercial polyacrylamide. The high molecular weight polysaccharides (2.0×106-4.7×107Da) in SMP-P, which enabled flocculation via the bridging mechanism and served as the dominant active constituent, were composed of glucose and arabinose at a molar ratio of 1: 0.03, with (1→4, 6)-linked glucose as the main backbone and a small proportion of branched structures. They contained hydroxyl and carboxyl, effective functional groups for the flocculation process, and displayed parallel self-orientation behavior in water. Efficient chemical oxygen demand removal was achieved during municipal wastewater treatment using SMP-P as the bioflocculant. This study demonstrates the feasibility of utilizing fugal SMP as bioflocculants and provides guidance for their practical application.

Rapid Production of a Novel Al(III) Dependent Bioflocculant Isolated From Raoultella ornithinolytica 160-1 and Its Application Combined With Inorganic Salts.

An efficient bioflocculant-producing strain, Raoultella ornithinolytica 160-1, was identified by 16S rRNA and mass spectrometry analyses. Rapid production of bioflocculant EPS-160 was obtained with 10.01 g/(L⋅d) after optimized by response surface methodology. With the aid of Al(III), more than 90% flocculation activity of EPS-160 at 8 mg/L dosage was achieved in 5 min. Thus, this novel Al(III) dependent bioflocculant was used in combined with chemical coagulants AlCl3 to remove kaolin suspensions and wastewater treatment. The results indicated that the addition of EPS-160 in aggregation system not only largely improved the flocculation ability than the individual use of chemical flocculant (over 30 percent), but also overcome the decrease of flocculation activity due to the overdose of AlCl3 and maintained the optimum dosage of AlCl3 in a wide range (11–23 mg/L). The zeta potentials and EPS-160 structure indicated that both charge neutralization and bridging were the flocculation mechanism with kaolin. During the wastewater treatment, this composite flocculants consisted of EPS-160 and AlCl3 also had great performance for turbidity elimination. Moreover, with the properties of high flocculation activity, hyperthermal stability, pH tolerance and non-toxicity, EPS-160 shows great potential applications.

Biosynthesis of bioflocculant passivated copper nanoparticles, characterization and application

There has been great progress in the ‘green’ chemistry approach for the synthesis of nanoparticles in recent years. Nanoparticles have gained special significance due to their unique properties. Herein we report a bioflocculant facilitated eco-friendly synthesis of copper nanoparticles (CuNPs). The copper nanoparticles were successfully synthesized through the reduction of copper sulphate (3 mM) solution by the bioflocculant (0.5 g). The synthesized nanoparticles were characterized by Scanning electron microscope equipped with elementary detector (SEM), X-ray diffractometer (XRD), Fourier Transform Infrared Spectrophotometer (FT-IR), Transmission electron microscopy (TEM), and UV spectroscope. CuNPs were applied in the treatment of both the domestic and industrial wastewater, removal of dyes and were confirmed for the antimicrobial effect against both Gram-negative and Gram-positive microorganisms. The synthesized nanoparticles showed great potential for industrial application when compared to the chemical flocculant. In comparison to FeCl3 and bioflocculant, the nanoparticles were found to be effective in BOD and COD removal in coalmine wastewater samples. The highest flocculating activity and removal efficiency was observed at the lowest dosage of 0.2 mg/mL. Moreover, both the Minimal inhibitory concentration (MIC) and Minimal bactericidal concentration (MBC) were observed at the concertation of 12.5 μL.

Using a novel polysaccharide BM2 produced by Bacillus megaterium strain PL8 as an efficient bioflocculant for wastewater treatment

In this study, the purification and characterization of a novel polysaccharide-based bioflocculant BM2 produced by a bacterium Bacillus megaterium strain PL8 with self-flocculating property were investigated. The results showed that BM2 was an acidic polysaccharide composed of Gal, GalUA, Glc, GlcUA and Man at a molar ratio of 45.1: 33.8:9.3:9.2:2.4, respectively. The molecular weight of BM2 was 4.55 × 106 Da. BM2 had high flocculation efficiencies across a wide pH ranged from 4 to 11 and a wide temperature ranged from 20 to 100 °C towards kaolin clay. BM2 was a cation-independent bioflocculant which could achieve high flocculation activity without the addition of other cations. Adsorption bridging was the main mechanism in the flocculation process of BM2 towards kaolin clay. The BM2 also displayed a high removal efficiency in terms of Congo red (88.14%) and Pb2+ ions (82.64%). These results suggested that BM2 had a great potential as an efficient bioflocculant candidate in wastewater treatment.

Influence of activated sludge derived-extracellular polymeric substance (ASD-EPS) as bio-flocculation of microalgae for biofuel recovery

Microalgae have great potential as an alternative feedstock for high-valued biofuel due to rapid growth and high lipid content. However, the harvesting process, which usually accounts for about 20–30% of total production cost, is a bottleneck in microalgal biofuel technology. This study characterizes the bio-flocculants potential of activated sludge derived-extracellular polymeric substance (ASD-EPS) for microalgae harvesting. The efficiency of two physical (thermal, sonication) and one chemical (NaOH) extracted EPS was compared to a control (i.e., without flocculant). The enhancement of flocculation activity of microalgae is closely related to the carbohydrate concentration of EPS. Thermal extracted EPS contains the highest carbohydrate and protein concentration. In contrast, the chemical protocol led to the extraction of a large amount of inorganic matter, and reduction in the lipid composition of the microalgal cell membrane. Thermal extraction is the most suitable protocol with the highest biomass (microalgae) recovery of up to 87.24% and is least harmful to the lipid composition of the cell membrane. Among the tested three algae strains, Chlorellavulgaris is an ideal candidate showing high flocculation activity with ASD-EPS and large lipid production.

Microalgal interstrains differences in algal-bacterial biofloc formation during liquid digestate treatment

In this study, the effect of microalgal strains on the formation of algal-bacterial biofloc was investigated in liquid digestate pretreated by a sequencing batch reactor (SBR), which loaded much aerobic bacteria from activated sludge. Six microalgal strains resulted in three cases: no-bioflocculation (Scenedesmus obliquus and Botryococcus braunii), optimal-bioflocculation with high flocculation activity and good growth (Chlorella sp. BWY-1, Haematococcus pluvialis and Dictyosphaerium ehnenbergianum) and over-bioflocculation with high flocculation activity and bad growth (Chlorella vulgaris). Chlorella sp. BWY-1 provided a better level of flocculation activity and growth. Polysaccharides and proteins were present in EPS of algal-bacterial biofloc, and their distribution was confirmed by staining with alcian blue and fluorescein isothiocyanate (FITC).

Comprehensive study of the ecological potential of aboriginal microorganisms in the Arctic region

As a result of the conducted research, the chemical composition of bioflocculant-producing microorganisms’ habitats was determined, which was characterized by a low content of organic substances and a large number of ammonium salts and phosphates in the studied aquatic ecosystems. Quantitative and qualitative composition of the studied bacteriocenosis in the studied hydro-ecosystems was presented as various physiological groups of bacteria with a quantitative predominance of heterotrophic nitrifying microorganisms, the main representatives of the active sludge. The shift of the optimal C/P ratio due to the low load on the bacteriocenosis of treatment facilities led to a slower growth of microbial biomass, and as a consequence, to a decrease in the degree of wastewater treatment. To achieve the full effect is possible, improving the ability of the sludge to sedimentation, to adsorb oxidized substances inside. The cultures of bacteria Pseudomonas lundensis, Aeromonas eucrenophyla and Pseudomonas fragi, experimentally extracted from the anthropogenically invaded water pools, confirmed the correlation between the primary morphological characteristics of the bacteria’s flocculating ability and the high flocculating activity of these microorganisms, as well as the conditions of their cultivation. The developed reference nutrient environments for the cultivation of allocated strains of bacteria differed significantly in the ratio of biogens (C/N, C/P and N/P). It was noted that the growth rate of the culture largely depended on the environmental characteristics that determine the intensity of metabolic processes. The growth rates of cultures on media of different composition varied widely and were most correlated with the relative content of phosphates in the environment. Optimum concentrations of bacteria cells required to implement the bio-potential are directly dependent on the phosphorus concentration load on the microorganisms. The phosphorus concentration did not have a significant effect on the studied bacterial cultures’ flocculation, but the limiting factor was the phosphorus nature.

Characterization of Marine Bioflocculant-producing Bacteria Isolated From Biofloc of Pacific Whiteleg Shrimp, Litopenaeus vannamei Culture Ponds

Characterization of marine bioflocculant-producing bacteria isolated from bioflocs of Pacific whiteleg shrimp, Litopenaeus vannamei culture ponds was prompted to explore the bacteria that enhanced bioflocculation process in aquaculture wastewater treatment. Certain marine bacteria were potentially secreted extracellular polymeric substances (EPS) which response to the physiological stress encountered in the natural environment that can act as bioflocculants. This study aimed to identify marine bioflocculant-producing bacteria isolated from biofloc; to evaluate their flocculating activities; and to characterize their protein in EPS. Phenotypic and genotypic identification of the bacteria including morphological and molecular approaches were employed, while their flocculating activities were examined via Kaolin clay suspension method and statistically analyzed. The EPS that acted as bioflocculants were extracted using cold ethanol precipitation method. Protein concentration was determined by Bradford assay and protein profiling was finally completed with Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) method. Six species of marine bacteria known as Halomonas venusta, Bacillus cereus, Bacillus subtilis, Bacillus pumilus, Nitratireductor aquimarinus and Pseudoalteromonas sp. were successfully identified as bioflocculant-producing bacteria. The highest flocculating activity was exhibited by Bacillus cereus at 93%, while Halomonas venusta showed the lowest record at 59%. All bioflocculant -producing bacteria species showed different protein concentration that ranged between 1.377 μg/mL to 1.455 μg/mL. Several protein bands with different molecular weight that ranged between 16 kDa to 100 kDa were observed. This study revealed that all the identified bacteria species have high potential characteristics to initiate aquaculture wastewater treatment and may play important roles in bioflocculation process.

Trichosporon fermentans biomass flocculation from soybean oil refinery wastewater using bioflocculant produced from Paecilomyces sp. M2-1.

The soybean oil refinery (SOR) wastewater contains a high concentration of chemical oxygen demand (COD) and lipid, so the direct emissions of SOR wastewater will result in environmental pollution and waste of resources. Oleaginous yeast Trichosporon fermentans can consume organic materials in SOR wastewater to synthesize microbial oil, which achieves the purpose of SOR wastewater resource utilization. The effective harvesting technology of oleaginous yeasts can improve the utilization efficiency. In this study, Paecilomyces sp. M2-1 with high flocculating activity was isolated. The flocculants produced by M2-1 (MBF2-1) include 75% (w/w) polysaccharides, rely on cations, and display the flocculation percentage of above 77% in the range of pH2-11. Especially under alkaline conditions, the flocculation percentage can be kept above 97%. The results of scanning electron microscope observation and zeta potential measurements suggested that the bridging, net trapping, and sweeping were the main flocculation mechanism of MBF2-1. MBF2-1 could flocculate T. fermentans that was used to reduce the organic matter in SOR wastewater and to produce microbial oil. Under the optimum conditions, the flocculation percentage of MBF2-1 against T. fermentans from SOR wastewater can reach 95%. Fatty acid content percent in microbial oil from T. fermentans was not almost affected by flocculation of MBF2-1. Moreover, MBF2-1 can further remove 55% and 53% of COD and oil content in the fermented SOR wastewater, respectively. The properties and high flocculating percentage displayed by MBF2-1 indicated its potential application prospect in oleaginous yeast harvest and food industry wastewater treatment.

Production of a Biopolymer By Using Hydrolyzate of Rice Stover and Its Application in Sludge Dewatering

The aim of this study was to harvest a biopolymer from acid hydrolyzed rice stover with phosphate salts as pH buffer, and to enhance sludge dewatering by using this biopolymer combined with chemicals. Rhodococcus erythropolis was first inoculated in 250 mL seed medium and incubated on a reciprocal shaker at 150 r min−1 and 35 °C for 24 h, and then, 2.0% (V/V) of the above inoculum was used to inoculate the cultivation medium and incubated in the same procedure to produce biopolymer. For sludge dewatering, the biopolymer was added into a 200 mL mixing chamber with 100 mL of sludge, and then the mixtures were stirred at the design agitation speed for 10 min, finally, dry solids (DS) and specific resistance to filtration (SRF) of the sludge were examined. Rhodococcus erythropolis obtained its maximum biomass (OD600) of 0.79 when 5 g L−1 K2HPO4 and 2 g L−1 KH2PO4 were presented in cultivation medium. The fermented broth from the medium with phosphate salts appeared high flocculating activity of 94.6%, higher than that from the phosphate-free medium. Meanwhile, the biopolymer performed a great potential in sludge dewatering, after treated by this biopolymer, DS and SRF of the sludge reached 18.4% and 4.8 × 1012 m kg−1, respectively. Sludge dewatering was further enhanced when the biopolymer and polyaluminum chloride (PAC) were used simultaneously, under the optimal sludge treatment conditions of biopolymer of 13.5 g kg−1, PAC of 19.4 g kg−1, and pH of 8.1, sludge SRF decreased by 73.5% and DS increased to 24.1%, respectively. It is meaningful to enhance the dewatering of the sludge by the composite use of the biopolymer and PAC.

CHARACTERIZATION OF BIOFLOCCULANT-PRODUCING BACTERIA ISOLATED IN VIETNAM FOR HARVESTING OF INDIGENOUS MICROALGAE

Bioflocculation producing bacteria isolated from soil and sediment in Da Lat City, Lam Dong Province, Vietnam, were characterized. Four bacterial strains that had high flocculation activity were Flavobacterium granuli CL, Hydrogenophaga pseudoflava DA, Alcaligenes cupidus PT2, Bacillus mucilaginosus PT3, with the flocculation efficiency of 91.37%, 83.12%, 76.92%, and 75.81%, respectively at 22°C, pH 10, the initial algae concentration (optical density at 690nm) of 1.25, and grown in media containing glucose as the carbon source. The bioflocculation efficiency was depended on the pH, carbon sources, the initial algae concentrations, bacteria strains, and the inital bioflocculant-producing bacteria concentrations. The temperature lightly affected the bioflocculation, no noticeable behavioral or activity changes were observed in mice that were orally administrated with four bacterial strains, and no treatment-related illness or death occurred after 72 hours. In general, the bioflocculation process is easy to operate, cost-effective, environment-friendly and therefore, it can be applied for industrial processing of microalgae.