Lipase-catalyzed acylation of naringin with palmitic acid in highly concentrated homogeneous solutions

Acylation reactions of naringin with palmitic acid were performed by a lipase after formation of highly concentrated homogeneous solutions. Their initial naringin concentration was 840–950 mM, which is 20–60 times greater than that in organic solvent media. The overall productivity of highly concentrated solutions was more than 15 times greater than those of organic phase media. The addition of DMSO (20–40%, w/w) to substrate mixtures lowered the melting temperature of a naringin–palmitic acid mixture (1:1 molar ratio) to about 40 °C. Reactions at 80 °C apparently followed Michaelis–Menten kinetics despite extremely high substrate concentrations. As the temperature increased from 60 °C to 80 °C, the apparent viscosity of the highly concentrated solution decreased remarkably from 4.31 Pa s to 0.063 Pa s. An activation energy of 7.65 kcal/mol obtained in a range of 60–75 °C suggests a diffusion-control. On the other hand, an activation energy of 17.09 kcal/mol in a range of 75–90 °C indicates a reaction-control. The highest product conversion yield of 33% (mol/mol) was obtained in a 10 h reaction at 80 °C. Addition of activated molecular sieves to the highly concentrated solution increased the product conversion yield by 7% (mol/mol), suggesting that the original equilibrium was disrupted by removing water and then a new equilibrium was reached.     

Synthesis and properties of pullulan acetate. Thermal properties, biodegradability, and a semi-clear gel formation in organic solvents

Pullulan acetate (AcPL) with various degree of substitution (DS: 1.0–3.0) was synthesized by the reaction of pullulan with acetyl chloride in the presence of pyridine. The product was characterized by gel permeation chromatography (GPC), infra-red (IR) and ¹H NMR spectroscopy. The weight average molecular weights of the products did not decrease less than 190,000 (GPC) in the acetylation reaction. Thermogravimetric analysis (TGA) revealed that AcPL has a higher decomposition temperature (306–363 °C) than unmodified pullulan (295 °C). Differential scanning calorimetry analysis (DSC) revealed that all the AcPLs exhibit a clear T_g, which decreased with increasing DS value in the range of DS 1.0–2.4. The AcPL with DS 2.4 showed the lowest T_g (153 °C), and the AcPL with DS 3.0 had a slightly higher T_g (163 °C). Tensile modulus of AcPL films was comparable to that of a popular cellulose acetate film. The biodegration rate of AcPL decreased with increasing degree of acetylation. The AcPL with DS 3.0 was found to form a semi-clear gel in organic solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and 1,4-dioxane.     

Preparation of sugarcane bagasse hemicellulosic succinates using NBS as a catalyst

The chemical modification of native sugarcane bagasse hemicelluloses with succinic anhydride using N-bromosuccinimide as a catalyst and N,N-dimethylacetamide/lithium chloride system as solvent was studied. The parameters optimised included succinic anhydride concentration by the molar ratio of succinic anhydride/anhydroxylose units in native hemicelluloses from 1:1 to 9:1, reaction time 0.5–6 h, NBS concentration 0.5–3.0%, and reaction temperature 25–85 °C required in the process. Results were also compared with other catalysts such as pyridine, DMAP, H₂SO₄, and other two tertiary amine catalysts, N-methyl pyrrolidine, and N-methyl pyrrolidinone. The degree of substitution of succinylated hemicelluloses ranged between 0.19 and 1.39, depending on the experimental conditions. FT-IR and ¹H and ¹³C NMR spectroscopic characterization of the esterified polymers indicated a monoester substitution. The thermal stability of the succinylated hemicelluloses decreased upon chemical modification.     

The effect of partial dehydration on the developmental capacity of mouse embryos stored in the supercooled state

The effect of partial dehydration on the ability of mouse blastocysts to withstand storage at subzero temperatures without freezing was studied. The embryos were equilibrated with a supercooling medium developed at the Centre for Food and Animal Research, containing 3% (Medium A) or 6% (Medium B) methanol and propanediol, and then with the same medium, A or B, containing 0–0.5 mol sucrose. The embryos were placed in 0.25 ml straws, cooled to −5°C or −10°C and stored for up to 3 days. After storage, the embryos were cultured for 48 h in M16 and their ability to develop into expanded blastocysts was used to gauge their survival in supercooled storage.

The maximal beneficial effect of partial dehydration occurred in media supplemented with 0.3–0.5 mol sucrose: the proportions of dehydrated embryos surviving 24 h storage at −5°C and −10°C were 84–85% and 91–100%, respectively, compared with only 58% and 52% of non-dehydrated, supercooled embryos. The corresponding figures for dehydrated embryos after 48 or 72 h storage at −5°C were 86–92% and 38–58% compared with 13% and 4% of non-dehydrated embryos. Similarly, 75–85% and 47–55% of partially dehydrated embryos survived storage for 48 h or 72 h, respectively, at −10°C, compared with 5% and 0% of non-hydrated embryos. Thus, reducing the water content of early mouse blastocysts improved their ability to withstand subzero storage.     

Biosynthesis and properties of an extracellular metalloprotease from the Antarctic marine bacterium Sphingomonas paucimobilis

An extracellular protease from the marine bacterium Sphingomonas paucimobilis, strain 116, isolated from the stomach of Antarctic krill, Euphausia superba Dana, was purified and characterized. The excretion of protease was maximal at temperatures from 5 to 10°C, i.e. below the temperature optimum for the strain growth (15°C). The highly purified enzyme was a metalloprotease [sensivity to ethylenediaminetetraacetic acid (EDTA)] and showed maximal activity against proteins at 20–30°C and pH 6.5–7.0, and towards N-benzoyl-tyrosine ethyl ester (BzTyrOEt) at pH 8.0. At 0°C the enzyme retained as much as 47% of maximal activity in hydrolysis of urea denatured haemoglobin (Hb) (at pH 7.0), and at −5 and −10°C, 37 and 30%, respectively. The metalloprotease was stable up to 30°C for 15 min and up to 20°C for 60 min. These results indicate that the proteinase from S. paucimobilis 116 is a cold-adapted enzyme.     

Factors affecting the production of prednisolone by immobilization of Bacillus pumilus E601 cells in poly(vinyl alcohol) cryogels produced by radiation polymerization

To increase the yield percent of prednisolone from hydrocortisone (cortisol), Bacillus pumilus E601 (a radioresistant microorganism) was incorporated into poly(vinyl alcohol) (PVA) cryogel grafted with hydroxyethyl-methacrylate (HEMA) as a crosslinking agent. The polymer was prepared by a radiation polymerization technique at 20 kGy from Co-60 source. The optimum temperature for the biotransformation of hydrocortisone by free cells, poly(PVA)/HEMA, and poly(PVA)/HEMA /N-isopropylacrylamide (N-IPAAm) was 30 °C. The highest yield % of prednisolone was obtained by immobilization of the cells on poly(PVA/HEMA), the addition of N-IPAAm to poly(PVA/HEMA) protected the immobilized cells from temperatures above 35 °C during the fermentation process. The optimal pH (buffered pH) of the biotransformation of hydrocortisone by immobilized and free cells was 7.0, but the maximum yield of prednisolone (60%) was obtained by immobilized cells in comparison with free cells (42%) also at pH 7.0. The prednisolone yield reached 60–65% with 1,2-propanediol cosolvent containing media and 60–62% in the case of ethanediol cosolvent containing media at 1% (v/v) of both cosolvents. 10 mg/50 ml Tween 80 the medium increased the prednisolone yield by only 1.1-fold compared with the control. The maximum bioconversion efficiency was obtained at a substrate concentration of 20 mg/50 ml medium. Stability studies showed that the immobilized cells can be used for seven times without any significant decrease in activity.     

Uracil-DNA N-glycosylase (UNG) from the marine, psychrophilic bacterium Vibrio salmonicida shows cold adapted features: A comparative analysis to Vibrio cholerae uracil-DNA N-glycosylase

The genes encoding uracil-DNA N-glycosylase (UNG) from the marine, psychrophilic bacterium Vibrio salmonicida and the mesophilic counterpart Vibrio cholerae have been cloned and expressed in Escherichia coli. The purified proteins have been characterized in order to reveal possible cold adapted features of the V. salmonicida UNG (vsUNG) compared to the V. cholerae UNG (vcUNG). Characterization experiments demonstrated that both enzymes possessed the highest activities at pH 7.0–7.5 and at salt concentrations in the range of 25–50 mM NaCl. Temperature optima for activity were determined to approximately 30 °C for vsUNG and 50 °C for vcUNG. Temperature stability of the enzymes was compared at 4 °C and 37 °C, and vsUNG was found to be more temperature labile than vcUNG. Kinetic studies performed at three different temperatures, 15 °C, 22 °C and 37 °C, demonstrated higher catalytic efficiency for vsUNG compared to vcUNG due to lower K_M-values. The increased substrate affinity of vsUNG is probably caused by an increased number of positively charged residues in the DNA-binding site of the enzyme compared to vcUNG. Thus, activity and stability measurements reveal typical cold adapted features of vsUNG.     

Dilute acid pretreatment, enzymatic saccharification and fermentation of wheat straw to ethanol

Wheat straw consists of 48.57 ± 0.30% cellulose and 27.70 ± 0.12% hemicellulose on dry solid (DS) basis and has the potential to serve as a low cost feedstock for production of ethanol. Dilute acid pretreatment at varied temperature and enzymatic saccharification were evaluated for conversion of wheat straw cellulose and hemicellulose to monomeric sugars. The maximum yield of monomeric sugars from wheat straw (7.83%, w/v, DS) by dilute H₂SO₄ (0.75%, v/v) pretreatment and enzymatic saccharification (45 °C, pH 5.0, 72 h) using cellulase, β-glucosidase, xylanase and esterase was 565 ± 10 mg/g. Under this condition, no measurable quantities of furfural and hydroxymethyl furfural were produced. The yield of ethanol (per litre) from acid pretreated enzyme saccharified wheat straw (78.3 g) hydrolyzate by recombinant Escherichia coli strain FBR5 was 19 ± 1 g with a yield of 0.24 g/g DS. Detoxification of the acid and enzyme treated wheat straw hydrolyzate by overliming reduced the fermentation time from 118 to 39 h in the case of separate hydrolysis and fermentation (35 °C, pH 6.5), and increased the ethanol yield from 13 ± 2 to 17 ± 0 g/l and decreased the fermentation time from 136 to 112 h in the case of simultaneous saccharification and fermentation (35 °C, pH 6.0).     

Novel substituted (Z)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-one and (Z)-(+/-)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-ol derivatives as potent thermal sensitizing agents

Use of ionizing radiation is essential for the management of many human cancers, and therapeutic hyperthermia has been identified as a potent radiosensitizer. Radiation therapy combined with adjuvant hyperthermia represents a potential tool to provide outstanding local-regional control for refractory disease. (Z)-(±)-2-(N-Benzylindol-3-ylmethylene)quinuclidin-3-ol (2) and (Z)-(±)-2-(N-benzenesulfonylindol-3-ylmethylene)quinuclidin-3-ol (4) were initially identified as potent thermal sensitizers that could lower the threshold needed for thermal sensitivity to radiation treatment. To define the structural requirements of the molecule that are essential for thermal sensitization, we have synthesized and evaluated a series of (Z)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-one (9), and (Z)-(±)-2-(N-benzylindol-3-ylmethylene)quinuclidin-3-ol (10) analogs that incorporate a variety of substituents in both the indole and N-benzyl moieties. These systematic structure–activity relationship (SAR) studies were designed to further the development and optimization of potential clinically useful thermal sensitizing agents. The most potent analog was compound 10 (R¹ = H, R² = 4-Cl), which potently inhibited (93% inhibition at 50 μM) the growth of HT-29 cells after a 41 °C/2 h exposure.     

Finger temperatures during military field training at 0 to −29 °C

1. Skin and rectal temperatures were recorded continuously in 70 measurements during typical tasks of infantry and artillery training at 0 to −29 °C. The duration of the measurements varied from 55 min to 9.5 h.

2. The distribution of finger skin temperatures was quite similar at ambient temperature ranges 0 to −10 °C and −10 to −20 °C, while at −20 to −30 °C the finger temperatures were clearly lower.

3. At different ambient temperature ranges, 20–69% of finger temperatures were low enough to cause cold thermal sensations.

4. Sensation of cold was experienced at a finger temperature of 11.6±3.7 °C (mean±SD).     

Influence of incubation temperature and time on resistant starch type III formation from autoclaved and acid-hydrolysed cassava starch

Raw cassava starch, having 74.94 and 0.44 g/100 g resistant starch type II and III (RS II and RS III), respectively, was autoclaved at 121 °C in water, 1, 10 or 100 mmol/L lactic acid. The formation of RS III was evaluated in relation to variable incubation temperature (−20 to 100 °C), incubation time (6–48 h) and autoclaving time (15–90 min). Negligible to low quantities of RS III (0.59–2.42 g/100 g) were formed from autoclaved starch suspended in 100 mmol/L lactic acid, whereas intermediate to high quantities (2.68–9.97 g/100 g) were formed from autoclaved starch suspended in water, 1 or 10 mmol/L lactic acid, except for treatments with water or 10 mmol/L lactic acid incubated at 100 °C for 6 h (1.74 g/100 g). Autoclaving times corresponding to maximum RS III contents were 15 and 45 min for water and 10 mmol/L lactic acid, respectively. Whereas, the RS III fractions from cassava starch suspended in water had melt transitions between 158 and 175 °C with low endothermic enthalpies (0.2–1.6 J/g), the thermal transitions of the acid treated samples were indistinct.     

Fractional and structural characterization of hemicelluloses isolated by alkali and alkaline peroxide from barley straw

Eight hemicellulosic fractions were obtained by sequential treatment of dewaxed barley straw with 0.1 M NaOH at 45 °C for 3 h, 0.25, 0.5, 1.0, 1.5, 2.0, and 3.0% H₂O₂ at 45 °C for 3 h at pH 11.5, and 10% KOH–1% Na₂B₄O₇·10H₂O at 28 °C for 15 h under continuous agitation. The yields of the fractions were 8.0, 3.1, 3.3, 3.3, 2.2, 2.0, 2.0, and 9.9%, respectively, of the initial amount of barley straw, corresponding to the dissolution of 21.6, 8.4, 8.9, 8.9, 5.9, 5.4, 5.4, and 26.7% of the original hemicelluloses. Meanwhile, the successive treatment also solubilized 29.1, 15.8, 14.6, 10.8, 4.5, 3.2, 2.7, and 3.7% of the original lignin, respectively. This sequential extraction together resulted in dissolution of 91.1% of the original hemicelluloses and 84.8% of the original lignin. The 0.1 M NaOH-soluble hemicellulosic fraction contained mainly xylose, glucose, and arabinose, 44.2, 15.7, and 15.2%, respectively, while the 10% KOH–1% Na₂B₄O₇·10H₂O-soluble fraction predominated in xylose, 75.0%. The six alkaline peroxide-soluble fractions were composed of 50.3–54.4% xylose, 14.7–16.9% arabinose, 6.8–10.7% glucose, 6.8–8.5% glucuronic acid or 4-O-methyl- -glucuronic acid, 0.4–1.5% mannose, and 0.3–1.2% rhamnose. All the hemicellulosic fractions contained substantial amounts of glucuronoarabinoxylans and noticeable quantities of β-glucans. In comparison, the six hemicellulosic fractions, isolated with alkaline peroxide, had much higher molecular weights (56,890–63,810 g mol⁻¹) than those of the two hemicellulosic preparations (28,000–29,080 g mol⁻¹), isolated with alkali in the absence of hydrogen peroxide. The thermal stability of the hemicelluloses increased with an increment of their molar mass.     

Thermo-alkali-stable catalases from newly isolated Bacillus sp. for the treatment and recycling of textile bleaching effluents

Three thermoalkaliphilic bacteria, which were grown at pH 9.3–10 and 60–65 °C were isolated out of a textile wastewater drain. The unknown micro-organisms were identified as thermoalkaliphilic Bacillus sp. Growth conditions were studied and catalase activities and stabilities compared. Catalases from Bacillus SF showed high stabilities at 60 °C and pH 9 (t_1/2=38 h) and thus this strain was chosen for further investigations, such as electron microscopy, immobilization of catalase and hydrogen peroxide degradation studies. Degradation of hydrogen peroxide with an immobilized catalase from Bacillus SF enabled the reuse of the water for the dyeing process. In contrast, application of the free enzyme for treatment of bleaching effluents, caused interaction between the denaturated protein and the dye, resulting in reduced dye uptake, and a higher color difference of 1.3 ΔE* of dyed fabrics compared to 0.9 ΔE* when using the immobilized enzyme.     

Effect of individual characteristics on a mathematical model of human thermoregulation

A multi-segmental mathematical model of human thermoregulation was tested for its capability to predict individualized physiological responses. We compared the model predictions obtained for an average person with measured individual responses of subjects exposed to mild cold. Secondly, body composition (BC) data, the resting metabolic rate (MR), and the actual measured MR during the test were used as input into the model.

The data was obtained from 20 subjects (age: 19–36 years; BMI: 17–32 kg/m²). BC, MR, rectal and skin temperatures were measured for 1 h at 22 °C, followed by 3 h at 15 °C.

A mean bias of 1.8 °C, with a standard error of 0.7 °C, resulted for the mean skin temperature of an average person at 15 °C. When subjective BC and measured MR were incorporated the bias was −0.2±0.9 °C. For the hand-back skin temperature the bias ± standard error fell from 5.3±2.8 °C for an average person to 2.0±2.5 °C, when using individualized characteristics. Trunk skin temperatures were not significantly affected by the adjustments.

In conclusion, this study shows that on a group level predictions of skin temperatures can be improved when adopting individualized body characteristics and measured MR, but the predictions on an individual level were not improved.     

Bioethanol production from barley hull using SAA (soaking in aqueous ammonia) pretreatment

Barley hull, a lignocellulosic biomass, was pretreated using aqueous ammonia, to be converted into ethanol. Barley hull was soaked in 15 and 30 wt.% aqueous ammonia at 30, 60, and 75 °C for between 12 h and 11 weeks. This pretreatment method has been known as “soaking in aqueous ammonia” (SAA). Among the tested conditions, the best pretreatment conditions observed were 75 °C, 48 h, 15 wt.% aqueous ammonia and 1:12 of solid:liquid ratio resulting in saccharification yields of 83% for glucan and 63% for xylan with 15 FPU/g-glucan enzyme loading. Pretreatment using 15 wt.% ammonia for 24–72 h at 75 °C removed 50–66% of the original lignin from the solids while it retained 65–76% of the xylan without any glucan loss.

Addition of xylanase along with cellulase resulted in synergetic effect on ethanol production in SSCF (simultaneous saccharification and co-fermentation) using SAA-treated barley hull and recombinant E. coli (KO11). With 3% w/v glucan loading and 4 mL of xylanase enzyme loadings, the SSCF of the SAA treated barley hull resulted 24.1 g/L ethanol concentration at 15 FPU cellulase/g-glucan loading, which corresponds to 89.4% of the maximum theoretical yield based on glucan and xylan.

SEM results indicated that SAA treatment increased surface area and the pore size. It is postulated that these physical changes enhance the enzymatic digestibility in the SAA treated barley hull.     

A miniswine model of heatstroke

We developed a miniswine model of passive heatstroke, in part, to explain the variable hyper-, normo- and hypokalemia seen in heatstroke victims. After a baseline period (T_amb=26–27°C), anesthetized and instrumented miniswine (n=13, mass=44.6 kg) were ramped to 41–43°C, 60% RH; 13 controls were treated identically, but T_re was maintained at 38°C. T_re of the experimental miniswine rose nearly linearly to 45–46°C until death (approx. 4 h). The response patterns of mean arterial pressure, heart rate, plasma K⁺, LPS, Ca²⁺, inorganic phosphate, lactate and a variety of other clinical chemical and physiological variables were determined. An explanation for the variability of plasma K⁺ in heatstroke victims was proposed. This model may be useful in characterizing the multisystemic pathology of severe heat injury and be useful for assessing innovative therapeutic regimens.     

Influence of sucrose on the rheology and granule size of cross-linked waxy maize starch dispersions heated at two temperatures

Cross-linked waxy maize (CWM) starch dispersions (STDs) of concentration 50 g kg⁻¹ were heated in sucrose solutions containing 0–600 g kg⁻¹ (g sucrose/kg dispersion) at 85 °C at low shear and in intermittently agitated cans at 110 °C. The STDs heated in 0–300 g kg⁻¹ sucrose exhibited antithixotropic behavior, while those heated in 400–600 g kg⁻¹ sucrose exhibited thixotropic behavior. The mean starch granule diameter of the starch dispersions did not show strong dependence on sucrose concentration. The dispersions, especially those with high sucrose concentrations and heated at 110 °C, exhibited G′ versus frequency (ω) profiles of gels. The STDs exhibited first normal stress differences that increased in magnitude with the concentration of sucrose. Values of the first normal stress coefficient of canned dispersions calculated from dynamic rheological data plotted against ω and experimental values plotted against shear rate of some of the STDs overlapped.     

Thermoregulatory behavior and critical thermal limits of the angelfish Pterophyllum scalare (Lichtenstein) (Pisces: Cichlidae)

(1)Final temperature preferendum of juvenile (0.9–1.9 g) and adult (5.2–12.5 g) angelfish Pterophyllum scalare were determined with acute and gravitation methods. The final preferenda were similar, independent of the method and development stage (29.0–31.1°C).

(2)The critical thermal maxima (CTMax) for juveniles were 36.9°C, 37.6°C, 40.6°C, 40.8°C and for adults 38.4°C, 38.6°C, 41.0°C, 42.1°C. Adult angelfish CTMax was slightly higher than in juveniles (1°C; P<0.05); the endpoint of CTMax was the onset of spasms.

(3)The acclimation response ratio for both stages had an interval of 0.33–0.44; these values are in agreement with results for subtropical and tropical fishes.

(4)Therefore it is recommended that angelfish cultivation should be consistent with temperatures that do not change abruptly throughout the year and temperature maximum does not exceed 30°C.

     

Chromosomal aberrations in environmentally exposed population in relation to metabolic and DNA repair genes polymorphisms

The capital city of Prague is one of the most polluted localities of the Czech Republic. Therefore, the effect of exposure to carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) adsorbed onto respirable air particles (<2.5 μm) on chromosomal aberrations was studied in a group of policemen (males, aged 22–50 years) working in the downtown area of Prague and spending daily >8 h outdoors (N = 53). Age- and sex-matched healthy volunteers spending > 90% daily time indoors were chosen as controls (N = 52). Ambient air particles (PM10, PM2.5) and c-PAHs were monitored using versatile air pollution sampler (VAPS), and personal exposure was evaluated using personal samplers during working shift. Chromosomal aberrations were analyzed by conventional cytogenetic analysis and fluorescent in situ hybridization (FISH). Urinary cotinine plasma levels of vitamins A, E and C, folate, total cholesterol, HDL, LDL cholesterols and triglycerides were also analyzed as possible effect modifiers. Genotypes CYP1A1*2A, CYP1A1*2C, GSTM1, GSTP1, GSTT1, EPHX1, NAT2, hOGG1, XRCC1, XPD, p53 BstI, p53 MspI, MTHFR677, and MS2656 were determined by PCR-based RFLP assays. The following levels of air pollution were recorded during the study period (mean from HiVol sampling): PM10 62.6 μg/m³, c-PAHs 24.7 ng/m³, B[a]P 3.50 ng/m³. The conventional cytogenetic analysis did not reveal any differences between the group of policemen exposed to the ambient air pollution and the control group. The cytogenetic analysis by FISH analysis used the whole chromosome painting probes for chromosomes #1 and #4 (Cambio, UK). It detected a significant increase in all studied endpoints in the policemen compared to controls (% AB.C. = 0.33 ± 0.25 versus 0.24 ± 0.18, p < 0.05, F_G/100 = 1.72 ± 1.57 versus 1.25 ± 1.11, p < 0.05, AB/1000 (aberrations/1000 cells) = 5.58 ± 4.62 versus 3.90 ± 3.06, p < 0.05). CYP1A1*2C (Ile/Ile), XPD 23 (Lys/Lys), and XPD 6 (CC) genotypes were associated with an increase of aberrant cells by conventional method. Factors associated with an increased level of translocations by FISH included age, smoking, B[a]P-like DNA adducts (corresponding to the exposure of c-PAHs), folate, polymorphisms of CYP1A1*2C, GSTP1, EPHX1, p53 MspI and MTHFR. Ambient air exposure to c-PAHs significantly increased FISH cytogenetic parameters in nonsmoking policemen. We may conclude that FISH indicates that the city policemen in Prague represent a group of increased genotoxic risk. This is the first study that has reported a relationship between DNA adducts (biomarker of exposure) and chromosomal aberrations by FISH (biomarker of effect).     

Production of xylanases from rice bran by Streptomyces actuosus A-151

In this study, the agricultural waste was used to screen for an organism that is capable of producing enzymes for degrading xylan and cellulose. Results showed that Streptomyces actuosus A-151, isolated from northern Taiwan, produced β-xylanase when rice bran was used as the sole carbon source. Four xylanases, designated as FI-A, FI-B, FII-A, FII-B, were identified and purified from the culture filtrate of S. actuosus A-151. Their specific activities after purification were 41.3, 86.2, 20.4, 85.2 U/mg, respectively. The pH stability of the four enzymes was: FI-A, 5–8; FI-B, 3–8; FII-A, 5–9; and FII-B, 3–9. The optimum pH for FII-B was 4, and the others were near 5–6. The optimum temperatures for enzyme activities were 60 °C for FII-B, and 70 °C for the others. The thermal stability for all four enzymes were up to 60 °C. The molecular weights of FI-A, FI-B, FII-A, and FII-B xylanases were 30,000, 45,000, 26,000, and 20,000, respectively, by sodium dodecylsulfate–polyacrylamide gel electrophoresis and 30,000, 43,000, 25,000, and 21,000, respectively, by gel filtration. Addition of xylan, shrimp and crab shell powder, and orange peel to the culture medium was found to enhance the production of xylanase.