Glucose-salts Medium Research Articles

The Evaluation of the Combination of Additives and Fungal Dyes to Produce Color for Textile Painting

Fungal dyes are an eco-friendly alternative to synthetic dye. This study aims to evaluate additives to dye, using mixed fungi, to paint the picture on cloth. In the present study, the cloth was painted with mixed Aspergillus and Paecilomyces dye. The mixed fungi were grown on a mineral salt glucose medium. Five tests were conducted to evaluate additives to dye from mixed fungi that could be used to paint pictures on cloths to evaluate the effect of additives, a combination of additives producing tidy colors and other additives, the dye pH, mordant, and a variety of different mordants and the dye pH on color tidiness and hue. The additives used were alkali, acid, salts, glycerine, and urea. The Royal Horticultural Society (RHS) color chart was used to measure the color of filtrate and range developed on the painted color on the cloth. The results showed that the mixture of vinegar or lemon as additives and the dye pH of 3 produced tidy colors. The mordant application had a more significant effect on the color that appears than pH treatment. Colors formed on images can add variations to textile painting.

Absorption of dyes from mixed fungi by cotton fabric with distinct mordants and dyeing pH

Cotton fabrics processed in dyes with different mordants and staining pH might alter colors variation and dye absorption. A recent study showed a mixture of Aspergillus and Paecilomyces can be used to dye cotton fabric using five different mordant chemicals, CuSO4.5H2O, FeSO4.7H2O, KAl (SO4)2.12H2O, K2Cr2O7, and MnSO4.H2O, and three distinctive dyeing pH (3, 7, and 11). Both fungi were collectively cultured on mineral salt glucose medium to a stationary stage in dark conditions for four weeks. The RHS color chart was used to determine the color of the filtrate and the spectrum of colors created on dyed materials. The results suggested that the color development and dye absorption of the fabrics were greatly affected by chemical compounds of mordant and the acidity degree of the dyeing process. The pH of the dyeing process has a greater impact on the absorption of fungal dyes by cloth than the mordant. Colors formed on cotton fabric can add colors variation to textile dyeing.

Effect of dyeing repetition and color reinforcement materials on color formation of cloth by mixed fungi dyes

Colors variation and aging on cloth can be obtained through dyeing repetition and the application of color reinforcement materials. In the present study, cloth was dyed with dyes from the mixed fungi of Aspergillus and Paecilomyces using three different dyeing repetitions (3, 6, and 9 times), three different mordants (CaCO3, FeSO4.7H2O, and KAI (SO4)2.12H2O), and three different other color reinforcement materials (salt, soda ash, and vinegar). The mixed fungi were grown on mineral salt glucose medium in stationary cultures in dark conditions for 4 weeks. By using the RHS color chart, the range of colors developed on dyed materials was measured. The result showed that different dyeing repetitions and the combination of those with color reinforcement materials had a great effect on the color formation of cloth by the mixed fungi dyes. The optimum condition of cloth dyeing by the fungal dyes depends on color reinforcement materials used. The combination of dyeing repetition and color reinforcement materials on the color formation of cloth by the fungal dyes generated various colors, adding a color variation on textile dyeing.

Combination of culture and dyeing conditions on cloth color dyed with mixed fungi dyes

This study aimed to examine the dyes production of mixed Aspergillus and Paecilomyces on different culture conditions and evaluate the combination between culture and dyeing conditions on cloth color by the fungal dyes. The different media consist of mineral salt glucose (MSG) medium and mineral salt sucrose (MSS) medium were evaluated. Additionally, different culture conditions such as C and N sources, incubation temperature, and pH of the media were evaluated together with variation of dyeing conditions including pH and mordants. The result showed that different culture conditions on media and the combination of those with dyeing conditions produce distinction colors on the fabric. The variation of dyed colors on the fabric was related to the dyes concentration produced by combination treatment of culture condition and dyeing pH. However, the effect was not observed on the combination between culture condition and mordants. Combination of culture and dyeing conditions on cloth color dyed with mixed fungi dyes generated various cloth colors, adding a color variation on textile dyeing.

Effect of Different Mordants on Cotton Cloth Dyed with Aspergillus and Penicillium Dyes

Natural dyes are an important alternative to potentially harmful synthetic dyes. This research was conducted using three kinds of Aspergillus dyes and six kinds of Penicillium dyes. In this study, Aspergillus and Penicillium were grown in mineral salts glucose medium. Premordanting technique was followed using different mordants, namely alum, CaCO3, CuSO4 5H2O, FeSO4 7H2O, K2Cr2O7 and MnSO4 H2O on cotton cloth. The colour of filtrate and range of colours developed on dyed materials were measured by RHS colour chart. The results indicated that the colour of dyed cloth was influenced by the addition of mordants, and different shades were obtained from the same dye filtrate using different mordants. FeSO4 7H2O was found as the most influential mordant. The present study shows a new source of fungal dyes, which can be used as an alternative for dyeing cloth.

Relevance of the Axis Spermidine/eIF5A for Plant Growth and Development.

One key role of the essential polyamine spermidine in eukaryotes is to provide the 4-aminobutyl moiety group destined to the post-translational modification of a lysine in the highly conserved translation factor eIF5A. This modification is catalyzed by two sequential enzymatic steps leading to the activation of eIF5A by the conversion of one conserved lysine to the unusual amino acid hypusine. The active translation factor facilitates the sequence-specific translation of polyproline sequences that otherwise cause ribosome stalling. In spite of the well-characterized involvement of active eIF5A in the translation of proline repeat-rich proteins, its biological role has been recently elucidated only in mammals, and it is poorly described at the functional level in plants. Here we describe the alterations in plant growth and development caused by RNAi-mediated conditional genetic inactivation of the hypusination pathway in Arabidopsis thaliana by knocking-down the enzyme deoxyhypusine synthase. We have uncovered that spermidine-mediated activation of eIF5A by hypusination is involved in several aspects of plant biology such as the control of flowering time, the aerial and root architecture, and root hair growth. In addition this pathway is required for adaptation to challenging growth conditions such as high salt and high glucose medium and to elevated concentrations of the plant hormone ABA. We have also performed a bioinformatic analysis of polyproline-rich containing proteins as putative eIF5A targets to uncover their organization in clusters of protein networks to find molecular culprits for the disclosed phenotypes. This study represents a first attempt to provide a holistic view of the biological relevance of the spermidine-dependent hypusination pathway for plant growth and development.

Biodegradation of polycyclic aromatic hydrocarbons by a thermotolerant white rot fungus Trametes polyzona RYNF13.

The biodegradation of three polycyclic aromatic hydrocarbons (PAHs), phenanthrene, fluorene, and pyrene, by a newly isolated thermotolerant white rot fungal strain RYNF13 from Thailand, was investigated. The strain RYNF13 was identified as Trametes polyzona, based on an analysis of its internal transcribed spacer sequence. The strain RYNF13 was superior to most white rot fungi. The fungus showed excellent removal of PAHs at a high concentration of 100 mg·L-1. Complete degradation of phenanthrene in a mineral salt glucose medium culture was observed within 18 days of incubation at 30°C, whereas 90% of fluorene and 52% of pyrene were degraded under the same conditions. At a high temperature of 42°C, the strain RYNF13 was still able to grow, and degraded approximately 68% of phenanthrene, whereas 48% of fluorene and 30% of pyrene were degraded within 32 days. Thus, the strain RYNF13 is a potential fungus for PAH bioremediation, especially in a tropical environment where the temperature can be higher than 40°C. The strain RYNF13 secreted three different ligninolytic enzymes, manganese peroxidase, laccase, and lignin peroxidase, during PAH biodegradation at 30°C. When the incubation temperature was increased from 30°C to 37°C and 42°C, only two ligninolytic enzymes, manganese peroxidase and laccase, were detectable during the biodegradation. Manganese peroxidase was the major enzyme produced by the fungus. In the culture containing phenanthrene, manganese peroxidase showed the highest enzymatic activity at 179 U·mL-1. T. polyzona RYNF13 was determined as a potential thermotolerant white rot fungus, and suitable for application in the treatment of PAH-containing contaminants.

Valorization of Egg Shell Biowaste and Brewery Wastewater for the Enhanced Production of Fumaric Acid

Two different industrial wastes, namely egg shells and brewery wastewater were valorized for the enhanced production of FA by adopting immobilization strategy. Egg shells were used both as a source of CaCO3 and as immobilizing support, while brewery wastewater was used as fermentation medium for fumaric acid production through submerged fermentation. To check the suitability as fermentation medium, compositional analysis of brewery wastewater was carried out. The filamentous fungus, Rhizopus oryzae 1526 was immobilized on egg shell surfaces that developed into thin (ca. 1 mm) biofilms. Biofilms were used for fumaric acid production at the optimized fermentation parameters (25 g L−1 total solids concentration of brewery wastewater, 30 °C and 150 rpm). Immobilized mycelia were also experimented with glucose salt medium for enhanced fumaric acid production. For biofilm formation, different parameters viz. number of egg shell for immobilization (three), spore concentration (1.0 × 106 per mL), incubation time (24 h) and flask shaking speed (150 rpm) were optimized. As compared to free-cell, biofilms mediated submerged fermentation markedly enhanced the production and volumetric productivity of fumaric acid from 30.23 ± 1.23 to 47.22 ± 0.77 g L−1 (i.e. by 56 %) and 0.419 to 1.657 g L−1 h−1 (i.e. by 3.95 times), respectively. The application of egg shells with dual functions (source of CaCO3 and immobilization device) for fumaric acid production was a new approach of valorization with economic and ecological benefits.

Degradation and detoxification of aflatoxin B1 by Pseudomonas putida

Aflatoxin is a mycotoxin produced by Aspergillus flavus and a common contaminant of food and feed, posing health hazards to humans and animals alike. The aim of this study is to explore the ability of Pseudomonas putida to degrade aflatoxin B1 (AFB1). The toxigenic strain of A. flavus was isolated from sugarcane and used to produce AFB1 in yeast extract sucrose medium. Two P. putida strains, MTCC 1274 and 2445, were cultured in mineral salt glucose medium (MSG) containing AFB1. The AFB1 was analyzed qualitatively and quantitatively by TLC and HPLC. It was found that Pseudomonas sp. can tolerate AFB1 in the medium (0.2 μg ml−1), and degrades it very efficiently. Within 24 h of incubation, AFB1 was reduced to an undetectable level in MSG medium. Analysis with TLC, HPLC, UV spectrophotometer, gas chromatography mass spectrometry (GC–MS), and Fourier transform infra-red spectroscopy (FT-IR) showed that AFB1 was bio-transformed to structurally different compounds (AFD1, AFD2, and AFD3), with the modified furan and lactone ring on the AFB1 molecule. A toxicity study on the HeLa cells showed that the new compounds formed are less toxic when compared with AFB1.

Unsterile and continuous production of polyhydroxybutyrate by Halomonas TD01

An unsterile and continuous fermentation process was developed based on a halophilic bacterium termed Halomonas TD01 isolated from a salt lake in Xinjiang, China. The strain reached 80g/L cell dry weight containing 80% poly(3-hydroxybutyrate) (PHB) on glucose salt medium during a 56h fed-batch process. In a 14-day open unsterile and continuous process, the cells grew to an average of 40g/L cell dry weight containing 60% PHB in the first fermentor with glucose salt medium. Continuous pumping of cultures from the first fermentor to the second fermentor containing the nitrogen-deficient glucose salt medium diluted the cells but allowed them to maintain a PHB level of between 65% and 70% of cell dry weight. Glucose to PHB conversions were between 20% and 30% in the first fermentor and above 50% in the second one. This unsterile and continuous fermentation process opens a new area for reducing the cost in polyhydroxyalkanoates production.

Mutual influence of soil basidiomycetes and white mustard plants on their enzymatic and catabolic activities

Liquid and volatile emanations in interactions of soil basidiomycetes with herbs affect fungal oxidoreductases and stress-related plant peroxidases (PO). In this study, gnotobiotic co-cultures between 6 non-pathogenic saprobes and 2 ectomycorrhizal basidiomycetes with the non-host plant white mustard were established on glucose-salt medium with the respective controls. Determined were oxidoreductase activities for culture fluids and plant tissues at initial fungal idiophase and degradation rates of Remazol-BBR and 5 PAHs. In culture fluids of Agaricus arvensis, A. porphyrizon, Lepista nebularis, Stropharia rugoso-annulata, and Hypholoma fasciculare (group-5), the laccase-deficient plant enabled activity increases in fungal laccase (by 2300-fold), in extracellular (fungal and?) plant-derived peroxidases (by 21-fold), and in the dissipation of phenanthrene and anthracene. Oxidative activities in roots rose by 46000-fold during adsorption of fungal laccases. Increases in the stress-related shoot-PO (by 4.1-fold) were exclusively elicited by group-5 saprobes and correlated with plant-phenolic-mediated formations of Mn(III) and increases in Remazol BBR bleaching. Agaricus bisporus and the ectomycorrhizal Hebeloma crustuliniforme and Suillus granulatus did not respond to plant emanations with elevated laccase activities but solubilized apparently root-surface PO. They failed to elicit stress-related activity increases of PO in white mustard shoot and prevented Mn(III) formation in several tissues. It is concluded that white mustard emanations promoted the catabolic performance of the plant-stress eliciting group-5 saprobes but not of A. bisporus and the ectomycorrhizal fungi with their low stress-inducing potential. The nature of the plant-released stimuli and the classes of fungus-released stress agents discussed must be determined in further studies.

The Siderophore Pyoverdine of Pseudomonas syringae pv. tabaci 6605 Is an Intrinsic Virulence Factor in Host Tobacco Infection

To investigate the role of iron uptake mediated by the siderophore pyoverdine in the virulence of the plant pathogen Pseudomonas syringae pv. tabaci 6605, three predicted pyoverdine synthesis-related genes, pvdJ, pvdL, and fpvA, were mutated. The pvdJ, pvdL, and fpvA genes encode the pyoverdine side chain peptide synthetase III L-Thr-L-Ser component, the pyoverdine chromophore synthetase, and the TonB-dependent ferripyoverdine receptor, respectively. The Delta pvdJ and Delta pvdL mutants were unable to produce pyoverdine in mineral salts-glucose medium, which was used for the iron-depleted condition. Furthermore, the Delta pvdJ and Delta pvdL mutants showed lower abilities to produce tabtoxin, extracellular polysaccharide, and acyl homoserine lactones (AHLs), which are quorum-sensing molecules, and consequently had reduced virulence on host tobacco plants. In contrast, all of the mutants had accelerated swarming ability and increased biosurfactant production, suggesting that swarming motility and biosurfactant production might be negatively controlled by pyoverdine. Scanning electron micrographs of the surfaces of tobacco leaves inoculated with the mutant strains revealed only small amounts of extracellular polymeric matrix around these mutants, indicating disruption of the mature biofilm. Tolerance to antibiotics was drastically increased for the Delta pvdL mutant, as for the Delta psyI mutant, which is defective in AHL production. These results demonstrated that pyoverdine synthesis and the quorum-sensing system of Pseudomonas syringae pv. tabaci 6605 are indispensable for virulence in host tobacco infection and that AHL may negatively regulate tolerance to antibiotics.

Assimilation of homotaurine-nitrogen byBurkholderiasp. and excretion of sulfopropanoate

Homotaurine (3-aminopropanesulfonate), free or derivatized, is in widespread pharmaceutical and laboratory use. Studies with enrichment cultures indicated that the compound is degradable as a sole source of carbon or as a sole source of nitrogen for bacterial growth. A pure culture of Burkholderia sp. was isolated which assimilated the amino group from homotaurine in a glucose-salts medium, and which released an organosulfonate, 3-sulfopropanoate, into the medium stoichiometrically. The deamination involved an inducible 2-oxoglutarate-dependent aminotransferase to yield glutamate, and 3-sulfopropanal. Release of the amino group was attributed to the measured NADP-coupled glutamate dehydrogenase.

Kinetics of biodegradation of free gossypol by Candida tropicalis in solid-state fermentation

In the present work experiments were carried out to study the effect of free gossypol on the growth of Candida tropicalis ZAU-1, evaluate its ability in biodegrading free gossypol, analyze the time course of solid-state fermentation, and model the microbial growth by determining the kinetics of dry matter weight loss, total carbohydrate concentration and the free gossypol content during solid-state fermentation. Results showed that the biomass in inorganic salts glucose medium were unaffected by free gossypol at 500 and 1000 mg/l levels, compared with the control group ( p > 0.05); degradation of free gossypol reached 95.12% and 94.12%, respectively. A logistic equation ( R 2 = 0.9922), describing the growth model of C. tropicalis ZAU-1 was obtained, with the maximum values of u m and X m at 0.0970 h −1 and 21.8631% of dry matter weight loss, respectively. A good-fit curvilinear regression model was achieved to describe the change pattern of total carbohydrate concentration ( R 2 = 0.9910), and the biodegradation pattern of free gossypol ( R 2 = 0.9825). These models could be used to predict the fermentation course by C. tropicalis ZAU-1 under solid-state fermentation.

Effect of metal ions on HIF-1α and Fe homeostasis in human A549 cells

Several metals are carcinogenic but little is known about the mechanisms by which they cause cancer. A pathway that may contribute to metal ion induced carcinogenesis is by hypoxia signaling, which involves a disruption of cellular iron homeostasis by competition with iron transporters or iron-regulated enzymes. To examine the involvement of iron in the hypoxia signaling activity of these metal ions we investigated HIF-1α protein stabilization, IRP-1 activity, and ferritin protein levels in human lung carcinoma A459 cells exposed to various agents in serum- and iron-free salt–glucose medium (SGM) or in normal complete medium. We also studied the effects of excess exogenous iron on these responses induced by nickel ion exposure. Our results show the following: (1) SGM enhanced metals-induced HIF-1α stabilization and IRP-1 activation (e.g., nickel and cobalt ions). (2) If SGM was reconstituted with a slight excess level (25 μM of FeSO 4) of iron, this enhancing ability was significantly decreased. (3) The effect of a high level of exogenous iron (500 μM of FeSO 4) on metal-induced hypoxia and iron metabolism was highly dependent on the order of addition. If treatment with the Fe and metal ions was simultaneous (co-treatment), the effects of nickel ion exposure were overwhelmed, since the added Fe reversed HIF-1α stabilization, decreased IRP-1 activity, and increased ferritin level. Pre-treatment with iron was not able to reverse the responses caused by nickel ion exposure. These results imply that it is important to consider the available iron concentration and suitable exposure design when studying metal-induced hypoxia or metal-induced disruption of Fe homeostasis.

Mineralization of p-nitrophenol by pentachlorophenol-degrading Sphingomonas spp.

Pentachlorophenol-degrading Sphingomonas sp. UG30 and Sphingomonas chlorophenolica strains RA2 and ATCC 39723 can transform p-nitrophenol in either mineral salts-glutamate or mineral salts-glucose medium after an initial lag period. However, mineralization of p-nitrophenol by these bacterial strains was observed only in mineral salts-glucose medium. When p-nitrophenol was the sole nitrogen source in the growth medium, UG30 mineralized 32% of 140 mM [14C]p-nitrophenol which was 10% higher than the amount of [14C]p-nitrophenol mineralized in mineral salts-glucose medium. UG30 did not transform or mineralize p-nitrophenol (in a growth medium) in the absence of glucose or glutamate. All three strains released nitrite during p-nitrophenol degradation in mineral salts-glucose medium and mineral salts-glutamate medium. The transformation rate of p-nitrophenol by UG30 was dependent on the initial p-nitrophenol concentration, with the optimal rate being found at 310 μM of p-nitrophenol and inhibition observed at ≥1100 μM of p-nitrophenol. Pre-exposure of UG30 cells to p-nitrophenol eliminated the initial lag phase of p-nitrophenol transformation. However, pre-growth of UG30 cells on pentachlorophenol did not reduce the lag period for p-nitrophenol transformation. Both p-nitrophenol- and pentachlorophenol-induced UG30 cells degraded pentachlorophenol without any lag phase. Thin layer chromatographic analysis of the reaction mixture suggested 4-nitrocatechol was an intermediate of p-nitrophenol transformation by UG30.

Citrate Synthase Mutants of Agrobacterium Are Attenuated in Virulence and Display Reduced vir Gene Induction

A citrate synthase (CS) deletion mutant of Agrobacterium tumefaciens C58 is highly attenuated in virulence. The identity of the mutant was initially determined from its amino acid sequence, which is 68% identical to Escherichia coli and 77% identical to Brucella melitensis. The mutant lost all CS enzymatic activity, and a cloned CS gene complemented a CS mutation in Sinorhizobium. The CS mutation resulted in a 10-fold reduction in vir gene expression, which likely accounts for the attenuated virulence. When a plasmid containing a constitutive virG [virG(Con)] locus was introduced into this mutant, the level of vir gene induction was restored to nearly wild-type level. Further, the virG(Con)-complemented CS mutant strain induced tumors that were similar in size and number to those induced by the parental strain. The CS mutation resulted in only a minor reduction in growth rate in a glucose-salts medium. Both the CS mutant and the virG(Con)-complemented CS strain displayed similar growth deficiencies in a glucose-salts medium, indicating that the reduced growth rate of the CS mutant could not be responsible for the attenuated virulence. A search of the genome of A. tumefaciens C58 revealed four proteins, encoded on different replicons, with conserved CS motifs. However, only the locus that when mutated resulted in an attenuated phenotype has CS activity. Mutations in the other three loci did not result in attenuated virulence and any loss of CS activity, and none were able to complement the CS mutation in Sinorhizobium. The function of these loci remains unknown.

Historical Perspectives

It began with Bob Guthrie’s second child. John was mentally retarded. Because of this, Guthrie was stimulated toward research that could prevent mental retardation and other developmental disabilities. In 1957, Guthrie was conducting cancer research at the Roswell Park Cancer Institute in Buffalo, NY. Because of John, Bob and his wife Margaret were very active in the Buffalo chapter of the New York State Association for Retarded Children. As Vice-President of the chapter, he was responsible for the program at the monthly meeting. He had heard that Dr Robert Warner, Director of the newly established Children’s Rehabilitation Center at Buffalo Children’s Hospital, was doing work in developmental disabilities, so he invited Dr Warner to speak about his work at one of the meetings. At the meeting, Dr Warner discussed his work in treating children with mental retardation, some of whom had metabolic disorders. Over coffee after the meeting, Guthrie mentioned his interest in the prevention of mental retardation. As a result of the meeting and especially the discussion after the meeting, the two kept in touch. About a year later, Dr Warner introduced Guthrie to phenylketonuria (PKU). Dr Warner explained that PKU was an inborn error of phenylalanine metabolism that caused mental retardation, but that when these retarded children received a special phenylalanine-restricted diet, not only did their blood phenylalanine levels decrease, but their behavior improved substantially. One problem in administering the diet, Dr Warner explained, was the difficulty with tests required to measure the blood phenylalanine levels for close monitoring of the patients. This persuaded Guthrie to try to produce a simpler method for measuring blood phenylalanine. Guthrie thought such a test might be possible by modifying the Bacillus subtilis or Escherichia coli bacteria assays he was using to screen for different antimetabolites in blood from patients who were …

DNA–Protein Crosslinks Induced by Nickel Compounds in Isolated Rat Lymphocytes: Role of Reactive Oxygen Species and Specific Amino Acids

Isolated rat lymphocytes in salts-glucose medium (pH 7.2) were incubated with nickel chloride, nickel acetate, nickel sulfate, and a soluble form of nickel subsulfide (0–2 mM) at 37°C for 2 h. The soluble form of nickel subsulfide induced a significant increase in DNA–protein crosslinks (DPXLs) (111%) beginning at 0.5 mM and a maximum increase of 700% from that of the control value was reached at a 2 mM concentration, whereas nickel sulfate produced only a 65% increase of such crosslinks at the 2 mM concentration only. No significant reduction in viability of rat lymphocytes (as measured by trypan blue exclusion) due to these nickel compounds was observed at any concentration used. Time-course studies of DPXLs and cellular viability due to 2 mM nickel subsulfide indicate that DPXL formation may not be due in part to cellular necrosis. Coincubation of nickel subsulfide (2 mM) with l-histidine (16 mM), l-cysteine (4 or 8 mM), or l-aspartic acid (24 mM) significantly reduced the DPXLs induced by 2 mM nickel subsulfide. But Mg2+ even at 24 mM failed to antagonize nickel subsulfide-induced increase in DPXLs. High concentrations of these amino acids significantly decreased the accumulation of Ni2+ from nickel subsulfide in lymphocytes, suggesting that such reduction of cellular uptake of Ni2+ by these amino acids is partly responsible for the potent protective effects of these amino acids against such genotoxicity of nickel subsulfide. In vitro exposure of lymphocytes to nickel subsulfide (0–2 mM) increased the formation of reactive oxygen species (ROS) in a concentration-dependent manner. Furthermore, coincubation of 2 mM nickel subsulfide with catalase, dimethylthiourea, mannitol, or vitamin C at 37°C for 2 h resulted in a significant decrease of nickel subsulfide-induced formation of DPXLs, suggesting that nickel subsulfide-induced DPXLs formation in isolated rat lymphocytes is caused by the formation of ROS. The amino acid treatment also abrogated Ni3S2-induced generation of ROS. Deferoxamine (a highly specific iron chelator) treatment prevented nickel subsulfide-induced DNA–protein crosslink formation, suggesting that Ni2+-induced DPXL formation in rat lymphocytes is caused by the induction of Fenton/Haber–Weiss reaction, generating hydroxyl radicals. The potent protective effects of these specific amino acids against nickel subsulfide-induced DPXL formation in isolated rat lymphocytes may be due in part to impaired cellular uptake of Ni2+, inhibition of the binding of Ni2+ to deproteinized DNA, and a reduction in reactive oxygen species.

Enhancement of hydrogen production from glucose by nitrogen gas sparging

The effect on hydrogen yield of N 2 sparging was investigated in non-sterile conditions using a hydrogen-producing mixed culture previously enriched from soya bean meal. A continuous stirred-tank reactor (CSTR) at 35°C and pH 6.0 was operated on a mineral salts-glucose (10 g l −1) medium at a hydraulic retention time (HRT) of 8.5 h, and organic loading rate of 27.02 g glucose litre reactor −1 day −1. Results are reported from an 8 week period of continuous operation, and the enrichment culture gave stable results over an extended period. A hydrogen yield of 0.85 moles H 2/mole glucose consumed was obtained after 5 HRT, the gas produced being 53.4% H 2. With N 2 sparging at a flow rate approximately 15 times the hydrogen production rate, the hydrogen yield was 1.43 moles H 2/mole glucose consumed. The specific hydrogen production rate increased from 1.446 ml hydrogen min −1g −1 biomass to 3.131 ml hydrogen min −1 g −1 biomass under sparging conditions. It is suggested that hydrogen partial pressure in the liquid phase was an important factor affecting hydrogen yield. Energy could be recovered as hydrogen from processes generating volatile fatty acids for fine chemicals and liquid bio-fuels or from acidification reactors preceding normal anaerobic biological treatment of sugary wastewaters.