Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Applied Microbiology and Biotechnology (v.50, #2)
Xanthan gum biosynthesis and application: a biochemical /genetic perspective by A. Becker; F. Katzen; A. Pühler; L. Ielpi (pp. 145-152).
Xanthan gum is a complex exopolysaccharide produced by the plant-pathogenic bacterium Xanthomonas campestris pv. campestris. It consists of D-glucosyl, D-mannosyl, and D-glucuronyl acid residues in a molar ratio of 2:2:1 and variable proportions of O-acetyl and pyruvyl residues. Because of its physical properties, it is widely used as a thickener or viscosifier in both food and non-food industries. Xanthan gum is also used as a stabilizer for a wide variety of suspensions, emulsions, and foams. This article outlines aspects of the biochemical assembly and genetic loci involved in its biosynthesis, including the synthesis of the sugar nucleotide substrates, the building and decoration of the pentasaccharide subunit, and the polymerization and secretion of the polymer. An overview of the applications and industrial production of xanthan is also covered.
Towards optimization of cyanobacteria as biotechnologically relevant producers of molecular hydrogen, a clean and renewable energy source by A. Hansel; P. Lindblad (pp. 153-160).
In discussions about alternatives to our current fossil energy sources, basic and applied research leading to biological production of molecular hydrogen utilizing cyanobacteria deserves serious attention. In these oxygenic phototrophic bacteria, hydrogen can be produced by the activity of either nitrogenases or reversible/bidirectional hydrogenases. Knowledge of the physiological and molecular basis of some of the processes involved in hydrogen metabolism in these peculiar microorganisms has increased during the last decade. However, further efforts are required in basic as well as applied research in order to obtain a clear impression of these processes and their regulation. This information might then constitute the basis for optimizing the efficiency of hydrogen evolution by cyanobacteria. Progress might be achieved by screening more cyanobacterial strains for their ability to produce and evolve hydrogen, by genetically manipulating specific strains as well as by improving the conditions for cultivation in bioreactors.
Candida bombicola : production of novel alkyl glycosides based on glucose/2-dodecanol by A. Brakemeier; D. Wullbrandt; S. Lang (pp. 161-166).
Candida bombicola produces glycolipids containing sophorose and a glycosidically/esterically bound ω- or (ω−1)-hydroxy C16(18) acid. Here we describe novel glycolipids from this source. Glucose and 2-dodecanol were used for the cultivation of the yeast, one part of the racemic secondary alcohol being connected directly with a glucose or a sophorose unit. A relatively high content of yeast extract, up to 4 g l−1, and subsequently higher biomass concentrations favoured the production of novel products. The provision of 150 g l−1 glucose and 15 g l−1 2-dodecanol resulted in maximum production of 22 g l−1 novel alkyl glycosides (more than 90% novel products). The molecular structures were analysed by gas chromatography, fast atom bombardment/mass spectrometry, 1H- and 13C-nuclear magnetic resonance and optical rotation studies. Sophorose and glucose were detected as carbohydrate moieties, (S)-(+)-2-dodecanol (88%) was found to be the major lipid moiety. The new glycolipids are suitable biosurfactants, reducing the surface tension of water from 72 mN m−1 to 32–38 mN m−1.
Enzymatic synthesis of alkyl-α-glucoside catalysed by a thermostable α-transglucosidase in solvent-free organic medium by M.-P. Bousquet; R.-M. Willemot; P. Monsan; E. Boures (pp. 167-173).
α-Transglucosidase from Talaromycesduponti was used to synthesize different alkyl-α-d-glucosides from α(1-4) linked carbohydrate donors. The enzymatic preparation, purified by a single step, consisting of hydrophobic interaction chromatography, was sufficiently pure for very stereospecific synthesis to be achieved. Biphasic and homogeneous organic media could be compared for such purposes. Yields appeared to be two- to threefold higher in low-water biphasic media. High concentrations of the glucosyl donor were present in the aqueous phase, while water-immiscible alcohols were used as glucosyl acceptors. The high efficiency of the method was attributed to the shift of the thermodynamic equilibrium thanks to the extraction of the product from the aqueous phase, where the reaction occurs, into the organic phase. Operated in a continuous biphasic reactor, T. dupontiα-transglucosidase showed a good thermostability with a half-life of 23 days at 30 °C.
Characterization of a novel Streptococcus thermophilus rolling-circle plasmid used for vector construction by D. K. Y. Solaiman; G. A. Somkuti (pp. 174-180).
The complete nucleotide sequence of pER371, a native plasmid in Streptococcus thermophilus ST137, was determined. A putative open reading frame coding for a replication protein, Rep371, was identified. A characteristic promoter sequence and ribosome-binding site were found upstream of rep371. Rep371 (247 amino acid residues) does not show homology with RepA and RepS of the small S. thermophilus cryptic plasmids pST1-No.29 and pST1 respectively. The plus-origin sequence and Rep371 are highly homologous to the corresponding elements of the Staphylococcus aureus plasmids pC194 and pSK89. A novel 140-nucleotide palindromic minus-origin sequence, which is structurally similar but does not show sequence homology to the palA region of pC194, was identified in pER371. A palindromic sequence capable of forming a putative hairpin structure was identified and subsequently recognized as being highly conserved among several lactococcal rolling-circle plasmids. Cloning vectors derived from pER371 should provide valuable gene-delivery vehicles for the genetic engineering of lactic acid bacteria.
Bacterial complementation as a means to test enzyme–ligand interactions by B. Canyuk; S. P. Craig III.; A. E. Eakin (pp. 181-186).
A bacterial complementation assay has been developed for the rapid screening of a large number of compounds to identify those that inhibit an enzyme target for structure-based inhibitor design. The target enzyme is the hypoxanthine phosphoribosyltransferase (HPRT). This enzyme has been proposed as a potential target for inhibitors that may be developed into drugs for the treatment of diseases caused by several parasites. The screening assay utilizes genetically deficient bacteria complemented by active, recombinant enzyme grown in selective medium in microtiter plates. By comparing absorbance measurements of bacteria grown in the presence and absence of test compounds, the effect of the compounds on bacterial growth can be rapidly assayed. IC50 values for inhibition of bacterial growth are a reflection of the ability of the compounds to bind and/or inhibit the recombinant enzyme. We have tested this bacterial complementation screening assay using recombinant HPRT from the parasites Plasmodium falciparum and Trypanosoma cruzi, as well as the human enzyme. The results of these studies demonstrate that a screening assay using bacterial complement selection can be used to identify compounds that target enzymes and can become an important part of structure-based drug design efforts.
Efficient production of intact human parathyroid hormone in a Saccharomyces cerevisiae mutant deficient in yeast aspartic protease 3 (YAP3) by H. A. Kang; S. J. Kim; E.-S. Choi; S.-K. Rhee; B. H. Chung (pp. 187-192).
When human parathyroid hormone (hPTH) is expressed as a secretory product in yeast, the main problem is the aberrant proteolytic cleavage that reduces the yield of intact protein. To overcome this problem, we developed an hPTH expression system using a host strain in which the YAP3 gene encoding yeast aspartic protease 3 (YAP3) was disrupted. After 48 h of culture, most of the hPTH secreted by the yap3 disruptant remained intact, whereas more than 90% of the hPTH secreted by the wild-type strain was cleaved. When the authentic hPTH was incubated in each of the culture supernatants of untransformed yap3 disruptant and wild-type strain, the proteolysis proceeded much more slowly in the culture supernatant of yap3 disruptant than in that of the wild type. The extent of hPTH proteolysis was also significantly reduced by the addition of pepstatin A, a specific aspartic protease inhibitor. The results suggest that YAP3 is involved in the internal cleavage of hPTH expressed in yeast. The correct processing of the intact hPTH secreted in the yap3 disruptant demonstrates that the yeast mutant lacking the YAP3 activity is a suitable host for the high-level expression of intact hPTH.
Production of trehalose synthase from a basidiomycete, Grifola frondosa, in Escherichia coli by K. Saito; H. Yamazaki; Y. Ohnishi; S. Fujimoto; E. Takahashi; S. Horinouchi (pp. 193-198).
The genomic DNA and cDNA for a gene encoding a novel trehalose synthase (TSase) catalyzing trehalose synthesis from α-d-glucose 1-phosphate and d-glucose were cloned from a basidiomycete, Grifola frondosa. Nucleotide sequencing showed that the 732-amino-acid TSase-encoding region was separated by eight introns. Consistent with the novelty of TSase, there were no homologous proteins registered in the databases. Recombinant TSase with a histidine tag at the NH2-terminal end, produced in Escherichia coli, showed enzyme activity similar to that purified from the original G. frondosa strain. Incubation of α-d-glucose 1-phosphate and d-glucose in the presence of recombinant TSase generated trehalose, in agreement with the enzymatic property of TSase that the equilibrium lay far in the direction of trehalose synthesis.
Photolimitation and photoinhibition as factors determining optimal dilution rate to produce eicosapentaenoic acid from cultures of the microalga Isochrysis galbana by J. M. Fernández Sevilla; E. Molina Grima; F. García Camacho; F. G. Acién Fernández; J. A. Sánchez Pérez (pp. 199-205).
Eicosapentaenoic acid (EPA) productivity from continuous cultures of the marine microalga Isochrysis galbana was studied, taking into account the irradiance on the reactor surface, that is, the photolimitation/photoinhibition regime to which the cells are exposed. Experiments were conducted under a wide variety of operating conditions. The dilution rate ranged from 0.005 h−1 to 0.040 h−1 at five external irradiances (820, 1620, 2050, 2450 and 3270 μmol photons m−2 s−1) covering photolimited to photoinhibited growth. Under these conditions, the specific growth rate (μ) was found to be the main factor influencing EPA content (ranging from 2.35% to 5.23% dryweight) and productivity (up to 0.88 mg l−1 h−1). The fatty acid content was not significantly affected by the external irradiance, but was influenced by the state of growth of the microalga, depending on whether the light regime was photolimiting or photoinhibiting. It might be suggested that light should no longer be considered an isolated factor affecting EPA synthesis, but an indirect influence through the photolimitation/photoinhibition regime and growth rate. At a given dilution rate, EPA content and biomass concentration are lower under photoinhibiting external irradiances than those corresponding to photolimiting conditions, and consequently EPA productivity decays. Since the effect of photoinhibition is less marked at high biomass concentration, a strategy to optimize EPA productivity from microalgal cultures could consist of reducing the dilution rate when the external irradiance increases above the phoinhibition threshold.
Composition of the cell walls of several yeast species by T. H. Nguyen; G. H. Fleet; P. L. Rogers (pp. 206-212).
Cell walls, representing 26%–32% of the cell dry weight, were prepared from several strains of the yeasts Kloeckera apiculata, Debaryomyces hansenii, Zygosaccharomyces bailii,Kluyveromyces marxianus and Saccharomyces cerevisiae. Extraction of the walls with potassium hydroxide at 4 °C, followed by saturation of the alkali-soluble extract with ammonium sulphate gave fractions of mannoprotein, alkali-soluble glucan and alkali-insoluble glucan. Chitin was associated with the alkali-insoluble glucan. The proportions of the different fractions within the walls varied with the species and strain. Mannoprotein comprised between 25% and 34% of the walls, the content of alkali-insoluble glucan ranged from 15% to 48%, and the content of alkali-soluble glucan ranged from 10% to 48%. There was significant variation in the physical appearance of the alkali-soluble glucans and the relative viscosity of suspensions of these glucans. The yeasts could represent novel sources of polysaccharides with industrial and medical applications.
Production and characterization of ferulic acid esterase activity in crude extracts by Streptomyces avermitilis CECT 3339 by B. L. García; A. S. Ball; J. Rodríguez; M. I. Pérez-Leblic; M. E. Arias; J. L. Copa-Patiño (pp. 213-218).
Streptomyces avermitilis CECT 3339 produces extracellular ferulic acid esterase (FAE) activity during growth on a range of lignocellulose substrates. Maximal levels of FAE activity were detected in culture filtrates from S. avermitilis CECT 3339 grown in media containing wheat bran and yeast extract as carbon and nitrogen sources respectively. Biochemical characterization of this enzyme activity revealed that it was 100-fold higher when wheat bran was pretreated with Celluclast (a mix of hydrolytic enzymes). FAE was found to be end-product-inhibited. Characterization of the properties of the enzyme showed that FAE exhibited an activity optimum pH at 6 with pH stability between pH 6 and 8. The optimum temperature was 50 °C while the temperature stability was between 30 °C and 40 °C, with rapid inactivation at 60 °C and above. The characteristics and stability of FAE from S. avermitilis CECT 3339 suggest a potential role for this enzyme in combination with endoxylanases for the upgrading of plant-residue silage and for biopulping.
Adaptation of the filamentous fungus Ashbya gossypii to hyperosmotic stress: different osmoresponse to NaCl and mannitol stress by C. Förster; S. Marienfeld; F. Wendisch; R. Krämer (pp. 219-226).
Osmoadaption mechanisms of the biotechnologically important hemiascomycete Ashbya gossypii were investigated, thereby distinguishing between halo- and osmotolerance by exposure to NaCl and mannitol stress. We studied the growth and ultrastructure of differently treated cells and quantified the intracellular contents of compatible solutes and inorganic ions. Mannitol affected growth of A. gossypii at concentrations above 0.8 M, whereas NaCl inhibited growth at 0.2 M. NaCl-treated cells differed from control cells in having smaller vacuoles, which occupied a smaller part of the cell volume. Glycerol was found to be the predominant compatible solute in A. gossypii; accumulation of inorganic ions could not be detected. Measurement of glycerol uptake under isosmotic conditions as well as upon hyperosmotic stress revealed the existence of a highly active glycerol-uptake system, which, however, was down-regulated under hyperosmotic stress. Investigation of glycerol biosynthesis by measuring glycerol-3-phosphate dehydrogenase activity under hyperosmotic conditions indicated that accumulation of glycerol in A. gossypii is almost solely due to biosynthesis.
Induction of only limited elongation instead of filamentation by inhibition of cell division in Corynebacterium glutamicum by N. Kijima; D. Goyal; A. Takada; M. Wachi; K. Nagai (pp. 227-232).
In order to characterize the cell-division mechanism of coryneform bacteria, we tried to isolate cell-division mutants from Corynebacterium glutamicum after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis, such as Escherichia coli fts mutants, which form long filaments at the restrictive temperatures. At the non-permissive temperature, most of the mutants formed club-shaped or dumbbell-shaped, elongated rod cells, but no filament formers were isolated. Then we examined the effects of cell division inhibitors on this organism. Cephalexin and sparfloxacin, which are the inhibitors of septation and DNA synthesis respectively, and are known to cause cell filamentation in E. coli, did not cause filamentation in C. glutamicum but induced morphological changes that were similar to those observed with the temperature-sensitive ts mutants of C.␣glutamicum. These results suggest that C. glutamicum has a unique regulation mechanism, that is, the inhibition of cell division leads to cessation of cell elongation.
Simultaneous degradation of chloro- and methyl-substituted aromatic compounds: competition between Pseudomonas strains using the ortho and meta pathway or the ortho pathway exclusively by A. C. Franck-Mokroß; E. Schmidt (pp. 233-240).
Pseudomonas sp. D7-4 and Pseudomonas sp. B13 FR1(pFRC20P) degraded mixtures of chloro- and methyl-substituted benzoates exclusively via an extended ortho pathway, whereas in Pseudomonas putida WR201 both ortho and meta fission were induced by mixtures of 3-chloro- and 3-methylbenzoate or even by 3-chlorobenzoate alone. The competition behaviour of these strains was compared in batch and in chemostat cultures. Despite misrouting of metabolites, strain WR201 was competitive, in a lot of the competition experiments, with mixtures of these substrates. Only in a narrow range of the mixing ratio of chloro- and methylbenzoate was the presence of both the meta and ortho pathways a disadvantage for competitiveness. Outside these ranges other attributes, such as high growth rates or short lag periods, of a respective strain were even more essential for one strain to outcompete another.
pH-mediated release of betalains from transformed root cultures of Beta vulgaris L. by U. Mukundan; V. Bhide; G. Singh; W. R. Curtis (pp. 241-245).
Brief exposure of Beta vulgaris root cultures to acidic medium resulted in release of betalain pigments while the capability for regrowth and continued pigment accumulation was retained. A 10-min exposure to pH 2 followed by return to standard growth medium (pH 5.5, 1.1 mM PO4) resulted in release of 0.59 mg pigment/g dry weight over the subsequent 24-h period. The released pigment corresponds to 36.8% of the total pigments. Further improvement in culture productivity was achieved through phosphate limitation. Specific pigment productivity increased fivefold for cultures grown in phosphate-free medium as compared to cultures grown in control medium (1.1 mM PO4). A maximum total pigment production of 25.2 mg/l was observed at an initial medium phosphate level 0.3 mM. When combined with phosphate limitation, low pH facilitated the release of 3.03 mg pigment/g dry weight, which corresponds to 50% of the total pigment. The permeabilized roots were capable of regrowth and continued pigment accumulation. A cytochemical assay for respiratory activity revealed that the basis of regrowth was lateral root initials that were unaffected during the acidic pH treatment.
The colonization of a simulator of the human intestinal microbial ecosystem by a probiotic strain fed on a fermented oat bran product: effects on the gastrointestinal microbiota by P. Kontula; J. Jaskari; L. Nollet; I. De Smet; A. von Wright; K. Poutanen; T. Mattila-Sandholm (pp. 246-252).
The effects of Lactobacillus-GG-fermented oat bran product on the microbiota and its metabolic activity in the human gut were investigated, using a simulator of the human intestinal microbial ecosystem (SHIME), by analysing the bacterial population, short-chain fatty acids and gas production. In addition, the effects of fermented oat bran supernatant and supernatant samples from reactors 4, 5 and 6 (large intestine) on the growth of Escherichia coli IHE 13047, Enterococcus faecalis VTT E-93203, Lactobacillus rhamnosus VTT E-94522 (Lactobacillus GG) and Lactococcus lactis subsp. lactis VTT E-90414 were monitored to ascertain possible stimulatory/inhibitory effects by an in vitro turbidometric method. Our experiments showed that Lactobacillus GG colonized the SHIME reactor and this colonization could be maintained for several weeks without extra supplementation. Oat bran feeding also favoured the growth of bifidobacteria and caused an increase in the production of acetic, propionic and butyric acid as well as CH4 and CO2. However, the effects of oat bran, either on bacterial populations or on their metabolic activity, were not directly dose-dependent. In turbidometric measurements, the supernatant of fermented oat bran exerted an inhibitory effect of Lactobacillus GG, but stimulated the growth of enterococci.
Antimould activity of sourdough lactic acid bacteria: identification of a mixture of organic acids produced by Lactobacillus sanfrancisco CB1 by A. Corsetti; M. Gobbetti; J. Rossi; P. Damiani (pp. 253-256).
Sourdough lactic acid bacteria, cultivated in wheat flour hydrolysate, produced antimould compounds. The antimould activity varied greatly among the strains and was mainly detected within obligately heterofermentative Lactobacillus spp. Among these, Lb. sanfrancisco CB1 had the largest spectrum. It inhibited moulds related to bread spoilage such as Fusarium, Penicillium, Aspergillus and Monilia. A mixture of acetic, caproic, formic, propionic, butyric and n-valeric acids, acting in a synergistic way, was responsible for the antimould activity. Caproic acid played a key role in inhibiting mould growth.
Detection of ferulic acid esterase production by Bacillus spp. and lactobacilli by J. Donaghy; P. F. Kelly; A. M. McKay (pp. 257-260).
The production of feruloyl esterase activity by Bacillus spp. and lactobacilli can be detected in an agar-plate assay. The assay involves the substitution of the main carbon source in specific agar with ethyl ferulate. A number of Bacillus spp., predominantly B. subtilis strains, were found to exhibit feruloyl esterase activity by this method. Of the examined lactobacilli, Lb. fermentum (NCFB 1751) showed the highest level of ferulic acid esterase activity. The enzyme was released from harvested cells by sonication and showed pH and temperature optima of 6.5 and 30 °C respectively.
Competition for Astragalus sinicus root nodule infection between its native microsymbiont Rhizobium huakuii bv. renge B3 and Rhizobium sp. ACMP18 strain, specific for Astragalus cicer by W. Malek; M. Inaba; H. Ono; Y. Kaneko; Y. Murooka (pp. 261-265).
Rhizobium huakuii bv. renge B3, a native symbiont of Astragalus sinicus, outcompeted Rhizobium sp. strain ACMP18, which was isolated from Astragalus cicer nodules, in the formation of root nodules on A.␣sinicus when plants were co-inoculated with these strains. The strains occupying the nodules were identified by antibiotic resistance and phage sensitivity markers and also by polymerase chain reaction (PCR) genomic fingerprintings, which were performed by using enterobacterial repetitive intergenic consensus sequences. In PCR genomic fingerprintings, the total genomic DNA isolated from pure bacterial culture and from squashed root nodules showed identical profiles, indicating that this technique can be a useful tool for identification of rhizobia in ecological studies. When Rhizobium sp. strain ACMP18 outnumbered R. huakuii bv. renge strain B3 by a factor of ten, and even when strain ACMP18 was added to plants 1 week before bacterization with strain B3, the strain B3 occupied most nodules. Dually infected nodules were not observed, although Rhizobium sp. ACMP18 formed active nodules on A. sinicus when the bacterial strain was inoculated alone.
The use of Escherichia coli bearing a phoN gene for the removal of uranium and nickel from aqueous flows by G. Basnakova; E. R. Stephens; M. C. Thaller; G. M. Rossolini; L. E. Macaskie (pp. 266-272).
A Citrobacter sp. originally isolated from metal-polluted soil accumulates heavy metals via metal-phosphate deposition utilizing inorganic phosphate liberated via PhoN phosphatase activity. Further strain development was limited by the non-transformability of this environmental isolate. Recombinant Escherichia coli DH5α bearing cloned phoN or the related phoC acquired metal-accumulating ability, which was compared with that of the Citrobacter sp. with respect to removal of uranyl ion (UO2 2+) from dilute aqueous flows and its deposition in the form of polycrystalline hydrogen uranyl phosphate (HUO2PO4). Subsequently, HUO2PO4-laden cells removed Ni2+ from dilute aqueous flows via intercalation of Ni2+ into the HUO2PO4 lattice. Despite comparable acid phosphatase activity in all three strains, the E. coli DH5α (phoN) construct was superior to Citrobacter N14 in both uranyl and nickel accumulation, while the E. coli DH5α (phoC) construct was greatly inferior in both respects. Expression of phosphatase activity alone is not the only factor that permits efficient and prolonged metal phosphate accumulation, and the data highlight possible differences in the PhoN and PhoC phosphatases, which are otherwise considered to be related in many respects.
Effect of polyphosphate limitation on the anaerobic metabolism of phosphorus-accumulating microorganisms by D. Brdjanovic; M. C. M. van Loosdrecht; C. M. Hooijmans; T. Mino; G. J. Alaerts; J. J. Heijnen (pp. 273-276).
There are two types of microbial populations described in the literature as being capable of anaerobic storage of acetic acid in activated-sludge processes: the polyphosphate-accumulating organisms (PAO) and the glycogen-accumulating non-polyphosphate organisms (GAO). Both groups use the conversion of glycogen to poly-hydroxyalkanoate to produce ATP and NADH; however, the first group can also produce ATP from polyphosphate (poly-P). No representative pure cultures are available from either group. The question arises: is the observed activity of GAO due to PAO that are depleted in poly-P ? In this study, using a laboratory sequencing batch reactor containing an enriched culture, the ability of the enriched PAO to utilize organic substrate (acetate) anaerobically was investigated under conditions of poly-P limitation and surplus glycogen content of the biomass. This study showed clearly that, under these conditions, almost no acetate was taken up. Furthermore, this strongly suggests that PAO can not use glycogen conversion to poly-hydroxyalkanoate as the sole energy source under anaerobic conditions, which seems to be the restricted to a separate group of GAO. On the basis of the results and literature data, an improved scheme for the anaerobic acetate accumulation is presented.
Effect of biofilm formation by Pseudomonas 8909N on the bioavailability of solid naphthalene by H. Mulder; A. M. Breure; D. van Honschooten; J. T. C. Grotenhuis; J. G. van Andel; W. H. Rulkens (pp. 277-283).
The effect of biofilm formation by Pseudomonas 8909N (DSM no. 11634) on the dissolution and biodegradation rates of solid naphthalene was quantified. Biofilms were cultivated on solid naphthalene as a model polycyclic aromatic hydrocarbon in continuous cultures. After different periods of incubation, the dissolution rate of naphthalene was determined by batch dissolution tests with active or inactivated biofilms and without biofilms. Results show that the naphthalene dissolution rate to the bulk liquid phase was reduced by over 90% after 7 days of biofilm formation. The degradation of naphthalene in the biofilm proved to be insignificant compared to the decrease in the bulk liquid conversion of naphthalene, and the overall biodegradation rate of the solid naphthalene decreased.
Application of the affinity binding of xylanases to oat-spelt xylan in the purification of endoxylanase CM-2 from Streptomyces chattanoogensis CECT 3336 by C. L. López-Fernández; J. Rodríguez; A. S. Ball; J. L. Copa-Patiño; M. I. Pérez-Leblic; M. E. Arias (pp. 284-287).
The use of the insoluble polysaccharides Avicel and oat-spelt xylan for the binding and subsequent purification of active xylanases from Streptomyces chattanoogensis was investigated. Maximum recovery of xylanases was achieved with oat-spelt xylan, using NaCl (2 M) to remove active protein. The application of this technique to the purification of xylanases resulted in the purification of an endoxylanase (CM-2) with high specific activity (729.5 U mg−1). The properties of the purified enzyme, exhibiting activity and stability between 40 °C and 60 °C and between pH 5 and 8, suggest a potential role for both the enzyme and the rapid purification protocol in the removal of hemicelluloses from kraft pulp prior to bleaching.