Check out our New Publishers' Select for Free Articles

Applied Microbiology and Biotechnology (v.78, #5)

Lipolytic enzymes in Mycobacterium tuberculosis by K. Côtes; J. C. Bakala N’Goma; R. Dhouib; I. Douchet; D. Maurin; F. Carrière; S. Canaan (pp. 741-749).

Mycobacterium tuberculosis is a bacterial pathogen that can persist for decades in an infected patient without causing a disease. In vivo, the tubercle bacillus present in the lungs store triacylglycerols in inclusion bodies. The same process can be observed in vitro when the bacteria infect adipose tissues. Indeed, before entering in the dormant state, bacteria accumulate lipids originating from the host cell membrane degradation and from de novo synthesis. During the reactivation phase, these lipids are hydrolysed and the infection process occurs. The degradation of both extra and intracellular lipids can be directly related to the presence of lipolytic enzymes in mycobacteria, which have been ignored during a long period particularly due to the difficulties to obtain a high expression level of these enzymes in M. tuberculosis. The completion of the M. tuberculosis genome offered new opportunity to this kind of study. The aim of this review is to focus on the recent results obtained in the field of mycobacterium lipolytic enzymes and although no experimental proof has been shown in vivo, it is tempting to speculate that these enzymes could be involved in the virulence and pathogenicity processes.

Keywords: Mycobacterium tuberculosis ; Lipase; Phospholipase; TAG; Lipidic inclusion bodies; Infection; Granuloma

Lactic acid production from lime-treated wheat straw by Bacillus coagulans: neutralization of acid by fed-batch addition of alkaline substrate by Ronald H. W. Maas; Robert R. Bakker; Mickel L. A. Jansen; Diana Visser; Ed de Jong; Gerrit Eggink; Ruud A. Weusthuis (pp. 751-758).

Conventional processes for lignocellulose-to-organic acid conversion requires pretreatment, enzymatic hydrolysis, and microbial fermentation. In this study, lime-treated wheat straw was hydrolyzed and fermented simultaneously to lactic acid by an enzyme preparation and Bacillus coagulans DSM 2314. Decrease in pH because of lactic acid formation was partially adjusted by automatic addition of the alkaline substrate. After 55 h of incubation, the polymeric glucan, xylan, and arabinan present in the lime-treated straw were hydrolyzed for 55%, 75%, and 80%, respectively. Lactic acid (40.7 g/l) indicated a fermentation efficiency of 81% and a chiral l(+)-lactic acid purity of 97.2%. In total, 711 g lactic acid was produced out of 2,706 g lime-treated straw, representing 43% of the overall theoretical maximum yield. Approximately half of the lactic acid produced was neutralized by fed-batch feeding of lime-treated straw, whereas the remaining half was neutralized during the batch phase with a Ca(OH)₂ suspension. Of the lime added during the pretreatment of straw, 61% was used for the neutralization of lactic acid. This is the first demonstration of a process having a combined alkaline pretreatment of lignocellulosic biomass and pH control in fermentation resulting in a significant saving of lime consumption and avoiding the necessity to recycle lime.

Keywords: Lime-treated wheat straw; Simultaneous saccharification and fermentation; Lactic acid; Calcium hydroxide; pH control

DO-stat fed-batch production of 2-keto-d-gluconic acid from cassava using immobilized Pseudomonas aeruginosa by Mei Chia; Thi Bich Van Nguyen; Won Jae Choi (pp. 759-765).

Bioconversion of cassava-derived glucose to 2-keto-d-gluconic acid (2-KDG) using resting cells of immobilized Pseudomonas aeruginosa IFO 3448 was investigated. The tuberous roots of cassava were selected as the feedstock as they are inexpensive and widely available, and possess high amounts of starch (approximately 70% (w/w) of dry mass). Immobilized bacteria was used in a fed-batch fermenter and recycled over a period of 2 weeks. Given that the formation of 2-KDG from glucose requires oxygen as a reagent, and that high glucose concentrations are detrimental to the production yield of 2-KDG by resting cells, a DO-stat control strategy was used, whereby the feed rate of cassava hydrolysate was regulated by coupling it with the control variable, dissolved oxygen. For 319 h of operation including three cycles of repeated fed batch, 72 g of 2-KDG was produced from hydrolysate derived from 110 g of dried cassava at a maximum production rate of 0.55 g/L/h and an average concentration of 35 g/L.

Keywords: 2-Keto-d-gluconic acid; Pseudomonas aeruginosa ; DO-stat fed batch; Cassava

Stabilization of water-in-oil emulsion by Rhodococcus opacus B-4 and its application to biotransformation by Kohsuke Honda; Shiho Yamashita; Hiroyuki Nakagawa; Yuka Sameshima; Takeshi Omasa; Junichi Kato; Hisao Ohtake (pp. 767-773).

Rhodococcus opacus B-4, which has recently been isolated as an organic solvent-tolerant bacterium, stabilized water-in-oil (w/o) emulsions by inhibition of droplet coalescence when the cells were dispersed in 90% (v/v) organic solvents. Confocal microscopy revealed that many bacterial cells assembled at the interface between oil and water droplets, though free cells were also detectable at the inside of water droplets. Bacterial cells in the w/o emulsion were capable of utilizing both a water-soluble (glucose) and an oil-soluble substrate (oleic acid) as an energy source. Availability of the w/o emulsion as an immobilized cell system in organic solvents was demonstrated using production of indigo from indole and production of o-cresol from toluene as model conversions. When glucose and oleic acid were simultaneously supplied as energy sources, the w/o emulsion culture of R. opacus B-4 produced indigo and o-cresol at levels of 0.217 and 2.12 mg ml⁻¹, respectively, by 12 h.

Keywords: Rhodococcus opacus ; Organic solvent-tolerant bacteria; Water-in-oil emulsion; Hydrophobicity

Enhancement of thermostability of fungal deglycating enzymes by directed evolution by Kozo Hirokawa; Atsushi Ichiyanagi; Naoki Kajiyama (pp. 775-781).

Fructosyl peptide oxidases are valuable for the determination of glycoproteins such as hemoglobin A1c. For practical use in clinical diagnosis, we applied directed evolution to improve the thermostability of these enzymes. After two rounds of random mutagenesis and high-throughput screening, six thermostabilizing amino acid substitutions were identified. Therefore, site-directed and cassette mutageneses were applied to combine these six stabilizing mutations. The simultaneous mutants showed that the stabilizing effect of the amino acid replacement was cumulative. The sextuple mutant enzyme, R94K/G184D/F265L/N272D/H302R/H388Y, had a half-life of thermal inactivation at 50°C that was 79.8-fold longer than that of the parental fructosyl peptide oxidase. The thermostable variants also showed increased tolerance to digestion by a protease. The sextuple mutant enzyme did not lose its activity on incubation with neutral protease, while the wild-type enzyme almost completely lost its activity. Furthermore, three amino acid substitutions were introduced into another fructosyl peptide oxidase with a different substrate specificity. The half-life of inactivation at 50°C was 3.61-fold longer than that of the parent enzyme. These engineered fructosyl peptide oxidases will be useful for industrial application to clinical diagnosis.

Keywords: Directed evolution; Enzymatic measurement of hemoglobin A1c; HbA1c; Fructosyl amino acid oxidase; Fructosyl peptide oxidase

Flavour formation in fungi: characterisation of KlAtf, the Kluyveromyces lactis orthologue of the Saccharomyces cerevisiae alcohol acetyltransferases Atf1 and Atf2 by Stijn D. M. Van Laere; Sofie M. G. Saerens; Kevin J. Verstrepen; Patrick Van Dijck; Johan M. Thevelein; Freddy R. Delvaux (pp. 783-792).

Volatile aroma-active esters are responsible for the fruity character of fermented alcoholic beverages, such as beer and wine. In the brewers’ yeast Saccharomyces cerevisiae, the major part of these esters is formed by two alcohol acetyltransferases, Atf1 and Atf2. In this paper, the existence of orthologues of these S. cerevisiae alcohol acetyltransferases in several ascomycetous fungi was investigated. Bioinformatic analysis of sequenced fungal genomes revealed the presence of multiple orthologues. The Saccharomyces sensu stricto yeasts all have two genes coding for orthologues. More distantly related fungi like Saccharomyces castelii, Candida glabrata, Kluyveromyces waltii and Kluyveromyces lactis have only one orthologue in their genome. The homology between the identified proteins and the S. cerevisiae alcohol acetyltransferases suggests a role for these orthologues in the aroma-active ester formation. To verify this, the K. lactis orthologue KlAtf was cloned and expressed in S. cerevisiae. Gas chromatographic analysis of small-scale fermentations with the transformant strains showed that, while S. cerevisiae ATF1 overexpression resulted in a substantial increase in acetate ester levels, S. cerevisiae ATF2 and K. lactis ATF overexpression only caused a moderate increase in acetate esters. This study is the first report of the presence of an ester synthesis gene in K. lactis.

Keywords: Esters; Aroma formation; Kluyveromyces lactis ; Saccharomyces cerevisiae ; Isoamyl acetate; Fermentation

Screening, cloning, expression, and purification of an acidic arylmalonate decarboxylase from Enterobacter cloacae KU1313 by Yoshito Yatake; Kenji Miyamoto; Hiromichi Ohta (pp. 793-799).

We have already isolated, purified, and characterized arylmalonate decarboxylases (AMDase; EC. 4.1.1.76) from Alcaligenes bronchisepticus KU1201 and Achromobacter sp. KU1311. These are unique enzymes that give optically pure α-arylpropionates from the corresponding α-aryl-α-methylmalonates. Recently, we have further screened novel AMDase producers from soil samples under acidic conditions and succeeded in isolating Enterobacter cloacae KU1313. The gene encoding the enzyme was cloned by polymerase chain reaction and sequenced. The AMDase gene consists of 720 nucleotides, which specifies a 240-amino-acid protein. The recombinant enzyme was purified and shown that the pH-activity profiles were quite different from those of known AMDases.

Keywords: Enterobacter cloacae ; Arylmalonate decarboxylase; AMDase; Asymmetric decarboxylation; Purification

Uncovering the gene knockout landscape for improved lycopene production in E. coli by Hal Alper; Gregory Stephanopoulos (pp. 801-810).

Systematic and combinatorial genetic approaches for the identification of gene knockout and overexpression targets have been effectively employed in the improvement of cellular phenotypes. Previously, we demonstrated how two of these tools, metabolic modeling and transposon mutagenesis, can be combined to identify strains of interest spanning the metabolic landscape of recombinant lycopene production in Escherichia coli. However, it is unknown how to best select multiple-gene knockout targets. Hence, this study seeks to understand how the overall order of gene selection, or search trajectory, biases the exploration and topology of the metabolic landscape. In particular, transposon mutagenesis and selection were employed in the background of eight different knockout genotypes. Collectively, 800,000 mutants were analyzed in hopes of exhaustively identifying all advantageous gene knockout targets. Several interesting observations, including clusters of gene functions, recurrence, and divergent genotypes, demonstrate the complexity of mapping only one genotype to one phenotype. One particularly interesting mutant, the ΔhnrΔyliE genotype, exhibited a drastically improved lycopene production capacity in basic minimal medium in comparison to the best strains identified in previous studies.

Keywords: Metabolic engineering; Lycopene; Knockout; Landscape; Search; Trajectory

Temporal regulation of enterohemorrhagic Escherichia coli virulence mediated by autoinducer-2 by Tarun Bansal; Palmy Jesudhasan; Suresh Pillai; Thomas K. Wood; Arul Jayaraman (pp. 811-819).

The autoinducer-2 (AI-2) molecule is produced by many bacterial species, including various human gastrointestinal (GI) tract commensal bacteria, and has been proposed to be involved in interspecies communication. Because pathogens are likely to encounter AI-2 in the GI tract, we studied the effects of AI-2 on various phenotypes associated with enterohemorrhagic Escherichia coli (EHEC) infections. AI-2 attracted EHEC in agarose plug chemotaxis assays and also increased swimming motility, as well as increased EHEC attachment to HeLa cells. The molecular basis underlying the stimulation of EHEC chemotaxis, motility, and colonization by AI-2 was investigated at the transcriptome level using DNA microarrays. We found that exposure to AI-2 altered the expression of 23 locus of enterocyte effacement (LEE) genes directly involved in the production of virulence determinants, as well as other genes associated with virulence (e.g., 46 flagellar/fimbrial genes, 24 iron-related genes), in a temporally defined manner. To our knowledge, this is the first study to report AI-2-mediated regulation of EHEC chemotaxis and colonization, as well as temporal regulation of EHEC transcriptome by AI-2. Our results suggest that AI-2 is an important signal in EHEC infections of the human GI tract.

Keywords: AI-2; Virulence; Enterohemorrhagic E. coli

A low-sodium-salt formulation for the fermentation of salinosporamides by Salinispora tropica strain NPS21184 by Ginger Tsueng; Kin S. Lam (pp. 821-826).

In this paper, we described the development of a potassium-chloride-based-salt formulation containing low sodium concentrations (5.0 to 11 mM) to support the growth of Salinispora tropica strain NPS21184 and its production of salinosporamide A (NPI-0052). The sodium present in the media was essentially derived from the complex nitrogen sources Hy Soy, yeast extract, and peptone used in the media. We demonstrated that good growth rate and yield of S. tropica strain NPS21184 were detected in both agar and liquid media containing the potassium-chloride-based-salt formulation with sodium concentration as low as 5.0 mM, significantly less than the critical seawater-growth requirement concentration of 50 mM sodium for a marine microorganism. We also observed good production of NPI-0052 (176 to 243 mg/l) by S. tropica strain NPS21184 grown in production media containing the potassium chloride-based-salt formulation. The production of deschloro analog, salinosporamide B (NPI-0047), was significantly lower in the low-sodium-salt-formulation medium than in the high-sodium-salt-formulation media. We demonstrated that while S. tropica strain NPS21184 is a novel marine actinomycete that requires high salt content for growth, it does not require sodium-chloride-based seawater-type media for growth and production of NPI-0052.

Keywords: Salinosporamide A; NPI-0052; Salinispora tropica ; Low-sodium-salt formulation; Non-saline fermentation; Non-seawater-growth requirement

Defined salt formulations for the growth of Salinispora tropica strain NPS21184 and the production of salinosporamide A (NPI-0052) and related analogs by Ginger Tsueng; Sy Teisan; Kin S. Lam (pp. 827-832).

Salinosporamide A (NPI-0052) is currently produced by a marine actinomycete, Salinispora tropica, via a saline fermentation process using a non-defined, commercially available synthetic sea salt, Instant Ocean. In order to control the consistency of the production of NPI-0052 and related analogs, two chemically defined salt formulations were developed to replace Instant Ocean. A chemically defined sodium-chloride-based salt formulation with similar sodium and chloride contents as in Instant Ocean was found to support higher production of NPI-0052 and a better metabolite production profile for downstream processing than Instant Ocean. A chemically defined sodium-sulfate-based salt formulation with low chloride concentration at 17 mM was found to support a similar NPI-0052 and metabolite production profile as Instant Ocean. The sodium-sulfate-based formulation is a robust formulation for large-scale production process due to its reduced corrosiveness in fermentation as compared with the saline fermentation utilizing Instant Ocean or the sodium-chloride-based salt formulation. The production of NPI-0052 in both chemically defined salt formulations was successfully scaled-up to a 42-l fermentor, indicating that these salt formulations can be used for large-scale manufacturing process.

Keywords: Salinosporamide A; NPI-0052; Salinispora tropica ; Saline fermentation; Salt formulation

Clavatol and patulin formation as the antagonistic principle of Aspergillus clavatonanicus, an endophytic fungus of Taxus mairei by Chu-Long Zhang; Bi-Qiang Zheng; Jia-Ping Lao; Li-Juan Mao; Shao-Yuan Chen; Christian P. Kubicek; Fu-Cheng Lin (pp. 833-840).

Many endophytic fungi are known to protect plants from plant pathogens, but the antagonistic mechanism has rarely been revealed. In this study, we wished to learn whether an endophytic Aspergillus sp., isolated from Taxus mairei, would indeed produce bioactive components, and if so whether (a) they would antagonize plant pathogenic fungi; and (b) whether this Aspergillus sp. would produce the compound also under conditions of confrontation with these fungi. The endophytic fungal strain from T. mairei was identified as Aspergillus clavatonanicus by analysis of morphological characteristics and the sequence of the internal transcribed spacers (ITS rDNA) of rDNA. When grown in surface culture, the fungus produced clavatol (2′,4′-dihydroxy-3′,5′-dimethylacetophenone) and patulin (2-hydroxy-3,7-dioxabicyclo [4.3.0]nona-5,9-dien-8-one), as shown by shown by NMR, MS, X-ray, and EI-MS analysis. Both exhibited inhibitory activity in vitro against several plant pathogenic fungi, i.e., Botrytis cinerea, Didymella bryoniae, Fusarium oxysporum f. sp. cucumerinum, Rhizoctonia solani, and Pythium ultimum. During confrontation with P. ultimum, A. clavatonanicus antagonized its growth of P. ultimum, and both clavatol as well as patulin were formed as the only bioactive components, albeit with different kinetics. We conclude that A. clavatonanicus produces clavatol and patulin, and that these two polyketides may be involved in the protection of T. mairei against attack by plant pathogens by this Aspergillus sp.

Keywords: Endophytic fungi; Aspergillus clavatonanicus ; Taxus mairei ; Antifungal activity

Thermophilic bacteria in cool temperate soils: are they metabolically active or continually added by global atmospheric transport? by Roger Marchant; Andrea Franzetti; Spyros G. Pavlostathis; Didem Okutman Tas; Isabel Erdbrűgger; Ali Űnyayar; Mehmet A. Mazmanci; Ibrahim M. Banat (pp. 841-852).

Thermophilic soil geobacilli isolated from cool temperate geographical zone environments have been shown to be metabolically inactive under aerobic conditions at ambient temperatures (−5 to 25°C). It is now confirmed that a similar situation exists for their anaerobic denitrification activity. It is necessary therefore to determine the mechanisms that sustain the observed significant viable populations in these soils. Population analysis of thermophiles in rainwater and air samples has shown different species compositions which support the view that long distance global transport and deposition in rainwater is a possible source of replenishment of the soil thermophile populations. Survival experiments using a representative Geobacillus isolate have indicated that while cells lose viability rapidly at most temperatures, populations can increase only when the temperature allows growth to take place at a rate which exceeds death rate. Long term (9-month) experiments at 4°C show population increases which can be accounted for by very slow growth rates complemented by negligible death rates. These results are interpreted in the context of current hypotheses on the biogeography patterns of bacteria.

Keywords: Thermophilic bacteria; Geobacillus ; Global transport; Cool soils; Rainwater; Atmospheric bacteria

Deletion of iscR stimulates recombinant clostridial Fe–Fe hydrogenase activity and H₂-accumulation in Escherichia coli BL21(DE3) by M. Kalim Akhtar; Patrik R. Jones (pp. 853-862).

Proteins that catalyze H₂-pathways often contain iron–sulfur (Fe–S) clusters and are sensitive to O₂. We tested whether deletion of the gene encoding the transcriptional negative regulator, IscR, could enhance the ability of Escherichia coli BL21 to synthesize active recombinant H₂-pathway components and stimulate ferredoxin-dependent H₂-accumulation in the presence or absence of oxygen. Under anoxic conditions, deletion of iscR stimulated recombinant Fe–Fe hydrogenase activity threefold, whilst plasmid-based overexpression of the isc operon had no effect on hydrogenase activity. After cultivation with 21% (v/v) O₂ in the headspace, no recombinant hydrogenase activity was observed in soluble extracts of wild-type BL21, although low levels of activity could be observed in the ΔiscR strain (700-fold lower than anoxic conditions, 180-fold greater than the limit of detection). Under closed batch conditions starting with 5% (v/v) O₂, ΔiscR strains displayed fivefold greater levels of total hydrogenase activity and recombinant ferredoxin-dependent H₂-accumulation relative to the control strain. In cultures starting with 10% (v/v) O₂, H₂-accumulation was stimulated 35-fold relative to the control. ΔiscR strains displayed enhanced synthesis and activity of integral H₂-pathway components under all tested conditions and enhanced H₂-accumulation under partially oxic conditions. Deletion of iscR is, therefore, a useful strategy to stimulate H₂-production, particularly if the hydrogenase catalyzes the rate-limiting reaction.

Quantitative assessment of phenol hydroxylase diversity in bioreactors using a functional gene analysis by Laura A. Basile; Leonardo Erijman (pp. 863-872).

We describe a quantitative analysis of the genetic diversity of phenol-degrading potential in bacterial communities from laboratory-scale activated sludge. Genomic DNA extracted from activated sludge from two sequential batch reactors fed with synthetic sewage plus phenol was amplified using conserved primers for the major subunit of the phenol hydroxylase (LmPH) gene and used to generate clone libraries. Following phylogenetic analysis, 59 sequences containing a 470-bp fragment clustered into six distinct subgroups with a genetic distance of 8%, most likely representing ecologically relevant variants of the enzyme. Seven sets of primers were designed to target the six clusters and used to obtain quantitative information on the dynamics of LmPH gene diversity using real-time PCR assays throughout 9 months of bioreactors operation. Total LmPH gene copy number remained approximately steady in phenol-amended and control reactors. However, a significant increase in phenol-degrading activity in the phenol-amended sludge was accompanied by a parallel increase in LmPH gene diversity, suggesting that phenol degradation in the activated sludge depends on the combined activity of a number of redundant species.

Keywords: Phenol biodegradation; Activated sludge; Real time PCR; DGGE

Brewery wastewater treatment using air-cathode microbial fuel cells by Yujie Feng; Xin Wang; Bruce E. Logan; He Lee (pp. 873-880).

Effective wastewater treatment using microbial fuel cells (MFCs) will require a better understanding of how operational parameters and solution chemistry affect treatment efficiency, but few studies have examined power generation using actual wastewaters. The efficiency of wastewater treatment of a beer brewery wastewater was examined here in terms of maximum power densities, Coulombic efficiencies (CEs), and chemical oxygen demand (COD) removal as a function of temperature and wastewater strength. Decreasing the temperature from 30°C to 20°C reduced the maximum power density from 205 mW/m² (5.1 W/m³, 0.76 A/m²; 30°C) to 170 mW/m² (20°C). COD removals (R _COD) and CEs decreased only slightly with temperature. The buffering capacity strongly affected reactor performance. The addition of a 50-mM phosphate buffer increased power output by 136% to 438 mW/m², and 200 mM buffer increased power by 158% to 528 mW/m². In the absence of salts (NaCl), maximum power output varied linearly with wastewater strength (84 to 2,240 mg COD/L) from 29 to 205 mW/m². When NaCl was added to increase conductivity, power output followed a Monod-like relationship with wastewater strength. The maximum power (P _max) increased in proportion to the solution conductivity, but the half-saturation constant was relatively unaffected and showed no correlation to solution conductivity. These results show that brewery wastewater can be effectively treated using MFCs, but that achievable power densities will depend on wastewater strength, solution conductivity, and buffering capacity.

Keywords: Microbial fuel cell; Beer brewery wastewater; Temperature; Solution conductivity

Optimization and modeling of phenanthrene degradation by Mycobacterium sp. 6PY1 in a biphasic medium using response-surface methodology by Arwa Abdelhay; Jean-Pierre Magnin; Nicolas Gondrexon; Stéphane Baup; John Willison (pp. 881-888).

In the present paper, the degradation of phenanthrene, a model polycyclic aromatic hydrocarbon compound, by the Mycobacterium strain 6PY1 was optimized in a biphasic culture medium. The optimization and modeling were performed using the design of experiments methodology. The temperature, the silicone oil/mineral salts medium volume ratio, and the initial cell concentration, were used as the central composite design parameters. In all experiments, the phenanthrene was degraded to undetectable levels. Response surface methodology was successfully employed to derive an empirical model describing the rate and time of degradation and to deduce the optimal degradation conditions. As a result of the optimization processes, the optimal responses for the degradation rate, the volumetric degradation rate, and the 90% degradation time were estimated to be 0.172 mg h⁻¹, 22 mg l⁻¹ h⁻¹, and 18 h, respectively.

Keywords: Polycyclic aromatic hydrocarbons; Phenanthrene; Mycobacterium ; Biodegradation; Biphasic culture; Design of experiments

Fluorescent in situ hybridization and flow cytometry as tools to evaluate the treatments for the control of slime-forming enterobacteria in paper mills by C. Esperanza Torres; Alicia Gibello; Mar Nande; Margarita Martin; Angeles Blanco (pp. 889-897).

Slime formation is a serious problem nowadays in the paper industry. Some enterobacteria are associated with the formation of slime deposits in paper and board mills. Detection and characterization of slime forming bacteria, belonging to the genus Enterobacter, Raoultella, and Klebsiella have been achieved by fluorescence in situ hybridization (FISH), using one probe based on the enterobacterial repetitive intergenic consensus sequence and other two rRNA targeted oligonucleotide probes. The effects of three kinds of antimicrobiological products (biocides, dispersants, and enzymes) on these enterobacterial cells were analyzed by flow cytometry (FC). Biocides Butrol 1009 and 1072 were the most effective microbiocides against all enterobacterial cells analyzed, reaching 90% of dead bacteria after 24 h. However, the enzymatic treatment (Buzyme) was not equally efficient on enterobacteria and its microbiocide capacity varied depending on the type of microorganism. FISH and FC were effective tools to detect important slime forming enterobacteria and to select specific treatments to control microbial problems in the paper industry.

Keywords: FISH; Flow cytometry; Papermaking; Slime control

Physiological characterization and interactions of isolates in phenol-degrading aerobic granules by Sunil S. Adav; Duu-Jong Lee (pp. 899-905).

This study isolated nine strains of aerobic phenol-degrading granules. These isolates (I1–I9) were characterized using 16S rRNA gene sequencing, with γ-Proteobacteria as the dominant strains in the aerobic granules. While most strains demonstrated either high phenol-degrading capabilities or auto-aggregation capabilities, three isolates, I2, I6, and I8 showed both features. These findings contradict the previous view that auto-aggregation and phenol degradation are mutually exclusive in aerobic granules. Strains I2 and I8 independently formed single-culture aerobic granules except for I3. Anti-microbial activity test results indicated that strains I2 and I8 inhibited growth of strain I3. However, co-culturing I3 with I2 or I8 helped to form granules.

Keywords: Aerobic granules; Phenol; Isolates; Interactions; Inhibition

Mass transfer limit of fluorescent dyes during multicolor staining of aerobic granules by Ming-Wei Tsai; Duu-Jong Lee; Juin-Yih Lai (pp. 907-913).

Multicolor fluorescence experiments are conducted to investigate the distributions of extracellular polymeric substances and/or cells in the bioaggregates. Successful staining requires that the dyes could fully stain the targeted substances of bioaggregates in a finite time. The mass transfer limit for one of the four fluorescent dyes, calcofluor white, concanavalin A conjugated with tetramethylrhodamine, Nile red, and SYTO 63, penetrating entire phenol-fed granules or those sectioned at 50 μm thick, was quantitatively determined. The former three dyes sufficiently stained the entire granule within prescribed time intervals. However, the SYTO 63 could not penetrate the 600-μm granule in a finite time. Simplified one-dimensional diffusional model estimated the apparent diffusivity of SYTO 63 in the aerobic granule matrix. This work revealed that each staining scheme should be examined for the possible mass transfer limit of dyes during staining.

Keywords: Mass transfer limit; Aerobic granule; SYTO 63; CLSM

Improved production of erythromycin A by expression of a heterologous gene encoding S-adenosylmethionine synthetase by Yong Wang; YiGuang Wang; Ju Chu; Yingping Zhuang; Lixin Zhang; Siliang Zhang (pp. 915-915).

Sections

Personal tools

Applied Microbiology and Biotechnology (v.78, #5)

Sections

Personal tools

Local resources

Applied Microbiology and Biotechnology (v.78, #5)