Characterization of an extracellular flocculating substance produced by a planktonic cyanobacterium, Anabaena sp.

Two planktonic cyanobacteria, Anabaena sp. N1444 and Anabaena sp. PC-1, and a green eukaryotic alga, Scene-desmus sp., produced extracellular flocculants. The flocculant of Anabaena PC-1, when purified, was found to be a macromolecular polysaccharide consisting of neutral sugars, uronic acids, and proteins, but not keto acids, hexosamines nor fatty acids. The flocculant bound a cationic dye, Alcian Blue, indicating it to be polyanionic. The flocculating activity was high under acidic conditions, slightly enhanced by the addition of salts and metals, and increased to about 40% upon heating at 100 °C for 7 min. The flocculant could flocculated various inorganic and organic compounds in solution. © Rapid Science Ltd. 1998     

黄孢原毛平革菌产絮凝剂营养条件优化

微生物絮凝剂与传统化学絮凝剂相比,安全无毒、无二次污染,具有开发潜力.黄孢原毛平革菌(Phanerochaete chrysosporium)能产生微生物絮凝剂,但目前缺少对其产絮凝剂营养条件的优化.使用高岭土并利用单因素法研究碳源、氮源、碳氮比、接种量对Phanerochaete chrysosporium产絮凝剂的...     

Flocculation of microalgae in brackish and sea waters

Flocculation is an essential step in the concentration and harvesting of microalgae from aquatic media. Salinity of brackish water and sea water requires high flocculant dosages and renders flocculation less effective than in freshwater algal media. Experiments with the marine microalgae Isochrysis galbana and Chlorella stigmatophora showed that effective alum or ferric chloride flocculation was obtained only with dosages which are 5 to 10 times higher than the dosages required for the flocculation of freshwater microalgae. The flocculant dosages required for removing over 90% of the algae from suspensions were found to increase linearly with salinity as expressed in ionic strength. High salinity was found to inhibit flocculation with polyelectrolytes which are quite effective in freshwater algae flocculation. This inhibition was diminished at reduced salinity levels and effective flocculation was attained at salinity levels of 5 g/liter and below, which is typical of desert brackish water. Two methods were found to induce flocculation in sea water: (a) combining polyelectrolytes with inorganic flocculants such as ferric chloride or alum, and (b) ozone oxidation pretreatment followed by flocculation with inorganic flocculants.     

Cationic tamarind kernel polysaccharide (Cat TKP): A novel polymeric flocculant for the treatment of textile industry wastewater

Synthesis of cationic tamarind kernel polysaccharide (Cat TKP), its detailed physicochemical characterization and application as an efficient flocculant for the treatment of textile industry wastewater have been investigated. N-3-Chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) was used as a cationic reagent to introduce quaternary amine groups onto the backbone of tamarind kernel polysaccharide (TKP). Various grades were synthesized to obtain the optimized one. Effect of reaction parameters onto the degree of cationization has also been investigated. The synthesized polymers were characterized by various macromolecular characterization techniques, which confirm that cationization does take place. Afterwards, the applicability of TKP and various grades of Cat TKP's as flocculants for the treatment of textile industry wastewater was investigated. The flocculation experiments showed that TKP alone contributes little to the flocculation. However, cationic TKP led to significant improvement as flocculant for the treatment of textile industry wastewater. The best performing Cat TKP (i.e. Cat TKP 3) was thereafter compared with a commercial flocculant, which is cationic in nature. It has been observed that Cat TKP 3 surpasses the flocculation efficiency over commercial flocculant.     

The flocculation of bacteria using cationic synthetic flocculants and chitosan

Summary Bacteria are flocculated with high molecular weight cationic synthetic flocculants and chitosan. High charge density polymers are the most effective of the synthetic flocculants. Only chitosan is effective in flocculating the E. coli and B. subtilis cultures in complex broth. The difference in effectiveness between the synthetic flocculants and chitosan for flocculating E. coli, B. subtilis and Z. mobilis may be attributed to hydrogen bonding between the polysaccharide flocculant and cell surface polymers in addition to electrostatic interactions, and, in complex media, complexation of synthetic polymers with anionic polyelectrolytes.     

Factors affecting the flocculation of bacteria by chemical additives

Pure bacterial cultures can be flocculated by a variety of chemical flocculants. Flocculation of bacteria will assist in their recovery, especially where the cells themselves are of interest, as in microbial protein production. Studies with several genera of bacteria indicate that the mechanism of flocculation is highly complex. Such interacting variables as temperature, ionic environment, physiological age, flocculant, bacterial genus, and surface shear have been observed. Jar test experiments with washed cells indicate that many of the variables are related to the release by the cell of proteins, nucleic acids, or polysaccharides. When released, these polymers may increase the required dosage of flocculant for recovery as in the case of E. coli, or the dosage may decrease as it does for Lactobacillus.     

Water-soluble polysaccharides of antarctic and cultured Phormidium species of the cyanophyceae

Hot water extraction of a Phormidium species from Antarctica and of a sample of Phormïdium foveolarum which had been cultured axenically led to the isolation of a water-soluble polysaccharide from both materials. Acidic hydrolysis of each gave a similar pattern of monosaccharides comprising arabinose, xylose, rhamnose, fucose, galactose, mannose and glucose, and both contained uronic acid. All attempts by a variety of methods to fractionate the Antarctic polysaccharide into more than a single entity were unsuccessful. Periodate oxidation, partial hydrolysis and methylation studies on this polysaccharide supported a highly branched molecule with 1,3-linked glucose and 1,4-linked galactose as dominant features.     

Coagulation/flocculation-based removal of algal-bacterial biomass from piggery wastewater treatment

Two conventional chemical coagulants (FeCl₃ and Fe₂(SO₄)₃) and five commercial polymeric flocculants (Drewfloc 447, Flocudex CS/5000, Flocusol CM/78, Chemifloc CV/300 and Chitosan) were comparatively evaluated for their ability to remove algal-bacterial biomass from the effluent of a photosynthetically oxygenated piggery wastewater biodegradation process. Chlorella sorokiniana, Scenedesmus obliquus, Chlorococcum sp. and a wild type Chlorella, in symbiosis with a bacterial consortium, were used as model algal-bacterial consortia. While the highest biomass removals (66-98%) for the ferric salts were achieved at concentrations of 150-250 mg L⁻¹, dosages of 25-50 mg L⁻¹ were required for the polymer flocculants to support comparable removal efficiencies. Process efficiency declined when the polymer flocculant was overdosed. Biomass concentration did not show a significant impact on flocculation within the concentration range tested. The high flocculant requirements herein recorded might be due to the competition of colloidal organic for the flocculants and the stationary phase conditions of biomass.     

Oil production by six microalgae: impact of flocculants and drying on oil recovery from the biomass

Oil production in batch photoautotrophic cultures of the following microalgae is reported: the freshwater microalgae Chlorella vulgaris, Choricystis minor, and Neochloris sp.; the marine microalgae Nannochloropsis salina and Cylindrotheca fusiformis; and C. vulgaris grown in a full-strength seawater medium. In all cases, the solvent extraction of lipids from freeze-dried biomass is compared with extraction from the fresh biomass paste. For all algae, the oils could be extracted equally effectively from freeze-dried samples and the paste samples (67–88 % moisture by weight). Moisture content determinations of the biomass using the freeze-drying method and the high-temperature oven drying were found to be equivalent for all algae. The biomass recovered by flocculation with metal salts (aluminum sulfate, ferric chloride) followed by centrifugation had a certain amount of the flocculant irreversibly bound to it. Washing failed to remove the adsorbed flocculants. For all algae, the adsorbed flocculants did not interfere with oil recovery by solvent extraction. The solvent system of chloroform–methanol–water proved highly effective for quantitative extraction of the lipids from all algae.     

Selection of optimal flocculant for effective harvesting of the fucoxanthin-rich marine microalga <Emphasis Type="Italic">Isochrysis galbana</Emphasis>

Flocculation harvesting of the fucoxanthin-rich marine microalga Isochrysis galbana has received little attention. Therefore, we attempted to screen for an optimal chemical flocculant and optimize flocculation conditions from five chemical flocculants—ferric chloride (FC), aluminum sulfate (AS), polyaluminum chloride (PAC), aluminum potassium sulfate (APS), and zinc sulfate (ZS)—for effective flocculation of I. galbana. The growth rate, photosynthetic performance, and fucoxanthin content were determined in re-suspended flocculated algal cells and in the flocculation supernatant cultured algal cells. The results showed that high growth rate and fucoxanthin accumulation were observed when FC was used as the flocculant in I. galbana cultures, which indicated that FC may cause less harm to I. galbana than the other aluminum-based flocculants. Furthermore, satisfactory flocculation efficiency was also observed when FC was used to flocculate I. galbana, and the FC dosage was less than that required for flocculation of I. galbana using PAC, APS, and AS. Thus, we selected FC as the optimal flocculant for harvesting I. galbana based on its flocculation efficiency together with algal physiological performance, growth rate, and fucoxanthin content.     

Regulation by Organic Acids of Polysaccharide-mediated Microbe-plant Interactions

A polysaccharide flocculant of Klebsiella pneumoniae H12 has been suggested to mediate microbe-plant interactions with the aid of Ca²⁺ [K. Nakata et al., Biosci. Biotechnol. Biochem., 64, 459-465, 2000]. Here, two-way regulation of polysaccharide-mediated interactions between K. pneumoniae and Raphanus sativus was studied using organic acids. Namely, 10 mM equivalents of organic acids promoted production of the polysaccharide by the bacterium, but inhibited flocculation of bacterial cells by the polysaccharide. These phenomena were counterbalanced by equi-molar equivalents of Ca²⁺, suggesting competition for Ca²⁺ between the carboxylic residues of the polysaccharide and those of the aliphatic acids. By electron microscopy observations, bacterial cell aggregates were sparsely distributed over the main roots and root hairs, had various sizes, and seemed to tightly adhere to root tissues. Their shapes seemed to be distorted and abundant in cavities. In brief, these microscopical observations may be explained by a two-way regulation system of bacterial adhesion to a plant by organic acids.     

Hydrocarbons,phenols and sterols of the testa and pigment strand in the grain of Hordeum distichon

Material from the testa of decorticated barley grains contained hydrocarbons, esters, triglycerides, free sterols, 5-n-alkylresorcinols, and traces of free alcohols, carbonyl compounds, and various polar, acidic materials. The hydrocarbon fraction was mainly a series of n-alkanes, extending at least from C₁₁ to C₃₆, in which the C₂₉ and C₃₁ components were prominent. Two minor series of alkanes were also present. Sometimes a trace of an unsaturated hydrocarbon was detected. The ester fraction contained sterols and alkanols esterified by fatty acids, which differed in relative amounts from the fatty acids found in the triglycerides. The triglycerides were thought to have leached from within the grain. At least five free sterols were present, including sitosterol and campesterol. The 5-n-alkylresorcinols were at least twelve members of a homologous series, of which four, C₂₅, C₂₇, C₂₉, and C₃₁, made 98% of the total. Members of the series with even numbers of carbon atoms were also present. It is suggested that they are partly responsible for excluding microorganisms from the interior of the grain. The testa membrane, with the associated pigment strand, contained an estolide of fatty acids and various hydroxyacids, a polysaccharide component, and uncharacterized material.     

Distribution of seed fatty acids and the taxonomy of Vochysiaceae

The distribution of seed fatty acids of 16 species of Vochysiaceae native to Brazil, corresponding to the genera Callisthene, Qualea, Salvertia and Vochysia, and amounting to 57 samples, were studied. The methyl esters of the fatty acids were analyzed by GC–EIMS. For most species, fatty acid patterns are seemingly useful for species characterization. Intraspecific variability of samples of Salvertia grandiflora seems to have geographic significance. With one exception, palmitic and oleic acids predominate in the fatty acids distribution of Qualea and Callisthene. Q. grandiflora possesses exceptional amounts of lauric acid. Relatively high amounts of either C_20–C₂₂ (saturated or monounsaturated) or stearic acids characterize Salvertia and Vochysia. UPGMA analysis of fatty acids distribution based on Euclidean distances resulted in a cluster combining Callisthene and all samples of Qualea, except Q. grandiflora. Samples of Vochysia are combined into several clusters. The dendrogram is suggestive of taxonomic relationships, allowing the distinction of taxa down to the sub-sectional level. V. pyramidalis, from section Ciliantha, subsection Ferrugineae, has closer chemical affinities with species of section Vochysiella, subsection Decorticantes. Comparing with monomers of polysaccharide seed cell walls of Vochysiaceae, fatty acid patterns revealed lower intraspecific variability and higher taxonomic resolution.     

Nutritional content of Liometopum apiculatum Mayr larvae (“escamoles”) by vegetation type in north-central Mexico

In Mexico the ant Liometopum apiculatum is an important insect nutritionally, economically and ecologically. Their larvae (“escamoles”) contain proteins, lipids, vitamins and minerals, the concentrations of which may be related with the type of vegetation where the ant forages. The objective of this study was to evaluate the content of macro and micro nutrients of L. apiculatum larvae collected in three types of vegetation in north-central Mexico. We determined content of moisture, crude protein, total lipids, crude fiber, ash, and nitrogen-free extract. The amino acids were analyzed by cationic Exchange chromatography with acid hydrolysis and fatty acids by gas chromatography and solvent extraction with sodium methoxide. The effect of vegetation type on nutrient content was determined with an ANOVA and Sheffé comparison of means (P?<?.05). The concentration of amino acids and fatty acids (FA) was analyzed with a Kruskall-Wallis test (P?<?.05). Significant differences were found in protein, lipids and ash (P?<?.0001) and moisture content (P?<?.0036). We identified 17 amino acids, which concentration differed by type of vegetation. There were no significant differences in fatty acids. It is likely that the differences in the concentrations of macronutrients are due to the diversity and differential density of the food components available in each type of vegetation for L. apiculatum, and that the number of types and quantity of amino acids and fatty acids depend on the chemical properties of the liquid secretions the ants obtain by trophobiosis.     

Chemical characteristics and endotoxic activity of the lipopolysaccharide of Rahnella aquatilis 2-95

The lipopolysaccharide (LPS) from a new Enterobacteriaceae species, Rahnella aquatilis 2-95, was isolated and investigated. The structural components of the LPS molecule, namely, lipid A, core oligosaccharide, and O-specific polysaccharide, were obtained by mild acid hydrolysis. In lipid A, 3-oxytetradecanoic and tetradecanoic acids were found to be the predominant fatty acids. The major monosaccharides of the core oligosaccharide were galactose, arabinose, fucose, rhamnose, and an unidentified component. The O-specific polysaccharide was found to be assembled of a repeated trisaccharide unit of the following structure: The R. aquatilis 2-95 LPS is less toxic and more pyrogenic than the LPS from the R. aquatilis 1-95 strain studied earlier. Both acyl and phosphate groups are essential for toxic and pyrogenic activity of R. aquatilis 2-95 LPS.     

Selective Enrichment of Omega-3 Fatty Acids in Oils by Phospholipase A1

Omega fatty acids are recognized as key nutrients for healthier ageing. Lipases are used to release ω-3 fatty acids from oils for preparing enriched ω-3 fatty acid supplements. However, use of lipases in enrichment of ω-3 fatty acids is limited due to their insufficient specificity for ω-3 fatty acids. In this study use of phospholipase A1 (PLA1), which possesses both sn-1 specific activity on phospholipids and lipase activity, was explored for hydrolysis of ω-3 fatty acids from anchovy oil. Substrate specificity of PLA1 from Thermomyces lenuginosus was initially tested with synthetic p-nitrophenyl esters along with a lipase from Bacillus subtilis (BSL), as a lipase control. Gas chromatographic characterization of the hydrolysate obtained upon treatment of anchovy oil with these enzymes indicated a selective retention of ω-3 fatty acids in the triglyceride fraction by PLA1 and not by BSL. ¹³C NMR spectroscopy based position analysis of fatty acids in enzyme treated and untreated samples indicated that PLA1 preferably retained ω-3 fatty acids in oil, while saturated fatty acids were hydrolysed irrespective of their position. Hydrolysis of structured triglyceride,1,3-dioleoyl-2-palmitoylglycerol, suggested that both the enzymes hydrolyse the fatty acids at both the positions. The observed discrimination against ω-3 fatty acids by PLA1 appears to be due to its fatty acid selectivity rather than positional specificity. These studies suggest that PLA1 could be used as a potential enzyme for selective concentrationof ω-3 fatty acids.     

Factors affecting the elicitation of sesquiterpenoid phytoalexin accumulation by eicosapentaenoic and arachidonic acids in potato

Eicosapentaenoic and arachidonic acids in extracts of Phytophthora infestans mycelium were identified as the most active elicitors of sesquiterpenoid phytoalexin accumulation in potato tuber slices. These fatty acids were found free or esterified in all fractions with elicitor activity including cell wall preparations. Yeast lipase released a major portion of eicosapentaenoic and arachidonic acids from lyophilized mycelium. Concentration response curves comparing the elicitor activity of the polyunsaturated fatty acids to a cell-free sonicate of P. infestans mycelium indicated that the elicitor activity of the sonicated mycelium exceeded that which would be obtained by the amount of eicosapentaenoic and arachidonic acids (free and esterified) present in the mycelium. Upon acid hydrolysis of lyophilized mycelium, elicitor activity was obtained only from the fatty acid fraction. However, the fatty acids accounted for only 21% of the activity of the unhydrolyzed mycelium and the residue did not enhance their activity. Centrifugation of the hydrolysate, obtained from lyophilized mycelium treated with 2n NaOH, 1 molarity NaBH₄ at 100°C, yielded a supernatant fraction with little or no elicitor activity. Addition of this material to the fatty acids restored the activity to that which was present in the unhydrolyzed mycelium. The results indicate that the elicitor activity of the unsaturated fatty acids is enhanced by heat and base-stable factors in the mycelium.     

Biodegradation of C5-C8 fatty acids and production of aroma volatiles by Myroides sp. ZB35 isolated from activated sludge

In the effluents of a biologically treated wastewater from a heavy oil-refining plant, C₅-C₈ fatty acids including pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and 2-methylbutanoic acid are often detected. As these residual fatty acids can cause further air and water pollution, a new Myroides isolate ZB35 from activated sludge was explored to degrade these C₅-C₈ fatty acids in this study. It was found that the biodegradation process involved a lag phase that became prolonged with increasing acyl chain length when the fatty acids were individually fed to this strain. However, when fed as a mixture, the ones with longer acyl chains were found to become more quickly assimilated. The branched 2-methylbutanoic acid was always the last one to be depleted among the five fatty acids under both conditions. Metabolite analysis revealed one possible origin of short chain fatty acids in the biologically treated wastewater. Aroma volatiles including 2-methylbutyl isovalerate, isoamyl 2-methylbutanoate, isoamyl isovalerate, and 2-methylbutyl 2-methylbutanoate were subsequently identified from ZB35 extracts, linking the source of the fruity odor to these esters excreted by Myroides species. To our best knowledge, this is the first finding of these aroma esters in bacteria. From a biotechnological viewpoint, this study has revealed the potential of Myroides species as a promising source of aroma esters attractive for food and fragrance industries.     

Production of New Unsaturated Lipids during Wood Decay by Ligninolytic Basidiomycetes

Lipids were analyzed by gas chromatography-mass spectrometry for a 7-week in vitro decay of eucalypt wood by four ligninolytic basidiomycetes. The sound wood contained up to 75 mg of lipophilic compounds per 100 g of wood. Hydrolysis of sterol esters, which represented 38% of total wood lipids, occurred during the fungal decay. The initial increase of linoleic and other free unsaturated fatty acids paralleled the decrease of sterol esters. Moreover, new lipid compounds were found at advanced stages of wood decay that were identified from their mass spectra as unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C-3 position of itaconic acid. These dicarboxylic acids were especially abundant in the wood treated with Ceriporiopsis subvermispora (up to 24 mg per 100 g of wood) but also were produced by Phlebia radiata, Pleurotus pulmonarius, and Bjerkandera adusta. We hypothesize that three main alkylitaconic acids (tetradecylitaconic, cis-7-hexadecenylitaconic, and hexadecylitaconic acids) are synthesized by fungi in condensation reactions involving palmitic, oleic, and stearic acids. We suggest that both wood unsaturated fatty acids (present in free form or released from esters during natural decay) and unsaturated metabolites synthesized by fungi could serve as a source for peroxidizable lipids in lignin degradation by white rot basidiomycetes.     

The rise of toxic benthic Phormidium proliferations: A review of their taxonomy,distribution, toxin content and factors regulating prevalence and increased severity

There has been a marked increase in the distribution, intensity and frequency of proliferations of some species of the benthic mat-forming, toxin-producing genus Phormidium in rivers globally over the last decade. This review summarises current knowledge on their taxonomy, distribution, toxin content, environmental drivers of proliferations, and monitoring and management strategies in New Zealand. Although toxic Phormidium proliferation occurs in rivers worldwide little is known about these factors in most countries. Proliferations, defined as >20% cover of a riverbed, have been identified in 103 rivers across New Zealand. Morphological and molecular data indicate the main species responsible is Phormidium autumnale. In New Zealand Phormidium produces anatoxins (anatoxin-a, homoanatoxin-a, dihydroanatoxin-a, and dihydrohomoanatoxin-a) and these were detected in 67% of 771 samples from 40 rivers. The highest concentration measured was 712 mg kg⁻¹ dried weight (Oreti River, Southland), with considerable spatial and temporal variability in anatoxin concentrations between and within rivers. A synthesis of field based studies suggests that Phormidium proliferations are most likely when there is some enrichment of dissolved inorganic nitrogen but when water-column dissolved reactive phosphorus is less than 0.01 mg L⁻¹. Once established Phormidium-dominated mats trap sediment and internal mat biogeochemistry can mobilise sediment-bound phosphorus, which is then available for growth. Removal of Phormidium-dominated mats is primarily due to shear stress and substrate disturbance, although there is also evidence for autogenic detachment. A combination of factors including; changes to riparian margins, increased nitrate and fine sediment loads, and alterations in flow regimes are likely to have contributed to the rise in Phormidium proliferations.