Adapting an enzymatic toxicity test to allow comparative evaluation of natural freshwater biofilms' tolerance to metals

A simple, low-cost and non-radioactive short-term toxicity test was developed to study the effects of urban metals on natural freshwater periphytic communities. β-glucosidase activity of natural freshwater biofilms collected in situ was chosen as an endpoint. Metals (Cd, Cu, Ni, Pb, and Zn) successfully inhibited bacterial enzymatic activity after a 1-h exposure enabling the calculation of EC(50). The EC(50) value of a biofilm sample varied with the Total Suspended Solids concentration (TSS) of the biofilm suspension, showing that EC(50) values (expressed as total added metal concentrations) are not representative of the bioavailable metal concentration during the toxicity test. For Cu, Cd, Ni, Zn and Pb, the EC(50) values increased linearly with the TSS concentration leading us to define a normalized EC(50): the value of the EC(50) divided by the corresponding TSS concentration. Normalized EC(50) proved to be a robust, reliable way to assess metal tolerance of a biofilm for Cd, Cu, Ni, Zn and Pb. Normalized EC(50) obtained, expressed as kg(metal)/g(TSS), varied between 0.2 to 7.6 for Cu, 1 to 8 for Cd, 1.8 to 92.3 for Ni, 1.8 to 76.6 for Zn and 25 to 189 for Pb.

Optimizing on-farm pretreatment of perennial grasses for fuel ethanol production

Switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.) were pretreated under ambient temperature and pressure with sulfuric acid and calcium hydroxide in separate experiments. Chemical loadings from 0 to 100g (kg DM)(-1) and durations of anaerobic storage from 0 to 180days were investigated by way of a central composite design at two moisture contents (40% or 60% w.b.). Pretreated and untreated samples were fermented to ethanol by Saccharomyces cerevisiae D5A in the presence of a commercially available cellulase (Celluclast 1.5L) and beta-glucosidase (Novozyme 188). Xylose levels were also measured following fermentation because xylose is not metabolized by S. cerevisiae. After sulfuric acid pretreatment and anaerobic storage, conversion of cell wall glucose to ethanol for reed canarygrass ranged from 22% to 83% whereas switchgrass conversions ranged from 16% to 46%. Pretreatment duration had a positive effect on conversion but was mitigated with increased chemical loadings. Conversions after calcium hydroxide pretreatment and anaerobic storage ranged from 21% to 55% and 18% to 54% for reed canarygrass and switchgrass, respectively. The efficacy of lime pretreatment was found to be highly dependent on moisture content. Moreover, pretreatment duration was only found to be significant for reed canarygrass. Although significant levels of acetate and lactate were observed in the biomass after storage, S. cerevisiae was not found to be inhibited at a 10% solids loading.

Optimizing on-farm pretreatment of perennial grasses for fuel ethanol production

Switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.) were pretreated under ambient temperature and pressure with sulfuric acid and calcium hydroxide in separate experiments. Chemical loadings from 0 to 100g (kg DM)(-1) and durations of anaerobic storage from 0 to 180days were investigated by way of a central composite design at two moisture contents (40% or 60% w.b.). Pretreated and untreated samples were fermented to ethanol by Saccharomyces cerevisiae D5A in the presence of a commercially available cellulase (Celluclast 1.5L) and beta-glucosidase (Novozyme 188). Xylose levels were also measured following fermentation because xylose is not metabolized by S. cerevisiae. After sulfuric acid pretreatment and anaerobic storage, conversion of cell wall glucose to ethanol for reed canarygrass ranged from 22% to 83% whereas switchgrass conversions ranged from 16% to 46%. Pretreatment duration had a positive effect on conversion but was mitigated with increased chemical loadings. Conversions after calcium hydroxide pretreatment and anaerobic storage ranged from 21% to 55% and 18% to 54% for reed canarygrass and switchgrass, respectively. The efficacy of lime pretreatment was found to be highly dependent on moisture content. Moreover, pretreatment duration was only found to be significant for reed canarygrass. Although significant levels of acetate and lactate were observed in the biomass after storage, S. cerevisiae was not found to be inhibited at a 10% solids loading.

Alterations of glucosylceramide-beta-glucosidase levels in the skin of patients with psoriasis vulgaris

Hydrolysis of glucosylceramides by the enzyme glucosylceramide-beta-glucosidase (GlcCer'ase) results in ceramide, a critical component of the intercellular lamellae that mediates the epidermal permeability barrier. A disturbance of ceramide formation is supposed to influence the transepidermal water loss in common skin diseases like atopic eczema or psoriasis. The aim of this study was to investigate whether GlcCer'ase levels were altered in the skin of subjects with psoriasis vulgaris. Skin punch biopsies were taken from lesional and non-lesional psoriatic skin and GlcCer'ase was evaluated both at the RNA and at the protein level. Normal skin from surgical patients provided the baseline GlcCer'ase expression in healthy subjects. Our results show that GlcCer'ase mRNA expression was decreased in psoriatic non-lesional skin compared to normal controls in all cases. Interestingly, in lesional psoriatic skin the level of GlcCer'ase was increased compared to non-lesional skin in all cases. For the immunohistochemical analysis, we used a newly synthesized monoclonal antibody anti-human GBC (GlcCer'ase-GST fusion protein). The results confirmed that GlcCer'ase, mainly present in the upper epidermis, was decreased in psoriatic skin compared to normal control and was increased in lesional compared to non-lesional psoriatic skin. Our findings support the concept that alteration in water permeability barrier in lesional psoriatic skin can serve as a trigger for the upregulation of the expression of enzymes like GlcCer'ase with consequent stimulation of ceramide generation.

Expression and functional characterization of mutated glucocerebrosidase alleles causing Gaucher disease in Spanish patients

BACKGROUND

Gaucher disease (GD) is a heterogeneous disease characterized by an impaired activity of the lysosomal glucocerebrosidase. This heterogeneity is attributed in part to the existence of a large number of mutations in the corresponding gene.

SUBJECTS AND METHODS

To establish genotype-phenotype relationships, we analyzed the residual enzyme activities of six naturally occurring mutations found in Spanish population in the glucocerebrosidase gene [c.160G > A (V15M), c.485T>C (M123T), c.914C>T (P266L), c.1124T>C (L336P), c.1207A>C (S364R) and c.1510-1512delTCT (S465del)]. The mutated genes were subcloned into the mammalian expression vector pCR 3.1 and expressed by transient transfection in COS cells. The enzymatic activity of the expressed protein were measured and compared with the wild-type human glucocerebrosidase cDNA. Also, two previously alleles, c.1226A>G (N370S) and c.1448T>C (L444P), were used for comparative purposes.

RESULTS

The residual activity of the expressed proteins using the synthetic substrate (4-methylumbelliferyl-beta-D-glucopyranoside, 4MU-Glu) ranged from 5.5% (for the 3-bp deletion) to 42.7% (for S364R mutation) of the activity of the wild-type enzyme.

CONCLUSION

The present analyses may help to better understand the molecular basis and the pathogenesis of Gaucher disease. However, results of expression of mutated enzymes are necessary but not sufficient to explain the ultimate clinical outcome of Gaucher disease.

[Analysis for four isomers of resveratrol in red wine by high performance liquid chromatography]

Red wine was treated by hydrolysis with beta-glucosidase, so the piceids in it were converted to resveratrols. The contents of cis- and trans-resveratrols before and after hydrolysis were determined by high performance liquid chromatography, thereby the contents of the four isomers of resveratrol in the red wine can be calculated. The analysis was performed on a Symmetry C18 column (3.9 mm i. d. x 150 mm) with a mixture of ethanol and 0.05% acetic acid solution (23:77, v/v) as the mobile phase at a flow rate of 1.0 mL/min and with UV detection at 306 nm. Results show that there was a good linear relationship (r > 0.999) for all the four isomers of resveratrol in the range of 0.2 - 50.0 mg/L. The detection limits of cis- and trans-resveratrol and the corresponding piceid isomers were 0.81, 1.20, 0.40 and 0.46 ng, respectively. The recovery of resveratrol was more than 98%. Relative standard deviations (RSDs) (n = 5) were from 0.5% to 8.5%. The ranges of concentration of total resveratrol were 0.84 - 7.33 mg/L in eleven dry red wines and 0.12 - 6.00 mg/L in three grape juices. The method is convenient, and there are good precision and repeatability. The method is applicable for the analysis of four isomers of resveratrol in red wines and grape juices.

Glycosidation of chlorophenols by Lemna minor

Metabolic fate of xenobiotics in plant tissues has an important role in the ultimate fate of these compounds in natural and engineered systems. Chlorophenols are an important class of xenobiotics used in a variety of biocides and have been shown to be resistant to microbial degradation. Three chlorophenyl glycosides were extracted from tissues of Lemna minor exposed to 2,4-dichlorophenol (DCP). The products were identified as 2,4-dichlorophenyl-beta-D-glucopyranoside (DCPG), 2,4-dichlorophenyl-beta-D-(6-O-malonyl)-glucopyranoside (DCPMG) and 2,4-dichlorophenyl-beta-D-glucopyranosyl-(6 --> 1)-beta-D-apiofuranoside (DCPAG). Identification was based on reverse phase retention (C18), electrospray mass spectra collected in negative and positive mode (ESI-NEG and ESI-POS, respectively), and nuclear magnetic resonance (NMR) spectra comparisons to reference materials synthesized in the laboratory. Liquid chromatography-mass spectrometry (LC-MS) analysis of plants exposed to 2,4,5-trichlorophenol (TCP) formed analogous compounds: 2,4,5-trichlorophenyl-beta-D-glucopyranoside (TCPG), 2,4,5-trichlorophenyl-beta-D-(6-O-malonyl)-glucopyranoside (TCPMG) and 2,4,5-trichlorophenyl-beta-D-glucopyranosyl-(6 --> 1)-beta-D-apiofuranoside (TCPAG). Enzyme catalyzed hydrolysis with beta-glucosidase was ineffective in releasing the beta-glucosides with chemical modifications at C6. Presence of these glucoconjugates confirmed that L. minor was capable of xenobiotic uptake and transformation. Identification of these products suggested that chlorophenols were incorporated into vacuoles and cell walls of L. minor.

Changes in Soil Chemical Properties and Microbial Activities in Response to the Fungicide Ridomil Gold Plus Copper

The purpose of the study was to investigate changes of soil chemical and biological properties changes resulting from a single application of the fungicide Ridomil Gold plus copper (Ridomil Gold plus)(mefenoxam 6% + copper oxide 60%) at the following rates 0.25, 0.5, 1, 2, and 10 g m(-2). Selected chemical properties generally differed between fungicide rates over longer incubation periods. Microbial activity indices (available N, ammonification rates and specific enzymatic systems) were more sensitive indicators of change. Values of these indicators generally increased with incubation period and decreased or increased at high rates. Significant changes in P availability occurred after 90 days of incubation at rates > or = 1 g m(-2). Incorporation of the fungicide significantly increased NH4+ levels in soil after 75 days of incubation. These changes stimulated soil microbial activity as evidenced by increased ammonification rates especially at long-term exposure. Of the enzyme activities studied, dehydrogenase and beta-glucosidase activities were the most sensitive to ridomil gold plus. This sensitivity was more pronounced with the dehydrogenase activity.

Type 2 Gaucher's disease in a Malian family

Gaucher's disease is a recessive autosomal disorder caused by an inherited deficiency of betaglucocerebrosidase. We report here the case of an 8 month old child, fourth in a family of four children, who presents the neuropathic form of the disease. The dosages of betaglucosidase activity using C (14 ) techniques have confirmed the diagnosis, and allowed the detection of the disease in the elder brother. Both parents were considered as responsible for the transmission of this disease to their progeny. The type 2 Gaucher's disease is rare in black population, and may be associated with phenotypes heterogeneity.

Structural basis for thermostability of beta-glycosidase from the thermophilic eubacterium Thermus nonproteolyticus HG102

The three-dimensional structure of a thermostable beta-glycosidase (Gly(Tn)) from the thermophilic eubacterium Thermus nonproteolyticus HG102 was determined at a resolution of 2.4 A. The core of the structure adopts the (betaalpha)(8) barrel fold. The sequence alignments and the positions of the two Glu residues in the active center indicate that Gly(Tn) belongs to the glycosyl hydrolases of retaining family 1. We have analyzed the structural features of Gly(Tn) related to the thermostability and compared its structure with those of other mesophilic glycosidases from plants, eubacteria, and hyperthermophilic enzymes from archaea. Several possible features contributing to the thermostability of Gly(Tn) were elucidated.

Bioaerosol health effects and exposure assessment: progress and prospects

Exposures to bioaerosols in the occupational environment are associated with a wide range of health effects with major public health impact, including infectious diseases, acute toxic effects, allergies and cancer. Respiratory symptoms and lung function impairment are the most widely studied and probably among the most important bioaerosol-associated health effects. In addition to these adverse health effects some protective effects of microbial exposure on atopy and atopic conditions has also been suggested. New industrial activities have emerged in recent years in which exposures to bioaerosols can be abundant, e.g. the waste recycling and composting industry, biotechnology industries producing highly purified enzymes and the detergent and food industries that make use of these enzymes. Dose-response relationships have not been established for most biological agents and knowledge about threshold values is sparse. Exposure limits are available for some contaminants, e.g. wood dust, subtilisins (bacterial enzymes) and flour dust. Exposure limits for bacterial endotoxin have been proposed. Risk assessment is seriously hampered by the lack of valid quantitative exposure assessment methods. Traditional culture methods to quantify microbial exposures have proven to be of limited use. Non-culture methods and assessment methods for microbial constituents [e.g. allergens, endotoxin, beta(1-->3)-glucans, fungal extracellular polysaccharides] appear more successful; however, experience with these methods is generally limited. Therefore, more research is needed to establish better exposure assessment tools and validate newly developed methods. Other important areas that require further research include: potential protective effects of microbial exposures on atopy and atopic diseases, inter-individual susceptibility for biological exposures, interactions of bioaerosols with non-biological agents and other potential health effects such as skin and neurological conditions and birth effects.

SO2-catalyzed steam explosion of corn fiber for ethanol production

Corn fiber, a by-product of the corn wet-milling industry, represents a renewable resource that is readily available in significant quantities and could potentially serve as a low-cost feedstock for the production of fuel-grade alcohol. In this study, we used a batch reactor to steam explode corn fiber at various degrees of severity to evaluate the potential of using this feedstock in the bioconversion process. The results indicated that maximum sugar yields (soluble and following enzymatic hydrolysis) were recovered from corn fiber that was pretreated at 190 degrees C for 5 min with 6% SO2. Sequential SO2-catalyzed steam explosion and enzymatic hydrolysis resulted in very high conversion (81%) of all polysaccharides in the corn fiber to monomeric sugars. Subsequently, Saccharomyces cerevisiae was able to convert the resultant corn fiber hydrolysates to ethanol very efficiently, yielding 90-96% of theoretical conversion during the fermentation process.

[Cloning and expression of a thermostable beta-glycosidase gene from Thermus nonproteolyticus HG102]

The gene coding for beta-glycosidase (EC3.2.1.21) from Thermus nonproteolyticus HG102 has been cloned and expressed in E. coli. The gene open reading frame was 1311 bp and it codes for 436 amino acids. The deduced amino acid sequence of the enzyme showed identity with members of glycosyl hydrolase family I. The enzyme had high content of hydrophobic amino acid (Ala 12.8%, Leu 10.9%), Arg(9.6%), Glu(9.4%) and Pro(8.0%), but low content Cys(0.45%) and Met (0.9%). From the alignment of enzyme amino acid sequence with other glycosyl hydrolase family I members, Glu164 and Glu338 were predicated as the proton donor and nucleophile group. The DNASTAR program was used to predict the secondary structure. According to the Chou-Fasman model, the enzyme has 41.4% of alpha-helics, 16.2%, beta-strands, 14.4%, beta-turns. 14 of the 35 Pro were located at the second sites of beta-turns. Hydrophobic interaction, ion bond, alpha-helics and Pro had important contribution to Tn-gly thermostability.

Overexpression, purification, crystallization and preliminary crystallographic studies on a thermostable beta-glycosidase from Thermus nonproteolyticus HG102

A thermostable beta-glycosidase (Tn-gly) from Thermus nonproteolyticus HG102 has been cloned and overexpressed in Escherichia coli. The recombinant enzyme, with a molecular mass of 48.9 kDa, was purified to homogeneity. It can hydrolyze a wide range of oligosaccharides and perform transglycosylation. Crystals of the recombinant enzyme were grown by the hanging-drop vapour-diffusion technique with MPD and NaCl as precipitants. They belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 66.7, b = 94.6, c = 176.5 A.

Assessing cyanogen content in cassava-based food using the enzyme-dipstick method

The cyanogen content of 35 cassava-based foods was determined using the enzyme-dipstick method. The analyses showed presence of residual cyanogens in these products, and they ranged from 2 to 88 mg HCN equivalent/kg. Foodstuff prepared from grated cassava roots exhibited a lower level of cyanogen content (2-31 mg HCN equivalent/kg) compared with those prepared as cassava root slices or from cassava flour (28-88 mg HCN equivalent/kg). These results showed that current commercial processing methods did not remove all the cyanogen present from cassava roots and it might be worthwhile re-examining these processing practices. In this respect, the report showed that an overnight treatment of cassava root slices with linamarase and cellulase might facilitate the removal of cyanogens. This study also demonstrated the usefulness of enzyme-dipsticks for assessing cyanogen content in cassava food products.

Cell wall biosynthesis: glycan containing oligomers in developing cotton fibers, cotton fabric, wood and paper

A series of oligomeric glycans can be extracted from the cell walls of developing cotton fibers with weak acid. Glycans that produce similar profiles on high pH anion chromatography with pulsed amperometric detection (HPAEC-PAD) are also found in a protein complex extracted from developing fibers and in amorphous aggregates found in association with immature fibers in developing, but not in mature cotton bolls. The quantity and composition of the glycans recovered from the carbohydrate-protein complex varies significantly with the time of day when the bolls are harvested. This diurnal variation is consistent with the hypothesis that secondary cell walls are deposited primarily at night. Incubation of re-hydrated cotton fibers in the presence of exogenous oligosaccharides, myo-inositol and glycerol substantially alters the apparent quantity of the oligomers extracted from the fibers. The same and similar glycans have also been extracted from cotton fabric, marine algae, various paper products and wood. While many of the oligomers isolated from the various cellulose sources display the same peaks by HPAEC-PAD, the specific number of oligomers and their relative quantities appear unique for each source of cellulosic material. Oligomeric glycans, as described in the preceding, are present in all cellulose sources that have been investigated. Their relative abundance changes in response to source, stage of development and other physiological variables. We hypothesize that the glycans are intermediates in the biological assembly of cellulose, and that their incorporation in cellulose is mediated by physicochemical and enzymatic mechanisms.

Cloning and expression of thermostable beta-glycosidase gene from Thermus nonproteolyticus HG102 and characterization of recombinant enzyme

The gene coding for beta-glycosidase (EC 3.2.1.21) from Thermus nonproteolyticus HG102 was cloned and expressed in Escherichia coli. The gene open reading frame was 1311 bp, and it codes for 437 amino acids. The deduced amino acid sequence of the enzyme showed identity with members of the glycosyl hydrolase family I. The enzyme had high content of Arg and Pro. The recombinant enzyme was purified to homogeneity with heat precipitation, ammonium sulfate precipitation, DEAE-cellulose (DE52) chromatography, and prepared slab polyacrylamide gel electrophoresis. The enzyme was monomeric and had a molecular mass of 48,900 Daltons and a pI of 5.2. The enzyme showed optimum activity at pH 5.6 and 90 degrees C. It catalyzed the hydrolysis of beta-D-glucoside, beta-D-galactoside, beta-D-fucoside, and beta-D-mannoside. Lineweaver-Burk plots showed that the kcat/Km ratio for beta-D-glucoside and beta-D-fucoside was higher than for beta-D-mannoside and beta-D-galactoside. The enzyme was extremely thermostable, with a half-life of 2.5 h at 90 degrees C, and was stable over a wide range of pH. It also had transglycosidic activity at high temperature.

Cloning and biochemical characterization of BglC, a beta-glucosidase from the cellulolytic actinomycete Thermobifida fusca

An operon, bglABC, that encodes two sugar permeases and a beta-glucosidase was cloned from a cellulolytic actinomycete, Thermobifida fusca, into Escherichia coli and sequenced. The bglC gene encoding an intracellular beta-glucosidase (beta-d-glucoside glucohydrolase, EC 3.2.1.21) belonging to glycosyl hydrolase family 1 was subcloned and expressed in E. coli. The purified enzyme (MW 53,407 Da; pI 4.69) hydrolyzed substrates containing both beta 1 --> 4 and beta 1 --> 2 glycosidic bonds, and was most active against cellobiose (Vmax = 29, Km = 0.34 mm), cellotriose, cellotetraose, and sophorose. The enzyme also showed aryl-beta-glucosidase activity on p-nitrophenyl-beta-d-glucopyranoside and p-nitrophenyl-beta-d-cellobioside. BglC had a pH optimum of 7.0 and a temperature optimum of 50 degrees C. The enzyme was stable at 60 degrees C, but was rapidly inactivated at 65 degrees C. BglC was inhibited by low concentrations of gluconolactone, but was insensitive to end-product inhibition by glucose and was not affected by Ca or Mg ions or EDTA. Its properties are well suited for use in a process to hydrolyze biomass cellulose to glucose.

Decreased scopolamine yield in field-grown Duboisia plants regenerated from hairy roots

Hairy root cultures were obtained from hybrid clones of Duboisia myoporoides x D. leichhardtii following transformation by Agrobacterium rhizogenes strain A4. Shoots spontaneously regenerating from the hairy root cultures were rooted and transferred to soil. The plants displayed typical morphological alterations known as hairy root syndrome to varying degrees. PCR analysis confirmed that all transformed plants contained the rolA, rolB and rolC genes, irrespective of the degree of morphological alterations. A field test of the transformed regenerated plants revealed that those plants displaying the strongest hairy root syndrome symptoms had the highest content of the tropane alkaloid scopolamine. However, the overall scopolamine and hyoscyamine yield of all transformed plants was clearly reduced compared to untransformed control plants. These results demonstrate that the A. rhizogenes-transformed plants tested in this study do not provide a viable alternative to agricultural farming of hybrid clones of D. myoporoides x D. leichhardtii obtained by conventional breeding.

Effect of chip size on steam explosion pretreatment of softwood

Although considerable progress has been made in technology for converting lignocellulosic biomass into ethanol, substantial opportunities still exist to reduce production costs. In biomass pretreatment, reducing milling power is a technological improvement that will substantially lower production costs for ethanol. Improving sugar yield from hemicellulose hydrolysis would also reduce ethanol production costs. Thus, it would be desirable to test innovative pretreatment conditions to improve the economics by reducing electrical power of the milling stage and by optimizing pretreatment recovery of hemicellulose, as well as to enhance cellulose hydrolysis. The objective of this study was to evaluate the effect of chip size (2-5, 5-8, and 8-12 mm) on steam-explosion pretreatment (190 and 210 degrees C, 4 and 8 min) of softwood (Pinus pinaster).

Molecular organization of the alkali-insoluble fraction of Aspergillus fumigatus cell wall

Physical and biological properties of the fungal cell wall are determined by the composition and arrangement of the structural polysaccharides. Cell wall polymers of fungi are classically divided into two groups depending on their solubility in hot alkali. We have analyzed the alkali-insoluble fraction of the Aspergillus fumigatus cell wall, which is the fraction believed to be responsible for fungal cell wall rigidity. Using enzymatic digestions with recombinant endo-beta-1,3-glucanase and chitinase, fractionation by gel filtration, affinity chromatography with immobilized lectins, and high performance liquid chromatography, several fractions that contained specific interpolysaccharide covalent linkages were isolated. Unique features of the A. fumigatus cell wall are (i) the absence of beta-1,6-glucan and (ii) the presence of a linear beta-1, 3/1,4-glucan, never previously described in fungi. Galactomannan, chitin, and beta-1,3-glucan were also found in the alkali-insoluble fraction. The beta-1,3-glucan is a branched polymer with 4% of beta-1,6 branch points. Chitin, galactomannan, and the linear beta-1, 3/1,4-glucan were covalently linked to the nonreducing end of beta-1, 3-glucan side chains. As in Saccharomyces cerevisiae, chitin was linked via a beta-1,4 linkage to beta-1,3-glucan. The data obtained suggested that the branching of beta-1,3-glucan is an early event in the construction of the cell wall, resulting in an increase of potential acceptor sites for chitin, galactomannan, and the linear beta-1,3/1,4-glucan.