Galactose Solution Research Articles

Thermostabilization of Aspergillus oryzae β-d-galactosidase.

The thermal stability of the Aspergillus oryzae β-d-galactosidase (β-gal) was evaluated at 60°C. The stability of β-gal was dependent on the pH, buffer, and additives. The β-gal exhibited its highest thermal stability in a 0.02 M phosphate buffer pH 6. Among all the tested additives, galactose, a competitive inhibitor of β-gal, was the upmost thermal stabilizer. A 0.15 M galactose solution caused β-gal to retain a whole of 98.65% of its initial activity after incubation at 60°C for 2 H. The second best thermal stabilizer of β-gal was raffinose. A 0.15M raffinose-β-gal mixture retained 84.41% of its initial activity after incubation at 60°C for 2H, whereas the control retained only 61.02%. The results of this study also revealed that all the tested positively charged polymers (diethylaminoethyl [DEAE] dextran and polyethyleneimine [PEI] 800, 2,000, 750,000 Da) significantly destabilized β-gal. However, these positively charged polymers exerted different effects on the β-gal's activity. PEI 750,000 significantly activated the enzyme, while DEAE dextran and PEI 800 did not exert any significant effects on the β-gal's activity. Nevertheless, PEI 2,000 significantly activated the enzyme.

Ethanol production from galactose by a newly isolated Saccharomyces cerevisiae KL17

A wild-type yeast strain with a good galactose-utilization efficiency was newly isolated from the soil, and identified and named Saccharomyces cerevisiae KL17 by 18s RNA sequencing. Its performance of producing ethanol from galactose was investigated in flask cultures with media containing various combination and concentrations of galactose and glucose. When the initial galactose concentration was 20g/L, it showed 2.2g/L/h of substrate consumption rate and 0.63g/L/h of ethanol productivity. Although they were about 70% of those with glucose, such performance of S. cerevisiae KL17 with galactose was considered to be quite high compared with other strains reported to date. Its additional merit was that its galactose metabolism was not repressed by the existence of glucose. Its capability of ethanol production under a high ethanol concentration was demonstrated by fed-batch fermentation in a bioreactor. A high ethanol productivity of 3.03g/L/h was obtained with an ethanol concentration and yield of 95 and 0.39g/L, respectively, when the cells were pre-cultured on glucose. When the cells were pre-cultured on galactose instead of glucose, fermentation time could be reduced significantly, resulting in an improved ethanol productivity of 3.46g/L/h. The inhibitory effects of two major impurities in a crude galactose solution obtained from acid hydrolysis of galactan were assessed. Only 5-Hydroxymethylfurfural (5-HMF) significantly inhibited ethanol fermentation, while levulinic acid (LA) was benign in the range up to 10g/L.

Separation of galactose, 5-hydroxymethylfurfural and levulinic acid in acid hydrolysate of agarose by nanofiltration and electrodialysis

A two-stage membrane process for the separation of galactose, 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) has been proposed. The first step of nanofiltration (NF) is to remove 5-HMF and LA from galactose solution obtained by the hydrolysis of agarose, the main component of red algal galactan for the reduction of its microbial toxicity. 5-HMF and LA are inhibitory to fermentation but at the same time useful compounds themselves with many applications. The second step of electrodialysis (ED) is to separate 5-HMF and LA in the permeate from NF. More than 91% of 5-HMF and up to 62% of LA could be removed from agarose hydrolysate, while galactose was almost completely retained by NF. Further removal of LA was expected to be possible with no loss of galactose by operating the NF process in a diafiltration mode. 5-HMF and LA could be effectively separated from each other by ED.

A new approach to facilitate diagnosis of nonalcoholic fatty liver disease through a galactose single point method in rats with fatty liver

BackgroundLiver biopsy reliably diagnoses nonalcoholic fatty liver disease, but its invasiveness and inter- and intra-observer errors limit its usefulness in monitoring. AimsUse a galactose single point method or combined biochemical parameters to improve assessments of nonalcoholic fatty liver disease in a rat model. MethodsThree nonalcoholic fatty liver disease severities were generated in 50 rats: a control group (n=18) on a standard diet, and 2 study groups on a choline-deficient diet (n=18), with and without treatment with silymarin (n=14). At weeks 4, 8, and 18, a galactose solution (0.5g/kg/body weight) was rapidly injected intravenously. Sixty minutes later, internal artery blood was taken for biochemical analyses, including galactose. The livers were then removed for haematoxylin–eosin staining and to measure the hepatic lipid content. ResultsAlkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, albumin, and total protein were each significantly correlated with nonalcoholic fatty liver disease severity. Regarding logistic regression, galactose single point method and total protein were significantly predictive. The optimal alanine aminotransferase cutoff point for nonalcoholic fatty liver disease prediction from the receiver-operating characteristic curve had 72.4% sensitivity and 52.4% specificity; galactose single point method alone had 82.8% and 72.4%, whereas galactose single point method+total protein showed 82.8% and 81.0%. ConclusionsBoth galactose single point method and galactose single point method+total protein had greater diagnostic sensitivity and specificity for nonalcoholic fatty liver disease than traditional biochemical tests.

Forskolin effect on the cryosurvival ofin vitro-produced bovine embryos in the presence or absence of fetal calf serum

The objective of this study was to assess the viability and cryotolerance of zebu embryos produced in vitro with or without the addition of fetal calf serum (FCS) and forskolin (F). Embryos produced in vivo were used as a control. Presumptive zygotes were cultured in modified synthetic oviductal fluid supplemented with amino acids (SOFaa), bovine serum albumin (BSA) and with (2.5%) or without (0%) FCS. On day 6 of growth, the embryos from each group were divided into treatments with or without 10 μM F to induce embryonic lipolysis, comprising a total of four experimental groups: 2.5% FCS, 0% FCS, 2.5% + F and 0% + F. For vitrification, embryos were exposed to vitrification solution 1 (5 M EG (ethylene glycol)) for 3 min and then transferred to vitrification solution 2 (7 M EG, 0.5 M galactose solution and 18% (w/v) Ficoll 70) before being introduced to liquid nitrogen. The presence of FCS in the culture medium resulted in the production of embryos with a similar rate of damaged cells compared with in vivo-produced embryos. After vitrification, the 2.5% FCS group had a significantly higher rate of damaged cells when compared with the other groups (P < 0.05). The results of this experiment indicated that the omission of FCS and the addition of forskolin do not have deleterious effect on embryo production rates. In addition, embryos produced in the presence of FCS had greater sensitivity to cryopreservation, but this effect was reversed when forskolin was added to the medium, which improved embryo survival without affecting embryo development and quality after vitrification.

Molecular interaction study of glycine in aqueous galactose solution and effect of sodium chloride at 298 to 318 K

Sound speed, density and viscosity of glycine in aqueous galactose solution at varying concentrations from 0.1035 to 1.0345 m at 298, 308 and 318 K have been determined. Density, viscosity and sound speed have been measured by using pre-calibrated bicapillary pycnometer, Ostwald's viscometer and single-frequency ultrasonic interferometer at 2 MHz frequency, respectively. The derived acoustic parameters like free volume (Vf ), adiabatic compressibility (β), hydration number (nH ) and Gibbs free energy for activation (ΔG) acoustic impedance (Z), intermolecular free length (Lf ) and relative association (RA ), internal pressure (πi ), Rao's constant (R), Wada's constant (W) have been calculated from experimental data. All the measurements have been carried out in a thermostatic water bath having PT-100 sensor with circulating medium with an accuracy of ± 0.1°C. Solute–solvent interactions dominate over solute–solute interactions and, the solute–solvent interactions increase with temperature.

Comparison of the reducing power of aldose solutions

Concentration and temperature dependences of the redox potentials of neutral and alkaline solutions of glucose, mannose, galactose, galacturonic acid, and xylose were measured. Axial orientation of the secondary hydroxy groups in epimeric hexopyranoses, oxidation of C6 to carboxy group, and the lack of primary hydroxy group in going to aldopentopyranose favor increasing (in the order of listing) destabilization of their cyclic structure, formation of the oxo form, and thermally activated retro-aldol reaction of the latter in alkaline medium. This leads to enhancement of their reducing power and chemical reactivity toward 5,5′,7,7′-tetrabromoindigo.

Grafted Glycopolymer-Based Receptor Mimics on Polymer Support for Selective Adhesion of Bacteria

A sugar-containing monomer (2-lactobionamidoethyl methacrylate, LAMA) was grafted on a polypropylene (PP) microfiltration membrane surface by UV-induced graft copolymerization. The degree of grafting can be controlled by variation of monomer concentration, UV irradiation time, and photoinitiator concentration. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to confirm the surface modification on the membranes. The water contact angle was used to evaluate the hydrophilicity change of the membrane surface before and after modification. Bacteria capture experiments showed that the membrane could selectively bind E. faecalis while adhesion of S. maltophilia was not influenced by the functionalization of PP with grafted poly(LAMA). The adhesion of E. faecalis onto poly(LAMA) grafted membrane could be inhibited by 200 mM galactose solution; however, glucose solution showed no inhibition effect. Moreover, occupying sugar residues on the membrane surface primarily by a galactose targeting lectin, peanut agglutinin, could significantly suppress the following adhesion of E. faecalis. All these results clearly demonstrate that this poly(LAMA) grafted PP membrane can selectively capture E. faecalis and that this selection is based on the interaction between galactose side groups on grafted flexible functional polymer chains on the membrane surface and galactose binding protein on the E. faecalis cell membrane.

Effects of six sugars on the longevity, fecundity and nutrient reserves of Microplitis mediator

Parasitoid adults can directly feed on floral nectar and honeydew containing monosaccharides and disaccharides. Oligosaccharides such as maltose, melezitose and raffinose are also found in honeydew but are rare in floral nectar. The effects of six different sugar resources on the longevity, fecundity and nutrient reserves of Microplitis mediator, a larval endoparasitoid in the cotton bollworm Helicoverpa armigera (Hübner) were determined in our laboratory. The results showed that both food and sex affected longevity of this wasp. Females and males of M. mediator fed with 1 M sucrose solution survived longer than controls fed with water (5.7- and 3.7-fold longer, respectively). When provided with sucrose, glucose or fructose solutions, the parasitoid generated 3.6- to 3.7-fold more offspring than controls, and 60–75% of these progenies were produced during the first 5 days. When separately given fructose, sucrose or glucose, this wasp accumulated fructose and total sugar at the highest level, which means a high sugar levels might lead to prolonging longevity and more offspring in M. mediator. In addition, compared with organisms fed galactose or raffinose, M. mediator fed sucrose or fructose accumulated high glycogen levels. Furthermore, in M. mediator, the lipid content declined with the advancing age. Females showed the slowest lipid metabolic rates when fed with sucrose, glucose, fructose, mannose and galactose solutions versus when fed with raffinose and control. In addition, only sucrose had a significant effect on lipid levels in males nearing the end of life.

N‐acetyl‐D‐galactosamine‐specific lectin isolation from soyflour with poly(HPMA‐GMA) beads

AbstractSoybean lectin was purified from seeds of Glycine max L.Merrill SA88. Poly(hydroxypropyl methacrylate‐glycidyl methacrylate) [poly(HPMA‐GMA)] beads were used as an affinity matrix and N‐acetyl‐D‐galactosamine (GalNAc) was used as an affinity ligand. Soybean lectin adsorption with GalNAc attached poly(HPMA‐GMA) beads from soybean lectin solution (in phosphate buffered saline) was 5.0 mg/g. Maximum adsorption capacity for soybean lectin from the soy flour extract was 26.0 mg/g. Elution of soybean lectin from adsorbent was accomplished by 0.5M galactose solution. Purity of soybean lectin was determined by SDS‐PAGE. It was observed that soybean lectin could be repeatedly adsorbed and desorbed with GalNAc‐attached poly(HPMA‐GMA) beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Monosaccharide Sensing Based on Multivariate Analysis of Voltammetric Data Acquired from a Pt:Ru Electrode Array

Predictive models for concentration of mixed monosaccharide solutions were developed based on combinatorial electrochemistry and chemometric techniques. The columns on a 10x10 array of Pt wires were electrodeposited with 10 different Pt:Ru alloys. Cyclic voltammograms were performed in 1M solutions of glucose, fructose, and galactose. Principal component analysis was applied to the resulting data sets; a scores plot allowed classification of the pure solutions. Fifteen solutions containing the three sugars in concentrations ranging from 10-1000mM were used to train partial least squares regression models. Twelve independent test solutions were also prepared in similar concentration ranges. For these test samples, root-mean-squared-error-of- predictions (RMSEPs) of 142mM and 120mM were obtained for glucose and galactose. The RMSEP for fructose between 10- 500mM was 128mM, but nonlinearities caused the model to fail at higher concentratio ns. These results demonstrate that with only a few electrode variants it is possible to differentiate monosaccharides in a semi-quantitative fashion.

The effect of galactose supplementation on endurance cycling performance

This study tested the hypothesis that supplementation with galactose before and during endurance exercise would spare carbohydrate (CHO), optimize fat utilization and improve performance compared with a typical sports drink formulation. Nine well-trained cyclists undertook three trials, each consisting of 120 min at 65 VO(2max) followed immediately by a set work, self-paced time trial (TT). Three treatments, allocated as a randomized balanced design, consisted of the following: (a) 8% (w/w) solution of galactose (Gal); (b) 8% solution of 50% galactose/50% glucose (Gluc/Gal); and (c) 8% solution of 80% glucose/20% fructose (Gluc/Fru). These were consumed as 0.67 g CHO per kg body wt 45-min pre-exercise; 1.0 g CHO per kg body wt per h for the first 120 min of exercise; 0.33 g CHO per kg body wt during the TT. Blood samples were collected before and during exercise; respiratory gas samples were collected only during fixed workload exercise. Mean TT power output was significantly less in Gal compared with Gluc/Gal (P=0.030). Blood glucose and insulin concentrations were lower, and free fatty acids higher in Gal compared with Gluc/Gal and Gluc/Fru. Respiratory exchange ratio was not significantly different between trials. Ingestion of an 8% galactose-only solution (12.5 ml per kg body wt per h) is detrimental to endurance performance compared with equivalent volumes of iso-osmotic solutions containing 50% galactose/50% glucose or 80% glucose/20% fructose. This may reflect the inability of the liver to convert galactose into glucose at a rate required to support strenuous exercise intensity.

Biosensors for Determination of Galactose with Galactose Oxidase Immobilized on Eggshell Membrane

A galactose biosensor was first fabricated using a galactose oxidase‐immobilized eggshell membrane and an oxygen electrode. The detection scheme was based on the depletion of dissolved oxygen content upon exposure to galactose solution, and the decrease in oxygen level was monitored and related to the galactose concentration. The effects of pH, buffer compositions, phosphate buffer concentration, and temperature on the biosensor were investigated. The linear range is 0.1 to 8.5 mM with relative standard deviation (RSD) is 3.74% and the response time is 100 s. Some possible interferents such as L‐ascorbic acid, ethanol, sucrose, glucose, maltose, and fructose did not give significant interference and retained 83.6% of initial enzyme activity after 3 months when stored in a pH 7.0 phosphate buffer solution at 4°C. The proposed biosensor was applied to the determination of galactose added to plasma samples with the recoveries of galactose is 94%–110%.

88ESTABLISHMENT OF PREGNANCIES AFTER VITRIFICATION OF EQUINE EMBRYOS

Vitrification of equine embryos has been limited, with only one study reporting transfer of vitrified embryos into recipients (1994 Theriogenology 42, 483–488). The objective of this study was to vitrify equine embryos in different stages of development based on a protocol that had been successful in sheep (Naitanas et al., 1996 Theriogenology 46, 813–824) and buffalo (2001 Theriogenology 55, 307). Embryos, Days 6.5 to 7.5, were assigned to a 3 (stage)×2 (media) factorial design (n=3 per group) based on diameter and developmental stage [(1) morulae+very early blastocysts; (2) blastocysts &amp;lt;300μm; (3) blastocysts &amp;gt;300μm] and base media [(1) PBS supplemented with 0.3mM pyruvate, 3.3mM glucose and 10% FCS or (2) HCDM (Olson SE and Seidel GE Jr. 2000 J. Anim. Sci. 78, 152–157) with Eagle’s essential and nonessential amino acids, 2mM glucose, 3mgmL−1 BSA and 20% FCS]. Embryos were placed sequentially in 200μL of 1.4M glycerol for 5min, 200μL of 1.4M glycerol+3.6M ethylene glycol for 5min, and 30μL of 3.4M glycerol+4.6 M ethylene glycol. Within 30s, the 30-μL drop containing the embryo was loaded into the center of a 0.25-mL straw separated by air from columns (30μL) of the same solution. Straw ends were loaded with columns (60μL) of 0.5M galactose in base medium. The straw was heat-sealed and exposed to liquid-nitrogen vapor for 1min before being plunged into liquid nitrogen. To warm embryos, straws were held in air for 10s and then immersed in 20°C water for 10s. Embryos were transferred into 200μL of 0.25M galactose solution for 5min, and then placed in PBS or HCDM. Within 10min, embryos (n=3 per recipient), grouped for stage and media, were transferred nonsurgically into the uteri of 6 recipients that had ovulated 6 days earlier. Ultrasound exams were done at 4, 6, 8 and 10 days after transfer. Three morulae or very early blastocysts and one blastocyst &amp;lt;300μm, all vitrified in PBS, formed embryonic vesicles. Two of 3 vesicles, in the same recipient, were manually removed on Day 16. The remaining vesicle and the single vesicle, from a blastocyst &amp;lt;300μm, had normal development until Day 38 when pregnancies were terminated. No pregnancies were observed on Day 16 after use of HCDM. Because numbers of embryos were low, it is not clear if HCDM had a detrimental effect (P&amp;gt;0.1). Embryos were transferred in October, at the end of the breeding season. Therefore, quality of available recipients could have affected pregnancy rates. No pregnancies were observed from expanded blastocysts. Potentially, the embryonic capsule, present at this stage, impeded diffusion of cryoprotectants. These preliminary results demonstrate the potential for vitrification of small equine embryos.

A semi-pilot-scale procedure for isolating and purifying soybean (Glycine max) lectin.

Availability of gram quantities of purified soybean lectin (SBL) to scientists will foster discovery of novel biomedical applications of the lectin and provide the opportunity to investigate the antinutritional effects of SBL in soybean-consuming food animals and poultry. Therefore, a semi-pilot-scale procedure for isolating and purifying SBL was designed. Defatted soyflour was extracted overnight with 0.9% NaCl at 4 degrees C. The extract obtained was filtered (0.45 microm membrane) and subjected to affinity chromatography using a column containing N-acetyl-D-galactosamine resin that is specific for SBL. Bound SBL was eluted off the column with 0.14 M galactose solution. The eluent was ultrafiltered (30 kDa), and the resulting solution (SBL and water) was freeze-dried. Electrophoretic analysis and hemagglutination assay revealed that the freeze-dried SBL was similar to Sigma-grade SBL in purity and activity (35 and 33 HU/mg protein, respectively). The procedure yielded 141 mg of SBL/100 g of soyflour.

Osmotic sensitivity of canine spermatozoa

The objective of this study was to determine osmotic tolerance of canine spermatozoa. The study comprised three experiments: (1) spermatozoa suspended either in an egg yolk–citrate (EYC) extender or in Kenney skim milk extender were exposed to NaCl solutions ranging from 290 to 1500 mOsm; (2) spermatozoa suspended in EYC were exposed to 550 to 1500 mOsm solutions of glucose, galactose, or fructose; and (3) spermatozoa suspended in EYC or glucose-bovine serum albumin (G-BSA) were exposed to 0.6 M (∼900 mOsm) or 1.2 M (∼1600 mOsm) solutions of glycerol, ethylene glycol (EG), or dimethyl sulfoxide (Me 2SO). In all experiments, motility and membrane integrity of spermatozoa were assessed after they were diluted into isotonic medium at 37 °C. Exposure of canine spermatozoa to solutions of either NaCl or monosaccharides at osmolalities >500 mOsm caused a significant reduction of motility ( P<0.01). Motility of spermatozoa was more affected by osmotic stress than their membrane integrity. Osmotic sensitivity of canine spermatozoa was dependent on the type of extender; spermatozoa suspended in the Kenney extender were more resistant to osmotic stress than those suspended in the EYC extender. Despite their sensitivity to exposure to high concentrations of nonpermeating agents, canine spermatozoa were rather resistant to exposure to glycerol and EG. However, Me 2SO was toxic to canine spermatozoa; motility was substantially reduced after spermatozoa were exposed to 0.6 M Me 2SO. The type of extender also affected the sensitivity of canine spermatozoa to Me 2SO; spermatozoa suspended in the EYC extender were more resistant than those suspended in G-BSA. It was concluded that canine spermatozoa are sensitive to osmotic stress, but are tolerant to shrinking and swelling caused by exposure to permeating cryoprotectants.

A comparison of nectar- and honeydew sugars with respect to their utilization by the hymenopteran parasitoid Cotesia glomerata

Fourteen naturally occurring sugars were individually tested with respect to their effect on Cotesia glomerata longevity. Parasitoids kept with solutions of either sucrose, glucose and fructose lived for >30 days. This constitutes a factor 15 increase in life span in comparison to control individuals kept with water only. Stachyose, mannose, melezitose, melibiose, maltose and erlose increased parasitoid longevity by a factor of 11.2–6.9. Solutions of galactose and trehalose had a marginal, but still significant effect. Lactose and raffinose did not raise parasitoid longevity, while rhamnose actually reduced parasitoid survival. In an additional experiment, the relationship between quantity of sugar consumption and longevity was established for all 14 sugars. To study the effect of an unsuitable sugar in sugar mixtures, a range of glucose:rhamnose mixtures was tested. Even at 20% of the sugar mixture rhamnose suppressed the nutritional benefit of the 80% glucose. The nutritional suitability of the sugars shows a positive correlation with the previously reported gustatory response towards the individual sugars. Patterns of sugar utilization are discussed with respect to hydrolytic enzymes and carbohydrate biochemical characteristics. Our findings for C. glomerata are compared to patterns of sugar utilization reported for other species. The comparison between C. glomerata and its host Pieris brassicae reveals that the parasitoid is capable of utilizing a range of sugars that are unsuitable to its herbivorous host. This specificity opens up opportunities to select food supplements for biological control programs that selectively target the antagonist, without concurrently enhancing herbivore fitness.

Receptor–ligand interactions in a reconstituted bilayer lipid membrane

A simple method is described to reconstitute membrane receptors into bilayer lipid membranes (BLMs). After reconstitution, the receptor still retains its ligand activity. Furthermore, the relationship between receptor–ligand interactions and electrical properties of reconstituted BLMs such as membrane capacitance ( C m) and membrane resistance ( R m) was studied. When glycophorin in erythrocyte and asialoglycoprotein in hepatocyte were taken as examples, it was found that the resistance of reconstituted BLM decreased when adding blood type monoclonal antibody or the solutions of galactose, respectively, and the decrease is ligand-concentration dependent; however, the membrane capacitance was not influenced. This provides a simple, practical approach to determining the interactions between the receptor and its ligand.

Galactose Consumption Induces Conditioned Flavor Avoidance in Rats

Recent findings revealed that intragastric infusions of galactose conditioned a flavor avoidance in adult rats. To determine whether the galactose-conditioned avoidance was due to the infusion procedure, we investigated the flavor conditioning effect of orally consumed galactose. Food-restricted rats drank a flavored galactose solution, a flavored fructose solution and a flavored saccharin solution in separate one-bottle training sessions; grape, cherry and orange flavors were used. Because fructose is sweeter than galactose, saccharin was added to the galactose solution to increase its palatability. Pre- and posttraining preferences for the galactose and fructose solutions were evaluated in two-bottle choice tests. Also, preferences for the sugar-paired flavors were evaluated in two-bottle tests with the flavors presented in saccharin. In Experiment 1, rats were trained with flavored 80 g/L fructose, 80 g/L galactose + 2 g/L saccharin, and 2 g/L saccharin solutions (20 mL/d). Their preference for the flavored galactose solution changed (P < 0.01) from 76% (pretraining) to 19% (posttraining). The rats also avoided (P < 0.05) the flavor paired with the galactose solution in choice tests with the fructose-paired flavor and the saccharin-paired flavor. Similar pre- to posttraining preference reversals were obtained in Experiments 2 and 3, which used 20 g/L galactose and fructose solutions, and 20 g/L galactose and fructose solutions mixed with 20 g/L glucose, respectively. These findings, together with the intragastric infusion data, demonstrate that galactose has aversive postingestive consequences in adult rats even at low concentrations (20 g/L). Unlike lactose intolerance, which is due to intestinal malabsorption, this galactose-induced flavor avoidance is presumably due to the slow and incomplete postabsorptive metabolism of galactose.

Gustatory Response by the Hymenopteran Parasitoid Cotesia glomerata to a Range of Nectar and Honeydew Sugars

The feeding response of food-deprived Cotesia glomerata to solutions of 14 naturally occurring sugars was determined. Glucose, fructose, sucrose, maltose, erlose, melezitose, trehalose, and stachyose all elicited a feeding response. The sugars differed, however, with respect to the lowest concentration at which they were accepted (acceptance threshold). The parasitoids showed no feeding response when presented with 2 M solutions of galactose, mannose, rhamnose, lactose, raffinose, and melibiose. Sugars from the latter group did not show a deterrent effect when offered to water-deprived parasitoids. When mannose, rhamnose, melibiose, or raffinose were combined with low molar solutions of either fructose or sucrose, sucrose acceptance was affected by mannose and raffinose, whereas no negative interactions were found in mixtures with fructose. Compared to acceptance thresholds reported in other insect systems, the responses of C. glomerata differ considerably with respect to both the range of saccharides accepted as well as the acceptance thresholds. The novel finding that the parasitoid accepts a number of sugars that fail to elicit a feeding response in its herbivorous hosts is of particular interest to the use of (selective) food supplements in biological control programs.