Characterisation of Paenibacillus jamilae strains that produce exopolysaccharide during growth on and detoxification of olive mill wastewaters

Molecular and eco-physiological responses of soil-borne lead (Pb2+)-resistant bacteria for bioremediation and plant growth promotion under lead stress

Lead (Pb) is the 2nd known portentous hazardous substance after arsenic (As). Being highly noxious, widespread, non-biodegradable, prolonged environmental presence, and increasing accumulation, particularly in arable land, Pb pollution has become a serious global health concern requiring urgent remediation. Soil-borne, indigenous microbes from Pb-polluted sites have evolved diverse resistance strategies, involving biosorption, bioprecipitation, biomineralization, biotransformation, and efflux mechanisms, under continuous exposure to Pb in human-impacted surroundings. These strategies employ a wide range of functional bioligands to capture Pb and render it inaccessible for leaching. Recent breakthroughs in molecular technology and understanding of lead resistance mechanisms offer the potential for utilizing microbes as biological tools in environmental risk assessment. Leveraging the specific affinity and sensitivity of bacterial regulators to Pb2+ ions, numerous lead biosensors have been designed and deployed worldwide to monitor Pb bioavailability in contaminated sites, even at trace levels. Besides, the ongoing degradation of croplands due to Pb pollution poses a significant challenge to meet the escalating global food demands. The accumulation of Pb in plant tissues jeopardizes both food safety and security while severely impacting plant growth. Exploring Pb-resistant plant growth-promoting rhizobacteria (PGPR) presents a promising sustainable approach to agricultural practices. The active associations of PGPR with host plants have shown enhancements in plant biomass and stress alleviation under Pb influence. They thus serve a dual purpose for plants grown in Pb-contaminated areas. This review aims to offer a comprehensive understanding of the role played by Pb-resistant soil-borne indigenous bacteria in expediting bioremediation and improving the growth of Pb-challenged plants essential for potential field application, thus broadening prospects for future research and development.

Efficacy of exopolysaccharide in dye-laden wastewater treatment: A comprehensive review

The discharge of dye-laden wastewater into the water streams causes severe water and soil pollution, which poses a global threat to aquatic ecosystems and humans. A diverse array of microorganisms such as bacteria, fungi, and algae produce exopolysaccharides (EPS) of different compositions and exhibit great bioflocculation potency to sustainably eradicate dyes from water bodies. Nanomodified chemical composites of EPS enable their recyclability during dye-laden wastewater treatment. Nevertheless, the selection of potent EPS-producing strains and physiological parameters of microbial growth and the remediation process could influence the removal efficiency of EPS. This review will intrinsically discuss the fundamental importance of EPS from diverse microbial origins and their nanomodified chemical composites, the mechanisms in EPS-mediated bioremediation of dyes, and the parametric influences on EPS-mediated dye removal through sorption/bioflocculation. This review will pave the way for designing and adopting futuristic green and sustainable EPS-based bioremediation strategies for dye-laden wastewater in situ and ex situ.

Galactosamine and mannosamine are integral parts of bacterial and fungal extracellular polymeric substances

Extracellular polymeric substances (EPS) are produced by microorganisms and interact to form a complex matrix called biofilm. In soils, EPS are important contributors to the microbial necromass and, thus, to soil organic carbon (SOC). Amino sugars (AS) are used as indicators for microbial necromass in soil, although the origin of galactosamine and mannosamine is largely unknown. However, indications exist that they are part of EPS. In this study, two bacteria and two fungi were grown in starch medium either with or without a quartz matrix to induce EPS production. Each culture was separated in two fractions: one that directly underwent AS extraction (containing AS from both biomass and EPS), and another that first had EPS extracted, followed then by AS determination (exclusively containing AS from EPS). We did not observe a general effect of the quartz matrix neither of microbial type on AS production. The quantified amounts of galactosamine and mannosamine in the EPS fraction represented on average 100% of the total amounts of these two AS quantified in cell cultures, revealing they are integral parts of the biofilm. In contrast, muramic acid and glucosamine were also quantified in the EPS, but with much lower contribution rates to total AS production, of 18% and 33%, respectively, indicating they are not necessarily part of EPS. Our results allow a meaningful ecological interpretation of mannosamine and galactosamine data in the future as indicators of microbial EPS, and also attract interest of future studies to investigate the role of EPS to SOC and its dynamics.

Sustainable vs. Conventional Approach for Olive Oil Wastewater Management: A Review of the State of the Art

The main goal of this review is to collect and analyze the recently published research concerning the conventional and sustainable treatment processes for olive mill wastewater (OMW). In the conventional treatment processes, it is noticed that the main objective is to meet the environmental regulations for remediated wastewater without considering the economical values of its valuable constituents such as polyphenols. These substances have many important environmental values and could be used in many vital applications. Conversely, sustainable treatment processes aim to recover the valuable constituents through different processes and then treat the residual wastewater. Both approaches’ operational and design parameters were analyzed to generalize their advantages and possible applications. A valorization-treatment approach for OMW is expected to make it a sustainable resource for ingredients of high economical value that could lead to a profitable business. In addition, inclusion of a recovery process will detoxify the residual OMW, simplify its management treatment, and allow the possible reuse of the vast amounts of processed water. In a nutshell, the proposed approach led to zero waste with a closed water cycle development.

Preparation of a bacterial flocculant by using caprolactam as a sole substrate and its application in amoxicillin removal

High cost is one of the limiting factors in the industrial production of bioflocculant. Simultaneous preparation of bioflocculant from the contaminants in wastewater was considered as a potential approach to reduce the production cost. In this study, caprolactam was verified as sole feedstock for the growth of strain Alcaligenes faecalis subsp. phenolicus ZY-16 in batch experiments. Chemical analysis showed that the as-prepared MBF-16 consisted of heteropolysaccharides (88.3%) and peptides (9.4%). XPS result indicated the plentiful acylamino, hydroxyl and amino groups in MBF-16, which have an indispensable role in amoxicillin flocculation. The flocculation of amoxicillin can be well stimulated by Freundlich isotherm equation, and the Kf was up to 178.6524 for amoxicillin. The kinetic fitting results proved that the flocculation of amoxicillin by MBF-16 was chemisorbed. This contribution may develop a novel technology for the preparation of bacterial flocculants that can consume toxic substrates (caprolactam) and have potential applications in amoxicillin removal.

Dynamics of bacterial communities and substrate conversion during olive-mill waste dark fermentation: Prediction of the metabolic routes for hydrogen production

The aim of this work was to study the biological catalysts and possible substrate conversion routes in mesophilic dark fermentation reactors aimed at producing H₂ from olive mill wastewater. Bacillus and Clostridium were the most abundant phylotypes during the rapid stage of H₂ production. Chemical analyses combined with predictive functional profiling of the bacterial communities indicated that the lactate fermentation was the main H₂-producing route. In fact, during the fermentation process, lactate and acetate were consumed, while H₂ and butyrate were being produced. The fermentation process was rich in genes that encode enzymes for lactate generation from pyruvate. Lactate conversion to butyrate through the generation of pyruvate produced H₂ through the recycling of electron carriers via the pyruvate ferredoxin oxydoreductase pathway. Overall, these findings showed the synergy among lactate-, acetate- and H₂-producing bacteria, which complex interactions determine the H₂ production routes in the bioreactors.

Bioaugmentation with PGP-trace element tolerant bacterial consortia affects Pb uptake by Helianthus annuus grown on trace element polluted military soils

In this study, we sought to compose consortia of plant growth-promoting (PGP) and trace element tolerant bacteria, to improve plant growth and inhibit uptake and translocation of trace elements, eventually allowing the cultivation of profitmaking crops on trace elements polluted soils, reducing the risks of entrance of these elements into the food chain. Sunflower (Helianthus annuus L.) was grown on two polluted military soils (MS1 and MS2) in greenhouse microcosms and inoculated with three different bacterial consortia (C1, C2, C3). Growth and physiological status of the plants were unaffected during the experiment with the inoculation. After 2 months, plants were harvested. Consortium C2 and C3 decreased Pb shoot bioaccumulation by respectively 80-85% when plants were grown in the MS1 and even to concentrations below detection limit in plants grown in MS2. Differences in uptake and (sub)cellular localization of Pb and Cd in selected bacterial isolates were investigated in vitro by TEM-EDX. Pb absorption was observed by Bacillus wiedmanni ST29 and Bacillus paramycoides ST9 cultures. While adsorption at the bacterial cell wall was observed by Bacillus paramycoides ST9 and retention in the extracellular matrix by Cellulosimicrobium cellulans ST54.

Genome-based reclassification of Paenibacillus jamilae Aguilera et al. 2001 as a later heterotypic synonym of Paenibacillus polymyxa (Prazmowski 1880) Ash et al. 1994

Paenibacillus is one of the genera that has high species diversity and Paenibacillus polymyxa, the type species of the genus, is mainly isolated from plant-associated environments. Among the plant-associated species, Paenibacillus jamilae B.3^T (=CECT 5266^T=DSM 13815^T=KACC 10925^T=KCTC 13919^T) was proposed to be a novel species according to 16S rRNA gene similarity and DNA-DNA relatedness with related species, including Paenibacillus polymyxa. Nevertheless, in the description of Paenibacillus jamilae the used strain of Paenibacillus polymyxa was not the type strain of this species. In this work we found that the type strains of both species showed 16S rRNA gene similarity of 99.6 %. Therefore, in this study, we sequenced the genome of Paenibacillus jamilae KACC 10925^T and compared it with those of the type strain of Paenibacillus polymyxa ATCC 842^T and other phylogenetically related species. Genome relatedness value calculated by DNA-DNA hybridization between type strains of Paenibacillus polymyxa and Paenibacillus jamilae was 73.5 %, which is higher than the threshold value (70 %). For more objective and repeatable results of genome relatedness, we analysed an average nucleotide identity (ANI) between two strains. Our results showed that ANI value between the type strains of Paenibacillus jamilae and Paenibacillus polymyxa is 98.5 %, a phylogenetic distance also higher than the threshold values (95~96 %). These values were proposed by Yoon et al. (2017). In addition, their phylogenetic distance based on 92 bacterial core genes is highly close compared to other species. These mean that Paenibacillus jamilae and Paenibacillus polymyxa should be reclassified as a single species. Based on the results from genomic level comparison as well as reexamination results of physiological and chemotaxonomic features, we propose reclassification of Paenibacillus jamilae as a later heterotypic synonym of Paenibacillus polymyxa.

Industrial scale bio-detoxification of raw olive mill wastewaters by the use of selected microbial yeast and bacterial strains to obtain a new source for fertigation

The Olive Mill Wastewaters (OMWs) are one of the most important agro-industrial wastes of the Mediterranean Countries and the disposal by draining them onto land has been proved to be damaging for soils, plants and groundwater due to their polluting power. The present report describes a new method for bio-detoxification of undiluted fresh OMW based on the driven selection of aerobic yeasts and bacteria. The identified yeast Candida boidinii A5y and the bacterium Paenibacillus albidus R32b strains allowed the treatment of freshly produced raw OMW characterized by very high COD value and phenolic content, when applied as sequential inoculum. The treated OMW showed the absence of antimicrobial effects and a strongly reduction of phytotoxic activity on the germination of several plant seeds. The process was successfully validated on an industrial scale without any pre-treatment, dilution and/or supplementation of the raw waste. Bio-detoxified OMW produced by this sustainable and low-cost process would be suitable for new non-chemical fertigation or soilless applications. The described procedure represents a virtuous example of circular economy efficaciously applied for a depleting agri-food resource.

Development of sequential and simultaneous bacterial cultures to hydrolyse and detoxify wood pre-hydrolysate for enhanced acetone-butanol-ethanol (ABE) production

The use of microorganisms is a promising option for an eco-efficient and successful conversion of hardwood hemicelluloses to biofuels. The focus of this work is the treatment of hemicellulosic pre-hydrolysate by flocculation, followed by simultaneous or separate detoxification with Ureibacillus thermosphaericus and Cupriavidus taiwanensis co-culture, and hydrolysis with Paenibacillus campinasensis. A reduction of phenolic compounds was achieved mainly after flocculation, applied as a first detoxification step, but no increase in sugars concentration was observed. The ABE fermentation of the hydrolysate obtained from the simultaneous hydrolysis and detoxification produced 6.8 g L^-1 of butanol after 116 h, which was higher than that generated with xylose synthetic medium. The higher biofuel concentration in the hydrolysate is attributed to the existence of carbon sources, other than xylose.

Sources for isolation of extracellular polymeric substances (EPSs) producing bacterial strains which are capable of using wastewater sludge as solo substrate

Isolation of extracellular polymeric substances (EPSs) producing bacterial strains capable of using sludge as low-cost growth substrate was carried out in this study. A total of 110 EPS-producing strains were isolated from different sources, which include sludge of beer and winery wastewater treatment plant (WWTP); young, 2-month-old and 10-year-old leachate. Thirty-seven isolated strains showed good growth in sludge medium with cell count varying from 10⁶ to 10¹⁰ most probable number (MPN)/mL and total EPS concentration from 2737 to 6639 mg/L. Twenty-one strains produced EPS with high flocculation activity (FA_max varied from 72.0% to 80.2%). The highest FA_max (80.2%) was observed with EPS produced by strain BES 19, which was isolated from sludge of beer WWTP. Sludge of beer WWTP, young leachate and 10-year-old leachate were good sources for isolation of EPS-producing bacteria.

Production and Characterization of a Bioflocculant Produced by Bacillus salmalaya 139SI-7 and Its Applications in Wastewater Treatment

The production, optimization, and characterization of the bioflocculant QZ-7 synthesized by a novel Bacillus salmalaya strain 139SI isolated from a private farm soil in Selangor, Malaysia, are reported. The flocculating activity of bioflocculant QZ-7 present in the selected strain was found to be 83.3%. The optimal culture for flocculant production was achieved after cultivation at 35.5 °C for 72 h at pH 7 ± 0.2, with an inoculum size of 5% (v/v) and sucrose and yeast extract as carbon and nitrogen sources. The maximum flocculating activity was found to be 92.6%. Chemical analysis revealed that the pure bioflocculant consisted of 79.08% carbohydrates and 15.4% proteins. The average molecular weight of the bioflocculant was calculated to be 5.13 × 10⁵ Da. Infrared spectrometric analysis showed the presence of carboxyl (COO-), hydroxyl (-OH), and amino (-NH₂) groups, polysaccharides and proteins. The bioflocculant QZ-7 exhibited a wide pH stability range from 4 to 7, with a flocculation activity of 85% at pH 7 ± 0.2. In addition, QZ-7 was thermally stable and retained more than 80% of its flocculating activity after being heated at 80 °C for 30 min. SEM analysis revealed that QZ-7 exhibited a clear crystalline brick-shaped structure. After treating wastewater, the bioflocculant QZ-7 showed significant flocculation performance with a COD removal efficiency of 93%, whereas a BOD removal efficiency of 92.4% was observed in the B. salmalaya strain 139SI. These values indicate the promising applications of the bioflocculant QZ-7 in wastewater treatment.

Degradation of olive mill wastewater by the induced extracellular ligninolytic enzymes of two wood-rot fungi

Olive mill wastewater (OMWW) is a major problem in olive oil - producing countries, due to its high organic load and concentration in phenols that are toxic for marine life, plants and soil microorganisms. In the present study, two mushroom species were tested in regard to their OMWW's oxidative capacity, Pleurotus citrinopileatus LGAM 28684 and Irpex lacteus LGAM 238. OMWW (25% v/v) degradation was investigated for several culture conditions, namely pH, agitation speed, nitrogen-based supplements and their concentration. The selected values were pH 6, agitation rate 150 rpm, 30 g L^-1 corn steep liquor as nitrogen source for P. citrinopileatus and 20 g L^-1 diammonium tartrate for I. lacteus. The two strains performed well in cultures supplemented with OMWW, generating very high titers of oxidative enzymes and achieving more than 90% color and phenols reduction within a 24 days cultivation period. In addition, the amount of glucans present in the fungal biomass was assessed. Hence, P. citrinopileatus and I. lacteus appear as potent degraders of OMWW with the ability to use the effluent as a substrate for the production of biotechnologically important enzymes and valuable fungal glucans.

Impact of extraction methods on bio-flocculants recovered from backwashed sludge of bio-filtration unit

Effect of ten extraction methods on flocculation activity and chemical composition of bio-flocculants recovered from backwashed sludge of bio-filtration unit was studied. The results showed that the chemical method was better than physical method with respect to the extracted BFs weight and its flocculation activity. Cell lysis did not affect to the flocculation activity of BFs. Among ten extraction methods, EDTA (20 g/L) was the best one with extracted BFs dry weight of 6242 mg/L and flocculation activity of 83%. Optimization of EDTA concentration showed that 5 g EDTA/L (or 0.2 g EDTA/g SS) was suitable for recovery of BFs from backwashed sludge. The flocculation activity of BFs was 94% when using 2.4 mg of BFs/g of kaolin. The outcome of this study suggested that backwashed sludge of the bio-filtration unit was a potential source for exploiting bio-flocculants.

Recent advances in exopolysaccharides from Paenibacillus spp.: production, isolation, structure, and bioactivities

This review provides a comprehensive summary of the most recent developments of various aspects (i.e., production, purification, structure, and bioactivity) of the exopolysaccharides (EPSs) from Paenibacillus spp. For the production, in particular, squid pen waste was first utilized successfully to produce a high yield of inexpensive EPSs from Paenibacillus sp. TKU023 and P. macerans TKU029. In addition, this technology for EPS production is prevailing because it is more environmentally friendly. The Paenibacillus spp. EPSs reported from various references constitute a structurally diverse class of biological macromolecules with different applications in the broad fields of pharmacy, cosmetics and bioremediation. The EPS produced by P. macerans TKU029 can increase in vivo skin hydration and may be a new source of natural moisturizers with potential value in cosmetics. However, the relationships between the structures and activities of these EPSs in many studies are not well established. The contents and data in this review will serve as useful references for further investigation, production, structure and application of Paenibacillus spp. EPSs in various fields.

Evaluation of an aerobic treatment for olive mill wastewater detoxification

Olive mill wastewater (OMWW) is a by-product of the olive oil extraction industry. Its dumping creates severe environmental problems in the Mediterranean countries. The phytoxicity of OMWW is due to the phenolic substances and is evaluated through a genotoxicity method. An aerobic treatment of OMWW was conducted during 45 days. Different concentrations of raw and treated OMWW were tested using the Vicia faba micronuclei test. Results showed that raw OMWW induced significant micronuclei formation at 10% of OMWW dilution. At 20% of dilution, no mitosis was recorded. The 45 days aerobic treatment OMWW showed an important decrease in the genotoxicity and also in the toxicity that was observed at 10% and 20% OMWW dilution. This could be correlated with the biodegradation of 76% of the total phenols. Indeed, qualitative analysis by high performance liquid chromatography shows the disappearance of the majority of phenolic compounds after 45 days of treatment. This study was completed by an agricultural test with V. faba plant. Data showed significant growth yield of 36.3% and 29.9% after being irrigated with 5 and 10 t/ha, respectively. These results supported the positive role of aerobic treatment on OMWW and their capacity to ameliorate the agronomic potential of these effluents.

Lead resistance in micro-organisms

Lead (Pb) is an element present in the environment that negatively affects all living organisms. To diminish its high toxicity, micro-organisms have developed several mechanisms that allow them to survive exposure to Pb(II). The main mechanisms of lead resistance involve adsorption by extracellular polysaccharides, cell exclusion, sequestration as insoluble phosphates, and ion efflux to the cell exterior. This review describes the various lead resistance mechanisms, and the regulation of their expression by lead binding regulatory proteins. Special attention is given to the Pbr system from Cupriavidus metallidurans CH34, which involves a unique mechanism combining efflux and lead precipitation.

Identification and characterization of psychrotolerant sporeformers associated with fluid milk production and processing

Psychrotolerant spore-forming bacteria represent a major challenge to the goal of extending the shelf life of pasteurized dairy products. The objective of this study was to identify prominent phylogenetic groups of dairy-associated aerobic sporeformers and to characterize representative isolates for phenotypes relevant to growth in milk. Analysis of sequence data for a 632-nucleotide fragment of rpoB showed that 1,288 dairy-associated isolates (obtained from raw and pasteurized milk and from dairy farm environments) clustered into two major divisions representing (i) the genus Paenibacillus (737 isolates, including the species Paenibacillus odorifer, Paenibacillus graminis, and Paenibacillus amylolyticus sensu lato) and (ii) Bacillus (n = 467) (e.g., Bacillus licheniformis sensu lato, Bacillus pumilus, Bacillus weihenstephanensis) and genera formerly classified as Bacillus (n = 84) (e.g., Viridibacillus spp.). When isolates representing the most common rpoB allelic types (ATs) were tested for growth in skim milk broth at 6°C, 6/9 Paenibacillus isolates, but only 2/8 isolates representing Bacillus subtypes, grew >5 log CFU/ml over 21 days. In addition, 38/40 Paenibacillus isolates but only 3/47 Bacillus isolates tested were positive for β-galactosidase activity (including some isolates representing Bacillus licheniformis sensu lato, a common dairy-associated clade). Our study confirms that Paenibacillus spp. are the predominant psychrotolerant sporeformers in fluid milk and provides 16S rRNA gene and rpoB subtype data and phenotypic characteristics facilitating the identification of aerobic spore-forming spoilage organisms of concern. These data will be critical for the development of detection methods and control strategies that will reduce the introduction of psychrotolerant sporeformers and extend the shelf life of dairy products.

Composition analysis and material characterization of an emulsifying extracellular polysaccharide (EPS) produced by Bacillus megaterium RB-05: a hydrodynamic sediment-attached isolate of freshwater origin

AIMS

This work was aimed to isolate, purify and characterize an extracellular polysaccharide (EPS) produced by a freshwater dynamic sediment-attached micro-organism, Bacillus megaterium RB-05, and study its emulsifying potential in different hydrocarbon media.

METHODS AND RESULTS

Bacillus megaterium RB-05 was found to produce EPSs in glucose mineral salts medium, and maximum yield (0.864 g l(-1) ) was achieved after 24-h incubation. The recovery rates of the polysaccharide material by ion-exchange and gel filtration chromatography were around 67 and 93%, respectively. As evident from HPLC and FT-IR analyses, the polysaccharide was found to be a heteropolymer-containing glucose, galactose, mannose, arabinose, fucose and N-acetyl glucosamine. Different oligosaccharide combinations namely hexose(3), hexose(4), hexose(5) deoxyhexose(1) and hexose(5) deoxyhexose(1) pentose(3) were obtained after partial hydrolysis of the polymer using MALDI-ToF-MS. The polysaccharide with an average molecular weight of 170 kDa and thermal stability up to 180°C showed pseudoplastic rheology and significant emulsifying activity in hydrocarbon media.

CONCLUSIONS

Isolated polysaccharide was found to be of high molecular weight and thermally stable. The purified EPS fraction was composed of hexose, pentose and deoxyhexose sugar residues, which is a rare combination for bacterial polysaccharides. Emulsifying property was either better or comparable to that of other commercially available natural gums and polysaccharides.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is probably one of the few reports about characterizing an emulsifying EPS produced by a freshwater sediment-attached bacterium. The results of this study contribute to understand the influence of chemical composition and material properties of a new microbial polysaccharide on its application in industrial biotechnology. Furthermore, this work reconfirms freshwater dynamic sediment as a potential habitat for bioprospecting extracellular polymer-producing bacteria. This study will improve our knowledge on the exploitation of a nonconventional renewable resource, which also seems to be ecologically significant.

Exopolysaccharides from extremophiles: from fundamentals to biotechnology

Exopolysaccharides (EPSs) make up a substantial component of the extracellular polymers surrounding most microbial cells in extreme environments like Antarctic ecosystems, saline lakes, geothermal springs or deep sea hydrothermal vents. The extremophiles have developed various adaptations, enabling them to compensate for the deleterious effects of extreme conditions, e.g. high temperatures, salt, low pH or temperature, high radiation. Among these adaptation strategies, EPS biosynthesis is one of the most common protective mechanisms. The unusual metabolic pathways revealed in some extremophiles raised interest in extremophilic microorganisms as potential producers of EPSs with novel and unusual characteristics and functional activities under extreme conditions. Even though the accumulated knowledge on the structural and theological properties of EPSs from extremophiles is still very limited, it reveals a variety in properties, which may not be found in more traditional polymers. Both extremophilic microorganisms and their EPSs suggest several biotechnological advantages, like short fermentation processes for thermophiles and easily formed and stable emulsions of EPSs from psychrophiles. Unlike mesophilic producers of EPSs, many of them being pathogenic, extremophilic microorganisms provide non-pathogenic products, appropriate for applications in the food, pharmaceutical and cosmetics industries as emulsifiers, stabilizers, gel agents, coagulants, thickeners and suspending agents. The commercial value of EPSs synthesized by microorganisms from extreme habitats has been established recently.

Enhanced production and partial characterization of an extracellular polysaccharide from newly isolated Azotobacter sp. SSB81

A strain was selected by its highest extracellular polysaccharide (EPS) production ability compare to other isolates from the same rhizospheric soil. The selected strain was identified by 16S rDNA sequencing and designated as SSB81. Phylogenetic analysis of the gene sequence showed its close relatedness with Azotobacter vinelandii and Azotobacter salinestris. Maximum EPS (2.52 g l(-1)) was recovered when the basal medium was supplemented with glucose (2.0%), riboflavin (1 mg l(-1)) and casamino acid (0.2%). The EPS showed a stable viscosity level at acidic pH (3.0-6.5) and the pyrolysis temperature was found to be at 116.73 degrees C with an enthalpy (DeltaH) of 1330.72 J g(-1). MALDI TOF mass spectrometric result suggests that polymer contained Hex(5)Pent(3) as oligomeric building subunit. SEM studies revealed that the polymer had a porous structure with small pore size distribution indicating the compactness of the polymer. This novel EPS may find possible application as a polymer for environmental bioremediation and biotechnological processes.