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Background & Aims: The intestinal microbiome might affect the development and severity of nonalcoholic fatty liver disease (NAFLD). We analyzed microbiomes of children with and without NAFLD., Methods: We performed a prospective, observational, cross-sectional study of 87 children (age range, 8-17 years) with biopsy-proven NAFLD and 37 children with obesity without NAFLD (controls). Fecal samples were collected and microbiome composition and functions were assessed using 16S ribosomal RNA amplicon sequencing and metagenomic shotgun sequencing. Microbial taxa were identified using zero-inflated negative binomial modeling. Genes contributing to bacterial pathways were identified using gene set enrichment analysis., Results: Fecal microbiomes of children with NAFLD had lower α-diversity than those of control children (3.32 vs 3.52, P = .016). Fecal microbiomes from children with nonalcoholic steatohepatitis (NASH) had the lowest α-diversity (control, 3.52; NAFLD, 3.36; borderline NASH, 3.37; NASH, 2.97; P = .001). High abundance of Prevotella copri was associated with more severe fibrosis (P = .036). Genes for lipopolysaccharide biosynthesis were enriched in microbiomes from children with NASH (P < .001). Classification and regression tree model with level of alanine aminotransferase and relative abundance of the lipopolysaccharide pathway gene encoding 3-deoxy-d-manno-octulosonate 8-phosphate-phosphatase identified patients with NASH with an area under the receiver operating characteristic curve value of 0.92. Genes involved in flagellar assembly were enriched in the fecal microbiomes of patients with moderate to severe fibrosis (P < .001). Classification and regression tree models based on level of alanine aminotransferase and abundance of genes encoding flagellar biosynthesis protein had good accuracy for identifying case children with moderate to severe fibrosis (area under the receiver operating characteristic curve, 0.87)., Conclusions: In an analysis of fecal microbiomes of children with NAFLD, we associated NAFLD and NASH with intestinal dysbiosis. NAFLD and its severity were associated with greater abundance of genes encoding inflammatory bacterial products. Alterations to the intestinal microbiome might contribute to the pathogenesis of NAFLD and be used as markers of disease or severity., (Copyright © 2019 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Thirteen extracellular polymeric substances (EPS) producing bacterial strains were cultivated (as mixed culture) in the sterilized sludge (suspended solids of 25 g/L) and the batch fermentation was carried out. Mixed culture revealed a high specific growth rate of 0.35/hr. The EPS production rate was higher up to 24 hours, which gradually decreased with further incubation. The kinetic estimates demonstrated growth-associated EPS production. Broth EPS revealed higher flocculation activity when combined with different cations (Ca(2+), Mg(2+), Fe(3+), and Al(3+)) in river water (≥90%), municipal wastewater (≥90%), and brewery wastewater (≥80%), respectively. A low dose (5 to 40 mg/L) of trivalent cations was required to achieve higher flocculation compared to the divalent cations (50 to 250 mg/L). Flocculation performance of EPS was comparable to Magnafloc-155 (chemical polymer) and, hence, it could be used as a flocculant.

Biopolymers are considered a potential alternative to conventional chemical polymers because of their ease of biodegradability, high efficiency, non-toxicity and non-secondary pollution. Recently, extracellular polymeric substances (EPS, biopolymers produced by the microorganisms) have been recognised by many researchers as a potential flocculent for their applications in various water, wastewater and sludge treatment processes. In this context, literature information on EPS is widely dispersed and is very scarce. Thus, this review marginalizes various studies conducted so far about EPS nature-production-recovery, properties, environmental applications and moreover, critically examines future research needs and advanced application prospective of the EPS. One of the most important aspect of chemical composition and structural details of different moieties of EPS in terms of carbohydrates, proteins, extracellular DNA, lipid and surfactants and humic substances are described. These chemical characteristics of EPS in relation to formation and properties of microbial aggregates as well as degradation of EPS in the matrix (biomass, flocs etc) are analyzed. The important engineering properties (based on structural characteristics) such as adsorption, biodegradability, hydrophilicity/hydrophobicity of EPS matrix are also discussed in details. Different aspects of EPS production process such as bacterial strain maintenance; inoculum and factors affecting EPS production were presented. The important factors affecting EPS production include growth phase, carbon and nitrogen sources and their ratio, role of other nutrients (phosphorus, micronutrients/trace elements, and vitamins), impact of pH, temperature, metals, aerobic versus anaerobic conditions and pure and mixed culture. The production of EPS in high concentration with high productivity is essential due to economic reasons. Therefore, the knowledge about all the aspects of EPS production (listed above) is highly essential to formulate a logical and scientific basis for the research and industrial activities. One of the very important issues in the production/application/biodegradation of EPS is how the EPS is extracted from the matrix or a culture broth. Moreover, EPS matrix available in different forms (crude, loosely bound, tightly bound, slime, capsular and purified) can be used as a bioflocculant material. Several chemical and physical methods for the extraction of EPS (crude form or purified form) from different sources have been analyzed and reported. There is ample information available in the literature about various EPS extraction methods. Flocculability, dewaterability and biosorption ability are the very attractive engineering properties of the EPS matrix. Recent information on important aspects of these properties qualitatively as well as quantitatively has been described. Recent information on the mechanism of flocculation mediated by EPS is presented. Potential role of EPS in sludge dewatering and biosorption phenomenon has been discussed in details. Different factors influencing the EPS ability to flocculate and dewaterability of different suspensions have been included. The factors considered for the discussion are cations, different forms of EPS, concentration of EPS, protein and carbohydrate content of EPS, molecular weight of EPS, pH of the suspension, temperature etc. These factors were selected for the study based upon their role in the flocculation and dewatering mechanism as well the most recent available literature findings on these factors. For example, only recently it has been demonstrated that there is an optimum EPS concentration for sludge flocculation/dewatering. High or low concentration of EPS can lead to destabilization of flocs. Role of EPS in environmental applications such as water treatment, wastewater flocculation and settling, colour removal from wastewater, sludge dewatering, metal removal and recovery, removal of toxic organic compounds, landfill leachate treatment, soil remediation and reclamation has been presented based on the most recent available information. However, data available on environmental application of EPS are very limited. Investigations are required for exploring the potential of field applications of EPS. Finally, the limitations in the knowledge gap are outlined and the research needs as well as future perspectives are highlighted., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Nanotechnology has attracted a great interest in recent years due to its expected impact on many areas such as energy, medicine, electronics, and space industries. This review provides the state-of-art knowledge on the synthesis of nanoparticles by microorganisms including bacteria, fungi, actinomycetes, and yeast, and their effect on microbiological processes. The available microbes and their predicted nanoparticle biosynthesis mechanism, the conditions to control the size/shape and monodispersity of particles, and microbiological reaction rate enhancement using nanoparticles as catalysts are presented. The current limitations and future scope for specific research are also discussed., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Wastewater treatment plants often face the problems of sludge settling mainly due to sludge bulking. Generally, synthetic organic polymer and/or inorganic coagulants (ferric chloride, alum and quick lime) are used for sludge settling. These chemicals are very expensive and further pollute the environment. Whereas, the bioflocculants are environment friendly and may be used to flocculate the sludge. Extracellular polymeric substances (EPS) produced by sludge microorganisms play a definite role in sludge flocculation. In this study, 25 EPS producing strains were isolated from municipal wastewater treatment plant. Microorganisms were selected based on EPS production properties on solid agar medium. Three types of EPS (slime, capsular and bacterial broth mixture of both slime and capsular) were harvested and their characteristics were studied. EPS concentration (dry weight), viscosity and their charge (using a Zetaphoremeter) were also measured. Bioflocculability of obtained EPS was evaluated by measuring the kaolin clay flocculation activity. Six bacterial strains (BS2, BS8, BS9, BS11, BS15 and BS25) were selected based on the kaolin clay flocculation. The slime EPS was better for bioflocculation than capsular EPS and bacterial broth. Therefore, extracted slime EPS (partially purified) from six bacterial strains was studied in terms of sludge settling [sludge volume index (SVI)] and dewatering [capillary suction time (CST)]. Biopolymers produced by individual strains substantially improved dewaterability. The extracted slime EPS from six different strains were partially characterized., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

One of the major problems in overall wastewater treatment process is sludge settling and dewatering. In general, sludge settling and dewatering is carried out using conventional physico-chemical methods that are known to be expensive, and these processes further increase the sludge volume and ultimate disposal costs. To overcome this problem, a suitable alternative could be the use of bioflocculants for sludge settling and dewatering. To achieve bioflocculation, extracellular polymeric substances (EPS) producing bacterial strains were isolated from the complex microbial community of wastewater sludge. Crude EPS produced in the form of bacterial broth was used to test kaolin flocculation activity. Three out of 10 bacterial strains (B2, B8 and B9) were pre-selected for sludge settling. Based on sludge settling and dewatering results, B8 possessed better flocculating property than other bacterial strains. These sludge microorganisms were identified based on their 16S rDNA sequences and bacterial strain B8 was identified as Serratia sps.

Polyhydroxyalkanoates (PHAs) accumulating bacteria were isolated from activated sludge samples collected from municipal wastewater treatment plants in Quebec. Twelve bacterial strains were screened for PHA production with acetate as sole carbon source. PHA granules exhibited a strong orange fluorescence when stained with Nile blue A observed under microscope (X100x). PHA was also analyzed by Gas Chromatography Linked to Mass Spectroscopy (GCMS) to further confirm the presence and the concentration of PHA. To compare the abilities of these PHA accumulating bacterial strains, synthetic media with acetate as carbon source was prepared to accumulate PHA in 500 mL Erlenmeyer flask containing 150 of the medium. These flasks were then inoculated with the isolated bacterial strains, incubated at 25 degrees C for 48 hours in a rotary shaker at 220 rpm. The results showed that the bacterial strains isolated from sludge possess different abilities for accumulating PHA. The maximum PHA content of 27.50% was obtained by strain PHA-SB3. The PHB/PHV ratio of the copolymer produced in the study changed in accordance with operating time and strains.

The volume of sludge produced annually is very high and poses serious disposal problems. The traditional methods of sludge disposal produce secondary pollutants. Therefore, the alternate or suitable solution is reuse of sludge in an ecofriendly approach. Biotechnology is an interesting tool to add value to the processes involved in wastewater and wastewater sludge disposal/reuse. In this context, a study was carried out on thermophilic bacterial strains that produce thermostable proteases. The bacterial strains were first isolated from municipal wastewater sludge. In contrast to the conventional strains used in industries, like Bacillus sp., the new strains were Gram-Negative type. In semi-synthetic medium, a maximal protease activity of 5.25 IU/ml (International Unit per ml) was obtained at a pH of 8.2 and at a temperature of 60 degrees C, which is higher than the stability temperature of 37 degrees C for a similar protease obtained from the conventional producer Bacillus licheniformis. Moreover, growth and protease activity of the strains were tested in wastewater sludge. It is expected that the complexity of sludge could stimulate/enhance the protease production and their characteristics. In conclusion, reuse of wastewater sludge will help to reduce their quantity as well as the value-added products produced will replace chemical products used in industries., (Copyright IWA Publishing 2008.)

This study investigates the changes in biodegradability, rheology and metal concentration of wastewater sludge--non-hydrolyzed (raw), sterilized, and hydrolyzed (thermal alkaline pre-treatment) at total solids concentration from 10-50 g l(-1) to ascertain the bioavailability of nutrients for subsequent fermentation. The dissolved solids concentration increased linearly with total solids. Irrespective of the wastewater sludge (raw or, pre-treated), percentage biodegradability in terms of total solids (26.5-44.5%), total COD (25.8-56.5%) and dissolved solids (41.9-66.9%) was maximum around 20 g l(-1) solids concentration. The pseudoplasticity of sludge decreased (consistency index decreased from 895.1 to 5.2 and flow behaviour index increased from 0.28 to 0.88, for all sludge types) with pre-treatment and increased with total solids concentration. The pre-treated sludge, namely, sterilized and hydrolyzed sludge showed higher microbial growth (1-2 log cycles increase in comparison to raw sludge) suggesting their susceptibility to microbial degradation. The C:N ratio decreased with pre-treatment (raw sludge > sterilized > hydrolyzed) during biodegradation. Although the metal concentration increased in incubated hydrolyzed sludge, the final concentration was within the regulatory norms for agriculture application. Thus, pretreatment of sludge resulted in increase in biodegradability making it an excellent proponent for fermented value-added products.

The microbial population encountered during a simultaneous thermophilic microbial leaching and digestion process at 50 degrees C, based on microbial sulfur oxidation, was investigated. The cell count of the sulfuric acid producer Thiobacillus thermosulfatus increased, followed by a decrease. In the absence of sulfur (control: conventional thermophilic digestion), Thiobacillus thermosulfatus population decreased under the detection limit. Acidophilic and neutrophilic heterotrophic populations increased during the leaching process, and the final acidophilic population count was higher than the neutrophilic population. During the thermophilic digestion (control), the final neutrophilic population count was higher than the acidophilic. Six heterotrophic bacterial strains were isolated and partially characterized. Bacillus was the most predominant genus. The type of bacterial populations in thermophilic microbial leaching and digestion, as well as the thermophilic digestion process (control), were the same, while only the relative concentrations changed. In both processes, the bacterial indicators decreased under the detection limit after 12 h. Mesophilic heterotrophic population was more affected by the thermophilic microbial leaching process than by thermophilic digestion. Sludge mineralization was probably more influenced by the final cell concentration rather than the presence of an individual species or mixed population.

Seventy-four bacterial isolates were recovered from 10 protein rich soil and water samples collected from Quebec City. On the basis of colony size, texture, and microscopic characteristics, the isolates were categorized into 33 types. Among these, five isolates showed good proteolytic activity (>5), eight isolates showed moderate activity (between >3.0 and <5.0), 12 isolates showed poor activity (between >2.0 and <3.0), and eight isolates exhibited very poor activity (below 2.0). The five promising isolates were identified as Bacillus strains, which produced higher amount of protease and maximum cell concentration in fermentor than a shake flask in a shorter time. The enzyme produced by five strains of Bacillus showed similar thermal activity and stability. The proteases retained 31 and 10% of their original activity after 2 h at 50° and 60°C, respectively, but lost all activity at 70°C. However, the optimum pH and pH stability of proteases was from 6.0 to 9.0 and 6.0 to 8.0, respectively. The enzyme activities were accelerated by the addition of Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Cu2+, and Na+, whereas these were inhibited by Hg2+ and EDTA. Thus, all evaluated isolates were suitable for the production of protease. [ABSTRACT FROM AUTHOR]

Activated sludge process is the most widely used technology for municipal and industrial wastewater treatment. The microbial community of activated sludge is a mixed population of microorganisms containing many species of viruses, bacteria, protozoa, fungi, metazoa, and algae. This review focuses on the recent advances in microbiology of the activated sludge process. The bacterial population in activated sludge system is examined. The standard procedure, medium used, analytical methods and biochemical characterization techniques required for isolation, and identification of bacteria responsible for the key process of wastewater treatment systems (nutrient removal, aerobic, anaerobic, etc.) are discussed in the paper. The effect of seasonal (winter and summer) temperature variations and salinity variation on the bacterial species for wastewater treatment is examined. In addition, soluble microbial products (SMP) is one of the important factors that affects not only microbial activities, but consequently the quality of the effluents from biological wastewater treatment systems; the identification, characterization, significance, and implications of SMP in the context of activated sludge processes are also covered in this paper. Today, most modern wastewater treatment processes rely on the composition and activity of their microbial communities in activated sludges. Recent developments in molecular methods for analysis of the microbial communities have retriggered public interest in the microbiology of activated sludge. Whereas traditional approaches may have reached the point of diminishing returns, the molecular analysis has the potential to increase our understanding of the activated sludge process, and thereby improve the process control. [ABSTRACT FROM AUTHOR]

An investigation on the effect of sludge solids concentration on bioleaching of Cr(III) and other metals from tannery sludge by indigenous sulphur-oxidizing bacteria was carried out. The sludge solids concentrations ranged from 13 to 60 g/L. The concentration of elemental sulphur was fixed at 30 g/L. The results showed that the lowest pH reached after 25 days of bioleaching at all studied sludge solids concentration was about 1.3. The optimum sludge solids concentration for maximum metal leaching from tannery sludge was 40 g/L and about 87% of Cr(III), 73% of Al, 72% of Fe, 62% of Mg, and 73% of Zn could be leached in this case. During bioleaching, the concentrations of total and volatile suspended solids of the tannery sludge significantly decreased. The sulphur-oxidizing bacteria could tolerate a Cr(III) concentration as high as 5,930 mg/L at pH 1.3. The leaching efficiencies of Cr(III), Al, and Fe for both chemical leaching and bioleaching of tannery sludge were similar at pH 1.3. The leaching efficiency of Ca, Mg, and Zn in both leaching processes were identical for pH values in the range of 1.3 to 3.0. [ABSTRACT FROM AUTHOR]