Showing papers in "Applied Microbiology and Biotechnology in 1993"
TL;DR: A stable digestion of cattle manure could be maintained with ammonia concentrations up to 6 g N/l after 6 months of operation, however, the methane yield was reduced and the concentration of volatile fatty acids increased from 1 to 3 g/l as acetate, compared to controls with an ammonia concentration of 2.5 gN/l.
Abstract: Ammonia concentrations of 4 g N/l or more inhibited thermophilic digestion of cattle manure. A stable digestion of cattle manure could be maintained with ammonia concentrations up to 6 g N/l after 6 months of operation. However, the methane yield was reduced and the concentration of volatile fatty acids increased from 1 to 3 g/l as acetate, compared to controls with an ammonia concentration of 2.5 g N/l. The temporary strong inhibition following an one-step increase in ammonia concentration was reduced by applying a gradual increase. The specific methanogenic activity of ammonia-inhibited reactors (6 g N/l) with acetate or hydrogen as substrate was reduced by 73 and 52%, respectively. Tests of ammonia toxicity on the acetate- and hydrogen-utilizing populations showed a higher sensitivity of the aceticlastic compared to the hydrogenotrophic methanogens; the specific growth rate for the aceticlastic methanogens was halved at ammonia concentrations of 3.5 g N/l, compared to 7 g N/l for the hydrogenotrophic methanogens.
765 citations
TL;DR: Limitations of xylose utilization in S. cerevisiae cells are very likely caused by an insufficient capacity of the non-oxidative pentose phosphate pathway, as indicated by accumulation of sedoheptulose-7-phosphate and the absence of fructose-1,6-bisph phosphate and pyruvate accumulation.
Abstract: We have performed a comparative study of xylose utilization in Saccharomyces cerevisiae transformants expressing two key enzymes in xylose metabolism, xylose reductase (XR) and xylitol dehydrogenase (XDH), and in a prototypic xylose-utilizing yeast, Pichia stipitis. In the absence of respiration (see text), baker's yeast cells convert half of the xylose to xylitol and ethanol, whereas P. stipilis cells display rather a homofermentative conversion of xylose to ethanol. Xylitol production by baker's yeast is interpreted as a result of the dual cofactor dependence of the XR and the generation of NADPH by the pentose phosphate pathway. Further limitations of xylose utilization in S. cerevisiae cells are very likely caused by an insufficient capacity of the non-oxidative pentose phosphate pathway, as indicated by accumulation of sedoheptulose-7-phosphate and the absence of fructose-1,6-bisphosphate and pyruvate accumulation. By contrast, uptake at high substrate concentrations probably does not limit xylose conversion in S. cerevisiae XYL1/XYL2 transformants.
663 citations
TL;DR: A five-stage reactor was developed to simulate the gastro-intestinal microbial ecosystem of humans and was found to be reprensentative for in-vivo gastro- gastrointestinal microbial communities as described in the literature.
Abstract: A five-stage reactor was developed to simulate the gastro-intestinal microbial ecosystem of humans The small intestine was simulated by a two-step “fill and draw” system, the large intestine by a three-step reactor A representative supply medium was developed to support a microbial community resembling that of the human gastro-intestinal tract The entire system was validated by monitoring fermentation fluxes and products, ie indicator bacterial groups, volatile fatty acids, enzymatic activities and headspace gases The simulator was operated with varying concentrations and combinations of arabinogalactan, xylan, pectin, dextrins and starch The resulting patterns of microbial diversity and activity were analyzed and compared with data for in-vivo gastro-intestinal microbial communities as described in the literature and found to be reprensentative
554 citations
TL;DR: Results indicate that regulatory phenomena, such as induction-repression or activation-inhibition, related to pectinase synthesis by A. niger CH4 are different in the two types of fermentation.
Abstract: A study was made to compare the production of pectinase by Aspergillus niger CH4 in solid-state (SSF) and submerged (SmF) fermentations. Production of endo- (endo-p) and exo-pectinase (exo-p) by SSF was not reduced when glucose, sucrose or galacturonic acid (up to 10%) were added to a culture medium containing pectin. Moreover, both activities increased when concentrations of the carbon sources were also increased. In SmF, these activities were strongly decreased when glucose or sucrose (3%) was added to culture medium containing pectin. The addition of galacturonic acid affected endo-p activity production to a lesser extend than exo-p. Final endo-p and exo-p activities in SSF were three and 11 times higher, respectively, than those obtained in SmF. The overall productivities of SSF were 18.8 and 4.9 times higher for endo-p and exo-p, respectively, than those in SmF. These results indicate that regulatory phenomena, such as induction-repression or activation-inhibition, related to pectinase synthesis by A. niger CH4 are different in the two types of fermentation.
218 citations
TL;DR: The superiority of Rhodococcus rhodochrous J1 nitrile hydratase was demonstrated in comparison with other acrylamide-producing bacteria and the high stability, high catalytic efficiency and other outstanding features of the J1 enzyme are analysed and discussed.
Abstract: As the third-generation biocatalyst for industrial production of acrylamide, the superiority of Rhodococcus rhodochrous J1 nitrile hydratase was demonstrated in comparison with other acrylamide-producing bacteria. R. rhodochrous J1 enzyme is much more heat stable and more tolerant to a high concentration of acrylonitrile than Pseudomonas chlororaphis B23 and Brevibacterium R312 enzymes. The J1 enzyme is peculiar in its extremely high tolerance to acrylamide. The hydration reaction of acrylonitrile catalysed by J1 cells proceeded even in the presence of 50% (w/v) acrylamide. The tolerance of J1 enzyme to various organic solvents such as n-propanol and isopropanol was prominent. Using R. rhodochrous J1 resting cells, the accumulation reaction was carried out by feeding acrylonitrile to maintain a level of 6%. After 10 h incubation, the accumulation of acrylamide was approximately 65.6% (w/v) at 10°C, 56.7% (w/v) at 15°C, and 56.0 (w/v) at 20°C. The high stability, high catalytic efficiency and other outstanding features of the J1 enzyme are analysed and discussed.
176 citations
TL;DR: The effect of pH and nitrogen source on pigment production by Monascus purpureus 192F using glucose as the carbon and energy source, was studied in pH-controlled, batch fermentor cultures using HPLC analysis to determine individual pigment concentrations.
Abstract: The effect of pH and nitrogen source on pigment production by Monascus purpureus 192F using glucose as the carbon and energy source, was studied in pH-controlled, batch fermentor cultures using HPLC analysis to determine individual pigment concentrations. A maximum of four pigments were detected in fungal extracts. These were the yellow pigments monascin and ankaflavin, the orange rubropunctatin and the red pigment monascorubramine. Monascorubramine was present as the major product in all instances. Fungal growth and ankaflavin synthesis were favoured at low pH (pH 4.0), whereas production of the other pigments was relatively independent of pH. The nature of the nitrogen source affected fungal growth and pigment production, independent of pH. Ammonium and peptone as nitrogen sources gave superior growth and pigment concentrations compared to nitrate. Ankaflavin was not detected in nitrate cultures. The highest red pigment production was obtained using a glucose-peptone medium at pH 6.5, due to the secretion of red pigments into the medium under these conditions.
163 citations
TL;DR: Oxalate was found to accumulate in liquid culture media from the growth of the white-rot basidiomycetes Coriolus versicolor, Heterobasidion annosum, Pleurotus florida and Phanerochaete chrysosporium, and millimolar concentrations of oxalate were detected in culture media during the stationary phase.
Abstract: Oxalate was found to accumulate in liquid culture media from the growth of the white-rot basidiomycetes Coriolus versicolor, Heterobasidion annosum, Pleurotus florida and Phanerochaete chrysosporium. Whereas little oxalate accumulated during active growth, millimolar concentrations of oxalate were detected in culture media during the stationary phase. The basidiomycete Agaricus bisporus, the cultivated mushroom, also accumulated oxalate in its culture medium in the stationary phase. In comparison, the brown-rot fungi Amyloporia xantha, Coniophora marmorata, C. puteana and Poria vaporaria accumulated oxalate in the primary metabolic phase and throughout growth up to 35 days. Oxalate accumulation (0.04–10.0 mm) in white-rot cultures did not lower the pH of the medium during growth, whereas in brown-rot cultures oxalate (2.0–20.0 mm) reduced the media pH during growth. Cultures of Agaricus bisporus, C. puteana and Coriolus versicolor grown on solid media containing high levels of calcium (50 or 100 mm calcium chloride) produced calcium oxalate crystals to varying extents on the surface of the hyphae.
162 citations
TL;DR: In this paper, the effect of sulfate on the anaerobic breakdown of mixtures of acetate, propionate and butyrate at three different sulfate to fatty acid ratios was studied in up-flow sludge blanket reactors.
Abstract: The effect of sulfate on the anaerobic breakdown of mixtures of acetate, propionate and butyrate at three different sulfate to fatty acid ratios was studied in upflow anaerobic sludge blanket reactors. Sludge characteristics were followed with time by means of sludge activity tests and by enumeration of the different physiological bacterial groups. At each sulfate concentration acetate was completely converted into methane and CO2, and acetotrophic sulfate-reducing bacteria were not detected. Hydrogenotrophic methanogenic bacteria and hydrogenotrophic sulfate-reducing bacteria were present in high numbers in the sludge of all reactors. However, a complete conversion of H2 by sulfate reducers was found in the reactor operated with excess sulfate. At higher sulfate concentrations, oxidation of propionate by sulfate-reducing bacteria became more important. Only under sulfate-limiting conditions did syntrophic propionate oxidizers out-compete propionate-degrading sulfate reducers. Remarkably, syntrophic butyrate oxidizers were well able to compete with sulfate reducers for the available butyrate, even with an excess of sulfate.
157 citations
TL;DR: The conversion of glycerol to 1,3-propanediol by Citrobacter freundii DSM 30040 was optimized in single- and two-stage continuous cultures and Glycerol dehydratase seemed to be the rate-limiting step in 1, 3-pro panediol formation.
Abstract: The conversion of glycerol to 1,3-propanediol by Citrobacter freundii DSM 30040 was optimized in single- and two-stage continuous cultures. The productivity of 1,3-propanediol formation was highest under glycerol limitation and increased with the dilution rate (D) to a maximum of 3.7 g·l−1·h−1. Glycerol dehydratase seemed to be the rate-limiting step in 1,3-propanediol formation. Conditions for the two-stage fermentation process were as follows: first stage, glycerol limitation (250mM), pH 7.2, D=0.1 h−, 31° C; second stage, additional glycerol, pH 6.6, D=0.05 h−1, 28° C. Under these conditions 875mM glycerol were consumed, the final 1,3-propanediol concentration was 545mM, and the overall productivity 1.38 g·1−1·h−1.
155 citations
TL;DR: Three different phenol oxidases produced by the basidiomycete fungus Pleurotus ostreatus have been isolated and their main structural, enzymatic and physico-chemical properties characterized and can be used for applying bioarectors to problems of environmental concern such as waste-water treatment.
Abstract: Three different phenol oxidases produced by the basidiomycete fungus Pleurotus ostreatus have been isolated and their main structural, enzymatic and physico-chemical properties characterized. Studies have focused on the most abundantly secreted of these proteins, a copper-enzyme specific towards ortho-diphenol substrates. This protein was purified to homogeneity and part of its primary structure determined by direct protein sequencing. The influence of pH, temperature and presence of water-soluble or water-insoluble organic solvents on the activity and stability of the enzyme were also investigated. These data can be used for applying bioreactors to problems of environmental concern such as waste-water treatment.
144 citations
TL;DR: The structural damage of pressure-treated cells was accompanied by the leakage of internal substances and amounts of individual metal ion release varied with the magnitude of hydrostatic pressures over 300 MPa, which suggests that the ions can be removed from the yeast cells separately by hydrostatic pressure treatment.
Abstract: The structural damage to and leakage of internal substances from Saccharomyces cerevisiae 0–39 cells induced by hydrostatic pressure were investigated. By scanning electron microscopy, yeast cells treated at room temperature with pressuresbellw 400 MPa for 10 min showed a slight alteration in outer shape. Transmission electron microscopy, however, showed that the inner structure of the cell began to be affected, especially the nuclear membrane, when treated with hydrostatic pressure around 100 MPa at room temperature for 10 min; at more than 400–600 MPa, further alterations appeared in the mitochondria and cytoplasm. Furthermore, when high pressure treatment was carried out at — 20° C, the inner structure of the cells was severely damaged even at 200 MPa, and almost all of the nuclear membrane disappeared, although the fluorescent nucleus in the cytoplasm was visible by 4,6-diamidino-2-phenylindole (DAPI) staining. The structural damage of pressure-treated cells was accompanied by the leakage of internal substances. The efflux of UV-absorbing substances including amino acid pools, peptides, and metal ions increased with increase in pressure up to 600 MPa. In particular, amounts of individual metal ion release varied with the magnitude of hydrostatic pressures over 300 MPa, which suggests that the ions can be removed from the yeast cells separately by hydrostatic pressure treatment.
TL;DR: The degradation of xylans from rice bran, oat spelts, wheat flour, larchwood, and birchwood xylan with two types of endo-(1,4)-β-xylanase (I and III) was investigated in this article.
Abstract: The degradation of [({4-O-methyl-}glucurono)arabino]xylans from rice bran, oat spelts, wheat flour, larchwood, and birchwood with two types of endo-(1,4)-β-xylanase (I and III), (1,4)-β-xylosidase, (1,4)-β-d-arabinoxylan arabinofuranohydrolase (AXH), and an acetyl xylan esterase (AE), single and in combinations was investigated. The endo-(1,4)-β-xylanases showed the highest initial release of reducing end-groups on oat spelt xylan, followed successively by larchwood xylan, wheat flour xylan, birchwood xylan and rice bran xylan. The extent of degradation governed by degree and pattern of substitution was highest for oat spelts, followed by wheat flour and larchwood xylan. The extent of hydrolysis for the commercially available birchwood xylan was low, due to the partly insoluble fraction. Rice bran arabinoxylan could only partly be degraded by the combined action of endo-(1,4)-β-xylanase and AXH. The combination of endo-(1,4)-β-xylanase I or III, with (1,4)-β-xylosidase and AXH, or AE, resulted in the highest degree of hydrolysis after 24 h of incubation.
TL;DR: Wild type cells of Rhodobacter sphaeroides and Rhodospirillum rubrum strains Ha and S1 as well as mutant cells defective in the synthesis of poly-(3-Hydroxybutyric acid) (PHB), were used to study the competition between PHB accumulation and photoproduction of hydrogen for reducing equivalents.
Abstract: Wild type cells of Rhodobacter sphaeroides and Rhodospirillum rubrum strains Ha and S1 as well as mutant cells defective in the synthesis of poly-(3-Hydroxybutyric acid) (PHB), were used to study the competition between PHB accumulation and photoproduction of hydrogen for reducing equivalents. Mutants were isolated after transposon (Tn5) or N-methyl-N′-nitro-N-nitrosoguanidine mutagenesis. The PHB-defective mutants of R. sphaeroides lacked PHB synthase activity. In two mutants Tn5 was inserted in the PHB synthase gene. No mutants occured that lacked the activity of β-ketothiolase or acetoacetyl-coenzyme A reductase. Pronounced competitive effects occured only with acetate as the organic substrate. With other organic acids or sugars, which are less readily converted to PHB than acetate, competitive effects were not significant or absent.
TL;DR: Polyacrylamide-gel-immobilized cells of Pseudomonas strain EPS 5028 were effective in the removal of uranium (U) from synthetic effluents and U binding could be interpreted in terms of the Freundlich adsorption isotherm indicating single-layer Adsorption.
Abstract: Polyacrylamide-gel-immobilized cells of Pseudomonas strain EPS 5028 were effective in the removal of uranium (U) from synthetic effluents. Metal accumulation was performed in an open system in columns filled with immobilized cells that were challenged with continuous flows containing U. Possible variables of the system were studied. Uranium uptake by the immobilized cells of this microorganism was affected by pH but not by temperature or flow rate. In addition, U binding could be interpreted in terms of the Freundlich adsorption isotherm indicating single-layer adsorption. The feasibility of reusing the immobilized cells was suggested after the recovery of U with a solution of 0.1 m sodium carbonate.
TL;DR: In this article, the technical possibilities of the microbial production of acetone, butanol and ethanol (ABE) from potato waste using in-line solvent recovery, are evaluated using a polypropylene perstraction system and a oleyl alcohol/decane mixture as the extractant.
Abstract: The technical possibilities of the microbial production of acetone, butanol and ethanol (ABE) from potato waste using in-line solvent recovery, are evaluated. Clostridium acetobutylicum DSM 1731 produces up to 20 g·l−1 of solvents when grown on a medium containing 14% (w/v) potato powder. Using a polypropylene perstraction system and a oleyl alcohol/decane mixture as the extractant, the product yield (based on total solvents and potato dry weight) increased from 0.13 g·g−1 to 0.23 g·g−1. The recovery system worked well for 50 h, after which membrane fouling frustrated proper operation. In the second system a microfiltration step was incorporated whereas the solvents were extracted through a hydrophilic membrane using fatty acid methyl esters from sunflower oil as an extractant. This process configuration resulted in a comparable increase of ABE production.
TL;DR: Nisin, a lanthionine-containing peptide antibiotic with bacteriocin properties, clearly behaved as a primary metabolite, since its formation was linked with active growth and was not suppressed by phosphate concentrations up to 5%.
Abstract: The influence of different phosphorus and nitrogen sources on Lactococcus lactis subsp. lactis NIZO 22186 growth and nisin production was studied in batch fermentations using a complex medium. KH2PO4 was found to be the best phosphorus source for nisin production. Increasing initial phosphate concentrations from 0 to 5% KH2PO4 exerted a double effect, creating favourable pH conditions and particularly stimulating the nisin production levels, which were highest at 5% KH2PO4. Up to now, no such high initial phosphate concentrations have been reported for the production of other antibiotics or bacteriocins. Nisin, a lanthionine-containing peptide antibiotic with bacteriocin properties, clearly behaved as a primary metabolite, since its formation was linked with active growth and was not suppressed by phosphate concentrations up to 5%. A complex medium supplemented with cotton seed meal as nitrogen source also gave very high nisin yields.
TL;DR: From genomic libraries of purple sulphur bacteria, fragments were cloned that encoded for proteins involved in the synthesis of poly(3-hydroxyalkanoic acids), PHA, and the most striking result was that a fragment harbouring the PHA-synthase gene of T. pfennigii conferred the ability to synthesize a niosynthetic polyester with this composition.
Abstract: From genomic libraries of purple sulphur bacteria, fragments were cloned that encoded for proteins involved in the synthesis of poly(3-hydroxyalkanoic acids), PHA. A 12.5- and a 15.0- plus a 15.6-kbp EcoRI-restriction fragment of Ectothiordospira shaposhnikovii of Thiocapsa pfennigii, respectively, which hybridized with a fragment encoding the Alcaligenenes eutrophus PHA-biosynthesis operon, were identified in δL47 libraries, whereas an 18.0-kbp EcoRI fragment of Lamprocytis roseopersicina, which phenotypically complemented a PHA-neagative mutant of A. eutrophus, was identified in a pVK100 cosmid library. Hybridization studies and enzymatic analysis of crued extracts derived from transconjugants of Escherichia coli and A. eutrophus harbouring these fragments revealed the presence of the genes for NADH-dependent acetoacetyl-CoA reductase and/or PHA synthase. The PHA-biosynthesis genes of T. pfennigii and L. roseopersicina as wells as of Chromatium vinosum, Thiocystis violacea, Rhodospirillum rubrum and Rodobacter sphaeroides were then analysed for thire ability to confer synthesis of PHA other poly(3-hydroxybutric acid) to PHA-negative mutants of PHA-accumulating bacteria. The most striking result was that a fragment harbouring the PHA-synthase gene of T. pfennigii conferred the ability to synthesize a polymer consisting of almost equimolar amounts of 3-hydroxybutyrate (48.5 mol%) and 3-hydroxyhexanote (47.3%) plus a small amount of 3-hydroxyoctanoate (4.2 mol %) to a PHA-negative mutant of Pseudomonas putida. A niosynthetic polyester with this composition has not been described before.
TL;DR: Kuwaiti desert samples contaminated with crude oil contained Bacillus stearothermophilus strains capable of growth on crude oil as a sole source of carbon and energy, obligately at high temperature.
Abstract: Kuwaiti desert samples contaminated with crude oil contained Bacillus stearothermophilus strains capable of growth on crude oil as a sole source of carbon and energy, obligately at high temperature. No thermophilic oil utilizers were present in water samples collected from the Arabian Gulf. Most of the desert strains had an optimum temperature of 60°C and grew best on pentadecane (C15), hexadecane (C16) and heptadecane (C17). n-Alkanes with shorter and longer chains, n-alkenes, and aromatic hydrocarbons were less readily utilized.
TL;DR: Tween 80 was a major factor in increasing mesenteroxin 5 production and specific production and most of the Listeria strains tested including L. monocytogenes were highly sensitive to the bacteriocin in the pH range 5.5 to 6.0.
Abstract: The effects of various parameters on production and activity of mesenterocin 5, a bacteriocin produced by Leuconostoc mesenteroides subsp mesenteroides UL5, were investigated Titres of bacteriocin and minimum inhibitory concentration values were determined by a critical dilution micromethod, using a sensitive strain of Listeria ivanovii as an indicator Production of the antimicrobial compound was optimal at 37 and 40°C after 9 h of incubation, and was maximized in an aerobic fermentor maintained at pH 50 Tween 80 was a major factor in increasing mesenteroxin 5 production and specific production Large quantities of bacteriocin could be obtained in whey and in whey permeate supplemented with yeast extract in the presence of the surfactant (01%) Most of the Listeria strains tested including L monocytogenes were highly sensitive to the bacteriocin in the pH range 55 to 60 and at a temperature of 20 to 25°C
TL;DR: Although xylanase was produced efficiently on cellulose as well as on xylan as the carbon source, significant production of cellulose was observed only on the cellulose-based medium and best production was at lower pH (4.0 minimum).
Abstract: Trichoderma reesei VTT-D-86271 (Rut C-30) was cultivatedon media based on cellulose and xylan as the main carbon source in fermentors with different pH minimum controls. Production of xylanase was favoured by a rather high pH minimum control between 6.0 and 7.0 on both cellulose- and xylan-based media. Although xylanase was produced efficiently on cellulose as well as on xylan as the carbon source, significant production of cellulose was observed only on the cellulose-based medium and best production was at lower pH (4.0 minimum). Production of xylanase at pH 7.0 was shown to be dependent on the nature of the xylan in the cultivation medium but was independent of other organic components. Best production of xylanase was observed on insoluble, unsubstituted beech xylan at pH 7.0. Similar results were obtained in laboratory and pilot (200-l) fermentors. Downstream processing of the xylanase-rich, low-cellulose culture filtrate presented no technical problems despite apparent autolysis of the fungus at the high pH. Enzyme produced in the 200-l pilot fermentor was shown to be suitable for use in enzyme-aided bleaching of kraft pulp. Due to the high xylanase/cellulase ratio of enzyme activities in the culture filtrate, pretreatment for removal of cellulase activity prior to pulp bleaching was unnecessary.
TL;DR: In this article, a study was conducted to determine whether a non-ionic surfactant (Novel II 1412-56) added to the surface of Lima silt loam would enhance the biodegradation of phenanthrene and biphenyl present within the soil.
Abstract: A study was conducted to determine whether a non-ionic surfactant (Novel II 1412-56) added to the surface of Lima silt loam would enhance the biodegradation of phenanthrene and biphenyl present within the soil. Water containing the surfactant at concentrations of 10 and 100 μg/ml was pumped through the soil. At 10 μg/ml, Novel II 1412-56 markedly enhanced the rate and extent of phenathrene mineralization and the extent but not the initial rate of biphenyl mineralization. The stimulation was less if the water added to the soil surface contained 100 μg surfactant/ml. Addition of the surfactant at the two concentrations did not result in leaching of either phenanthrene or biphenyl, but products of the degradation were found in the soil leachate with or without the surfactant. We suggest that surfactants at low concentrations may be useful for in-situ bioremediation of sites contaminated with hydrophobic pollutants without causing movement of the parent compounds to ground-waters.
TL;DR: Treating kraft pulps with the crude xylanase from Streptomyces roseiscleroticus followed by alkali extraction reduces the kappa number in a linear manner with enzyme doses up to about 3 IU/gm of oven-dry pulp.
Abstract: Treating kraft pulps with the crude xylanase from Streptomyces roseiscleroticus followed by alkali extraction reduces the kappa number in a linear manner with enzyme doses up to about 3 IU/gm of oven-dry pulp. The enzyme complex consists of four isoenzymes designated Xyl1, Xyl2, Xyl3 and Xyl4. Each can release chromophores when used alone and each can facilitate alkali extraction to reduce the kappa number, but their relative abilities are different. Of the four isozymes, Xyl4 releases the least color and 237-nm-absorbing material whereas Xyl3 releases the most. Xyl4 best enhances the ability of alkali to reduce the kappa number. The UV absorption spectrum of the material released by alkali extraction differs significantly from the spectral characteristics of that released during enzyme treatment. The alkali-solubilized material has a maximum absorptivity at 265 nm and relatively little absorptivity at 237 nm. The material released during enzyme treatment absorbs strongly at 205 and 237 nm. UV/VIS spectroscopy of the enzyme- or alkali-released material does not show a characteristics lignin peak at 280 nm, nor does it reveal any notable peaks in the visible region. Analysis of the material released by enzyme treatment revealed more than 40 product peaks after fractionation by reversed-phase HPLC. We observed many products with strong UV absorption. These were relatively hydrophilic. Fewer products absorbed in the visible region. These were more hydrophobic. All four isoenzymes exhibit endo-action patterns; none forms xylose from oat-spelt xylan. The action patterns fell into two groups: endo-1 enzymes (Xyl1 and Xyl3) formed xylotriose (X3) and other lower oligosaccharides as the predominant products; endo-2 enzymes (Xyl2 and Xyl4) formed roughly equimolar amounts of X3, xylotetraose (X4), and xylopentaose (X5), and tended to leave larger amounts of undigested higher oligosaccharides.
TL;DR: The composition of the biosynthetic poly(3HV) was confirmed by various nuclear magnetic resonance spectroscopic methods and differential scanning calorimetry analysis of four samples that were isolated from different batches of cells revealed glass transition temperatures between −10 and −12°C and melting points between 107 and 112°C.
Abstract: Chromobacterium violaceum DSM 30191 accumulated a homopolyester of 3-hydroxyvaleric acid (3HV) up to 65% of the cellular dry matter during cultivation in fed-batch cultures with valeric acid as sole carbon source and during cell starvation of the nitrogen source. From fructose, gluconate, propionate or hexanoate a homopolyester of 3-hydroxybutyrate (3HB) was accumulated. Poly(3HV) homopolyster was also accumulated by two different strains of C. violaceum, whereas two other strains of C. violaceum and three strains of Janthinobacterium lividum accumulated poly(3HB-co-3HV) copolyesters from valerate. The composition of the biosynthetic poly(3HV) was confirmed by various nuclear magnetic resonance spectroscopic methods. Differential scanning calorimetry analysis of four poly(3HV) samples that were isolated from different batches of cells revealed glass transition temperatures between −10 and −12°C and melting points between 107 and 112°C. Viscosity measurements gave intrinsic viscosities between 62.5 and 124.8 × 10−2 dl/g for these samples, indicating approximate relative molecular masses between 60 000 and 145 000 of the biosynthetic poly(3HV).
TL;DR: The laboratory results of xylanase production have been successfully scaled up to VABIO (Voest-Alpine Biomass Technology Center) scale using a 15-m3 fermentor and some properties of the enzyme in crude culture filtrate produced on corn cobs are presented.
Abstract: Thermomyces lanuginosus, isolated from self-heated jute stacks in Bangladesh, was able to produce a very high level of cellulase-free xylanase in shake cultures using inexpensive lignocellulosic biomass. Of the nine lignocellulosic substrates tested, corn cobs were found to be the best inducer of xylanase activity. The laboratory results of xylanase production have been successfully scaled up to VABIO (Voest-Alpine Biomass Technology Center) scale using a 15-m3 fermentor for industrial production and application of xylanase. In addition, some properties of the enzyme in crude culture filtrate produced on corn cobs are presented. The enzyme exhibited very satisfactory storage stability at 4–30°C either as crude culture filtrate or as spray- or freeze-dried powder. The crude enzyme was active over a broad range of pH and had activity optima at pH 6.5 and 70–75°C. The enzyme was almost thermostable (91–92%) at pH 6.5 and 9.0 after 41 h preincubation at 55°C and lost only 20–33% activity after 188 h. In contrast, it was much less thermostable at pH 5.0 and 11.0. Xylanases produced on different lignocellulosic substrates exhibited differences in thermostability at 55°C and pH 6.5.
TL;DR: The results indicated that possible O2 limitation may be alleviated without compromising the maximum cell yield by lowering the incubation temperature from 27° C to 25° C.
Abstract: The effect of temperature and O2 saturation on the production of recombinant proteins β-galactosidase and human glucocerebrosidase by Spodoptera frugiperda cells (Sf9) infected with recombinant Autographa californica nuclear polyhedrosis virus was investigated. The rates of cell growth, glucose consumption, O2 consumption and product expression were measured at temperatures between 22° C and 35° C. The results indicated that possible O2 limitation may be alleviated without compromising the maximum cell yield by lowering the incubation temperature from 27° C to 25° C. The expression level of the recombinant proteins at 27° C was similar to that obtained at 22° C and 25° C; lower protein yields were obtained at 30° C. An increase in temperature from 22° C to 27° C led to earlier production of the proteins and to an increase in the proportion of the product released outside the cells.
TL;DR: A sulfate-reducing bacterium, Desulfovibrio sp. (B strain) isolated from an anaerobic reactor treating furfural-containing waste-water was studied for its ability to metabolize trinitrotoluene (TNT).
Abstract: A sulfate-reducing bacterium, Desulfovibrio sp. (B strain) isolated from an anaerobic reactor treating furfural-containing waste-water was studied for its ability to metabolize trinitrotoluene (TNT). The result showed that this isolate could transform 100 ppm TNT within 7 to 10 days of incubation at 37°C, when grown with 30 mm pyruvate as the primary carbon source and 20 mm sulfate as electron acceptor. Under these conditions, the main intermediate produced was 2,4-diamino-6-nitrotoluene. Under culture conditions where TNT served as the sole source of nitrogen for growth with pyruvate as electron donor and sulfate as electron acceptor, TNT was first converted to 2,4-diamino-6-nitrotoluene within 10 days of incubation. This intermediate was further converted to toluene by a reductive deamination process via triaminotoluene. Apart from pyruvate, various other carbon sources such as ethanol, lactate, formate and H2 + CO2 were also studied as potential electron donors for TNT metabolism. The rate of TNT biotransformation by Desulfovibrio sp. (B strain) was compared with other sulfate-reducing bacteria and the results were evaluated. This new strain may be useful in decontaminating TNT-contaminated soil and water under anaerobic conditions in conjunction with toluene-degrading denitrifiers (Pseudomonas spp.) or toluene-degrading sulfate reducers in a mixed culture system.
TL;DR: Using a model based on dissolution Kinetics for substrate availability and Monod kinetics for bacterial growth it was possible to simulate bacterial growth on naphthalene and this model is widely applicable for growth of micro-organisms on poorly water-soluble substrates and can easily be adapted to a more complex system.
Abstract: Bacterial growth on crystalline naphthalene was measured and found to be related to the dissolution rate of the substrate. No evidence for enhancement of substrate availability due to bacterial influence could be detected. Using a model based on dissolution kinetics for substrate availability and Monod kinetics for bacterial growth it was possible to simulate bacterial growth on naphthalene. This model is widely applicable for growth of micro-organisms on poorly water-soluble substrates and can easily be adapted to a more complex system such as microbial growth on substrates adsorbed to matrices.
TL;DR: This report describes the use of a new selenate-respiring bacterium, Thauera selenatis, for the bioremediation of selenium (Se) in drainage water from the Westlands Water District, San Joaquin Valley.
Abstract: This report describes the use of a new selenate-respiring bacterium, Thauera selenatis, for the bioremediation of selenium (Se, as selenate) in drainage water from the Westlands Water District, San Joaquin Valley. The organism respires selenate anaerobically using acetate as the preferred electron donor. The reduction of selenate is not inhibited by nitrate; both electron acceptors are reduced concomitantly. T. selenatis was inoculated into, and was maintained in, a biological reactor system for anaerobic treatment of selenate-nitrate containing drainage water; a population of denitrifying bacteria was also present. When the pH of inflowing water was 6.9, and 2 mm acetate plus 0.56 mm ammonium chloride were fed into the reactor, selenate/selenite levels were reduced from 350–450 μg Se/l to 5.39±3.6 μg Se/l. The final product of selenate reduction was elemental Se. Analysis of reactor contents revealed that T. selenatis was the only selenate-respiring organism present in the system. Nitrate in the drainage water was also reduced in the reactor system by 98%. The lab-scale biological reactor system consisted of recycled sludge-blanket (1 l; 400 g sand) and fluidized-bed (1 l; 300 g sand) reactors. At a system flow rate of 6.5 ml/min, the retention time was 140 min.
TL;DR: A model relating steady-state dilution rates to internal average light intensity has been proposed, the parameter values of which obtained by non-linear regression were maximum specific growth rate (μmax) and the affinity of cells to light (Ik).
Abstract: Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid productivities from chemostat cultures of an isolate of Isochrysis galbana have been studied. The productivities reached in the interval of dilution rates between 0.0295 h−1 and 0.0355 h−1 were 1.5mg·1−1·h−1 for lipids, 300 μg·1−1·h−1 for EPA and 130μg1·1−1·h−1 for DHA. Furthermore, light attenuation by mutual shading, and agitation speed influences on growth and fatty acid composition were analysed. A model relating steady-state dilution rates to internal average light intensity has been proposed, the parameter values of which obtained by non-linear regression were: maximum specific growth rate (μmax)=0.0426 h−1; the affinity of cells to light (Ik) = 10.92 W·m−2; the exponent (n) = 5.13; regression coefficient (r2)=0.9999.
TL;DR: Adsorption measurements of several actinide [thorium (Th), uranium (U)] and lanthanide [lanthanum (La), europium (Eu), ytterbium (Yb)] cations by Mycobacterium smegmatis showed that sorption kinetics followed a three-phase pattern.
Abstract: Adsorption measurements of several actinide [thorium (Th), uranium (U)] and lanthanide [lanthanum (La), europium (Eu), ytterbium (Yb)] cations by Mycobacterium smegmatis showed that sorption kinetics followed a three-phase pattern. For 5% (w/w) bacterial suspensions at pH 1, maximum cation biosorption per gram dry biomass corresponded to 170 μmol Th4+ and 187 μmol UOinf2sup2+. Adsorption of all cations studied obeyed the Brunauer-Emmett-Teller isotherm, which assumes multilayer binding at constant energy. Plots for the Scatchard model showed the existence of at least two types of cation complexation site, with strong and weak affinity and negative cooperation. Th4+ was preferentially adsorbed with respect to the other cations, although all species appeared to compete for the same sites independently of bacterial viability. Adsorption of these cations was accompanied by partial release of magnesium from the cell wall, indicating that exchange reactions occurred at magnesium (Mg)-bonding sites.