Effect of the substrate concentration and water activity on the yield and rate of the transfer reaction of β-galactosidase from Bacillus circulans

Prebiotic galactosyl oligosaccharides (GOS) are produced from lactose by the enzyme β-galactosidase. It is widely reported that the highest GOS levels are achieved when the initial lactose concentration is as high as possible; however, little evidence has been presented to explain this phenomenon. Using a system composed of the commercial β-galactosidase derived from Bacillus circulans known as Biolacta FN5, lactose and sucrose, the relative contribution of water activity, and substrate availability were assessed. Oligosaccharide levels did not appear to be affected by changes in water activity between 1.0 and 0.77 at a constant lactose concentration. The maximum oligosaccharide concentration increased at higher initial concentrations of lactose and sucrose, while initial reaction rates for transfer increased but remained constant for hydrolysis. This suggests that the high oligosaccharide levels achieved at the raised initial saccharide concentration are due to increases in reactions that form oligosaccharides rather than decreases in concurrent reactions, which degrade oligosaccharides. There were different effects from changing the initial concentration of lactose compared to sucrose, suggesting that the ability of lactose to act as a donor saccharide may be more important for increasing maximum oligosaccharide concentrations than the combined ability of both saccharides to act as galactosyl acceptors.     

Matrix effects in analysis of β-agonists with LC-MS/MS: influence of analyte concentration, sample source, and SPE type

The synergistic influences of analyte concentration, sample source, and solid-phase extraction (SPE) type on matrix effects in the multiresidue analyses of eight β-agonists with LC-ESI-MS/MS were evaluated. Porcine muscle and liver extracts and urine from diverse sources were purified by strong or mixed-mode cation exchange and molecularly imprinted polymer SPE cartridges, respectively. Three spiked concentrations (2, 10, and 20 ng/mL) of eight β-agonists in the purified matrices and the different sample sources were analyzed. The results show that for most β-agonists there are significant differences in matrix effects between analyte concentrations or sample sources (P < 0.05), whereas there is no significant difference in matrix effects between different SPE cartridges (P > 0.05). Results from main effects testing indicated that analyte concentration was the main effector.     

Effects of soil compaction and water‐filled pore space on soil microbial activity and N losses

Abstract

Soil compaction is a significant production problem for agriculture because of its negative impact on plant growth, which in many cases has been attributed to changes in soil N transformations. A laboratory experiment was conducted to study the effect of soil compaction and water‐filled pore space on soil microbial activity and N losses. A hydraulic soil compaction device was used to evenly compress a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudults) soil into 50 mm diameter by 127 mm long cores. A factorial arrangement of three bulk density levels (1.4, 1.6, and 1.8 Mg/m³) and four water‐filled pore space levels (60, 65, 70, 75%) was used. Fertilizer application of 168 kg N/ha was made as 1.0 atom % ¹⁵N as NH₄NO₃. Soil cores were incubated at 25°C for 21 d. Microbial activity decreased with both increasing water‐filled pore space and soil bulk density as measured by CO₂‐C entrapment. Nitrogen loss increased with increasing bulk density from 92.8 to 334.4 g N/m³ soil at 60% water‐filled pore space, for 1.4 and 1.8 Mg/m³, respectively. These data indicate that N loss and soil microbial activity depends not only on the pore space occupied by water, but also on structure and size of soil pores which are altered by compaction.     

The influence of the herbicide paraquat ‘Gramaxon’ on growth and metabolic activity of three chlorophytes

The acute toxicity of commercial herbicide, Paraquat was determined by 96-hr static bioassay on the freshwater chlorophytes Scenedesmus dimorphus (Trup.) Kuetz., Scenedesmus quadricauda (Trup.) de Brebisson and Ankistrodesmus falcatus (Cord) Ralfs. The 96-hr EC50 values of Paraquat for reducing growth and metabolic products of the three algae were determined. The number of days required for cell division increased with increasing Paraquat concentration. The three algae and their test parameters respond differently to Paraquat. Scenedesmus dimorphus was the most susceptible alga and the chlorophyll a was the most sensitive response parameter. On the other hand, the dry weight of the test algae was the most resistant parameter. It was observed that Paraquat has inhibitory effect on the primary producers.     

Transformation of soil and plant cover contaminated with oil and salt water in the middle Ob’ river basin

Changes in the soil and plant cover caused by contamination with oil and salt water in the middle Ob’ river region were estimated using geoinformatic and geostatistic approaches. The largest technogenically salinized areas include oligotrophic peat soils due to the extensive spill of highly saline waters on the flat bog surface and eutrophic soils located in lower topographic positions. The natural self-purification of salinized mineral forest soils proceeds within 1–2 years after the spill. The dominant species of secondary plant communities were detected. Correlations were revealed between the residual oil and chloride contents and the total projective plant cover.     

Quantifying the influence of thermal process parameters on in vitro β-carotene bioaccessibility: a case study on carrots

This study describes a detailed and systematic investigation on the effect of thermal processing in terms of temperature and time (kinetic study) on β-carotene in vitro bioaccessibility in carrots. β-Carotene in vitro bioaccessibility increased with increasing processing temperature and time until steady-state conditions were reached after prolonged heating. The bioaccessibility values in steady-state conditions were temperature dependent. The experimental bioaccessibility data could adequately be modeled with a fractional conversion model. For the first time, modeling of processing-induced bioaccessibility changes is reported in literature. The results of the present kinetic study were used to estimate the impact of industrially relevant thermal processes on β-carotene bioaccessibility in carrots by simulation. It was shown that, to achieve a high β-carotene bioaccessibility, processing of carrots is essential (i.e., on the one hand, intense thermal processing or, on the other hand, mild thermal processing combined with intense mechanical processing).     

Effects of copper on the decomposition of plant residues,microbial biomass,and β-glucosidase activity in soils

Abstract

Two types of soils (Brown Lowland soil and Ando soil), which were artificially enriched with different amounts of Cu, were incubated with or without pulverized orchard grass for 12 weeks at 25°C. For both soils with and without orchard grass amendment, the amount of CO₂ evolved over the 12-week period of incubation decreased by the enrichment with Cu at a concentration exceeding 1,000 mg kg^?1 soil. The decrease of the mineralization of added orchard grass in the Cu-enriched soil was conspicuous especially during the initial period of incubation. The amount of microbial biomass C at the end of the incubation was significantly reduced by the Cu enrichment regardless of the amendment with orchard grass. The relative decrease of the soil microbial biomass was much greater than that of the soil respiration. The amount of biomass C was negatively correlated with the amount of 0.1 M CaCl₂-extractable Cu as a logarithmic function. On the other hand, the β-glucosidase activity at the end of the incubation was not significantly affected by the presence of Cu in the soils without orchard grass amendment and increased with the increase in the amount of enriched Cu in the orchard grass-amended soils.     

In vivo nitrate reductase activity in carex pseudocyperus L.: The influence of nitrate ‐ ammonium concentration ratios and correlation with growth

Abstract

The influence of the nitrate nutritional status and increasing ammonium concentrations on the nitrate reductase activity of shoots and roots of Carex pseudocyperus L. was investigated. The activity of this enzyme was correlated with the relative growth rates of the plant. Nitrate reductase activity was determined by a modified in vivo test (1). A specially developed test system allowed a large amount of samples to be handled easily.

The optimization procedure of the incubation buffers led to different assay conditions for the shoot and the root, respectively. Enzyme activity in the shoot was dependent on the length of the incubated leaf pieces. Incubation had to take place under dark, anaerobic conditions.

Enzyme activity was influenced by an evident diurnal rhythm with an optimum six hours after starting illumination, so that harvesting occurred always at that day time.

Increasing nitrate concentrations of up to 2.5mM NO₃‐ in the nutrient solution induced an increasing nitrate reductase activity in the shoot. The enzyme activity of the root was already fully induced at 1mM NO₃ ^?. A nitrate concentration above 5mM NO₃ ^? inhibited enzyme activity in shoots as well as in roots. The addition of increasing amounts of ammonium to a solution containing 2mM NO₃ ^? led to a significant inhibition of the enzyme activity in both parts of the plant.

Relative growth rates of the shoot, as a function of increasing nitrate concentrations in the nutrient solution, were highly positively correlated to the corresponding nitrate reductase activity, but only a slight, negative correlation was observed between these two parameters in the root.     

Tree influence on soil biological activity: What can be inferred from the optical examination of humus profiles?

Humus forms may vary in different forest stands, but the local influence of trees upon soil microbial and faunal activities is still imperfectly known. Optical methods could help to discern processes of litter transformation and formation of organo-mineral assemblages, allowing a better diagnostic of tree influences upon humus-soil development. The microstratification of humus was studied under a beech (Fagus crenata), a mixed oak forest (Quercus crispula and Quercus serrata), and a cedar (Cryptomeria japonica) plantation. The three sites are located in Kyoto (Japan), and share similar environmental conditions. Litter decomposition rates and soil fauna were also investigated. At the beech site, which had the thickest O horizon, the main process was the gradual fragmentation of litter. This process, together with shallow root and weak fungal development, gave rise to a stable sandwich-like structure in the O horizon. In contrast, the oak site showed a two-step transformation of litter. Initially, litter decomposition was triggered by the activity of white rot fungi, and the discarded litter decayed much more slowly thereafter. The cedar site exhibited a sharp vertical delineation between upper thick Oe horizon developed since plantation time and a relict A horizon. The optical method thus demonstrated differences in soil biological activities and litter transformation patterns under the three sites.     

Does the influence of earthworms on water infiltration, nitrogen leaching and soil respiration depend on the initial soil bulk density? A mesocosm experiment with the endogeic species Metaphire posthuma

Soil compaction has a negative impact on both earthworm abundance and diversity. Recent studies, however, suggest that earthworm cast properties are not influenced by the initial soil bulk density. With time, earthworms could therefore transform soils with different bulk densities into a soil with the same physical state and thus with a similar ecological functioning. This study aimed to test this hypothesis in two laboratory incubation experiments. First, we measured the influence of soil bulk density (1.1 or 1.4?g?cm^?3) on the production of cast by the endogeic earthworm species Metaphire posthuma. In a second experiment, we investigated the effect of M. posthuma on water infiltration, NH ₄ ⁺ , and NO ₃ ^? leaching and soil respiration at the same two soil bulk densities. Although initially higher, earthworm casting activity in soil at 1.4?g?cm^?3 decreased until it reached the same level of activity as earthworms in soil at 1.1?g?cm^?3. This behavioral plasticity led to a transformation of compacted and loose soils, with their own functioning, to a third and similar state with similar hydraulic conductivity, nitrogen leaching, and soil respiration. The consequences for soil organization and soil functioning are discussed.     

Influence of oil and stratal water contamination on the ash composition of oligotrophic peat soils in the oil-production area (the Ob’ region)

The mineral contamination of peat soils in the oil-production area differs considerably in the places of oil or stratal water spills. The time elapsed since the spill occurred is also an important factor of the changes in the chemical composition of the peat ash. The ash content rises drastically in the oil-contaminated peat, and the peat ash becomes rich in heavy metals (Mn, Ni, and Sr) and lanthanides (La and Ce). The content of K and Fe decreases, and that of P, S, Mg, Ca, Ni, and Pb increases with time at the site of old oil contamination. In the course of the self-rehabilitation of oil-contaminated peat, the content of Cl decreases more intensely than that of the heavier halogen Br. The ash content rises to a lesser extent in the peat contaminated with stratal water. The ash of the salinized peat is enriched in heavy alkaline-earth elements, i.e., Ba and Sr. Although most of the elements are leached with time, the content of Ba and Sr still remains 4–6 times higher than the background one even after long-term (more than 10 years) leaching. The concentrations of halogens rise considerably in the salinized peat, that of Cl in the peat ash decreases by 10 times, and the content of Ba virtually remains the same.     

Interaction of curcumin and bixin with β-cyclodextrin: complexation methods, stability, and applications in food

This work aimed to compare methods for the formation of complexes of bixin and curcumin with β-cyclodextrin (β-CD) and to evaluate the stability of the complexes formed by these methods and their food applications. The stoichiometric relationship between curcumin and β-CD was 1:2 and that between bixin and β-CD was 1:1. Curcumin-β-CD and bixin-β-CD complexes formed by kneading, coprecipitation, and simple mixing were evaluated by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), or nuclear magnetic resonance (NMR-H). For both curcumin and bixin, the best method of complexation was coprecipitation. Complexation of colorants with β-CD promoted an intensification of color and increased water solubility; however, stabilization in the presence of light occurred only for bixin. Application of curcumin-β-CD in cheese and yogurt and bixin-β-CD in the curd did not alter the initial characteristics of the products, which were sensorialy well accepted. Therefore, the complexation of these natural colorants with β-CD favors their use in low-fat foods, broadening the field of industrial application.     

Hydrolysis of cellobiose by β-glucosidase in the presence of soil minerals - Interactions at solid-liquid interfaces and effects on enzyme activity levels

Extracellular enzymatic activities in soils are essential for the cycling of organic matter. These activities take place in multiphase environments where solid phases profoundly affect biocatalytic activities. Aspergillus niger is ubiquitous in soils; its β-glucosidase plays an important role in the degradation of cellulose, and therefore in the global carbon cycle and in the turnover of soil organic matter. However, the information on the interactions of this protein with soil minerals is very limited, and even less is known about their consequences for the hydrolysis of the natural substrate cellobiose. We therefore characterised the sorptive interactions of this enzyme with the soil minerals montmorillonite, kaolinite and goethite and quantified the resulting changes in the hydrolysis rate of cellobiose. Fractions of adsorbed protein, and the resulting catalytic activity loss, were lower for montmorillonite than for kaolinite and goethite at given experimental conditions; adsorption was 9.7 ± 7.3% for montmorillonite, 70.3 ± 3.1% for kaolinite and 71.4 ± 1.8% for goethite, respectively. Adsorption of the protein to the minerals caused a total decrease in the catalytic activity of 18.8 ± 3.4% for kaolinite and 17.9 ± 4.7% for goethite whereas it was not significant for montmorillonite. The average catalytic activity lost by the pool of adsorbed molecules was 26.8% for kaolinite and 25.0% for goethite. Both the amount of adsorbed protein and the resulting loss of catalytic activity were found to be independent of the specific surface areas yet were influenced by the electrical properties of the mineral surfaces. Under the experimental conditions, montmorillonite and kaolinite are negatively charged whereas goethite is positively charged. However, because of the adsorption of phosphate anions from the buffer, a charge reversal took place at the surface of goethite. This was confirmed by zeta (ζ)-potential measurements in phosphate buffer, revealing negative values for all the tested minerals. Indeed goethite interacted with the enzyme as a negatively charged surface: the amount of adsorbed protein and the resulting catalytic activity loss were very similar to those of kaolinite. Our results show that, even if an important fraction of β-glucosidase is adsorbed to the minerals, the catalytic activity is largely retained. We suggest that this strong activity retention in presence of soil minerals results from a selective pressure on A. niger, which benefits from the activity of the adsorbed, and thus stabilized, enzyme pool.     

Effect of herbicide used with years (8 + 1) on soil enzymic activity and microbial population diversity

Purpose

Soil microbes play important roles in plant nutrition and soil conservation, and the diversity and population of soil microbe are influenced by abiotic and biotic factors associated with different soil managements. However, the information concerning soil microbe diversity and population structure and its relation with soil fertility and enzyme activities are scarce in crop rotation under different soil management system.

Materials and methods

This paper reports the effects of three weeding managements (herbicide (2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetomide, C1₄H₂₀ClNO₂), manual weeding, and no weeding (CK)), on soil microbial diversity, population structure, and its relationship with soil active organic matter (AOM) and pH, and the activity of soil enzymes like sucrase, catalase, and urease activities from long-term test area in red soil upland field in southeast China, which was set up since 2006. Soil samples at 0–20-cm depths were collected before (8 years) and after (8 + 1 years) weeding management in April 2014.

Results and discussion

Soil enzymes (sucrase, catalase, and urease activity) and soil microbial populations had no significant difference (P > 0.05) under the three weeding treatments. Based on richness of microbial population up to 0.10%, the phyla Proteobacteria and Actinobacteria highly dominated the three soil treatments, averagely accounting for 21.76 and 21.44%. Chloroflexi was the next phylum, about accounting for 6.84%. Firmicutes, Verrucomicrobia, and Planctomycetes phylum accounted for 4.98, 4.78, and 4.23%, respectively. The percentage of Gemmatimonadetes was 2.76%, and that of Bacteroidetes was about 1.45%. Armatimonade and Nitrospira were the lowest, with 0.69 and 0.26%, respectively. Among the 20 phyla, only 5 had significant correlation with some of the soil properties. Twenty-one in 46 classes had significant correlation with some of the soil properties. Armatimonadetes and Fusobacteria had positive correlation with moisture. Acidobacteria_Gp3, Deltaproteobacteria, Chthonomonadetes, Armatimonadetes_gp4, and Euryarchaeota also were positively correlated with moisture. Negative correlation between Armatimonadetes, Chloroflexi, Chthonomonadetes, and Armatimonadetes_gp5 and AOM exists, and Armatimonadetes, Chthonomonadetes, Clostridia, Armatimonadetes, and pH were negatively correlated. Fusobacteria was positively correlated with catalase. Acidobacteria_Gp10 and Armatimonadia were positively correlated with catalase. Chthonomonadetes, Clostridia, and Armatimonadetes_gp5 were correlated with urease. Gammaproteobacteria and Flavobacteria were correlated with sucrase.

Conclusions

For long-term herbicide experiment conducted on the Dongxiang upland site, no significant effect of herbicide on soil microbial community composition and enzyme activities was found. Further work is needed to relate microbial community structure and function in different herbicide systems or season sampling, even to detect herbicide effect on community structure during the growing season.

     

Spatial distribution of glomalin-related soil protein and its relationships with root mycorrhization,soil aggregates,carbohydrates, activity of protease and β-glucosidase in the rhizosphere of Citrus unshiu

Relationships between the spatial distributions of glomalin-related soil protein (GRSP) and soil aggregates, carbohydrates or relevant enzymes are poorly studied. We found that two categories of GRSP, the easily extractable Bradford-reactive soil protein (EE-BRSP) and total BRSP (T-BRSP), respectively ranged between 0.3–0.6 and 0.5–0.8 mg/g DW soil, and these two BRSPs decreased with the increase of soil depth (0–40 cm) in the rhizosphere of a 22-year-old Citrus unshiu orchard. Both EE-BRSP and T-BRSP were significantly positively correlated with mycorrhization, 0.25–0.50 mm soil water-stable aggregates, water-extractable or hydrolyzable carbohydrates, and β-glucosidase, but significantly negatively correlated with protease. Our results demonstrate that the spatial distribution of GRSP is significantly affected by mycorrhization, soil carbohydrate, β-glucosidase and protease.     

Effects of fine bubble aeration at the sediment‒water interface on distributions of organic phosphorus fractions and related microbial activity in a heavily urban river

Journal of Soils and Sediments - Effects of aeration on distribution and release potential of organic phosphorus in sediments are of great significance. The aim of this study was to investigate...     

Effects of fertilization with urban and agricultural organic wastes in a field trial – Waste imprint on soil microbial activity

In the past decades a significant change in composition of urban organic waste products has occurred in many first world countries, due to cleaner technologies as well as outsourcing of heavy industries. However, the societal perception of organic urban waste has become increasingly negative, leading to widespread advocacy of incineration. Therefore we established the ‘CRUCIAL’ long-term field trial in 2003, with the rationale that by approaching the known limits for a number of heavy metals below which no profound disturbance should be observed on key soil ecological functions, it should be possible to discern if some of the many unknown components in the composite urban waste as well as agriculturally based fertilizers have measurable impacts. The following treatments were established: human urine, sewage sludge (normal N-level and accelerated level aiming at three times normal N-level), degassed and subsequently composted organic municipal waste (normal and accelerated level), deep litter, cattle slurry, cattle manure (accelerated level), NPK fertilizer, unfertilized but with clover undersown and an unfertilized control. After 4 years the soil organic matter (SOM) C content, basal CO₂ respiration and soil microbial biomass (SMB) C was significantly affected by treatments. All soils having received organic fertilizer had higher SMB C than those with no added fertilizer (unfertilized and unfertilized with clover undersown) and inorganic fertilizer. The treatment effect on qCO2 (CO₂/SMB C) was not significant, but the unfertilized treatments showed the highest values. Treatments with accelerated levels of composted household waste and sewage sludge had the highest number of colony forming heterotrophic bacteria. Sole carbon source utilization in EcoPlates indicated a very robust microbial community in the treatments. Cumulative input of heavy metals was less than that required for reaching the heavy metal ecotoxicological limits, even after accelerated loading with sewage sludge corresponding to approximately 55 years of normal application. This could indicate that it is possible use organic urban waste for an extended period on a given site, without compromising soil functioning as long as ecotoxicological guidelines for heavy metal content are observed.     

Effects of overwinter cover on nitrate loss and drainage from a sandy soil: consequences for water management?

Abstract. A lysimeter study from April 1993 to June 1997 assessed the effects of winter cover crops and unfertilized grass on both the volume of water draining over winter and the amounts of nitrate leached. There were three to five replicates of each treatment in a fully randomized design. The lysimeters were undisturbed monoliths of loamy medium sand, 1.2 m deep and 0.8 m diameter. There were six treatments: sown cover before spring-sown crops (SC), natural regeneration (‘tumbledown’) before spring-sown crops (T), unfertilized grass (UG), bare soil permanent fallow, (PF), winter barley (WB) and conventional overwinter fallow before spring-sown crops (WF). Sugarbeet replaced cereals in 1996 as a disease break, and in consequence no cover was established in SC and T in autumn 1996. Of the four years of the study, two were above-average rainfall, while two were of less than average rainfall. Results are only quoted if statistically significantly different from WB (P=0.10). Over the first winter, NO₃―N losses were similar under UG (26 kg ha^?1) and PF (29 kg ha^?1), due to the slow establishment and growth of the grass. In the following three winters NO₃―N losses under UG were small (c. 6 kg ha^?1), giving an overall mean of c. 11 kg ha^?1. Sown cover crops and T gave means of c. 16 and 22 kg ha^?1 respectively, compared with c. 27–31 kg ha^?1 under PF, WB and WF. Mean NO₃―N concentrations were smallest under UG (4.4 mg l^?1) and SC (10.6 mg l^?1), although both T (13.7 mg l^?1) and PF (12.4 mg l^?1) were less than under WB and WF (15.8–18.7 mg l^?1). Overwinter drainage was greatest from UG and PF, at 239 and 247 mm respectively. In the three winters that cover crops were grown, drainage was decreased by, on average, 30 mm year^?1 compared with WF. However, there were large differences in effects between years, with significant decreases in only one year. We conclude that the widespread adoption of cover crops before spring-sown crops will reduce overwinter drainage in UK Nitrate Vulnerable Zones by no more than c. 2%, compared with no cover before spring-sown crops.