Presence Of Different Sugars Research Articles

Defining the role of slight acidic conditions on membrane potential and pH variations of Thermus scotoductus K1 cells in presence of different sugars

Defining the role of slight acidic conditions on membrane potential and pH variations of Thermus scotoductus K1 cells in presence of different sugars

Sugars induced exfoliation of porous graphitic carbon nitride for efficient hydrogen evolution in photocatalytic water-splitting reaction

Photocatalytic hydrogen evolution holds great promise for addressing critical energy and environmental challenges, making it an important area in scientific research. One of the most popular photocatalysts is graphitic carbon nitride (gCN), which has emerged as a noteworthy candidate for hydrogen generation through water splitting. However, ongoing research aims to enhance its properties for practical applications. Herein, we introduce a green approach for the fabrication of porous few-layered gCN with surface modifications (such as oxygen doping, carbon deposition, nitrogen defects) with promoted performance in the hydrogen evolution reaction. The fabrication process involves a one-step solvothermal treatment of bulk graphitic carbon nitride (bulk-gCN) in the presence of different sugars (glucose, sucrose, and fructose). Interestingly, the conducted time-dependent process revealed that porous gCN exfoliated in the presence of fructose at 180 °C for 6 h (fructose_6h) exhibits a remarkable 13-fold promotion of photocatalytic hydrogen evolution compared to bulk-gCN. The studied materials were extensively characterized by microscopic and spectroscopic techniques, allowing us to propose a reaction mechanism for hydrogen evolution during water-splitting over fructose_6h. Furthermore, the study highlights the potential of employing a facile and environmentally friendly fructose-assisted solvothermal process to improve the efficiency and stability of catalysts based on graphitic carbon nitride.

Size Discrimination of Carbohydrates via Conductive Carbon Nanotube@Metal Organic Framework Composites.

Traditional chemical sensing methodologies have typically relied on the specific chemistry of the analyte for detection. Modifications to the local environment surrounding the sensor represent an alternative pathway to impart selective differentiation. Here, we present the hybridization of a 2-D metal organic framework (Cu3(HHTP)2) with single-walled carbon nanotubes (SWCNTs) as a methodology for size discrimination of carbohydrates. Synthesis and the resulting conductive performance are modulated by both mass loading of SWCNTs and their relative oxidation. Liquid gated field-effect transistor (FET) devices demonstrate improved on/off characteristics and differentiation of carbohydrates based on molecular size. Glucose molecule detection is limited to the single micromolar concentration range. Molecular Dynamics (MD) calculations on model systems revealed decreases in ion diffusivity in the presence of different sugars as well as packing differences based on the size of a given carbohydrate molecule. The proposed sensing mechanism is a reduction in gate capacitance initiated by the filling of the pores with carbohydrate molecules. Restricting diffusion around a sensor in combination with FET measurements represents a new type of sensing mechanism for chemically similar analytes.

Biofilm-forming lactic acid bacteria of honey bee origin intended for potential probiotic use.

Scientists around the world are focusing their interest on the use of probiotics in honey bees as an alternative method of prophylaxis against causative agents of both American and European foulbrood. In our study we tested inhibitory activity against Paenibacillus larvae and the biofilm formation activity by various lactic acid bacteria isolated from honey bee guts or fresh pollen samples in the presence of different sugars added to the cultivation media. In addition, we tested the probiotic effect of a newly selected Apilactobacillus kunkeei V18 in an in situ experiment in bee colonies. We found antibacterial activity against P. larvae in four isolates. Biofilm formation activity of varying intensity was noted in six of the seven isolates in the presence of different sugars. The strongest biofilm formation (OD570 ≥ 1) was noted in A. kunkeei V18 in the presence of fructose; moreover, this isolate strongly inhibited the growth of P. larvae under laboratory conditions. Inhibition of P. larvae and Melissococcus plutonius by A. kunkeei V18 in situ was confirmed in a pilot study.

Transcriptomic Studies Reveal that the Rhizobium leguminosarum Serine/Threonine Protein Phosphatase PssZ has a Role in the Synthesis of Cell-Surface Components, Nutrient Utilization, and Other Cellular Processes.

Rhizobium leguminosarum bv. trifolii is a soil bacterium capable of establishing symbiotic associations with clover plants (Trifolium spp.). Surface polysaccharides, transport systems, and extracellular components synthesized by this bacterium are required for both the adaptation to changing environmental conditions and successful infection of host plant roots. The pssZ gene located in the Pss-I region, which is involved in the synthesis of extracellular polysaccharide, encodes a protein belonging to the group of serine/threonine protein phosphatases. In this study, a comparative transcriptomic analysis of R. leguminosarum bv. trifolii wild-type strain Rt24.2 and its derivative Rt297 carrying a pssZ mutation was performed. RNA-Seq data identified a large number of genes differentially expressed in these two backgrounds. Transcriptome profiling of the pssZ mutant revealed a role of the PssZ protein in several cellular processes, including cell signalling, transcription regulation, synthesis of cell-surface polysaccharides and components, and bacterial metabolism. In addition, we show that inactivation of pssZ affects the rhizobial ability to grow in the presence of different sugars and at various temperatures, as well as the production of different surface polysaccharides. In conclusion, our results identified a set of genes whose expression was affected by PssZ and confirmed the important role of this protein in the rhizobial regulatory network.

Comparison of gal-lac operons in wild-type galactose-positive and -negative Streptococcus thermophilus by genomics and transcription analysis.

Streptococcus thermophilus is one of the most important homo-fermentative thermophilic bacteria, which is widely used as a starter culture in dairy industry. Both wild-type galactose-negative (Gal-) S. thermophilus AR333 and galactose-positive (Gal+) S. thermophilus S-3 in this study were isolated from Chinese traditional dairy products. Here, to access the mechanism of the difference of galactose utilization between strains AR333 and S-3, the expression of gal-lac operons was examined using real-time qPCR in the presence of different sugars, and the gene organization of gal-lac operons was characterized using comparative genomics analysis. As compared with medium containing glucose, the expression of gal-lac operons in AR333 and S-3 was significantly activated (> 5-fold) in the presence of galactose or lactose in the medium. More importantly, the expression of gal operon in S-3 was higher than that of AR333, suggesting that the strength of gal promoter in AR333 and S-3 may be different. The genomes of AR333 and S-3 were the first time sequenced to provide insight into the difference of gal-lac operons in these two strains. Comparative genomics analysis showed that gene order and individual gene size of gal-lac operons are conserved in AR333 and S-3. The DNA sequence of gal operon responsible for galactose utilization between AR333 and S-3 is almost identical except that galK promoter of S-3 possesses single base pair mutation (G to A substitution) at -9 box galK region. Moreover, the expression of red fluorescent protein can be activated by galK promoter of S-3, but cannot by galK promoter of AR333 in galactose medium, suggesting that gal operon is silent in AR333 and active in S-3 under galactose-containing medium. Overall, our results indicated that single point mutation at -9 box in the galK promoter can significantly affect the expression of gal operon and is largely responsible for the Gal+ phenotype of S. thermophilus.

Antarctic Pseudomonas spp. promote wheat germination and growth at low temperatures

The development of cold-active biofertilizers and biopesticides could help improve sustainable agriculture in mountainous regions. With this aim, both psychrophilic and psychrotolerant microorganisms have been prospected in cold regions around the world and tested for their plant-growth promoting (PGP) effects. Interestingly, very little is known about the PGP effects of polar microorganisms in commercial crops. This study aimed at isolating cold-active plant-growth promoting Pseudomonas spp. from Antarctic soils and testing their PGP effects, both in vitro and on wheat (Triticum aestivum). Twenty-five Pseudomonas spp. strains isolated from Antarctic soils at Greenwich Island (South Shetland Islands, Antarctic Peninsula) were tested. The isolates grew well at temperatures ranging from 4 to 30 °C and were therefore considered as eury-psychrophiles. The isolates solubilized tri-calcium phosphate at 8 and 16 °C in the presence of different sugars as sole carbon sources. Besides producing indole-acetic acid, siderophores and hydrogen cyanide, several isolates inhibited growth of three plant pathogenic fungi (Fusarium oxysporum, Pythium ultimum and Phytophtora infestans) by means of both soluble- and volatile-secondary metabolites. Bacterization of T. aestivum seeds with selected isolates significantly enhanced root elongation. Moreover, when grown in sterile soil and in a temperature-controlled growth chamber at 14 ± 1 °C, inoculated T. aestivum seedlings showed a significant increase in their root- and shoot-lengths compared to untreated controls. Overall, the results suggest that some of these Antarctic Pseudomonas spp. isolates could act as cold-active biofertilizers.

Soluting-out effect of carbohydrates on the surface active ionic liquid 1-decyl-3-methylimidazolium bromide in aqueous solutions

Herein, with the aim of shedding light on the effect of non-ionic co-solute (carbohydrate) stereochemistry on the aggregation and surface behaviour of ionic liquid-based surfactant 1-decyl-3-methylimidazolium bromide ([C10mim][Br]) in aqueous solution, we studied the surface tension, electrical conductivity, volumetric and compressibility properties for the aqueous solutions of [C10mim][Br] in the presence of different sugars containing pentose monosaccharides (xylose, ribose and arabinose), hexose monosaccharides (glucose, and mannose), disaccharides (sucrose and lactose) and trisaccharide (raffinose) at different temperatures. From the electrical conductivity measurements, the values of the degree of ionization of the counter ion on the micelles (α) and thermodynamic properties of micellization (ΔGm) for [C10mim][Br] in aqueous carbohydrate solutions were obtained. The various parameters such as apparent molar volume (Vϕ), isentropic compressibility (κs), apparent molar isentropic compressibility (Kϕ) and the change of apparent molar properties upon micellization (ΔVϕ,m and ΔKϕ,m) were derived from the experimental density and speed of sound data. The surface tension measurements provided a series of parameters, including surface tension at the cmc (γcmc), effectiveness of surface tension reduction (Πcmc), maximum surface excess concentration (Γmax) and minimum surface area per molecule (Amin) at interface of air/solution for the investigated surfactant in the presence of different sugars at 298.15K. All the investigated carbohydrates have soluting-out effect (favouring the micelle formation) and their abilities to reduce the cmc of [C10mim][Br] in aqueous solutions increase with an increase in the hydrophilicity of the carbohydrate.

A Comparative Study of the Influence of Sugars Sucrose, Trehalose, and Maltose on the Hydration and Diffusion of DMPC Lipid Bilayer at Complete Hydration: Investigation of Structural and Spectroscopic Aspect of Lipid-Sugar Interaction.

It is well-known that sugars protect membrane structures against fusion and leakage. Here, we have investigated the interaction between different sugars (sucrose, trehalose, and maltose) and phospholipid membrane of 1,2-dimyristoyl-sn-glycero-3-phoshpocholine (DMPC) using dynamic light scattering (DLS), transmission electron microscopy (TEM), and other various spectroscopic techniques. DLS measurement reveals that the addition of sugar molecule results a significant increase of the average diameter of DMPC membrane. We have also noticed that in the presence of different sugars the rotational relaxation and solvation time of coumarin 480 (C480) and coumarin 153 (C153) surrounding DMPC membrane increases, suggesting a marked reduction of the hydration behavior at the surface of phospholipid membrane. In addition, we have also investigated the effect of sugar molecules on the lateral mobility of phospholipids. Interestingly, the relative increase in rotational, solvation and lateral diffusion is more prominent for C480 than that of C153 because of their different location in lipid bilayer. It is because of preferential location of comparatively hydrophilic probe C480 in the interfacial region of the lipid bilayer. Sugars intercalate with the phospholipid headgroup through hydrogen bonding and replace smaller sized water molecules from the membrane surface. Therefore, overall, we have monitored a comparative analysis regarding the interaction of different sugar molecules (sucrose, trehalose, and maltose) with the DMPC membrane through DLS, TEM, solvation dynamics, time-resolved anisotropy, and fluorescence correlation spectroscopy (FCS) measurements to explore the structural and spectroscopic aspect of lipid-sugar interaction.

Size and molecular flexibility of sugars determine the storage stability of freeze-dried proteins.

Protein-based biopharmaceuticals are generally produced as aqueous solutions and stored refrigerated to obtain sufficient shelf life. Alternatively, proteins may be freeze-dried in the presence of sugars to allow storage stability at ambient conditions for prolonged periods. However, to act as a stabilizer, these sugars should remain in the glassy state during storage. This requires a sufficiently high glass transition temperature (Tg). Furthermore, the sugars should be able to replace the hydrogen bonds between the protein and water during drying. Frequently used disaccharides are characterized by a relatively low Tg, rendering them sensitive to plasticizing effects of residual water, which strongly reduces the Tg values of the formulation. Larger sugars generally have higher Tgs, but it is assumed that these sugars are limited in their ability to interact with the protein due to steric hindrance. In this paper, the size and molecular flexibility of sugars was related to their ability to stabilize proteins. Four diverse proteins varying in size from 6 kDa to 540 kDa were freeze-dried in the presence of different sugars varying in size and molecular flexibility. Subsequently, the different samples were subjected to an accelerated stability test. Using protein specific assays and intrinsic fluorescence, stability of the proteins was monitored. It was found that the smallest sugar (disaccharide trehalose) best preserved the proteins, but also that the Tg of the formulations was only just high enough to maintain sufficient vitrification. When trehalose-based formulations are exposed to high relative humidities, water uptake by the product reduces the Tgs too much. In that respect, sugars with higher Tgs are desired. Addition of polysaccharide dextran 70 kDa to trehalose greatly increased the Tg of the formulation. Moreover, this combination also improved the stability of the proteins compared to dextran only formulations. The molecularly flexible oligosaccharide inulin 4 kDa provided better stabilization than the similarly sized but molecularly rigid oligosaccharide dextran 6 kDa. In conclusion, the results of this study indicate that size and molecular flexibility of sugars affect their ability to stabilize proteins. As long as they maintain vitrified, smaller and molecularly more flexible sugars are less affected by steric hindrance and thus better capable at stabilizing proteins.

Assessment of expression of Leloir pathway genes in wild-type galactose-fermenting Streptococcus thermophilus by real-time PCR

In this study, four galactose-positive (Gal+) Streptococcus thermophilus strains viz. AJM, JM1, KM3 and AUKD8 and one galactose-negative (Gal−) S. thermophilus NCDC 218 were used to characterize the organization of Leloir pathway genes using long-range PCR, and expression of these genes were studied using real-time PCR, in presence of different sugars. Long-range PCR results showed that both Gal+ and Gal− isolates, the gal–lac gene order (galRKTEM–lacSZ), are conserved including the size of individual genes. The promoter sequence of the three Gal+ isolates (AJM, JM1 and KM3) possessed single base pair deletion at −28 region of galR and C to T substitution at −9 box galK region. In contrast, Gal+ AUKD8 had A to T substitution at preceding −25 region of galR. The expression of galK and galM grown in the presence of galactose was significantly higher in case of AJM (30- and 7.6-fold, respectively), followed by KM3 and JM1. In addition, galR, galT and galE showed higher expression in galactose, than in lactose and glucose medium. This study gives a preliminary idea on Leloir pathway gene expression in wild Gal+S. thermophilus, and further studies may throw more light on the role of gal–lac operon in galactose metabolism.

Induction of Vesicle Formation by Exposing Apple Tissue to Vacuum Impregnation

This paper demonstrates that vacuum impregnation of mature apple tissue in the presence of different sugars results in the formation of membrane vesicles inside the cells. Vesiculation is regarded to be a metabolic consequence of the impregnation process. Vesiculation is shown when the endocytic marker FM4-64 was impregnated into the apple tissue together with the sugar solutions. Vesicles were formed at the plasma membrane already 30 min after impregnation and remained inside the cells for at least 24 h, a metabolic process that was inhibited in the presence of chloroquine, a specific endosomic inhibitor. This phenomenon was not dependent on the osmotic strength when sucrose was used for impregnation. However, the vesiculation drastically dropped when a hypertonic trehalose solution was impregnated. We suggest that the impregnated sugars may not totally remain in the extracellular space between the cells, as normally believed, but at least a fraction might be incorporated into the cells.

Influence of carbohydrates on cell properties of Lactobacillus rhamnosus

AbstractLactobacilli represent normal commensals of the human body, particularly in the gut and vagina where they protect these environments from incoming pathogens via a variety of mechanisms. The influence of the carbohydrate source present in reconstituted MRS growth medium on the different cell properties of two Lactobacillus rhamnosus strains were examined. Two human vaginal isolates, BGHV719 and exopolysaccharide producer strain BGHV954 were analyzed. The results demonstrated that unlike in reconstituted MRS with glucose as a carbon source, the presence of fructose, mannose, or rhamnose, significantly reduced cell surface hydrophobicity of both strains. In addition, differences in cell wall protein composition of L. rhamnosus BGHV719 and alterations in colony mucoidity of L. rhamnosus BGHV954 were also demonstrated. Light and SEM microscopy revealed differences on the cellular level when BGHV719 was cultivated in the presence of different sugars. The results of this study point out the importance of complex relationships between growth medium composition and the different aspects of bacterial behavior, and call for more detailed analyses of versatile bacterial responses to the changes in the environment, including vaginal ecosystem. This is especially important since lactobacilli are amongst the most widely used of probiotics.

Electrochemical characterization of in situ functionalized gold p-aminothiophenol self-assembled monolayer with 4-formylphenylboronic acid for recognition of sugars

The surface of a gold (Au) electrode was modified with p-aminothiophenol (p-ATP) and well-packed monomolecular layers through a sulfur–Au bond were formed. Functionalization of Au–ATP self-assembled monolayer (SAM) with 4-formylphenylboronic acid (BA) via Schiff's base formation, through in situ method, to fabricate Au–ATP–BA electrode is presented. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were used to investigate the changes in electrode behavior after each assembly step. The surface pK a value of the Au–ATP–BA SAM electrode was estimated by CV and EIS. In the presence of sugar, the terminal groups of Au–ATP–BA SAM electrode can react with sugar by forming the phenylboronate esters of sugar on the surface of the electrode; the pK a values for the Au–ATP–BA SAM electrode in the presence of different sugars (D-glucose, D-fructose, and D-mannose) were obtained. The fabricated electrode can be used as a novel biosensor for determining sugars on the basis of the change in i p of the Fe(CN) 6 3−/4− ion in the presence of sugars. The biosensor exhibited excellent performance in determining D-glucose, D-fructose, and D-mannose, with low detection limits, wide linear ranges and good sensitivities.

Variation in the Nature of Organic Acid Secretion and Mineral Phosphate Solubilization by Citrobacter sp. DHRSS in the Presence of Different Sugars

A novel phosphate solubilizing bacterium (PSB) was isolated from the rhizosphere of sugarcane and is capable of utilizing sucrose and rock phosphate as the sole carbon and phosphate source, respectively. This PSB exhibited mineral phosphate solubilizing (MPS) phenotype on sugars such as sucrose and fructose, which are not substrates for enzyme glucose dehydrogenase (GDH), along with GDH substrates, viz., glucose, xylose, and maltose, as carbon sources. PCR amplification of the rRNA gene and sequence analysis identified this bacterium as Citrobacter sp. DHRSS. On sucrose and fructose Citrobacter sp. DHRSS liberated 170 and 100 microM free phosphate from rock phosphate and secreted 49 mM (2.94 g/L) and 35 mM (2.1 g/L) acetic acid, respectively. Growth of Citrobacter sp. DHRSS on sucrose is mediated by an intracellular inducible neutral invertase. Interestingly, in the presence of GDH substrates like glucose and maltose, Citrobacter sp. DHRSS produced approximately 20 mM (4.36 g/L) gluconic acid and phosphate released was 520 and 570 microM, respectively. Citrobacter sp. DHRSS GDH activity was found when grown on GDH and non-GDH substrates, indicating that it is constitutive and could act on a wide range of aldose sugars. This study demonstrates the role of different organic acids in mineral phosphate solubilization by rhizobacteria depending on the nature of the available carbon source.

A group of Escherichia coli and Salmonella enterica O antigens sharing a common backbone structure

The O-antigen moiety of the LPS is one of the most variable cell surface components of the Gram-negative bacterial outer membrane. Variation is due to the presence of different sugars and sugar linkages. Here, it is reported that a group of Escherichia coli O serogroups (O17, O44, O73, O77 and O106), and the Salmonella enterica serogroup O : 6,14 (H), share a common four-sugar backbone O-subunit structure, and possess almost identical O-antigen gene clusters. Whereas the E. coli O77 antigen does not have any substitutions, the other O antigens in this group differ by the addition of one or two glucose side branches at various positions of the backbone. The O-antigen gene clusters for all members of the group encode only the proteins required for biosynthesis of the common four-sugar backbone. The identification of three genes within a putative prophage in the E. coli O44 genome is also reported; these genes are presumably involved in the glucosylation of the basic tetrasaccharide unit. This was confirmed by deletion of one of the genes, which encodes a putative glucosyltransferase. Structural analysis of the O antigen produced by the mutant strain demonstrated the absence of glucosylation. An O-antigen structure shared by five E. coli and one S. enterica serogroups, all of which have a long evolutionary history, suggests that the common backbone may be important for the survival of E. coli strains in the environment, or for their pathogenicity.

Sugar bioprotective effects on thermal denaturation of lysozyme: Insights from Raman scattering experiments and molecular dynamics simulation

The bioprotective properties of trehalose, sucrose and maltose on lysozyme protein are studied using Raman spectroscopy and molecular dynamics simulation. The temperature dependencies of the α-helical unfolding processes are determined in presence of different sugars and at various concentrations using the amide I band. The energies of stabilization and acting forces are discussed. The problem of the threshold sugar concentration needed to protect proteins is addressed. The results point out that the three sugars exhibit very similar bioprotective behaviors in the investigated temperature and concentration ranges and suggest that the difference between their respective effects arise mostly from the different denaturated states of lysozyme in the three sugar solutions. Indeed, trehalose gives rise to a significantly more important shift of the denaturation temperature Tm and of the Gibbs net free energy Δ(ΔGND) of stabilization of lysozyme with respect to the two other sugars.

THE THERMAL STABILITY OF ASPERGILLUS ORYZAE ALPHA‐AMYLASE IN PRESENCE OF SUGARS AND POLYOLS

ABSTRACT The aim of this study was to test whether it is possible to estimate the heat stability of Aspergillus oryzae alpha‐amylase (α‐amylase) based on the amount of hydroxyl (OH) groups provided in a buffer solution. The thermal stability of the enzyme in a presence of different sugars (sucrose and trehalose) and polyols (mannitol, sorbitol, lactitol and glycerol) was investigated in the temperature range of 62–68C on a kinetic basis. It was investigated if the protective effect of additional substances was correlated to the number of hydroxyl groups (nOH) provided by each of them (per volume unit of the enzyme solution nOH). All additives showed a protective effect on the enzyme's heat stability, which was strongly dependent on the added compound concentration. Among all stabilizing compounds investigated, sucrose exhibited the largest protective effect. The decimal reduction time of α‐amylase activity increased by 33.9 times when 420 mg/mL of sucrose was added to the environment. When the same concentration of trehalose was used, the D‐value increased by 6.4 times compared to the value in the buffer system. The nOH provided in the enzyme solution could not be related to the D‐values for the enzyme thermal inactivation, meaning that the enzyme heat stability was not dependent on the nOH.

Thermostable α-galactosidase from Bacillus stearothermophilus (NCIM 5146) and its application in the removal of flatulence causing factors from soymilk

Thermostable, neutral, extracellular α-galactosidase with wide pH stability was produced by a newly isolated strain of Bacillus stearothermophilus (NCIM 5146) grown on cheap agricultural residues at 60 °C, under submerged fermentation conditions. The maximum α-galactosidase activity (2.0 U/ml) was found when soybean meal was used as a carbon source along with yeast extract and ammonium sulphate as a nitrogen source. The pH optimum of α-galactosidase was 6.5–7.0 and the enzyme was stable in the pH range of 3–10. The enzyme exhibited an optimum temperature of 65 °C. The half-life of the enzyme at 70 °C was 80 min. The enzyme was active against synthetic as well as natural substrates. The K m values determined for pNPG, stachyose, raffinose and melibiose were 0.625, 3.33, 6.66 and 13.33 mM, respectively. The V max values were 4.3×10 7, 18.03, 12.65 and 6.3×10 3 μmol/min mg, respectively, for the above substrates. Enzyme activity was strongly inhibited by Ag +, Hg 2+ and Cu 2+ metal salts. No significant inhibition was found in the presence of different sugars. The enzyme hydrolyzes flatulence causing galacto-oligosaccharides, viz. raffinose and stachyose present in the soymilk at 65 °C within 2 h of treatment, suggesting its potential application in soymilk and related food industry.

Yeast cells sucrose biosensor based on a potentiometric oxygen electrode

A new microbial biosensor based on an immobilised microorganisms ( Saccharomyces cerevisiae) and a potentiometric oxygen electrode is described. Determination is based on the respiratory activity of the microorganism in presence of different sugars (sucrose and glucose). A response time of ca. 4 min for the steady-state method and 2 min for the initial slope method was obtained. Potentiometric detection has the advantage of an extended calibration range and a low detection limit. The calibration curve for sucrose was linear in the range 1×10 −5 to 3×10 −2 M. This biosensor was used for selective monitoring of sucrose in the presence of glucose, using a second anti-interference enzymatic layer with glucose oxidase (GOD) and catalase (CAT). Interference of glucose in the determination of sucrose decreases from 15% for a microbial biosensor to a maximum 3.5% for the hybrid biosensor. The hybrid biosensor was used to determine sucrose in soft drinks. A good correlation between the results for the biosensor and a spectrophotometric method with dinitrosalicylic acid was achieved.