Implementation of batchwise bioscouring of cotton knits

The examination of critical factors determining the performance of bioscouring showed that a short treatment of the fabric at greater than 80°C after pectinase treatment at 60°C was essential for removal of waxes from the fabric as demonstrated by diminished intensities of methylene peaks in FT-IR measurements. Batch-wise bioscouring of cotton knits was carried out several times with post-treatment at 80°C using a rapid dyeing machine. The dye-ability of bioscoured knits was as good as the company's alkaline scoured ones with slightly higher K/S values. Water pollution caused by effluents of bioscouring and alkaline processes were estimated, as well as that due to the input of chemicals and enzymes. Higher BOD:COD_Cr ratios for enzymes indicated their biodegradable character. After calculation of energy consumption using a simulation program, an economic evaluation of the two processes was done on the basis of one ton production by considering the costs of chemicals and enzyme, water usage, energy consumption and waste water treatment charge.     

New development for combined bioscouring and bleaching of cotton-based fabrics

A thorough investigation into conditions appropriate for effecting combined eco-friendly bioscouring and/or bleaching of cotton-based fabrics was undertaken. Fabrics used include cotton, grey mercerized cotton, cotton/polyester blend 50/50 and cotton/polyester blend 35/65. The four cotton-based fabric were subjected to bioscouring by single use of alkaline pectinase enzymes or by using binary mixtures of alkaline pectinase and cellulase enzymes under a variety of conditions. Results of bioscouring show that, the bioscoured substrates exhibit fabrics performances which are comparable with these of the conventional alkali scouring. It has been also found that, incorporation of ethylenediaminetetraacetic acid (EDTA) in the bioscouring with mixture from alkaline pectinase and cellulase improves the performance of the bioscoured fabrics. Addition of β-cyclodextrin to the bioscouring solution using alkaline pectinase in admixtures with cellulase acts in favor of technical properties and performance of the bioscoured fabrics. Concurrent bioscouring and bleaching by in situ formed peracetic acid using tetraacetylethylenediamine (TAED) and H₂O₂ was also investigated. The results reveal unequivocally that the environmentally sound technology brought about by current development is by far the best. The new development involves a single-stage process for full purification/preparation of cotton textiles. The new development at its optimal comprises treatment of the fabric with an aqueous formulation consisting of alkaline pectinase enzyme (2 g/L), TAED (15 g/L), H₂O₂ (5 g/L), nonionic wetting agent (0.5 g/L) and sodium silicate (2 g/L). The treatment is carried out at 60 °C for 60 min. Beside the advantages of the new development with respect to major technical fabric properties, it is eco-friendly and reproducible. This advocates the new development for mill trials.     

Green bioprocess of degumming of jute fibers and bioscouring of cotton fabric by recombinant pectin methylesterase and pectate lyases from Clostridium thermocellum

Enzymatic processes are emerging as important green biotechnological processes in textile industry. The application of recombinant pectin methylesterase (CtPME) and pectate lyase (CtPL1B) from Clostridium thermocellum for enzymatic degumming of jute or bioscouring of cotton was evaluated. The effectiveness of processes by combination of two enzymes were evaluated that effective degumming of jute and bioscouring of cotton as compared with individual enzyme. The optimum concentrations of two enzymes mixture for both processes, degumming of jute and bio scouring of cotton were 5 mg/mL (2.1 U/mL) of CtPME and 5 mg/mL (3.0 U/mL) of CtPL1B under optimized conditions of 60 min, 100 rpm and 50 °C. FESEM images showed more effective removal of pectin from jute fiber and cotton fabric by enzyme mixture, nevertheless similar to NaOH treatment. Wettability analysis showed mixture of enzymes and NaOH treated cotton fabric absorbed a water drop in 10 s and 8 s, respectively. UTM analysis showed higher tensile strength and Young’s modulus for jute fiber and cotton fabric treated with enzyme mixture than untreated and were similar to those of NaOH treated. These results showed that the CtPME and CtPL1B mixture can be used for replacing the chemical process by green bioprocess in textile industry.     

Pectinase production by Bacillus subtilis and its potential application in biopreparation of cotton and micropoly fabric

An alkaline and thermostable pectinase production from Bacillus subtilis SS was optimized under submerged fermentation and its application was tested in textile industry for desizing and bioscouring of cotton and micropoly fabrics. Desizing of fabric was the best with 5 U/g pectinase treatment for 120 min at pH 9.5 and 65 °C. Under optimized conditions of bioscouring, desized cotton showed highest reducing sugar liberation and weight loss than desized micropoly. Along with enzyme, addition of chelating (EDTA) and wetting agent markedly enhanced the weight loss compared to single use of enzyme or EDTA alone. Agitation (50 ± 2) enhanced the weight loss values of cotton (1.9%) and micropoly fabric (1.7%) at pH 9.5 after treatment time of 2 h. Bioscouring of fabrics with pectinase resulted in enhancement of various physical properties of fabrics viz. whiteness (1.2%), tensile strength (1.6%) and tearness (3.0%) over conventionally alkaline scoured fabrics.     

Characterization and high-level expression of a metagenome-derived alkaline pectate lyase in recombinant Escherichia coli

Alkaline pectate lyases (PLs) play an important role in mild and eco-friendly bioscouring pretreatment processes in the textile industry. However, to date, only a few PLs can be applied in industrial-scale production, and many of them exhibit high production cost, low activity, and/or do not meet the treatment requirements. In this study, an alkaline PL gene was cloned from the metagenomic DNA of alkaline environment soils. The gene pelB consisted of 1263 nucleotides and encoded a mature protein (PelB) of 399 amino acids, which was expressed in Escherichia coli. The maximum catalytic activity of the enzyme exhibited a bimodal distribution at pH 8.1 and 9.8 and an optimal temperature of 55 °C. The K_m and V_max values of PelB were 1.78 g/L and 1084.8 μmol/(L min) at 45 °C, respectively. Substrate specificity analysis demonstrated the high cleavage capability of PelB on a broad range of substrates of natural methylated pectin. Based on the degradation products, PelB was considered to be an endo-acting lyase. Using high-cell-density cultivation in 7-L bioreactor, the highest PL activity (1816.2 U/mL) was achieved. Thus, the recombinant PelB, with promising properties for use in bioscouring in the textile pretreatment process, should be a potential enzyme for industrial applications.     

Immobilization of recombinant pectate lyase from Clostridium thermocellum ATCC‐27405 on magnetic nanoparticles for bioscouring of cotton fabric

Recombinant pectate lyase from family 1 polysaccharide lyase (PL1B) was immobilized on synthesized magnetic nanoparticles (MNPs) after 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride activation. At 70 mg/mL MNPs 100% binding of 1 mg/mL PL1B was achieved. The immobilized PL1B‐MNP displayed activity of 20.3 and 18.2 U/mg against polygalacturonic acid and citrus pectin, respectively, which was higher than the activity of free PL1B, on the same substrates of 17.8 and 16.2 U/mg. The immobilized PL1B‐MNP showed 32 fold and 14 fold enhanced thermal stability at 80°C and 90°C, respectively as compared with free PL1B at same temperatures. At high temperature the immobilized PL1B‐MNP retained its activity for a longer duration than free PL1B. The immobilized PL1B‐MNP could be reused till five cycles and after that it retained 70% of initial activity. It could be easily recovered from the reaction mixture with the help of a magnet. Bioscouring of cotton fabric was carried out with immobilized PL1B‐MNP which showed efficient removal of pectin from the fabric surface. The enhanced wettability of fabric resulted in the decrease of the water absorbing time period from 3 min taken by the free PL1B treated fabric to 15 s taken by the immobilized PL1B‐MNP treated fabric. As per our knowledge this is the first attempt of bioscouring of coarse cotton fabric by pectinase immobilized on magnetic nanoparticles. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:231–244, 2017     

The characterization of a pectin-degrading enzyme from Aspergillus oryzae grown on passion fruit peel as the carbon source and the evaluation of its potential for industrial applications

An extracellular pectinase (PEC-I) was isolated from the crude extract of Aspergillus oryzae when grown on passion fruit peel (PFP) as the carbon source and partially purified by ultra filtration, gel filtration and ion-exchange chromatography procedures. Pectinase activity was predominantly found in the retentate. The pectinase from retentate (PEC-Ret) was most active at 50?°C and pH 7.0 and stable at 50?°C with a half-life of approximately 8?h. PEC-I showed higher activity at pH 4.5 and 55?°C, 70?°C and 75?°C and was inhibited by cations (Ag⁺, Fe²⁺, Fe³⁺, Co²⁺, Ca²⁺ and Hg²⁺), EDTA, tannic acid and vanillin. On the other hand, PEC-I was activated by Cu²⁺, ferulic acid, cinnamic acid and 4-hydroxybenzoic acid. The gel under denaturing conditions of PEC-Ret and PEC-I samples showed a protein band of ～45?kDa coincident with that found by staining for pectinase activity. In the bioscouring of cotton fabric the PEC-Ret pectinase preparation led to a better wettability and removed more pectin from the cotton fibers than the commercial enzyme preparation Viscozyme L, but was less effective than a commercial alkaline pectate lyase preparation and alkaline scouring. The incubation of PEC-Ret with guava juice resulted in a 4.15% decrease in juice viscosity.     

Biochemical Properties of A Thermophilic Alkalophile

A thermophilic alkalophile (IC strain) which can grow well in an alkaline medium at over 55°C was isolated from soil samples, and identified as Bacillus licheniformis; its growth on a neutral medium was, however, very poor. This strain was able to grow at 37°C as well as at 55°C, but the specific growth rate at 55°C was about twice as high as that at 37°C under alkaliné conditions.

The intracellular pH remained below 9.5 when Na⁺ was present in the medium. Na ⁺ stimulated the alanine uptake by cells or membrane vesicles, but was not required ATP synthesis.

Intracellular enzymes were stable on heat treatment up to 60°C. The residual activity of enolase after heating at 60°C for 10 min was about 80%. Cytochrome oxidase in membrane vesicles was completely stable up to 58°C for 30 min. These enzymes were also resistant to SDS treatment, more than 50% of their activities remaining at 5% SDS.     

Assessment of the potential suitability of selected commercially available enzymes for cleaning-in-place (CIP) in the dairy industry

The potential suitability of 10 commercial protease and lipase products for cleaning-in-place (CIP) application in the dairy industry was investigated on a laboratory scale. Assessment was based primarily on the ability of the enzymes to remove an experimentally generated milk fouling deposit from stainless steel (SS) panels. Three protease products were identified as being most suitable for this application on the basis of their cleaning performance at 40°C, which was comparable to that of the commonly used cleaning agent, 1% NaOH at 60°C. This was judged by quantification of residual organic matter and protein on the SS surface after cleaning and analysis by laser scanning confocal microscopy (LSCM). Enzyme activity was removed/inactivated under conditions simulating those normally undertaken after cleaning (rinsing with water, acid circulation, sanitation). Preliminary process-scale studies strongly suggest that enzyme-based CIP achieves satisfactory cleaning at an industrial scale. Cost analysis indicates that replacing caustic-based cleaning procedures with biodegradable enzymes operating at lower temperatures would be economically viable. Additional potential benefits include decreased energy and water consumption, improved safety, reduced waste generation, greater compatibility with wastewater treatment processes and a reduction in the environmental impact of the cleaning process.     

Effect of ammonia and urea treatments on digestibility and nitrogen content of dehydrated lucerne

Dehydrated lucerne of low (L: 0.53), normal (N: 0.55) and high (H: 0.73) in vivo dry matter (DM) digestibility were treated with ammonia or urea to study the effects on in situ and pepsin-cellulase DM digestibilities, water solubility and nitrogen content (Experiments 1, 2, 4) and on cell wall composition and degradability (Experiment 3). (1) N lucerne was treated with 30 g NH₃ kg⁻¹ DM for 1 to 12 weeks at 30°C and 2 to 6 days at 80°C; (2) L, N and H lucerne were treated with increasing ammonia levels: 15 to 100 g kg⁻¹ DM for 3 weeks at 30°C and 4 days at 80°C; (3) L, N and H lucerne were treated with 60 g NH₃ kg⁻¹ DM for 3 weeks at 30°C and 4 days at 80°C; (4) L, N and H lucerne were treated with 60 g urea kg⁻¹ DM without addition of urease for 3 and 6 weeks at 30°C. All treatments were carried out at 40% humidity.In situ and pepsin-cellulase DM digestibilities increased significantly (P < 0.05) with the duration of treatment (up to 3 weeks at 30°C and 4 days at 80°C) and with the level of ammonia (P < 0.01) (up to 30 g kg⁻¹ DM). The greatest improvements (similar at both temperatures) were for L, N and H of 7.3, 7.2 and 3.9 points for in situ and of 10.6, 11.3 and 6.3 points for cellulase digestibilities, respectively. Water solubility also increased with duration of treatment and level of ammonia (P < 0.01) and was greater at 80°C than at 30°C. Urea treatment significantly improved (P < 0.01) digestibilities and water solubility but the doubling of treatment duration had no influence. The degree of ureolysis was only 50 to 60%. Ammonia and urea treatments considerably increased (P < 0.01) nitrogen content.Treatment with 60 g NH₃ kg⁻¹ DM induced a decrease in ethanol insoluble residue content, which was significant (P < 0.01 for L and N, P < 0.05 for H) at 80°C but not at 30°C, and was greater for L and N than for H (about 12 and 5 points, respectively). This decrease was essentially due to solubilisation of hemicelluloses (− 15%) and uronic acids (− 26%). Thus, at 30°C, the chemical solubility of the cell wall was lower than at 80°C for the same total increase in microbial degradation. This result indicates that other phenomena are involved, such as an increase in cell wall porosity and consequently improved accessibility of cell wall polysaccharides to glycolytic enzymes.     

Effects of Thermobifida fusca cutinase-carbohydrate-binding module fusion proteins on cotton bioscouring

Previously, we presented a novel approach for increasing Thermobifida fusca cutinase adsorption on cotton fibers by fusing cutinase with a carbohydrate-binding module (CBM). A preliminary study showed that two fusion proteins, namely cutinase-CBM_Cel6A and cutinase-CBM_CenA, with similar stabilities and catalytic properties, had potential applications in bioscouring. In the present study, an indepth analysis of both cutinase-CBMs in bioscouring was explored. Effects of cutinase-CBMs on cotton bioscouring were investigated by characterizing the chemical and physical surface changes in enzyme-treated cotton fabrics. Gas chromatography/mass spectrometry was used to analyze the degradation of the cotton fabric cuticle; Fourier transform infrared microspectroscopy was used to study changes in the chemical composition of the cotton fabric epidermal layer; and scanning electron microscopy was used to monitor minor changes in the morphology of the fiber surface. Our results indicated that cutinase-CBMs in combination with pectinase had a greater effect on cotton fabric than did cutinase. Following scouring with cutinase-CBMs and pectinase, the performance of cotton fabric in terms of its wettability and dyeability was similar to that following alkali scouring. Our study provides a foundation for the further application of cutinase-CBM to bioscouring.     

Kinetics of Low-Temperature Oxidation of Enzymatic Lignin from Pine Wood (Pinus silvestris) in an Aqueous Alkaline Medium

The kinetics of oxidation of the enzymatic lignin from pine wood (brown rotted wood) by oxygen in an aqueous alkaline medium at 90–160°C was investigated. It was established that the vanillin yield increased gradually with the temperature increase in this range from 3.4 to 5.6 wt % with respect to lignin. The observed activation energy of the process of oxygen consumption varies in the range 6–19 kJ/mol depending on the process conditions. The process order with respect to oxygen pressure calculated from the rates of O₂ consumption during the first two hours of oxidation at 90–120°C is 1.02 ± 0.05. The low value of activation energy of the process as well as the first order in oxygen indicates a diffusion-controlled process under these conditions. The kinetic data demonstrate that the role of degenerate chain branching processes increases with the increase in the degree of oxidation as a result of decomposition of the hydroperoxides formed. The hydroperoxide decomposition during oxidation in quantity of more than 16 mol % with respect to the initial lignin was registered using a volumetric method based on the oxygen release. The main causes and features determining the monotonically increasing function of the dependence of the selectivity of lignin oxidation to aromatic aldehydes on temperature were discussed.

     

Amino silicones finished fabrics for lipase immobilization: Fabrics finishing and catalytic performance of immobilized lipase

Finishing of silk fabric was achieved by using amino-functional polydimethylsiloxane (PDMS) and lipase from Candida sp. 99-125 was immobilized on the treated silk fabrics. Hydrophobic fabrics were obtained by dipping the native fabric in 0.125–0.25% (w/v) PDMS solution and dried at 70 °C. The direct adsorption on PDMS-treated fabric was verified to be a better strategy for lipase immobilization than that by covalent binding. Compared to unfinished fabrics, the hydrolytic activity of immobilized enzyme on the finished fabric was improved by 1.6 times. Moreover, the activity of immobilized enzymes on hydrophobic fabrics was significantly improved in different concentrations of strong polar solvents such as methanol and ethanol, and in common organic solvents with different octanol–water partition coefficients (Log P). Enzymatic activity and stability in 15% water content system (added water accounted for the total reaction mixtures, v/v) showed more than 30% improvement in each batch. The amino–silicone finished fabric surface was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. The hydrophobic fabric immobilized enzyme could be recycled for more than 80 times with no significant decrease in esterification activity. PDMS-treated woven silk fabrics could be a potential support for lipase immobilization in catalytic esterification processes.     

Characterization of microbial endo-β-glucanase immobilized in alginate beads

Endo-β-glucanase (endo-β-1,4-glucano-glucanase EC 3.2.1.4), isolated from Trichoderma reesei, was immobilized in calcium alginate beads, retaining 75% of its original activity. The polyanionic moiety surrounding the immobilized enzyme displaced the pH-activity profile to alkaline regions with respect to that of the free enzyme. The enzyme was inhibited by carboxymethylcellulose, but this inhibition appeared to be decreased by immobilizatíon. The enzyme immobilized in alginate beads showed a K_m value (1.02% w/v) lower than that of the enzyme (1.31%). The apparent V_max of immobilized cellulase preparations (238.3 μmol glucose/ml × h) decreased by a factor of 0.59 with respect to that of the soluble enzyme. The optimum temperature (60°C) of the free and entrapped enzymes remained unaltered. In contrast, the half-life of the endoglucanase immobilized in calciumalginate beads was 4.6 h at 55°C and 5.4 h at 60°C, while that of the free enzyme was 3.0 h at 55°C and 1.2 h at 60°C. A technological application of the immobilized enzymes was tested using wheat straw as a source of fermentable sugars. The hydrolytic degradation of straw, by means of a crude extract of free and immobilized cellulases and β-glucosidase, released a large amount of reducing sugars from wheat straw after 48 h (between 250–720 mg glucose/g straw), carrying out more than a 90% saccharification. A mixture of immobilized β-glucosidase and free cellulases maintained 80% of the activity of the soluble counterparts, and the co-immobilization of both types of enzymes reduced by hydrolytic efficiency to half.     

Discovery of pectin-degrading enzymes and directed evolution of a novel pectate lyase for processing cotton fabric

There is a growing need in the textile industry for more economical and environmentally responsible approaches to improve the scouring process as part of the pretreatment of cotton fabric. Enzymatic methods using pectin-degrading enzymes are potentially valuable candidates in this effort because they could reduce the amount of toxic alkaline chemicals currently used. Using high throughput screening of complex environmental DNA libraries more than 40 novel microbial pectate lyases were discovered, and their enzymatic properties were characterized. Several candidate enzymes were found that possessed pH optima and specific activities on pectic material in cotton fibers compatible with their use in the scouring process. However, none exhibited the desired temperature characteristics. Therefore, a candidate enzyme was selected for evolution. Using Gene Site Saturation Mutagenesistrade mark technology, 36 single site mutants exhibiting improved thermotolerance were produced. A combinatorial library derived from the 12 best performing single site mutants was then generated by using Gene Reassemblytrade mark technology. Nineteen variants with further improved thermotolerance were produced. These variants were tested for both improved thermotolerance and performance in the bioscouring application. The best performing variant (CO14) contained eight mutations and had a melting temperature 16 degrees C higher than the wild type enzyme while retaining the same specific activity at 50 degrees C. Optimal temperature of the evolved enzyme was 70 degrees C, which is 20 degrees C higher than the wild type. Scouring results obtained with the evolved enzyme were significantly better than the results obtained with chemical scouring, making it possible to replace the conventional and environmentally harmful chemical scouring process.     

LCA Study and Environmental Benefits for Low Temperature Disinfection Process in Commercial Laundry (12 pp)

Background, Aims and Scope

This study aims to compare the energy requirements and potential environmental impacts associated with three different commercial laundry processes for washing microbiologically contaminated hospital and care home laundry. Thermal disinfection relies mainly on a 90°C washing temperature and hydrogen peroxide, while the chemothermal disinfection uses a combination of chemicals (mainly peracetic acid) and 70°C washing temperature. The chemical disinfection process relies on a combination of chemicals used at 40°C. Currently, chemothermal processes are the most commonly used in professional laundries. Traditional chemical processes are uncommon due to drawbacks of longer residence time and high chemical requirements. However, the innovative Sterisan chemical process based on phthalimidoperoxyhexanoic acid (PAP) – which is the key subject of this Life Cycle Assessment – was designed to overcome these technical limitations.

Methods

This study is based on a screening Life Cycle Assessment (LCA) prepared in 2002 by Öko-Institut (Germany), which was carried out following the requirements of the ISO 14040 series standards. It includes energy resource consumption, water resource consumption, climate change, eutrophication and acidification potential as relevant environmental indicators. In 2004/2005, the study was further updated and broadened to include the aquatic eco-toxicity potential, photochemical oxidant formation and ozone depletion potential in order to represent the environmental burdens associated with the chemicals used.Based on available data, the system boundaries include detergent manufacturing, the professional wash process, waste water treatment, but excluding the laundry finishing process. The selected functional unit was 1kg washed hygiene laundry.

Results and Discussion

The LCA indicates that the Sterisan chemical process has a lower potential environmental impact than thermal or chemothermal treatment for six out of seven key indicators. This includes a 55% lower energy and a 46% lower water consumption. The global warming potential and acidification potential are approximately halved, while the photochemical oxidant formation potential and eutrophication potential are almost reduced to one third. By contrast, for the aquatic eco-toxicity, the thermal- and chemothermal processes have an approximately 17 fold lower impact. The worse aquatic toxicity score for the Sterisan process is mainly caused by a solvent component in the formulation.

Conclusion

The comparison of the thermal, chemothermal and Sterisan commercial laundry processes shows that the Sterisan process allows for very substantial reductions in energy and water consumption, as well as significant reductions in climate change, photochemical oxidant formation potential, air acidification potential and eutrophication potential. Yet, Sterisan has a clear disadvantage with regards to aquatic eco-toxicity potential.

Recommendation and Perspective

Based on a current hygiene laundry volume of approx. 584000 tons of linen washed per year by commercial laundries in Germany, a full substitution of the market to the Sterisan process could potentially allow a primary energy saving of ~750000 GJ/year (roughly equivalent to the residential primary energy consumption of 23500 German citizens or the overall energy demand of approx. 6000 German citizens). In terms of improvements to the respective processes, the chemothermal and thermal process could benefit from a reduction of water volume, and change of detergent composition to reduce the eutrophication potential. As the washing temperature is an essential factor, only slight improvements for the energy consumption indicator can be obtained, e.g. by choosing green electricity and reducing the amount of water to be heated. The Sterisan process could be improved by lowering the solvent use, although for perspective, the current aquatic eco-toxicity score of the Sterisan process is still lower than that of a typical domestic laundry product.

     

Scouring of cotton using marine pectinase

Bioscouring refers to the enzymatic removal of impurities from cotton fibre, which endows it with improved hydrophilicity for further wet processes. In this study, the efficacy of pectinase from newly isolated marine bacteria Bacillus subtilis, isolated from marine sediment; collected from Chinchani beach, Tarapore, India has been evaluated for scouring of cotton fabric and compared with conventional alkaline scouring of cotton. Use of Citrus limetta peel powder as pectin substrate for enzyme production renders pectinase production process more economically viable. Scouring carried out with pectinase dose of 10% (2.8 IU/g of the fabric) on the weight of the fabric at pH 7, 60 °C for 120 min yielded hydrophilic fabric. Physicochemical and mechanical properties of the pectinase scoured fabric were similar to alkaline scoured fabric. Scouring with pectinase preserves fiber's structure and prevents it from deterioration as observed from tensile strength, FTIR and SEM studies against alkaline scoured fabric. Enhanced dye uptake was also observed in case of pectinase scoured cotton fabric as compared to alkaline scoured fabric.     

Respiration rates of subitaneous eggs from a marine calanoid copepod: monitored by nanorespirometry

The oxygen consumption rate during embryogenesis of Acartia tonsa subitaneous eggs were measured at different temperatures (10, 15, 17, 21, 24 and 28°C) with nanorespirometry. The oxygen consumption was constant during the embryogenesis but increased rapidly at hatching time. The mean ± SD oxygen consumption rate increased exponentially with temperature and ranged from 0.09 ± 0.04 (10°C) to 0.54 ± 0.09 nmol O₂ egg⁻¹ h⁻¹ (28°C). The mean ± SD Q₁₀-value was 2.51 ± 0.15. Calculations of energy consumption during embryogenesis ranged from 1.86 to 18.28 mJ depending on temperature and development time. We conclude that the effect of temperature on oxygen consumption rate was far less important than the prolonged development time when calculating the energy consumed during embryogenesis.     

Effects of acute temperature changes on the swimming abilities and oxygen consumption of Ptychobarbus kaznakovi from the Lancang River

Water temperature is known to be a particularly important environmental factor that affects fish swimming performance, but it is unknow how acute temperature changes affect the fish performance of Ptychobarbus kaznakovi. P. kaznakovi in the Lancang River have declined quickly in recent years, and this species was used to examine the effects of acute temperature changes on swimming abilities and oxygen consumption in a Brett‐type swimming tunnel respirometer. The standard metabolic rate (SMR) and routine metabolic rate (RMR) showed 216% and 134% increases, respectively, at 22°C (an acute increase from 17 to 22°C) compared to those at 12°C (an acute decrease from 17 to 12°C). Moreover, the RMR was approximately 1.7, 1.6 and 1.3 times the value of the SMR at 12°C, 17°C and 22°C, respectively. The critical swimming speed (U_crit) of P. kaznakovi at 22°C was 5.45 ± 0.45BL/S, which was 45% higher than that at 12°C (3.77 ± 0.92BL/S). The oxygen consumption rates (MO₂) reached their maximum values at swimming speeds near the U_crit for all the temperature treatments. The maximum metabolic rate (MMR) values at 12°C, 17°C and 22°C were 274.53 ± 142.60 (mgO₂ kg^?1 hr^?1), 412.85 ± 216.34 (mgO₂ kg^?1 hr^?1) and 1,095.73 ± 52.50 (mgO₂ kg^?1 hr^?1), respectively. Moreover, there was a narrow aerobic scope at 12°C compared to that at 17°C and 22°C. The effect of acute temperature changes on the swimming abilities and oxygen consumption of P. kaznakovi indicated that water temperature changes caused by dam construction could directly affect energy consumption during the upstream migration of fish.     

Purification and Characterisation of Xylanolytic Enzymes of a Cellulase-free Thermophilic strain of Clostridium absonum CFR-702

Two endo-β-1-4-xylanases (EC 3.2.1.8), xylanase-I and xylanase-II, were purified fromClostridium absonum CFR-702 by ammonium sulphate precipitation and chromatographed on DEAE-Cellulose and phenyl-Sepharose. The enzymes in sodium dodecyl sulphate polyacrylamide gels resolved as proteins corresponding to molecular mass 150 and 95 kDa for xylanase-I and xylanase-II, respectively. The optimum pH and temperature ranges for the enzyme activities on birchwood xylan were between 6.5 and 7.5 and 75°C for xyl-I and 7.5 and 80°C for xyl-II. Xyl-I was stable up to 60°C whereas xyl-II was stable at 50°C. Both the enzymes liberated xylobiose, xylotriose and xylotetraose from birchwood xylan. Xyl-I and xyl-II with birchwood xylan had K_mvalues of 1.1 and 1.4%, and V_maxvalues of 454.54 and 363.63 μmol/min/mg protein respectively.