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Applied Microbiology and Biotechnology (v.90, #5)

Overcoming substrate inhibition during biological treatment of monoaromatics: recent advances in bioprocess design by Andrew J. Daugulis; M. Concetta Tomei; Benoit Guieysse (pp. 1589-1608).

The biological removal of monoaromatic compounds from contaminated environments, usually arising from industrial activity, is challenging because of the inherent toxicity of these compounds to microorganisms, particularly at the concentrations that can be encountered in industrial waste streams. A wide range of bioprocess designs have been proposed and tested with the aim of achieving high removal efficiencies, with varying degrees of technical success, and potential for practical implementation. This review reports on the progress on variations of well-known themes made in the last 3–4 years, as well as new bioprocess technologies that address the cytotoxicity of monoaromatics directly. Areas for further research are also proposed.

Keywords: Monoaromatics; Bioprocess designs; Cytotoxicity

Mechanistic aspects in the biogenic synthesis of extracellular metal nanoparticles by peptides, bacteria, fungi, and plants by Nelson Durán; Priscyla D. Marcato; Marcela Durán; Alka Yadav; Aniket Gade; Mahendra Rai (pp. 1609-1624).

Metal nanoparticles have been studied and applied in many areas including the biomedical, agricultural, electronic fields, etc. Several products of colloidal silver are already on the market. Research on new, eco-friendly and cheaper methods has been initiated. Biological production of metal nanoparticles has been studied by many researchers due to the convenience of the method that produces small particles stabilized by protein. However, the mechanism involved in this production has not yet been elucidated although hypothetical mechanisms have been proposed in the literature. Thus, this review discusses the various mechanisms provided for the biological synthesis of metal nanoparticles by peptides, bacteria, fungi, and plants. One thing that is clear is that the mechanistic aspects in some of the biological systems need more detailed studies.

Keywords: Silver; Nanobiotechnology; Nanoparticles; Biogenic; Mechanisms

Prospects of molecular markers in Fusarium species diversity by Nayaka S. Chandra; E. G. Wulff; A. C. Udayashankar; B. P. Nandini; S. R. Niranjana; C. N. Mortensen; H. S. Prakash (pp. 1625-1639).

Recent developments in genomics have opened up for newer opportunities to study the diversity and classification of fungi. The genus Fusarium contains many plant pathogens that attack diverse agricultural crops. Fusarium spp. are not only pathogenic to plants but are also known as toxin producers that negatively affect animal and human health. The identification of Fusarium species still remains one of the most critical issues in fungal taxonomy, given that the number of species recognized in the genus has been constantly changing in the last century due to the different taxonomic systems. This review focuses of various molecular-based techniques employed to study the diversity of Fusarium species causing diseases in major food crops. An introduction of fusarial diseases and their mycotoxins and molecular-marker-based methods for detection introduce the concept of marker application. Various well-known molecular techniques such as random amplified polymorphic DNA, amplification fragment length polymorphism, etc. to more modern ones such as DNA microarrays, DNA barcoding, and pyrosequencing and their application form the core of the review. Target regions in the genome which can be potential candidates for generation of probes and their use in phylogeny of Fusarium spp. are also presented. The concluding part emphasizes the value of molecular markers for assessing genetic variability and reveals that molecular tools are indispensable for providing information not only of one Fusarium species but on whole fungal community. This will be of extreme value for diagnosticians and researchers concerned with fungal biology, ecology, and genetics.

Keywords: Fusarium ; Mycotoxins; Diversity; Molecular markers; Genetic variability

Tools for genetic manipulations in Corynebacterium glutamicum and their applications by Jan Nešvera; Miroslav Pátek (pp. 1641-1654).

Corynebacterium glutamicum is an important industrial producer of various amino acids with great potential for the production of other metabolites. The complete genome sequences of two C. glutamicum strains were determined and the use of genome-based approaches (transcriptomics, proteomics, metabolomics, and fluxomics) provided large amounts of data on the metabolism of this bacterium and its regulation. Many tools for genetic manipulations in C. glutamicum have been developed and used for the analysis of gene functions as well as for the construction and improvement of production strains. These tools include various types of plasmid vectors (cloning, promoter–probe, and expression vectors), DNA transfer methods, cloning heterologous genes, introducing protein secretion systems and gene replacement and genome rearrangement methods. Here we summarize the latest developments in the field of genetic engineering in C. glutamicum, give examples of the use of these new tools, and mention the challenges which stand in the way of fully implementing these tools and this acquired knowledge for the construction of superior production strains.

Keywords: Corynebacterium glutamicum ; Plasmid vectors; Promoters; Gene replacement; Genome manipulations; Amino acid-producing strains

Functionalization of biomolecules on nanoparticles: specialized for antibacterial applications by Murugan Veerapandian; Kyusik Yun (pp. 1655-1667).

Biological efficiency of existing antimicrobial agents is still inadequate to ensure optimal therapeutic index. Developing biocompatible advanced functional materials with antimicrobial properties could be promising for environmentally benign applications. Nanoparticles and other nanoscale materials are of great interest due to their multiple potential applications in material science, medicine, and industry. Nanomaterials possess well renowned antimicrobial activity against several microorganisms; however, it has some non-specific toxicity. Biofunctionalization of nanomaterials is one such topic to address this issue. Rational selection of therapeutically active biomolecules for design of nanoparticles will certainly increase the biological applicability. The present paper describes the current status of different types of biofunctionalized nanoparticles and their antibacterial applications. Key principles such as strategies involved at bio-/nanointerface, the structural activity relationship, and mechanism of action involved in the antibacterial activity of functionalized nanoparticles are briefly discussed. This knowledge is important from the objective of generation of advanced functional nanomaterials with antimicrobial properties.

Keywords: Biomolecules; Nanoparticles; Functionalization; Bio-/nanointerface; Antibacterial application

Anaerobic thermophilic fermentation for carboxylic acid production from in-storage air-lime-treated sugarcane bagasse by Zhihong Fu; Mark T. Holtzapple (pp. 1669-1679).

Wet storage and in situ lime pretreatment (50 °C, 1-atm air, 56 days, excess lime loading of 0.3 g Ca(OH)₂/g dry biomass) of sugarcane bagasse (4,000 g dry weight) was performed in a bench-scale pile pretreatment system. Under thermophilic conditions (55 °C, NH₄HCO₃ buffer, methane inhibitors), air-lime-treated bagasse (80 wt.%) and chicken manure (20 wt.%) were anaerobically co-digested in 1-L rotary fermentors by a mixed culture of marine microorganisms (Galveston, TX). During four-stage countercurrent fermentation, the resulting carboxylic acids consisted of primarily acetate (average 87.7 wt.%) and butyrate (average 9.0 wt.%). The experimental fermentation trains had the highest yield (0.47 g total acids/g volatile solids (VS) fed) and highest selectivity (0.79 g total acids/g VS digested) at a total acid concentration of 28.3 g/L, which is equivalent to an ethanol yield of 105.2 gal/(tonne VS fed). Both high total acid concentrations (>44.7 g/L) and high substrate conversions (>77.5%) are predicted for countercurrent fermentations of bagasse at commercial scale, allowing for an efficient conversion of air-lime-treated biomass to liquid transportation fuels and chemicals via the carboxylate platform.

Keywords: Mixed-culture fermentation; Air-lime pretreatment; Carboxylate platform; Ultimate consolidated bioprocessing; Simultaneous storage and pretreatment; Marine microorganisms

High-flux isobutanol production using engineered Escherichia coli: a bioreactor study with in situ product removal by Antonino Baez; Kwang-Myung Cho; James C. Liao (pp. 1681-1690).

Promising approaches to produce higher alcohols, e.g., isobutanol, using Escherichia coli have been developed with successful results. Here, we translated the isobutanol process from shake flasks to a 1-L bioreactor in order to characterize three E. coli strains. With in situ isobutanol removal from the bioreactor using gas stripping, the engineered E. coli strain (JCL260) produced more than 50 g/L in 72 h. In addition, the isobutanol production by the parental strain (JCL16) and the high isobutanol-tolerant mutant (SA481) were compared with JCL260. Interestingly, we found that the isobutanol-tolerant strain in fact produced worse than either JCL16 or JCL260. This result suggests that in situ product removal can properly overcome isobutanol toxicity in E. coli cultures. The isobutanol productivity was approximately twofold and the titer was 9% higher than n-butanol produced by Clostridium in a similar integrated system.

Keywords: Biofuels; Isobutanol; E. coli ; Gas stripping; Bioreactor

Trimerization of murine TNF ligand family member LIGHT increases the cytotoxic activity against the FM3A mammary carcinoma cell line by Tatsuo Ito; Keiji Iwamoto; Isamu Tsuji; Hideto Tsubouchi; Hiroaki Omae; Takayuki Sato; Hiroyoshi Ohba; Tomofumi Kurokawa; Yoshio Taniyama; Yasushi Shintani (pp. 1691-1699).

LIGHT is a member of the tumor necrosis factor ligand superfamily, which plays important roles in inflammatory and immune responses. LIGHT forms a membrane-anchored homotrimeric complex on the cell surface and is often processed as a soluble protein. Recombinant soluble human LIGHT produced by mammalian cells or Escherichia coli is functional at nanomolar concentrations. However, there is little information about the biological activity of mouse LIGHT (mLIGHT) because of the difficulty in producing bioactive soluble mLIGHT. In this study, recombinant trimeric soluble mLIGHT, or Foldon-mLIGHT, was produced by fusing mLIGHT with the trimerization domain foldon from bacteriophage T4 fibritin. Foldon-mLIGHT was secreted from 293F cells as a 68-kDa trimeric protein. The recombinant protein potently inhibited the growth of the FM3A mouse mammary carcinoma cell line with an IC₅₀ of 77 pM; however, the monomer or dimer forms of mLIGHT produced by E. coli or mammalian cell systems showed weak or no inhibitory activity. These data clearly indicated that trimerization of soluble mLIGHT is essential for its biological activity.

Keywords: LIGHT; Foldon; Trimer; FM3A; Lymphotoxin β receptor; Herpes virus entry mediator

Characterization of an exo-β-1,3-d-galactanase from Sphingomonas sp. 24T and its application to structural analysis of larch wood arabinogalactan by Tatsuji Sakamoto; Hiromasa Tanaka; Yuichi Nishimura; Megumi Ishimaru; Naoya Kasai (pp. 1701-1710).

A type II arabinogalactan-degrading enzyme, termed Exo-1,3-Gal, was purified to homogeneity from the culture filtrate of Sphingomonas sp. 24T. It has an apparent molecular mass of 48 kDa by SDS–PAGE. Exo-1,3-Gal was stable from pH 3 to 10 and at temperatures up to 40 °C. The optimum pH and temperature for enzyme activity were pH 6 to 7 and 50 °C, respectively. Galactose was released from β-1,3-d-galactan and β-1,3-d-galactooligosaccharides by the action of Exo-1,3-Gal, indicating that the enzyme was an exo-β-1,3-d-galactanase. Analysis of the reaction products of β-1,3-galactotriose by high-performance anion-exchange chromatography revealed that the enzyme hydrolyzed the substrate in a non-processive mode. Exo-1,3-Gal bypassed the branching points of β-1,3-galactan backbones in larch wood arabinogalactan (LWAG) to produce mainly galactose, β-1,6-galactobiose, and unidentified oligosaccharides 1 and 2 with the molar ratios of 7:19:62:12. Oligosaccharides 1 and 2 were enzymatically determined to be β-1,6-galactotriose and β-1,6-galactotriose substituted with a single arabinofuranose residue, respectively. The ratio of side chains enzymatically released from LWAG was in good agreement with the postulated structure of the polysaccharide previously determined by chemical methods.

Keywords: Sphingomonas sp; Arabinogalactan; Exo-β-1,3-d-galactanase; Larch wood

A conidial protein (CP15) of Beauveria bassiana contributes to the conidial tolerance of the entomopathogenic fungus to thermal and oxidative stresses by Sheng-Hua Ying; Ming-Guang Feng (pp. 1711-1720).

Aerial conidia are central dispersing structures for most fungi and represent the infectious propagule for entomopathogenic fungus Beauveria bassiana, thus the active ingredients of commercial mycoinsecticides. Although a number of formic-acid-extractable (FAE) cell wall proteins from conidia have been characterized, the functions of many such proteins remain obscure. We report that a conidial FAE protein, termed CP15, isolated from B. bassiana is related to fungal tolerance to thermal and oxidative stresses. The full-length genomic sequence of CP15 was shown to lack introns, encoding for a 131 amino acid protein (15.0 kDa) with no sequence identity to any known proteins in the NCBI database. The function of this new gene with two genomic copies was examined using the antisense-RNA method. Five transgenic strains displayed various degrees of silenced CP15 expression, resulting in significantly reduced conidial FAE protein profiles. The FAE protein contents of the strains were linearly correlated to the survival indices of their conidia when exposed to 30-min wet stress at 48°C (r ² = 0.93). Under prolonged 75-min heat stress, the median lethal times (LT₅₀s) of their conidia were significantly reduced by 13.6–29.5%. The CP15 silenced strains were also 20–50% less resistant to oxidative stress but were not affected with respect to UV-B or hyperosmotic stress. Our data indicate that discrete conidial proteins may mediate resistance to some abiotic stresses, and that manipulation of such proteins may be a viable approach to enhancing the environmental fitness of B. bassiana for more persisting control of insect pests in warmer climates.

Keywords: Beauveria bassiana ; Conidial protein; Formic acid extraction; Fungal thermotolerance; Antisense-RNA mediated gene silence

Metabolic engineering of 1,2-propanediol pathways in Corynebacterium glutamicum by Satoko Niimi; Nobuaki Suzuki; Masayuki Inui; Hideaki Yukawa (pp. 1721-1729).

We analyzed 1,2-propanediol (1,2-PD) production in metabolically engineered Corynebacterium glutamicum. Wild-type C. glutamicum produced 93 μM 1,2-PD after 132 h incubation under aerobic conditions. No gene encoding the methylglyoxal synthase (MGS) which catalyzes the first step of 1,2-PD synthesis from the glycolytic pathway was detected on the C. glutamicum genome, but several genes annotated as encoding putative aldo-keto reductases (AKRs) were present. AKR functions as a methylglyoxal reductase in the 1,2-PD synthesis pathway. Expressing Escherichia coli mgs gene in C. glutamicum increased 1,2-PD yield 100-fold, suggesting that wild-type C. glutamicum carries the genes downstream of MGS in the 1,2-PD synthesis pathway. Furthermore, simultaneous overexpression of mgs and cgR_2242, one of the genes annotated as AKRs, enhanced 1,2-PD production to 24 mM. This work establishes that 1,2-PD synthesis by C. glutamicum, previously unknown, is possible.

Keywords: 1,2-Propanediol; Corynebacterium ; Aldo-keto reductase

Transesterification of phosphatidylcholine in sn-1 position through direct use of lipase-producing Rhizopus oryzae cells as whole-cell biocatalyst by Shinji Hama; Kazunori Miura; Ayumi Yoshida; Hideo Noda; Hideki Fukuda; Akihiko Kondo (pp. 1731-1738).

The enzymatic process presents an advantage of producing specified phospholipids that rarely exist in nature. In this study, we investigated the regiospecific modification of phosphatidylcholine (PC) in the sn-1 position using immobilized Rhizopus oryzae. In a reaction mixture containing egg yolk PC and exogenous lauric acid (LA) in n-hexane, lipase-producing R. oryzae cells immobilized within biomass support particles (BSPs) showed a much higher transesterification activity than lipase powders. To improve the product yield, several parameters including substrate ratio and reaction time were investigated, resulting in the incorporation of 44.2% LA into the product PC after a 48-h reaction. The analysis of the molecular structure showed that a large proportion of exogenous LA (>90%) was incorporated in the sn-1 position of the enzymatically modified PC. Moreover, the BSP-immobilized R. oryzae maintained its activity for more than 12 batch cycles. The presented results, therefore, suggest the applicability of BSP-immobilized R. oryzae as a whole-cell biocatalyst for the regiospecific modification of phospholipids.

Keywords: Phospholipids; Transesterification; Lipase regiospecificity; Cell immobilization; Biomass support particles

Profiling of biodegradation and bacterial 16S rRNA genes in diverse contaminated ecosystems using 60-mer oligonucleotide microarray by Ashutosh Pathak; Rishi Shanker; Satyendra Kumar Garg; Natesan Manickam (pp. 1739-1754).

We have developed an oligonucleotide microarray for the detection of biodegradative genes and bacterial diversity and tested it in five contaminated ecosystems. The array has 60-mer oligonucleotide probes comprising 14,327 unique probes derived from 1,057 biodegradative genes and 880 probes representing 110 phylogenetic genes from diverse bacterial communities, and we named it as BiodegPhyloChip. The biodegradative genes are involved in the transformation of 133 chemical pollutants. Validation of the microarray for its sensitivity specificity and quantitation were performed using DNA isolated from well-characterized mixed bacterial cultures also having non-target strains, pure degrader strains, and environmental DNA. Application of the developed array using DNA extracted from five different contaminated sites led to the detection of 186 genes, including 26 genes unique to the individual sites. Hybridization of 16S rRNA probes revealed the presence of bacteria similar to well-characterized genera involved in biodegradation of various pollutants. Genes involved in complete degradation pathways for hexachlorocyclohexane (lin), 1,2,4-trichlorobenzene (tcb), naphthalene (nah), phenol (mph), biphenyl (bph), benzene (ben), toluene (tbm), xylene (xyl), phthalate (pht), Salicylate (sal), and resistance to mercury (mer) were detected with highest intensity. The most abundant genes belonged to the enzyme hydroxylases, monooxygenases, and dehydrogenases which were present in all the five samples. Thus, the array developed and validated here shall be useful in assessing not only the biodegradative potential but also the composition of environmentally useful bacteria, simultaneously, from hazardous ecosystems.

Keywords: BiodegPhyloChip; 60-mer oligoarray; Biodegradation genes; 16S rRNA genes

Synthesis of a citrulline-rich cyanophycin by use of Pseudomonas putida ATCC 4359 by Lars Wiefel; Anna Bröker; Alexander Steinbüchel (pp. 1755-1762).

Synthesis of cyanophycin (multi-l-arginyl-poly-l-aspartic acid, CGP) in recombinant organisms is an important option to obtain sufficiently large amounts of this polymer with a designed composition for use as putative precursors for biodegradable technically interesting chemicals. Therefore, derivates of CGP, harbouring a wider range of constituents, are of particular interest. As shown previously, cyanophycin synthetases with wide substrate ranges incorporate other amino acids than arginine. Therefore, using an organism, which produces the required supplement by itself, was the next logical step. Former studies showed that Pseudomonas putida strain ATCC 4359 is able to produce large amounts of l-citrulline from l-arginine. By expressing the cyanophycin synthetase of Synechocystis sp. PCC 6308, synthesis of CGP was observed in P. putida ATCC 4359. Using an optimised medium for cultivation, the strain was able to synthesise insoluble CGP amounting up to 14.7 ± 0.7% (w/w) and soluble CGP amounting up to 28.7 ± 0.8% (w/w) of the cell dry matter, resulting in a total CGP content of the cells of 43.4% (w/w). HPLC analysis of the soluble CGP showed that it was composed of 50.4 ± 1.3 mol % aspartic acid, 32.7 ± 2.8 mol % arginine, 8.7 ± 1.6 mol % citrulline and 8.3 ± 0.4 mol % lysine, whereas the insoluble CGP contained less than 1 mol % of citrulline. Using a mineral salt medium with 1.25 or 2% (w/v) sodium succinate, respectively, plus 23.7 mM l-arginine, the cells synthesised insoluble CGP amounting up to 25% to 29% of the CDM with only a very low citrulline content.

Keywords: Cyanophycin; l-Citrulline; Pseudomonas putida

Involvements of S-nitrosylation and denitrosylation in the production of polyphenols by Inonotus obliquus by Weifa Zheng; Yubing Liu; Shenyuan Pan; Weihua Yuan; Yucheng Dai; Jiangchun Wei (pp. 1763-1772).

Nitric oxide (NO) has been evidenced to mediate biosynthesis of polyphenols in Inonotus obliquus. However, it remains unknown how NO regulates their biosynthesis. Here we show that higher cellular NO levels coincided with higher accumulation of S-nitrosothiols (SNO; the products of NO combined with a specific residue in glutathione or proteins) and polyphenols, and higher activity of denitrosylated S-nitrosoglutathione reductase (GSNOR) and thioredoxin reductase (TrxR). This homeostasis was breached by GSNOR or TrxR inhibitors. Inhibiting GSNOR boosted TrxR activity, but reduced SNO formation, coinciding with an enhanced production of polyphenols. Likewise, inhibiting TrxR increased GSNOR activity and SNO production, but downregulated accumulation of polyphenols. Inhibiting GSNOR or TrxR also modified the polyphenolic profiles of I. obliquus. Suppressing GSNOR-enhanced biosynthesis of phelligridins C and H, inoscavin C and methyl inoscavin B, but reduced that of phelligridin D, methyl inoscavin A, davallialactone and methyl davallialactone, the typical polyphenols in I. obliquus. Similarly, downregulating TrxR increased production of phelligridin D, methyl inoscavin A, davallialactone, and methyl davallialactone, but shrinking that of phelligridins C and H, methyl inoscavin B and inoscavin C. Thus, in I. obliquus, the state of S-nitrosylation and denitrosylation affects not only the accumulation of polyphenols, but also their metabolic profiles.

Keywords: Inonotus obliquus ; Nitric oxide; S-nitrosylation; Denitrosylation; Polyphenols

Spontaneous bacterial cell lysis and biofilm formation in the colon of the Cape Dune mole-rat and the laboratory rabbit by Sanet H. Kotzé; Zoie E. Holzknecht; Anitra D. Thomas; Mary Lou Everett; Shanna Taylor; Larry D. Duckett; John Whitesides; Patrice McDermott; Shu S. Lin; William Parker (pp. 1773-1783).

A wide range of techniques, including high-throughput DNA sequencing methods, have been applied to the evaluation of the normal intestinal flora. However, the inability to grow many of those species in culture imposes substantial constraints on the techniques used to evaluate this important community. The presence of biofilms in the normal gut adds further complexity to the issue. In this study, a flow cytometric analysis was used to separate intact bacterial cells, cell debris, and other particulate matter based on bacteria-specific staining and particle size. In addition, an analysis of biofilm formation using fluorescent light microscopy was conducted. Using these approaches, the ratio of bacterial cell debris to intact bacterial cells as a measure of spontaneous lysis of bacterial cells in the gut of the Cape dune mole-rat (Bathyergus suillus) and the laboratory rabbit (Oryctolagus cuniculus) was examined, and the degree of biofilm formation was semi-quantitatively assessed. The results suggest that the degree of spontaneous cell lysis was greater in the appendix than in the cecum in both the mole-rat and the rabbit. Further, the results point toward extensive epithelial-associated biofilm formation in the proximal mole-rat and rabbit large bowel, although the biofilms may be less structured than those found in laboratory rodents and in humans.

Keywords: Biofilm; Cecal appendix; Flow cytometry; Mole-rat; Rabbit; Spontaneous lysis

Impacts of cell surface characteristics on population dynamics in a sequencing batch yeast reactor treating vegetable oil-containing wastewater by Wenzhou Lv; Abd El-Latif Hesham; Yu Zhang; Xinchun Liu; Min Yang (pp. 1785-1793).

Ten yeast strains acquired from different sources and capable of utilizing vegetable oil or related compounds (fatty acid or oleic acid) as sole carbon sources were inoculated into a sequencing batch reactor (SBR) for the treatment of high-strength vegetable oil-containing wastewater. The SBR system stably removed >89% of chemical oxygen demand (COD) and >99% of oil when fed with wastewater containing 15 g/L COD and 10 g/L oil in average. Denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 26S rRNA genes showed that among the ten yeast strains, only Candida lipolytica, Candida tropicalis, and Candida halophila were dominant in the system. To elucidate the major factors affecting the selection of yeast strains in the SBR system, the three dominant strains were compared with two non-dominant strains in terms of COD removal performance, biomass yield, cell settleability, cell flocculation ability, cell emulsification ability, and surface hydrophobicity. Results showed that hydrophobicity and emulsification ability of yeast cells were the two most important factors determining the selection of yeast strains in the treatment of high-strength oil-containing wastewater.

Keywords: Yeast; Population dynamics; Vegetable oil-containing wastewater; Cell surface properties; Hydrophobicity; Emulsification ability

Biodegradation behavior of natural organic matter (NOM) in a biological aerated filter (BAF) as a pretreatment for ultrafiltration (UF) of river water by Guocheng Huang; Fangang Meng; Xing Zheng; Yuan Wang; Zhigang Wang; Huijun Liu; Martin Jekel (pp. 1795-1803).

In this study, biodegradation of natural organic matter (NOM) in a biological aerated filter (BAF) as pretreatment of UF treating river water was investigated. Photometric measurement, three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy and liquid chromatography with online organic carbon detector (LC-OCD) were used to investigate the fate of NOM fractions in the BAF + UF process. Results showed that the BAF process could effectively remove particles and parts of dissolved organic matter, which led to a lower NOM loading in the UF system, but different NOM fractions showed different biodegradation potentials. Further biodegradation batch experiments confirmed this observation and identified that polysaccharides and proteins (quantified using photometric methods) contained a large proportion of readily biodegradable matter while humic substances were mainly composed of inert organic substances. According to EEM measurements, it is evident that protein-like substances were more readily eliminated by microorganisms than humic-like substances. LC-OCD data also supported the phenomena that the polysaccharides and large-size proteins were more degradable than humic substances.

Keywords: Drinking water treatment; Membrane fouling; Biological aerated filter; Natural organic matter

Electrogenic capacity and community composition of anodic biofilms in soil-based bioelectrochemical systems by David B. Ringelberg; Karen L. Foley; Charles M. Reynolds (pp. 1805-1815).

Although a number of bacteria are known to be capable of generating an electrical current, the diversity of electrogenic bacteria in soils and the commonality across soil types is relatively unknown. Simple bioelectrochemical cells were constructed to measure the electrogenic capacity and community composition of bacteria originating on cell anodes from three biogeochemically distinct soil types. All three soils supported electrogenic activity, amounting to a maximum sustained current of 1.5–2.1 mA over 55 days. Analysis of fatty acids identified differences in microbial community composition between anode biofilms and far-field soil materials. Anode communities showed greater percentages of fatty acids indicative of Gram-negative bacteria and Actinomycetes. By analysis of anode biofilm genomic DNA via terminal-restriction fragment-length polymorphisms, commonalities in community composition across the three soil types were identified, specifically, the putative presence of bacterial species belonging to the α- and ß-Proteobacteria and the Firmicutes. Subsequent culture and isolation of bacteria from the anodes confirmed the presence of similar classes of bacteria. Results showed that, under saturated conditions, different soils can support electrogenic activity and that the bacterial communities that develop on the anodes share certain common inherent community traits.

Keywords: Bioelectrochemical system (BES); Anode biofilm; Community composition

Electrogenic capacity and community composition of anodic biofilms in soil-based bioelectrochemical systems by David B. Ringelberg; Karen L. Foley; Charles M. Reynolds (pp. 1805-1815).

Keywords: Bioelectrochemical system (BES); Anode biofilm; Community composition

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Applied Microbiology and Biotechnology (v.90, #5)