A novel flocculant biopolymer produced by Pestalotiopsis sp. KCTC 8637P

Summary A white rot fungus was isolated from rotted leaves and identified as Pestalotiopsis sp. KCTC 8637P. It produced a flocculant biopolymer. A flocculant was partially purified from the culture broth by series of precipitations with 95% ethanol and named as Pestan. The components of Pestan were consisted of glucose : glucosamine : glucuronic acid : rhamnose with a approximately molar ratio of 100:3.5:1.6:1.3.In kaolin suspension(final concentration was 4,800 mg/l), the highest flocculating activity was attained at the biopolymer flocculant concentration of 1 mg/l . The flocculating activity was observed most highest by the addition of cationic solutions, especially 8mM CaCl₂ · 2H₂O or 8mM FeCl₃. The thermal stability of Pestan was sustained up to 70 °C.     

Flocculation properties of xanthan produced by Xanthomonas campestris

Summary Xanthan had a flocculating activity in a kaolin suspension and high flocculating activity was obtained in the suspension (pH 7.0) adding Al³⁺, Fe³⁺ or Fe²⁺. Xanthan had high flocculating activity not only in other inorganic suspensions such as active carbon and acid clay but also in organic suspensions of cellulose and yeast. From these flocculation properties, xanthan is anticipated to be utilized in wide areas as a new biodegradable, harmless biopolymer flocculant.     

Production of a biopolymer flocculant from Bacillus licheniformis and its flocculation properties

Bacillus licheniformis CCRC 12826 produced extracellularly an excellent biopolymer flocculant in a large amount when it was grown aerobically in a culture medium containing citric acid, glutamic acid and glycerol as carbon sources. The biopolymer flocculant was an extremely viscous material with a molecular weight over 2 x 10(6) by gel permeation chromatography. It could be easily purified from the culture medium by ethanol precipitation. It was shown to be a homopolymer of glutamic acid by amino acid analysis and thin layer chromatography and presumed to be poly-glutamic acid (PGA). This bioflocculant efficiently flocculated various organic and inorganic suspensions. It flocculated a suspended kaolin suspension without cations, although its flocculating activity was synergistically stimulated by the addition of bivalent or trivalent cations Ca2+, Fe3+ and Al3+. However, the synergistic effects of metal cations were most effective at neutral pH ranges. The comparison of the flocculating activity between the present biopolymer and a commercial lower molecular weight product showed that the biopolymer of the present study had much higher activity. The high productivity and versatile applications of PGA make its development as a new biodegradable, harmless, biopolymer flocculant economical and advantageous.     

Characterization of a bioflocculant produced by the marine myxobacterium Nannocystis sp. NU-2

The marine myxobacterium strain NU-2, which can grow on high concentrations (up to 7%) of NaCl, was isolated from a salt soil sample collected from the coast of the Huanghai Sea, China. Morphological properties and 16S rDNA sequence analysis indicated that the isolate is a novel species related to the genus Nannocystis. Nannocystis sp. NU-2 produced a new kind of flocculating substance in a starch medium with a yield of 14.8 g l^–1. The NU-2 flocculant was composed of 40.3% proteins and 56.5% polysaccharides, of which glucose, mannose and glucuronic acid were the principal constituents in the relative proportions of 5:4:1. The flocculation activity of the NU-2 flocculant depends strongly on cations such as Fe³⁺ and Al³⁺. When a 30 mg l^–1 FeCl₃ solution is present in kaolin clay suspension, 30 mg l^–1of the flocculant produced a high flocculating activity value of 90%, which remained unchanged over an extensive pH range (pH 2.0–13.0). The flocculant was tested for its ability to bleach dyeing liquors, and the bleaching activities were 98.2% for acid red in 100 mg l^–1of the flocculant and 99.0% for direct emerald blue in 50 mg l^–1of the flocculant under test conditions. Use of the flocculant to bleach basic pink and cation emerald blue liquors was not effective. Electronic Publication     

Characterization and flocculating properties of an extracellular biopolymer produced from a Bacillus subtilis DYU1 isolate

Biopolymer DYU500 produced from Bacillus subtilis DYU1 was found to have excellent flocculating ability. With the addition of 40 mg-DYU500/L and 50 mM CaCO₃, the optimum temperature for flocculation performance of DYU500 was 30 °C, giving the highest flocculating activity and rate of 13.5 and 97%, respectively. Analysis with Fourier transform infrared spectrophotometry (FT-IR), nuclear magnetic resonance spectrometry (NMR) and amino acid identification shows that the DYU500 biopolymer mainly possesses the structure of poly-glutamic acid (PGA). The average molecular weight of DYU500 was about (3.16–3.20) × 10⁶ Da as determined by gel permeation chromatography. The major components of biopolymer DYU500 were total sugars, uronic acids, proteins and polyamides (homopolymer of glutamic acid), accounting for a weight ratio of approximate 14.9, 2.7, 4.4 and 48.7% (w/w), respectively. The flocculating activity of DYU500 in the kaolin suspension was markedly stimulated by the addition of bivalent cations Ca²⁺ or Mg²⁺ in optimum concentration ranges of about 0.15–0.90 and 0.10–0.90 mM, respectively. The synergistic effect of cations was most effective at a weak acidic or neutral pH (6.0–7.0). The flocculating activity of DYU500 linearly decreased with an increase in incubation temperature and the activity was completely lost when heating upon 120 °C, arising from the destruction of the polyamides structure of DYU500. Moreover, mechanisms describing the flocculation process with DYU500 were proposed based on the experimental observations.     

Biopolymer flocculant produced by an Pseudomonas sp.

A biopolymer flocculant produced by Pseudomonas sp. A-99 had flocculating activity both in inorganic suspensions containing Ca2, Mg2 or Fe3 and in organic suspensions containing Fe2, Fe3 or Al3. The flocculant was an acidic protein and contained a small amount of an acidic polysaccharide consisting of galacturonic acid, glucose and galactose. Productivity of the flocculant was about 450 mg/l medium. © Rapid Science Ltd. 1998     

Biopolymer flocculant produced by an Enterobacter sp.

A new biopolymer flocculant was produced by Enterobacter sp. BY-29. Flocculating activity increased in the presence of Al , Fe or Fe . The flocculant had flocculating activity not only in inorganic suspensions of kaolin and active carbon but also in organic suspensions of cellulose and yeast. The flocculant was an acidic polysaccharide consisting of glucose, galactose, xylose and galacturonic acid, and its MW was about 2.5 ¥ 10 6 Da.     

Poly‐γ‐glutamic acid produced from Bacillus licheniformis CGMCC 2876 as a potential substitute for polyacrylamide in the sugarcane industry

As an environmentally friendly and industrially useful biopolymer, poly‐γ‐glutamic acid (γ‐PGA) from Bacillus licheniformis CGMCC 2876 was characterized by the high‐resolution mass spectrometry and ¹H NMR. A flocculating activity of 11,474.47 U mL^?1 obtained with γ‐PGA, and the effects of carbon sources, ions, and chemical properties (D‐/L‐composition and molecular weight) on the production and flocculating activity of γ‐PGA were discussed. Being a bioflocculant in the sugar refinery process, the color and turbidity of the sugarcane juice was IU 1,877.36 and IU 341.41 with 0.8 ppm of γ‐PGA, respectively, which was as good as the most widely used chemically synthesized flocculant in the sugarcane industry—polyacrylamide with 1 ppm. The γ‐PGA produced from B. licheniformis CGMCC 2876 could be a promising alternate of chemically synthesized flocculants in the sugarcane industry. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1287–1294, 2015     

Antifungal substances produced by Penicillium oxalicum strain PY-1—potential antibiotics against plant pathogenic fungi

This paper reports the isolation from soil of Penicillium strain PY-1 with strong antagonistic activity against plant pathogenic fungi. On the basis of its morphological characteristics and the sequence of the ITS region, strain PY-1 was identified as P. oxalicum. Strain PY-1 produces antifungal substances that suppress the mycelial growth of Sclerotinia sclerotiorum and many other plant pathogenic fungi tested; the highest antagonistic activity was detected at 72 h when cultured in a 250-ml flask containing 80 ml potato dextrose broth. Compared with carbendazim, the relative activity of the antifungal substances produced by strain PY-1 was approximately 4 μg active ingredient (a.i.) per milliliter. The antifungal substances were extracted with ethyl acetate and further separated by high-performance liquid chromatography (HPLC); at least two active components were discovered. The ability to control plant disease with strain PY-1 was confirmed with S. sclerotiorum, a widespread pathogenic fungus that attacks rapeseed (Brassica napus) and other plants. Spores (10⁶ or 10⁷ ml⁻¹) and filtrate (tenfold diluted or undiluted) of strain PY-1 could significantly suppress infection and/or the extent of infection by S. sclerotiorum of plants at seven-true-leaves stage. The potential of strain PY-1 for identifying new antibiotics to control fungal disease and for biological control of plant disease, for example oilseed rape stem rot, is discussed.     

一株絮凝剂产生菌的筛选及其絮凝特性研究

目的:筛选并研究对有毒物质有一定耐受性的絮凝剂产生菌。方法:利用含苯酚、邻苯二甲酸二丁酯和Pb2(SO4)3的分离培养基从土壤和活性污泥中分离筛选絮凝剂产生菌,对所得的菌种进行摇瓶发酵试验,分别考察其产絮凝剂的周期、絮凝活性分布以及对有毒物质的耐受性等特征,通过提取絮凝剂,将其絮凝活性与其它絮凝剂进行比较。结果:得到一株对苯酚具有一定耐受性的絮凝剂产生菌B2(Serratiasp.),其产絮凝剂的最佳培养时间为48h,絮凝率高于80%。苯酚浓度达0.6g/L时,B2菌的絮凝活性仍高于70%。其90%的絮凝物质集中于菌体,且热稳定性好,对多种悬浊液的絮凝活性高于硫酸铝、PAC。结论:新型絮凝剂产生菌B2对苯酚耐受性强,且絮凝剂提取简便,具有重要的研究价值。     

Characteristics and flocculating mechanism of a novel bioflocculant HBF-3 produced by deep-sea bacterium mutant Halomonas sp. V3a’

A novel bioflocculant HBF-3 produced by deep-sea bacterium mutant Halomonas sp. V3a’ was investigated with regard to its flocculating characteristics and mechanism. 4.0 m g l⁻¹ HBF-3 showed the maximum flocculating activity of 96.9% in 5.0 g l⁻¹ Kaolin suspension containing 11.25 mM CaCl₂, and that its flocculating activity was more than 90% within 5–40°C and over 80% in a wide pH range (3.0–11.0). Chemical analyses indicated that the biopolymer HBF-3 was mainly a polysaccharide, including neutral sugar residues (20.6%), uronic acid residues (7.6%), amino sugar residues (1.6%) and sulfate groups (5.3%). Fourier transform infrared (FTIR) spectrum showed the presence of carboxyl and hydroxyl groups in HBF-3 molecular. The average molecular mass of HBF-3, as determined by gel filtration chromatography (GFC), was approximately 590 kDa. Flocculation of Kaolin suspension with HBF-3 acted as a model to explore the flocculating mechanism in which bridging mediated by Ca²⁺ was proposed as the primary action based upon the experimental observations.     

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.     

Bioconversion of lignocellulose and simultaneous production of cellulase,ligninase and bioflocculants by Alcaligenes faecalis-X3

Lignocelluloses have been used as carbon sources for bioflocculant production. However, the low bioconversion efficiency of lignocellulose to bioflocculants is a major challenge. In this study, a lignocellulolytic strain of Alcaligenes faecalis-X3 was cultivated in ramie bio-degumming wastewater. Optimal production of ligninase, cellulase and bioflocculants (MBF-X3) was evaluated. The highest activity of MBF-X3 under the optimal conditions of pH 6.0 at 48 h of fermentation was 95.44%, with the maximum production of ligninase and cellulase (0.27 and 0.12 U/mL, respectively). The crude ligninase and cellulase had optimum activities at pH 5.0 and 40 °C and pH 6.0 and 50 °C, respectively. The cellulase activity was increased by Mn²⁺, Ca²⁺, Zn²⁺, and Mg²⁺ at 1 mM. The ligninase activity was significantly enhanced in the presence of Zn²⁺ at 10 mM. The flocculating activity of MBF-X3 was not changed by the addition of any metal cation. The results demonstrated that A. faecalis possesses an excellent enzyme system for the efficient bioconversion of lignocellulose into MBF-X3. Additionally, MBF-X3 has a high flocculating efficiency of Disperse Blue-2BLN (85.7%) at a dose of 1.0 g/L.     

Production and characterization of bioflocculants from bacteria isolated from wastewater treatment plant in South Africa

Bioflocculants produced by six bacteria obtained from activated sludge at a wastewater treatment plant were quantified, purified, and characterized. Effects of pH, temperature, cationic salt content, and specific potential inhibitors on the flocculating activities of the bioflocculants were also determined. Bioflocculants produced by the different bacterial isolates ranged between 6.33 and 27.66 g/L in concentration and were composed of both carbohydrate and protein in varying amounts, as well as a relatively high concentration of uronic acid. The flocculating activity of the broth culture increased during the logarithmic phase of bacterial growth with a maximum ranging from 2.395 to 3.709/OD. Optimum pH for the flocculating activity of the bioflocculants was between 8 and 9, with generally higher flocculating activity observed at 28°C. Of the cations tested, Mg²⁺ and Mn²⁺ improved flocculating activity up to 5.2 fold. The stability of these bacterial bioflocculants under various environmental and nutritional conditions suggests their possible use in the industries and environmental applications. Therefore, this study details important implications in providing a safer alternative flocculation method for wastewater treatment.     

Screening of flocculant-producing microorganisms and some characteristics of flocculants

Summary 27 strains of microorganisms including moulds, bacteria, actinomyces and yeasts, which produced substances that flocculated a kaolin clay, were screened. One strain, identified as Arthrobacter sp., secreted bioflocculant during growth. The flocculant (MF-6) was purified to electrophoretic homogeneity by precipitation with ethanol and gel chromatography. Its molecular weight was higher than 10⁶ Da. It could efficiently flocculate all suspended solids tested in aqueous solution and colored water like dye solution, and its flocculating ability was significantly enhanced by adding Ca²⁺, Mn²⁺, Mg²⁺, etc.     

Production of an exopolysaccharide bioflocculant by Sorangium cellulosum

AIMS: To isolate a new exopolysaccharide bioflocculant produced by the myxobacterium Sorangium cellulosum NUST06, and to characterize its chemical composition and expolysaccharide production relative to carbon source. METHODS AND RESULTS: Exopolysaccharide levels and biomass production by S. cellulosum NUST06 were analysed relative to carbon source. Glucose in the medium at a level of 3 g l(-1) completely inhibited cell growth and exopolysaccharide production, but low concentrations of glucose (1-2 g l(-1)) could stimulate cell utilization of starch. The chemical composition and flocculating activity of the NUST06 exopolysaccharide was investigated. The flocculant comprised 38.3% proteins and 58.5% carbohydrates, of which glucose, mannose and glucuronic acid were present at 51.3%, 39.2% and 10.5%, respectively. The flocculating activity of the NUST06 flocculant depended strongly on cations. CONCLUSIONS: It is feasible to produce an exopolysaccharide bioflocculant by the strain NUST06 in a mineral salts medium using starch as a carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: This strain may be advantageous for commercial bioflocculant production and may enrich existing knowledge of myxobacteria.     

Harvesting <Emphasis Type="Italic">Neochloris oleoabundans</Emphasis> using commercial organic flocculants

Microalgal cultures are inherently dilute, and increasing their concentration is essential for volume reduction and further processing. Flocculation is a classical operation in water treatment that is also used as a concentration step in microalgal biotechnology. However, flocculation is highly dependent on the physicochemical characteristics of the system, such as cell charge and concentration, pH, and solutes in the system, and the coagulant or flocculant to be used. This paper describes the efficiency of nine flocculating agents applied to Neochloris oleoabundans flocculation: low molecular weight chitosan; Zetag® 8165, 8185, 7652, and 4120; Magnafloc® LT22 and 351; and Tanfloc® SG and SH. The influence of flocculant concentration (from 3 to 16 mg L^?1) and pH (from 6 to 10) was evaluated, showing a small influence of pH and a large influence of the type and concentration of flocculating agent. These effects are discussed regarding the flocculant charge and the zeta potential of the cells. The best flocculants were Zetag® 8185, Zetag® 8165, and chitosan, with floc sedimentation efficiencies higher than 95%. These flocculants were further evaluated for their efficiency in various concentrations at the native pH of N. oleoabundans cultures, with good efficiency.

Open image in new window

Graphical abstract ?

     

Harvesting the microalgae Phaeodactylum tricornutum with polyaluminum chloride, aluminium sulphate, chitosan and alkalinity-induced flocculation

The purpose of this study was to explore efficient methods of harvesting the microalga Phaeodactylum tricornutum. Natural sedimentation experiments, performed at different light and temperature conditions, did not yield significant improvements in efficiency even after 1?week. When alkalinity-induced flocculation was performed, both the flocculation efficiency and the concentration factor dramatically improved at pH?=?9.75 (0.5–0.7 units over the original pH of the culture) after 10?min settling time. Sedimentation rates are documented at pH ranging between pH?9.75 and 11.0. The results of the application of two conventional flocculants used in wastewater treatment, polyaluminium chloride and aluminium sulphate, are also presented. Chitosan was also used as a natural flocculating agent to improve possible contamination problems in the downstream process. pH was adjusted in order to determine optimum flocculation efficiency of chitosan in combination with a high concentration factor. Satisfactory results were found with chitosan at an adjusted pH of 9.9 using concentrations as low as 20?mg?L^?1, after testing a flocculant range of 5–200?mg?L^?1.     

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.     

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.