Production of a novel bioflocculant by fed-batch culture of Citrobacter sp.

Production of a novel bioflocculant by a fed-batch culture of Citrobacter sp. TKF04 was investigated using acetic acid as a sole carbon source. Synthesis of the bioflocculant was favored by dissolved O₂ tension at 20% of air saturation and C/N ratio (mol acetic acid/mol ammonium) of 10:1 in the feed solution. Under optimal conditions, 4.6 g crude bioflocculant per liter broth was produced, whose flocculating activity was 22 300 units. This activity was 9 times higher than that of the control (only acetic acid was supplied).     

Harvesting of Chlorella vulgaris using a bioflocculant from Paenibacillus sp. AM49

Microbial flocculants for harvesting mass cultured Chlorella vulgaris were screened and that from Paenibacillussp. AM49 was identified as the best. The flocculation efficiency of this bioflocculant increased with the pH within a range of pH 5–11 and was 83%, which was higher than the 72% and 78% produced by aluminum sulfate and polyacrylamide, respectively. The highest flocculation efficiency was with 6.8 mm CaCl₂ as co-flocculant. The bioflocculant from Paenibacillussp. AM49 can be used effectively to harvest C. vulgaris from large-scale cultures.     

Characterization and application of bioflocculant prepared by Rhodococcus erythropolis using sludge and livestock wastewater as cheap culture media

A new bioflocculant was produced by culturing Rhodococcus erythropolis in a cheap medium. When culture pH was 7.0, inoculum size was 2 % (v/v), Na₂HPO₄ concentration was 0.5 g L^?1, and the ratio of sludge/livestock wastewater was 7:1 (v/v), a maximum flocculating rate of 87.6 % could be achieved. Among 13 different kinds of pretreatments for sludge, the optimal one was the thermal-alkaline pretreatment. Different from a bioflocculant produced in a standard medium, this bioflocculant was effective over a wide pH range from 2 to 12 with flocculating rates higher than 98 %. Approximately, 1.6 g L^?1 of crude bioflocculant could be harvested using cold ethanol for extraction. This bioflocculant showed color removal rates up to 80 % when applied to direct and disperse dye solutions, but only 23.0 % for reactive dye solutions. Infrared spectrum showed that the bioflocculant contained functional groups such as –OH, –NH₂, and –CONH₂. Components in the bioflocculant consisted of 91.2 % of polysaccharides, 7.6 % of proteins, and 1.2 % of DNA. When the bioflocculant and copper sulfate (CuSO₄) were used together for decolorization in actual dye wastewater, the optimum decolorization conditions were specified by the response surface methodology as pH 11, bioflocculant dosage of 40 mg/L, and CuSO₄ 80 mg/L, under which a decolorization rate of 93.9 % could be reached.     

Purification and Characterization of Lipid Bioflocculant Produced by Rhodococcus erythropolis

The bioflocculant produced by Rhodococcus erythropolis S-1 was found to exist as huge assemblies, the molecular mass of which is over one million daltons, composed of many polypeptides and lipids in aqueous solution. We have isolated and purified this lipid bioflocculant by ultracentrifugation, extracting with 90% acetone, and two successive silica gel chromatographies from the culture broth. It was homogeneous on silica gel thin-layer chromatography. ¹H-NMR and HPLC studies showed that it was a kind of glycolipid that contained a C₁₆ methylene chain on the average and glucose in its chemical structure. The flocculating activity against kaolin clay suspension was dependent on the Ca²⁺ concentration.     

The production of bioflocculants by Bacillus licheniformis using molasses and its application in the sugarcane industry

A bioflocculant produced by B. licheniformis was investigated with regard to a low-cost culture medium and its industrial application. Molasses replaced sucrose as the sole carbon source in bioflocculant fermentation. The optimum low-cost culture medium was determined to be composed of 20 g/L molasses, 0.4 g/L urea, 0.4 g/L NaCl, 0.2 g/L KH₂PO₄, 1.6 g/L K₂HPO₄, and 0.2 g/L MgSO₄. The bioflocculant from B. licheniformis was then applied to treat sugarcane-neutralizing juice to remove colloids, suspended particles, and coloring matters in a sugar refinery factory. The optimal operation conditions were a bioflocculant dosage of 21 U/mL, pH 7.3 and a heating temperature of 100°C. The color and turbidity of the sugarcane juice reached IU 1267 and IU 206, respectively, after clarification with the bioflocculant; these values were almost the same as those acquired following treatment with polyacrylamide (PAM), the most widely applied flocculant in sugar industries. These results suggest the great potential for use of bioflocculants in the sugar refinery process.     

Evaluation of the flocculation potential and characterization of bioflocculant produced by Micrococcus sp. Leo

Bioflocculants are safe, biodegradable and environmentally friendly biopolymeric materials. These merits portend it as preferred alternative to inorganic and organic synthetic polymeric flocculants. The culture conditions optimal for the production of bioflocculant by Micrococcus sp. Leo with subsequent evaluation of the properties of the produced compound were investigated. Optimum culture conditions for bioflocculant production included 2% (vol/vol) inoculum size, incubation temperature of 28°C, agitation speed of 160 rpm and initial pH of 4.0. Glucose and (NH₄)₂SO₄ and Al³⁺ were the best as sole carbon, nitrogen and cation sources, respectively. The purified bioflocculant flocculated kaolin suspension optimally at a dosage of 0.2 mg/mL following jar test, and flocculating activity of about 70% was retained after heat treatment of 100°C. Chemical analysis showed that the bioflocculant was composed of 28.4% polysaccharide, 2.6% protein and 9.7%. uronic acid. Thermogravimetric analysis demonstrated that the bioflocculant could not decompose completely at 400°C. FTIR spectra revealed the presence of hydroxyl, carboxyl and amino groups as the main functional groups. The bioflocculant produced by Micrococcus sp. Leo appears to hold promise as an alternative to conventional flocculants commonly used in water/wastewater treatment.     

Characterization and flocculating properties of a novel bioflocculant produced by <Emphasis Type="Italic">Bacillus circulans</Emphasis>

We studied a novel bioflocculant, PX, that is produced from Bacillus Bacillus circulans X3, and has excellent flocculating activity with regard to its characterization and flocculating properties. The bioflocculant was purified from supernatant by ethanol precipitation, dialysis and gel permeation chromatography (GPC). The major component of PX was an acid polysaccharide including uronic (19.8%), pyruvic (6.5%) and acetic acids (0.7%). It consisted of galactose, mannose, xylitol, rhamnose and galacturonic acid in an approximate molar ration of 5:4.1:3:2:1.2. The molecular weight of PX was about 4.85 × 10⁴ Da as determined by GPC. The infrared spectrum of the bioflocculant indicated the presence of carboxyl, hydroxyl, amino and methoxyl groups. Studies of the flocculating properties revealed that it was stable at 60–100°C and pH 4–10. Moreover, it could flocculate a kaolin suspension over a wide range of pH and temperature in the presence of CaCl₂.     

Characterization and flocculation properties of biopolymeric flocculant (glycosaminoglycan) produced by Cellulomonas sp. Okoh

Aims

Bioflocculant production potential of an actinobacteria isolated from a freshwater environment was evaluated and the bioflocculant characterized.

Methods and Results

16S rDNA nucleotide sequence and BLAST analysis was used to identify the actinobacteria and fermentation conditions, and nutritional requirements were evaluated for optimal bioflocculant production. Chemical analyses, FTIR, 1H NMR spectrometry and SEM imaging of the purified bioflocculant were carried out. The 16S rDNA nucleotide sequences showed 93% similarities to three Cellulomonas species (strain 794, Cellulomonas flavigena DSM 20109 and Cellulomonas flavigena NCIMB 8073), and the sequences was deposited in GenBank as Cellulomonas sp. Okoh (accession number HQ537132 ). Bioflocculant was optimally produced at an initial pH 7, incubation temperature 30°C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 1·5 × 10⁸ cfu ml^?1. Glucose (88·09% flocculating activity; yield: 4·04 ± 0·33 g l^?1), (NH₄)₂NO₃ (82·74% flocculating activity; yield: 4·47 ± 0·55 g l^?1) and MgCl₂ (90·40% flocculating activity; yield: 4·41 g l^?1) were the preferred nutritional source. Bioflocculant chemical analyses showed carbohydrate, protein and uronic acids in the proportion of 28·9, 19·3 and 18·7% in CPB and 31·4, 18·7 and 32·1% in PPB, respectively. FTIR and 1H NMR indicated the presence of carboxyl, hydroxyl and amino groups amongst others typical of glycosaminoglycan. SEM imaging revealed horizontal pleats of membranous sheets closely packed.

Conclusion

Cellulomonas sp. produces bioflocculant predominantly composed of glycosaminoglycan polysaccharides with high flocculation activity.

Significance and Impact of the Study

High flocculation activity suggests suitability for industrial applications; hence, it may serve to replace the hazardous flocculant used in water treatment.     

Study on the flocculability of the Arthrobacter sp., an actinomycete resuscitated from the VBNC state

A bioflocculant with high flocculating activity, LC13-SF, produced by strain LC13^T which was in a viable but nonculturable (VBNC) state, and which was woken up by Rpf (resuscitation promoting factor), was systematically investigated with regard to its fermentation conditions and flocculating activity. The key parameters influencing the bioflocculant LC13-SF were investigated through measuring the optical density at 660 (OD₆₆₀) of the fermentation liquid and the optical density at 550 (OD₅₅₀) of the centrifugal supernatant. The flocculating efficiency and the Zeta potentials were chosen as the response variables for the study of the flocculating activity. The results showed that the optimal conditions for bioflocculant LC13-SF production were a fermentation time of 72 h, an initial pH of 7.0, a fermentation temperature of 30°C and a shaking speed of 150 r/min. The optimized flocculating process was as follows: a final volume percentage of bioflocculant LC13-SF and 0.5% (w/w) CaCl₂ were 1.5 and 5%, respectively in a 4 g/L Kaolin suspension, and the system pH was adjusted to 8.0. Under these conditions, the flocculating efficiency and the absolute value of the Zeta potential reached 94.83% and 4.37, respectively.     

Simultaneous production of hydrogen and bioflocculant by Enterobacter sp. BY-29

Hydrogen and a bioflocculant could be produced simultaneously by anaerobic culture of Enterobacter sp. BY-29. For production of hydrogen and the bioflocculant by cell culture of the bacterium in batch cultures, cultivation at 37 °C in a medium containing glucose as a carbon source and Polypepton as a nitrogen source was found to be suitable. In continuous production of hydrogen and the bioflocculant by cell culture or immobilized cells of the bacterium, the hydrogen production rate and hydrogen yield by the immobilized cells on porous glass beads in stirred and column reactors were higher than those by the cell culture in a stirred reactor. However, production of the bioflocculant by the cell culture was superior to that by the immobilized cells in continuous production.     

Novel bioflocculant produced by salt-tolerant,alkaliphilic strain Oceanobacillus polygoni HG6 and its application in tannery wastewater treatment

The optimized production of MBF-HG6, which is a novel salt-tolerant alkaliphilic bioflocculant produced by Oceanobacillus polygoni with its application in tannery wastewater treatment was investigated in this study. It was found the optimal carbon source, nitrogen source, cation, and initial pH of the medium for bioflocculant production were starch, urea, Fe²⁺, and pH 9.0, respectively. The best stability in the temperature range was from 0 to 80°C and the purified MBF-HG6 contained polysaccharides of 81.53% and proteins of 9.98%. The carboxyl, hydroxyl, and amino groups were determined in bioflocculants, while the optimized bioflocculating activity was observed as 90.25% for the dosages of 6.96mL MBF-HG6, 4.77mL CaCl₂ (1%, m/v), and 19.24g/L NaCl using response surface methodology. In addition, SS and turbidity removal rates of the tannery wastewater (4g/L MBF-HG6) could, respectively, reach 46.49% and 91.08%, indicating that the great potential was emerged in enhancement of tannery wastewater treatment by MBF-HG6.     

Production of a Bioflocculant by Rhodococcus erythropolis S-1 Grown on Alcohols

Rhodococcus erythropolis strain S-1, which was isolated from soil, produces a bioflocculant. We have found that alcohols are useful carbon sources for its flocculant production. Ethanol was best for flocculant production and culture time. The bioflocculant produced on ethanol medium flocculated a wide range of suspended soils, alkaline and acid.     

Production of a novel bioflocculant MNXY1 by Klebsiella pneumoniae strain NY1 and application in precipitation of cyanobacteria and municipal wastewater treatment

Aims: To isolate and characterize the novel bioflocculant‐producing bacteria, to optimize the bioflocculant production and to evaluate its potential applications. Methods and Results: Klebsiella pneumoniae strain NY1, a bacterium that produces a novel bioflocculant (MNXY1), was selected on the chemically defined media. It was classified according to the 16S rRNA gene sequence, morphological and microscopic characteristics. MNXY1 was characterized to contain 26% protein and 66% total sugar. The constituent sugar monomers of MNXY1, revealed by NMR analysis, are glucose, galactose and quinovose. Favourable culture conditions for MNXY1 production were determined. Strain NY1 produces a high level (14.9 g l^?1) of MNXY1. MNXY1 is thermostable and tolerant to the extreme pH. It precipitated 54% of cyanobacteria from laboratory culture and 72% of the total suspended solids from raw wastewater. Conclusions: Strain NY1 was identified to produce a novel bioflocculant MNXY1. The outstanding performance of MNXY1 in practical applications and its availability in copious amounts make it attractive for further investigation and development for industrial scale applications. Significance and Impact of the Study: This is first report for the identification of a quinovose‐containing bioflocculant and application of a protein–polysaccharide complex bioflocculant in precipitation of cyanobacteria. These findings suggest that MNXY1 holds great potential for use in management of harmful algae and city wastewater treatment.     

Production of a novel bioflocculant by Bacilluslicheniformis X14 and its application to low temperature drinking water treatment

A novel bioflocculant ZS-7 produced by Bacillus licheniformis X14 was investigated with regard to its synthesis and application to low temperature drinking water treatment. The effects of culture conditions including pH, carbon source, nitrogen source, temperature, inoculum size and shaking speed on ZS-7 production were studied. The purified bioflocculant was identified as a glycoprotein consisting of polysaccharide (91.5%, w/w) and protein (8.4%, w/w), with an approximate molecular weight of 6.89 × 10⁴ Da. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) indicated the presence of amino, amide, carboxyl, methoxyl and hydroxyl groups. This bioflocculant showed good flocculating performance and industrial potential for treatment of low temperature drinking water, and the maximum removal efficiencies of COD_Mn and turbidity were 61.2% and 95.6%, respectively, which were better than conventional chemical flocculants. Charge neutralization and bridging were proposed as the reasons for the enhanced performance based upon the experimental observations.     

Medium optimization for the production of a novel bioflocculant from Halomonas sp. V3a′ using response surface methodology

The novel exopolysaccharide bioflocculant HBF-3 is produced by Halomonas sp. V3a′, which is a mutant strain of the deep-sea bacterium Halomonas sp. V3a. Response surface methodology (RSM) was employed to optimize the production medium for increasing HBF-3 production. Using a Plackett–Burman experimental design to aid in the first step of optimization, edible glucose, MgSO₄·7H₂O, and NH₄Cl were found to be significant factors affecting HBF-3 production. To determine the optimal concentration of each significant variable, a central composite design was employed. Based on response surface and canonical analysis, the optimum concentrations of the critical components were obtained as follows: edible glucose, 16.14 g/l; MgSO₄·7H₂O, 2.73 g/l; and NH₄Cl, 1.97 g/l. HBF-3 production obtained by using the optimized medium was 4.52 g/l, which was in close agreement with the predicted value of 4.55 g/l. By scaling up fermentation from flask to fermenter, HBF-3 production was further increased to 5.58 g/l.     

Phormidium J-1 bioflocculant: production and activity

Phormidium J-1, a benthic filamentous cyanobacterium, isolated from a drainage channel, was found to produce a high molecular weight polymer. This substance can flocculate bentonite particles from suspensions. At the stationary phase of growth the cells excreted this bioflocculant into the surrounding medium. Production was enhanced by reduction of the calcium content in the growth medium or by increasing its EDTA content. Above the isoelectric point (pH 3.5) the bioflocculant is negatively charged. The presence of minimal concentrations of divalent cations in the reaction mixture is required for its flocculating activity. The production of bioflocculant could be of great importance in clarification of turbid water bodies, thus allowing light penetration to the sediment/water interface. Bioflocculant production and excretion was not found in several other benthic cyanobacteria.Dedicated to Prof. Dr. H.-G. Schlegel on the occasion of his 60th birthday     

Bioflocculant production by Bacillus sp. Gilbert isolated from a marine environment in South Africa

In our previous study we reported on the bioflocculant production by a Bacillus species isolated from sediment samples of Algoa Bay in the Eastern Cape Province of South Africa. In the current study we carried out further evaluation on the effect of different culture conditions on the bioflocculant production, as well as characterised the bioflocculant produced in detail. The bacteria produced bioflocculant optimally under the following conditions: using sodium carbonate (95.2% flocculating activity) and potassium nitrate (76.6% flocculating activity) as carbon and nitrogen sources, respectively; inoculum size of 3% (v/v); initial pH 9.0; and Al³⁺ as coagulant aid. The crude bioflocculant retained 44.2% residual flocculating activity after heating at 100°C for 15 min. Chemical analysis of the Bacillus sp. Gilbert purified bioflocculant demonstrated that it was composed mainly of polysaccharide. Fourier transform infrared spectroscopy analysis revealed the presence of hydroxyl, carboxyl and methylene groups in the bioflocculant and energy-dispersive X-ray analysis detected the elemental composition in mass proportion (% w/w) of C, N, O, S and P as 4.12:7.40:39.92:3.00:13.91. Scanning electron micrograph image of the bioflocculant revealed an amorphous compound.     

Global research trends on bioflocculant potentials in wastewater remediation from 1990 to 2019 using a bibliometric approach

The preference of biofloculants over chemical flocculants in water and wastewater remediation systems has gained wider attention due to their biodegradability, innocuousness, safety to human and environmental friendliness. The present study aimed to evaluate research outputs on bioflocculant potentials in wastewater remediation from 1990 to 2019 using bibliometric analyses. To the best of our knowledge, this is the first bibliometric report in bioflocculant research. The subject bibliometric dataset was extracted from the Web of Science Core Collection (WoSCC) and Scopus using the Boolean, ‘bioflocculant* and waste*’ and analysed for indicators such as a yearly trend, productivity (authors, articles, country, institution and journal source), conceptual framework and collaboration network. We found 119 documents with 347 authors from 78 journal sources on the subject, an annual growth rate of 12·1%, and average citations/document of 15·08. Guo J. and Wang Y. were the top researchers with 15 and 12 outputs respectively. China (42%) and South Africa (9·24%) ranked the top two dominant countries in the field. The top journals were Bioresource Technology (9 papers, 506 citations), Applied Microbiology and Biotechnology (5 papers, 268 citations), whereas, the top institution was Chengdu University of Information and Technology (n = 9 documents) followed by Sichuan Univ. Sci. & Engn, China (n = 8 documents). This study found that lack of intercountry collaboration and research funding adversely affects research participants in the field.     

Bioflocculant produced by Chlamydomonas reinhardtii

Bioflocculants of Chlamydomonas reinhardtii were investigated under axenic conditions. C. reinhardtii was found to produce significant amounts of bioflocculants. Flocculating activity by C. reinhardtii began in the linear phase of growth and continued until the end of the stationary phase. The highest flocculating efficiency of the culture broth was 97.06%. The purified C. reinhardtii bioflocculant was composed of 42.1% (w/w) proteins, 48.3% carbohydrates, 8.7% lipids, and 0.01% nucleic acid. The optimum condition for bioflocculant production of C. reinhardtii was as follows: under temperature of 15°C to 25°C, pH 6–10 and illumination of 40–60 μmol photons m^?2 s^?1. The bioflocculants produced by C. reinhardtii showed maximum activity in pH ranges from 2 to 10. The flocculating activity was significantly enhanced by the addition of CaCl₂ as a co-flocculant at an optimal concentration of 4.5 mM.     

Characterization of a compound bioflocculant produced by mixed culture of <Emphasis Type="Italic">Rhizobium radiobacter</Emphasis> F2 and <Emphasis Type="Italic">Bacillus sphaeicus</Emphasis> F6

A compound bioflocculant CBF-F26, produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its physicochemical and flocculating properties. It was identified as a polysaccharide bioflocculant composed of rhamnose, mannose, glucose, and galactose, respectively, in a 1.3: 2.1: 10.0: 1.0 molar ratio. The average molecular weight was determined as 4.79 × 10⁵ Da by gel-permeation chromatography. Infrared spectrum and X-ray photoelectron spectroscopy revealed the presence of carboxyl, hydroxyl and amino groups in its structure. Thermostability test suggested that CBF-F26 was thermostable and high flocculating activity was maintained. Thermogravimetric property, intrinsic viscosity and surface morphology of CBF-F26 were also studied. CBF-F26 was effective under neutral and weak alkaline conditions (pH 7.0–9.0), and flocculating activities of higher than 90% were obtained in the concentration range of 8–24 mg l⁻¹ at pH 8.0. The flocculation could be stimulated by cations Ca²⁺, Zn²⁺, Fe²⁺, Al³⁺, and Fe³⁺. In addition, the probable flocculation mechanisms were proposed.