Colorimetric determination of reducing sugars in soils
ABSTRACT Reducing sugars are the end products of many biological processes and enzymatic reactions in soils. They are determined in assay of several soil enzymes, including cellulase activity. Five colorimetric methods [phenol-sulfuric acid, anthrone-sulfuric acid, dinitrosalicylic acid (DNS), reaction with potassium ferric hexa-cyanide reagent (Prussian blue), and the Somogyi-Nelson (molybdenum blue) methods] were evaluated for determination of reducing sugars and total saccharides extracted from soils. Results showed that the Prussian blue and the molybdenum blue methods were the most sensitive and accurate for determination of reducing sugars in soils. Metals extracted from soils interfered with molybdenum blue color development. These metals, however, could be removed by K-saturated resin before analysis. The trace amount of metals extracted from soils did not interfere with the Prussian blue color development, but this method is too sensitive to be useful for determination of reducing sugars in soil extracts. Unlike the Prussian blue method, which is very sensitive and has 1 h color stability, the molybdenum blue method has color stability of at least 24 h. Reducing sugar values in soils increased significantly upon air-drying of field-moist soils or incubation of soils with acetate buffer (50 mM, pH 5.5) at 30°C for 24 h, suggesting enzymatic hydrolysis of the native substrates. Calibration graphs showed that the phenol-sulfuric acid, DNS, and anthrone-sulfuric acid methods are not as sensitive as the other two methods.
- SourceAvailable from: link.springer.com[Show abstract] [Hide abstract]
ABSTRACT: The enzyme maltase (glucoinvertase; glucosidosucrase; maltase-glucoamylase; α-glucopyranosidase; glucosidoinvertase; α-d-glucosidase; α-glucoside hydrolase; α-1,4-glucosidase EC 220.127.116.11), is involved in the exo-hydrolysis of 1,4-α-glucosidic linkages and certain oligosaccharides into glucose which is an important energy source for soil microbes. This enzyme originates from different sources, which include plants, seaweeds, protozoa, fungi, bacteria, vertebrates, and invertebrates. The assay of soil maltase using maltose as substrate and the released glucose determined using a glucose oxidase–peroxidase system has not been explored or investigated to the best of our knowledge. A simple assay protocol using this system is proposed to evaluate and characterize maltase activity in soils. The protocol involves the release of glucose (determined using a glucose oxidase–peroxidase colorimetric approach) when 1 g soil is treated with toluene and incubated with 5 mM maltose in 67 mM sodium acetate buffer (pH 5.0) at 37 °C for 1 h. The optimal activity using this procedure was at pH 5.0 and decreased at temperatures above 70 °C. The calculated K m values ranged from 0.8 to 6.5 mM, and are comparable to those of enzymes purified from microorganisms. The Arrhenius equation plots for the activity in the four soils were linear between 20 and 70 °C. The activation energy values ranged from 34.1 to 57.2 kJ mol−1, the temperature coefficients (Q 10) ranged from 1.5 to 1.9 (avg. = 1.7), and the coefficients of variation (CV) of the proposed assay protocol for the soils used was <6%. While we recognize the availability of established assay protocols to determine soil α-glucosidase (referred in other literature as maltase) activity based on the p-nitrophenol (artificial product) released from p-nitrophenyl-α-d-glucopyranoside (artificial substrate), our interest was to assay its activity by determining the glucose (natural product) released from maltose (natural substrate).3 Biotech. 09/2012; 2(3).
- [Show abstract] [Hide abstract]
ABSTRACT: The objective of this work was to evaluate the changes in soil enzyme activities due to application of pig slurry under different soil tillage systems. The experiment was conducted in a clayey Oxisol in Palotina, PR, using different quantities of pig slurry (0, 30, 60 and 120 m3 ha-1 year-1) applied to the soil prior to the summer and winter crop season under conventional tillage (CT) and no tillage (NT), with three replicates. The areas were cultivated with soybean (Glycine max L.) and maize (Zea mays L.) in the summers of 1998 and 1999, respectively, and with wheat (Triticum sativum Lam.) in the winters of both years. The soil samples were collected in March and October of 1998 and 1999 at depths of 0-5 cm, 5-10 cm and 10-20 cm. The pig slurry application and the soil tillage systems influenced enzyme activities in the soil. The increase of pig slurry application decreased the ratio of soil enzyme activities to microbial biomass carbon. The phosphatase activity had a negative relationship with soil-available phosphorus. The acid phosphatase activity decreased both under CT and NT systems at all depth studied due to pig slurry application.Acta Scientiarum Agronomy 12/2011; 33(4):729-737. · 0.63 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The inhibitory activities of two polymethoxylated flavone (PMFs) monomers (nobiletin and tangeretin) have been investigated against Pseudomonas fluorescens and Pseudomonas aeruginosain vitro. The effects on cell morphology, the release of cell constituents, the synthesis of proteins and the activities of key dehydrogenase were examined to elucidate their antibacterial mechanism. The concentration of transaminase and reducing sugar in bacterial solutions increased significantly when treated with nobiletin and tangeretin. Electron microscopy showed that the structure of the bacterial cells was destroyed and accompanied with induced cells plasmolysis. Nobiletin and tangeretin also inhibited the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH), and reduced proteins synthesis in bacterial cells. It is proposed that nobiletin and tangeretin destroyed the permeability of the cell membrane, with release of the cell constituents, leading to metabolic dysfunction, inhibition of protein synthesis, and eventually to cell pyknosis and death.Food Chemistry 06/2012; 132(4):1883–1890. · 3.26 Impact Factor