Screening of flocculant-producing microorganisms and flocculating activity

A strain saccharomycete STSM-1 with high flocculanting activity was isolated from activated sludge with conventional methods. The high production rate and the low cost STSM-1 medium was obtained by selecting different kinds of media, carbon source, nitrogen source and inorganic salt ion. The best flocculant-producing conditions were found by changing medium initial pH, culture temperature and ventilation flow. The best flocculating effect was obtained by changing positive ion types, density and concentration of flocculant.

Bacillus Licheniformis Dhs-40, a Flocculating Active Strain and Its Flocculating Activity

Microbial flocculants have become a hot spot in recent years. A bacterial strain with high flocculating activity was isolated from seawater samples. The strain was defined as Bacillus licheniformis dhs-40 by 16S rDNA identification and Biolog test. Ultrasonication test confirmed the flocculating activity of the strain was both in fermentation supernatant and cell. According to flocculating activity curve, the ideal fermentation time for collecting flocculating active substances was two days. The flocculating activity of the strain was sensitive to pH. The strain could only preserve flocculating activity while pH varied from 7 to 11. However, it could preserve flocculating activity while temperature varied from -20℃to 100 ℃ Saccharide, protein, lipid, nucleic acids qualitative test and RNase, Proteinase K treatment confirmed the flocculating active substances were proteins. Their flocculating activities were insensitive to Proteinase K.

Isolation and Identification of Bioflocculant Producing Stain and Analysis on Its Flocculating Characteristics

[Objective] The aim was to indentify a bioflocculatnt producing strain W5 isolated from soil samples and analyze its flocculating characteristics. [Method] The universal primers of bacterial 16S rDNA were used for PCR amplification of its genome; effects of the medium pH,carbon and nitrogen sources on its flocculating activity were analyzed by using single factor method; and infrared spectroscopy was used for functional groups analysis. [Result] The results of homology comparison showed that strain W5 belonging to Gram-negative,long bacilli and had 98.34% of homology with Hymenobacter gelipurpurascens,. In addition,the optimum carbon source,nitrogen source,pH for fermentation condition were glucose,yeast extract and pH 7.04,respectively. Microbe flocculant produced by W5 strain （MBF-W5） was extracted and purified to obtain reddish and flocculent products. Fourier-transform infrared （FTIR） spectroscopy indicated that the major functional groups of MBF-W5 were hydroxyl,carboxyl and amino. [Conclusion] More than 85% of flocculating activity was achieved under the conditions of 150-500 μl bioflocculation dosage,5-65 ℃ temperature and pH 2-10.

Flocculating Properties and Production of the Compound Bioflocculant by Rhizobium Radiobacter F2 and Bacillus Sphaeicus F6

A compound bioflocculant CBF,produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its production and flocculating properties. The optimization of the culture medium constituents including carbon source,nitrogen source and C / N ratio,metal ions and ionic strength on CBF production were studied. Flocculating properties of CBF were examined by a series of experiments and CBF had good flocculating activities in kaolin suspension with divalent cations and stable over wide range of p H. Studies of the flocculating properties revealed that the flocculation could be stimulated by cations Ca2+,Mg2+,Fe2+,Al3+and Fe3+. In addition,it was stable at 4-30 ℃ in the presence of Ca Cl2. It was found to be effective for flocculation of a kaolin suspension under neutral and weak alkaline conditions( p H 7. 0- 9. 0),and flocculating activities of higher than 95% were obtained when the CBF concentrations among 6- 14 mg / L at p H 8. 0. The results of this study indicate that CBF is a potential replacement of conventional synthetic flocculants and is widely applied in water treatment and downstream processing of food and fermentation industries.

Screening of a Novel Bioflocculant-producing Strain and Research on Its Flocculation

[Objective] This study aimed to screen a bacterial strain capable of producing bioflocculant. [Method] A bacterial strain T-11 capable of producing bioflocculant was isolated from activated sludge. Detailed tests on the morphological, physiological and biochemical characteristics were carried out and identification was performed to identify the strain. Finally, the bioflocculant was isolated and purified, and the flocculating activity and chemical characteristics were measured. [Result] It was identified as Serratia plumuthica based on its morphological, physiological and biochemical characteristics. This strain secreted flocculant best in a culture medium which included sucrose and NaNO3. The maximal cell growth was achieved within 10 h and the flocculating activity paralleled to it. It was found to be effective for flocculation of kaolin suspension, when added at a final concentration of 0.7 mg/L, over a range of pHs （2-7）, and temperature （approximately 30-80 ℃）. Chemical analysis indicated that the bioflocculant was an acidic polysaccharide consisting of glucose, glucuronic acid and galactose, talose and altrose. Infrared spectrum analysis also revealed typical characteristics of polysaccharides. [Conclusion] The biofloccu- lants produced by strain T-11 can greatly improve the ability of activated sludge to settle.

Characterization of a bioflocculant from a newly isolated Vagococcus sp. W31

Screening of microorganisms producing flocculating substances was carried out. A strain secreting a large amount of bioflocculant was isolated from wastewater samples collected from the Little Moon River in Beijing. Based on the morphological properties and 16S rDNA sequence analysis, the isolate (designated W31) was classified as Vagococcus sp. A bioflocculant (named MBFW31) produced by W31 was extracted from the culture broth by ethanol precipitation and purified by gel chroma-tography. MBFW31 was heat-stable and had strong flocculating activity in a wide range of pH with relatively low dosage re-quirement. MBFW31 was identified as a polysaccharide with molecular weight over 2×106. It contained neutral sugar and uronic acid as its major and minor components, respectively. Infrared spectra showed the presence of hydroxyl, carboxyl and methoxyl group in its molecules. The present results suggested that MBFW31 had potential application in wastewater treatment.

Characteristics and Culture Conditions of a Bioflocculant Produced by Penicillium sp.

Objective To study the characteristics of a bioflocculant named MBF7 produced by Penicillum strain HHE-P7 and the effects of cultivation conditions on bioflocculant production. Methods The chemical group in the bioflocculant molecules was shown by Fourier transform infrared （FTIR） spectra, and the average molecular weight of MBF7 was estimated by gel permeation chromatography. The effects of medium components on bioflocculant production and flocculating activity were studied. Results Phospho-, amino-, hydroxyl, and carboxyl groups were the major fractions of MBF7, and the molecule weight was about 3.0 × 10^5 Da. In addition, the carbon and nitrogen sources favorable for the bioflocculant production were glucose and yeast extract respectively. When the initial pH of the medium was adjusted to 5.0, high flocculant efficiency could be achieved. Conclusion The bioflocculant MBF7 is a new macromolecule with high flocculating efficiency for Kaolin suspension, and could be produced under appropriate culture conditions.

Studies on Bioflocculant Production by Pseudoalteromonas sp. NUM8, a Marine Bacteria Isolated from the Circulating Seawater

A bioflocculant producing potential bacteria was isolated from the circulating seawater of bio-filter using streak plate methods.The bacteria was identified through biochemical characteristics,partial 16S ribosomal ribonucleic acids(rRNA),nucleo-tide sequencing,and BLAST analysis of the gene sequence that showed the bacteria have 99%similarity to Pseudoalteromonas sp.and deposited in GenBank as Pseudoalteromonas sp.NUM8 with accession number JX435820.Influences of time course assay,carbon sources,nitrogen sources,inoculum size,as well as initial pH on the bacteria producing extracellular bioflocculant activity were investigated.The results showed that the strain optimal production period of microbial bioflocculant was at 72 h(flocculating activity of 94.5%),then dropped slowly.The bacteria optimally produced the bioflocculant when 1.0%sucrose and 0.5%sodium nitrate were used as sole sources of carbon and nitrogen with flocculating activities of 92.8%and 93.8%respectively.Also,the bacteria produced the bioflocculant optimally when initial pH of the medium was 5.0(flocculating activity 93.2%),and when Ca^(2+)was used as cation(flocculating activity 93.4%).The culture condition of inoculum size of 3%(v/v)was optimal flocculant pro-duction(flocculating activity 94.4%).Composition analyses indicated the bioflocculant to be principally a glycoprotein made up of about 34.3%protein and 63.4%total carbohydrate.

Screening of Bioflocculant-Producing Strains and Characteristics of Microbial Flocculation

A high effective bioflocculant-producing strain named LB1 was isolated and screened from the leachate by routine micro- method. The strain was identified as genus Pseudomonas according to the morphologic and physiological-biochemical characteristics of the strain. The biological characteristics of the microbial flocculants produced by LB1 were investigated. The results show that the optimal production period of microbial flocculant using LB1 is 96 h; and the products, found in the fermentation liquor, comprise the extracellular organic matter （EOM） of LB1 generated during LB1 growth and the secondary metabolites in the anaphase of LB1. Meanwhile, the mycelia can improve the performance of the microbial flocculants. Because heat has a greater influence on the active substance in the microbial flocculants than other factors, the activity of the flocculants decreases with increasing temperature and the time of heating. The flocculants can flocculate mud-containing and melanin-containing wastewater effectively with a flocculation ratio of 85.1% and 92.2%, respectively. The optimal heating temperature varies from 20 to 45 ℃. When flocculating the two wastewater, the flocculating activity of the flocculants is above 57.7% and 70.9%, respectively, in a wide pH range from 3 to 11.

PREPARATION AND PROPERTIES OF EXTRACELLULAR BIOPOLYMER FLOCCULANT

The biopolymer flocculant （named PS-2） producing by Pseudomonas fluorescens was investigated. The PS-2 had high efficiency with small dosage, when dealing with kaolin suspension, formed larger floc, with big sedimentation rate, over a wide range of temperatures. Distributing of flocculating activity test showed that the biopolymer flocculant was an extracellular product. The composition analysis of purified biopolymer flocculant showed that it composed mainly of polysaccharide and nucleic acid. The content of polysaccharide was 86. 7%, which determined by using phenol-vitriol method, and the content of nucleic acid was 7.8%, which determined by UV absorption method. The biopolymer flocculant as a powder form showed much better stability than that as a supernatant. The character of biopolymer flocculant was stable even it was heated to 100℃ when it in acidic condition. The optimal conditions to flocculate kaolin suspension were as follows： pH 8-12, flocculant dosage lmL/L, and Ca^2＋ as the optimal cation.

The biological effect of metal ions on the granulation of aerobic granular activated sludge

As a special biofilm structure,microbial attachment is believed to play an important role in the granulation of aerobic granular activated sludge（AGAS）.This experiment was to investigate the biological effect of Ca^2＋,Mg^2＋,Cu^2＋,Fe^2＋,Zn^2＋,and K＋which are the most common ions present in biological wastewater treatment systems,on the microbial attachment of AGAS and flocculent activated sludge（FAS）,from which AGAS is always derived,in order to provide a new strategy for the rapid cultivation and stability control of AGAS.The result showed that attachment biomass of AGAS was about 300%higher than that of FAS without the addition of metal ions.Different metal ions had different effects on the process of microbial attachment.FAS and AGAS reacted differently to the metal ions as well,and in fact,AGAS was more sensitive to the metal ions.Specifically,Ca^2＋,Mg^2＋,and K＋could increase the microbial attachment ability of both AGAS and FAS under appropriate concentrations,Cu^2＋,Fe^2＋,and Zn^2＋were also beneficial to the microbial attachment of FAS at low concentrations,but Cu^2＋,Fe^2＋,and Zn^2＋greatly inhibited the attachment process of AGAS even at extremely low concentrations.In addition,the acylated homoserine lactone（AHL）-based quorum sensing system,the content of extracellular polymeric substances and the relative hydrophobicity of the sludges were greatly influenced by metal ions.As all these parameters had close relationships with the microbial attachment process,the microbial attachment may be affected by changes of these parameters.