Mixture Of D-glucose Research Articles

Density, dynamic viscosity, conductivity and refractive index for mixture D-glucose and deep eutectic solvent (choline chloride + urea) at different temperatures

ABSTRACT To convert carbohydrates into platform compounds, the deep eutectic solvent (DES) based on choline chloride and urea (molar ratio 1:2) was adopted as a green solvent. The physical properties of density, dynamic viscosity, conductivity and refractive index were determined for the mixture of D-glucose and DES including neat reline at a temperature from 293.15 K to 363.15 K at 101.3 kPa. The measured data of density, dynamic viscosity, conductivity and refractive index were correlated, respectively. Meanwhile, the molecular volume, standard molar entropy, lattice energy and free volume were calculated. The spectra of FTIR indicates that the hydrogen bond was changed in the mixture with increasing the content of D-glucose.

A novel aldose-aldose oxidoreductase for co-production of D-xylonate and xylitol from D-xylose with Saccharomyces cerevisiae.

An open reading frame CC1225 from the Caulobacter crescentus CB15 genome sequence belongs to the Gfo/Idh/MocA protein family and has 47 % amino acid sequence identity with the glucose-fructose oxidoreductase from Zymomonas mobilis (Zm GFOR). We expressed the ORF CC1225 in the yeast Saccharomyces cerevisiae and used a yeast strain expressing the gene coding for Zm GFOR as a reference. Cell extracts of strains overexpressing CC1225 (renamed as Cc aaor) showed some Zm GFOR type of activity, producing D-gluconate and D-sorbitol when a mixture of D-glucose and D-fructose was used as substrate. However, the activity in Cc aaor expressing strain was >100-fold lower compared to strains expressing Zm gfor. Interestingly, C. crescentus AAOR was clearly more efficient than the Zm GFOR in converting in vitro a single sugar substrate D-xylose (10 mM) to xylitol without an added cofactor, whereas this type of activity was very low with Zm GFOR. Furthermore, when cultured in the presence of D-xylose, the S. cerevisiae strain expressing Cc aaor produced nearly equal concentrations of D-xylonate and xylitol (12.5 g D-xylonate l−1 and 11.5 g D-xylitol l−1 from 26 g D-xylose l−1), whereas the control strain and strain expressing Zm gfor produced only D-xylitol (5 g l−1). Deletion of the gene encoding the major aldose reductase, Gre3p, did not affect xylitol production in the strain expressing Cc aaor, but decreased xylitol production in the strain expressing Zm gfor. In addition, expression of Cc aaor together with the D-xylonolactone lactonase encoding the gene xylC from C. crescentus slightly increased the final concentration and initial volumetric production rate of both D-xylonate and D-xylitol. These results suggest that C. crescentus AAOR is a novel type of oxidoreductase able to convert the single aldose substrate D-xylose to both its oxidized and reduced product.

Simultaneous uptake of lignocellulose‐based monosaccharides by Escherichia coli

Lignocellulosic waste is a naturally abundant biomass and is therefore an attractive material to use in second generation biorefineries. Microbial growth on the monosaccharides present in hydrolyzed lignocellulose is however associated with several obstacles whereof one is the lack of simultaneous uptake of the sugars. We have studied the aerobic growth of Escherichia coli on D-glucose, D-xylose, and L-arabinose and for simultaneous uptake to occur, both the carbon catabolite repression mechanism (CCR) and the AraC repression of xylose uptake and metabolism had to be removed. The strain AF1000 is a MC4100 derivative that is only able to assimilate arabinose after a considerable lag phase, which is unsuitable for commercial production. This strain was successfully adapted to growth on L-arabinose and this led to simultaneous uptake of arabinose and xylose in a diauxic growth mode following glucose consumption. In this strain, a deletion in the phosphoenolpyruvate:phosphotransferase system (PTS) for glucose uptake, the ptsG mutation, was introduced. The resulting strain, PPA652ara simultaneously consumed all three monosaccharides at a maximum specific growth rate of 0.59 h(-1) , 55% higher than for the ptsG mutant alone. Also, no residual sugar was present in the cultivation medium. The potential of PPA652ara is further acknowledged by the performance of AF1000 during fed-batch processing on a mixture of D-glucose, D-xylose, and L-arabinose. The conclusion is that without the removal of both layers of carbon uptake control, this process results in accumulation of pentoses and leads to a reduction of the specific growth rate by 30%.

Ion association of glycine, a-alanine and ß-alanine in water and water+ D-glucose mixtures at different temperatures

Ion association of glycine, a-alanine and ß-alanine in water and water+ D-glucose mixtures at different temperatures

Confirmation and Elimination of Xylose Metabolism Bottlenecks in Glucose Phosphoenolpyruvate-Dependent Phosphotransferase System-Deficient Clostridium acetobutylicum for Simultaneous Utilization of Glucose, Xylose, and Arabinose

Efficient cofermentation of D-glucose, D-xylose, and L-arabinose, three major sugars present in lignocellulose, is a fundamental requirement for cost-effective utilization of lignocellulosic biomass. The Gram-positive anaerobic bacterium Clostridium acetobutylicum, known for its excellent capability of producing ABE (acetone, butanol, and ethanol) solvent, is limited in using lignocellulose because of inefficient pentose consumption when fermenting sugar mixtures. To overcome this substrate utilization defect, a predicted glcG gene, encoding enzyme II of the D-glucose phosphoenolpyruvate-dependent phosphotransferase system (PTS), was first disrupted in the ABE-producing model strain Clostridium acetobutylicum ATCC 824, resulting in greatly improved D-xylose and L-arabinose consumption in the presence of D-glucose. Interestingly, despite the loss of GlcG, the resulting mutant strain 824glcG fermented D-glucose as efficiently as did the parent strain. This could be attributed to residual glucose PTS activity, although an increased activity of glucose kinase suggested that non-PTS glucose uptake might also be elevated as a result of glcG disruption. Furthermore, the inherent rate-limiting steps of the D-xylose metabolic pathway were observed prior to the pentose phosphate pathway (PPP) in strain ATCC 824 and then overcome by co-overexpression of the D-xylose proton-symporter (cac1345), D-xylose isomerase (cac2610), and xylulokinase (cac2612). As a result, an engineered strain (824glcG-TBA), obtained by integrating glcG disruption and genetic overexpression of the xylose pathway, was able to efficiently coferment mixtures of D-glucose, D-xylose, and L-arabinose, reaching a 24% higher ABE solvent titer (16.06 g/liter) and a 5% higher yield (0.28 g/g) compared to those of the wild-type strain. This strain will be a promising platform host toward commercial exploitation of lignocellulose to produce solvents and biofuels.

Transcriptional analysis of catabolite repression in Clostridium acetobutylicum growing on mixtures of d-glucose and d-xylose

Clostridium acetobutylicum is a strict anaerobic organism that is used for biotechnological butanol fermentation. It ferments various hexoses and pentoses to solvents but prefers glucose presumably using a catabolite repression mechanism. Accordingly during growth on a mixture of d-glucose and d-xylose a typical diauxic growth pattern was observed. We used DNA microarrays and real-time RT-PCR to study gene expression during growth on d-glucose, d-xylose mixtures on a defined minimal medium together with monitoring substrate consumption and product formation. We identified two putative operons involved in d-xylose degradation. The first operon (CAC1344–CAC1349) includes a transporter, a xylulose-kinase, a transaldolase, a transketolase, an aldose-1-epimerase and a putative xylose isomerase that has been annotated as an arabinose isomerase. This operon is induced by d-xylose but was catabolite repressed by d-glucose. A second operon (CAC2610–CAC2612) consists of a xylulose-kinase, a hypothetical protein and a gene that has been annotated as a l-fucose isomerase that might in fact code for a xylose isomerase. This operon was induced by d-xylose but was not subject to catabolite repression. In accordance with these results we identified a CRE site in the catabolite repressed operon but not in the operon that was not subject to catabolite repression.

Formation of Mutagenic/Carcinogenic Heterocyclic Amines under Moderate Conditions

More than 10 kinds of heterocyclic amines (HCAs), showing mutagenic and carcinogenic potency, have been isolated from cooked fish and meat. But many researchers say that the contribution ratio of HCAs to human cancer is very low. Our purpose in this experiment was to investigate the possibility of the formation of HCAs under moderate conditions, including in vivo. A mixture of d-glucose, creatinine, and amino acid such as glycine, methionine, threonine, and proline was dissolved in phosphate-buffered solution (pH7.4) and incubated at 37 degrees C, 50 degrees C, 128 degrees C. At an appropriate time, an aliquot of the reaction solution was treated with blue cotton. HCAs were separated from the blue cotton by elution with 2% ammoniacal methanol. The eluates were submitted to the Ames test, the micronucleus test for determination of mutagenicity, and also LC-MS analysis for the detection of HCAs. Nonadsorbates to blue cotton were treated with dichloromethane and then subjected to the mutagenicity test. In the Ames test, the mutagenic activity of the reaction mixture increased with an increase of the reaction temperature. The HCA fraction from 50 degrees C incubated solution showed high frequency in the micronucleus test using HepG2 cells. The dichloromethane fractions contained other type of mutagens different from HCAs. In HCA fractions, IQ, MeIQx, 4,8-DiMeIQx, and 7,8-DiMeIQ were identified. It is said that the heating process is an essential factor in the formation of HCAs. But our experiment shows that HCAs are produced not only in the cooking process, but also in moderate conditions such as 37 degrees C and 50 degrees C.

Improved xylanase production by Trichoderma reesei grown on l-arabinose and lactose or d-glucose mixtures

Trichoderma reesei Rut C-30 was grown on eight different natural or rare aldopentoses as the main carbon source and on mixtures of an aldopentose with D-glucose or lactose. The fungal cells consumed all aldopentoses tested, except L-xylose and L-ribose. The highest total xylanase and cellulase activities were achieved when cells were grown on L-arabinose as the main carbon source. The total xylanase activity produced by cells grown on L-arabinose was even higher than that produced by cells grown on an equal amount of lactose. In co-metabolism of D-glucose (15 g l(-1)) and L-arabinose (5 g l(-1)), the total volumetric and specific xylanase productivities were improved (derepressed) approximately 23- and 18-fold, respectively, compared to a cultivation on only D-glucose (20 g l(-1)). In a similar experiment, in which cells were grown on a mixture of lactose and L-arabinose, the xylanase productivity was approximately doubled, compared to a cultivation on only lactose. The cellulase productivities, however, were not improved by the addition of L-arabinose. Compared with a typical industrial fungal enzyme production process with lactose as the main carbon source, better volumetric and specific xylanase productivities were achieved both on a lactose/arabinose mixture and on a glucose/arabinose mixture.

Formation of mutagenic and carcinogenic heterocyclic amines in the model systems without heating

Cooked food-borne heterocyclic amines (HCAs) show strong mutagenic activity toward Salmonella typhimurium TA98 strain in the presence of metabolic activation system. They also induce several kinds of tumors in mice and rats. Among them, 2-amino-3, 4-dimethylaminoimidazo [4,5-f] quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) are also isolated from a reaction mixture consisting of d-glucose, amino acid and creatinine by heating at 128 °C for 2 h. There is no report on the formation of HCAs under mild conditions. In the present study, a mixture of d-glucose, glycine and creatinine was dissolved in 0.2 M phosphate buffer solution (pH7.4) and kept at 37 °C for 84 days. Aliquots of the reaction solution were treated with blue cotton and the adsorbates were extracted with NH4OH–MeOH mixture. By applying the extract to HPLC and LC-MS analysis, MeIQx was isolated and identified. When phenylalanine was used instead of glycine in the above model system, PhIP was formed. These results show that heating process is not essential for the formation of HCAs. Therefore, HCAs may be formed in our body tissues and in the long storage of manufactured foods.

Comparative study of the fermentation of D-glucose/D-xylose mixtures with Pachysolen tannophilus and Candida shehatae

We have performed a comparative analysis of the fermentation of the solutions of the mixtures of D-glucose and D-xylose with the yeasts Pachysolen tannophilus (ATCC 32691) and Candida shehatae (ATCC 34887), with the aim of producing bioethanol. All the experiments were performed in a batch bioreactor, with a constant aeration level, temperature of 30 °C, and a culture medium with an initial pH of 4.5. For both yeasts, the comparison was established on the basis of the following parameters: maximum specific growth rate, biomass productivity, specific rate of substrate consumption (qs) and of ethanol production (qE), and overall ethanol and xylitol yields. For the calculation of the specific rates of substrate consumption and ethanol production, differential and integral methods were applied to the kinetic data. From the experimental results, it is deduced that both Candida and Pachysolen sequentially consume the two substrates, first D-glucose and then D-xylose. In both yeasts, the specific substrate-consumption rate diminished over each culture. The values qs and qE proved higher in Candida, although the higher ethanol yield was of the same order for both yeasts, close to 0.4 kg kg−1.

Ethanol fermentation of mixed-sugars using a two-phase, fed-batch process: method to minimize D -glucose repression of Candida shehatae D -xylose fermentations

cells pre-grown on D-xylose simultaneously consumed mixtures of D-xylose and D-glucose, under both non-growing (anoxic) and actively growing conditions (aerobic), to produce ethanol. The rate of D-glucose consumption was independent of the D-xylose concentration for cells induced on D-xylose. However, the D-xylose consumption rate was approximately three times lower than the D-glucose consumption rate at a 50% D-glucose: 50% D-xylose mixture. Repression was not observed (substrate utilization rates were approximately equal) when the percentage of D-glucose and D-xylose was changed to 22% and 78%, respectively. In fermentations with actively growing cells (50% glucose and D-xylose), ethanol yields from D-xylose increased, the % D-xylose utilized increased, and the xylitol yield was significantly reduced in the presence of D-glucose, compared to anoxic fermentations (YETOH,xylose = 0.2–0.40 g g−1, 75–100%, and Yxylitol = 0–0.2 g g−1 compared to YETOH,xylose = 0.15 g g−1, 56%, Yxylitol = 0.51 g g−1, respectively). To increase ethanol levels and reduce process time, fed-batch fermentations were performed in a single stage reactor employing two phases: (1) rapid aerobic growth on D-xylose (μ = 0.32 h−1) to high cell densities; (2) D-glucose addition and anaerobic conditions to produce ethanol (YETOH,xylose = 0.23 g g−1). The process generated high cell densities, 2 × 109 cells ml−1, and produced 45–50 g L−1 ethanol within 50 h from a mixture of D-glucose and D-xylose (compared to 30 g L−1 in 80 h in the best batch process). The two-phase process minimized loss of cell viability, increased D-xylose utilization, reduced process time, and increased final ethanol levels compared to the batch process.

Molecular cloning and functional expression in lactobacillus plantarum 80 of xylT, encoding the D-xylose-H+ symporter of Lactobacillus brevis.

A 3-kb region, located downstream of the Lactobacillus brevis xylA gene (encoding D-xylose isomerase), was cloned in Escherichia coli TG1. The sequence revealed two open reading frames which could code for the D-xylulose kinase gene (xylB) and another gene (xylT) encoding a protein of 457 amino acids with significant similarity to the D-xylose-H+ symporters of E. coli, XylE (57%), and Bacillus megaterium, XylT (58%), to the D-xylose-Na+ symporter of Tetragenococcus halophila, XylE (57%), and to the L-arabinose-H+ symporter of E. coli, AraE (60%). The L. brevis xylABT genes showed an arrangement similar to that of the B. megaterium xylABT operon and the T. halophila xylABE operon. Southern hybridization performed with the Lactobacillus pentosus xylR gene (encoding the D-xylose repressor protein) as a probe revealed the existence of a xylR homologue in L. brevis which is not located with the xyABT locus. The existence of a functional XylR was further suggested by the presence of xylO sequences upstream of xylA and xylT and by the requirement of D-xylose for the induction of D-xylose isomerase, D-xylulose kinase, and D-xylose transport activities in L. brevis. When L. brevis was cultivated in a mixture of D-glucose and D-xylose, the D-xylose isomerase and D-xylulose kinase activities were reduced fourfold and the D-xylose transport activity was reduced by sixfold, suggesting catabolite repression by D-glucose of D-xylose assimilation. The xylT gene was functionally expressed in Lactobacillus plantarum 80, a strain which lacks proton motive force-linked D-xylose transport activity. The role of the XylT protein was confirmed by the accumulation of D-xylose in L. plantarum 80 cells, and this accumulation was dependent on the proton motive force generated by either malolactic fermentation or by the metabolism of D-glucose. The apparent affinity constant of XylT for D-xylose was approximately 215 microM, and the maximal initial velocity of transport was 35 nmol/min per mg (dry weight). Furthermore, of a number of sugars tested, only 6-deoxy-D-glucose inhibited the transport of D-xylose by XylT competitively, with a Ki of 220 microM.

Spore Germinability of Bacillus coagulans and Acidophile Bacillus spp. Isolated from PET-bottled Tea and Juices.

We examined the optimal conditions for germination of the spores of Bacillus coagulans and an acidophile Bacillus spp isolated from PET-bottled drinks on the market containing Japanese tea or orange or apple juice. Among the spores of B. coagulans BUB strains, isolated from Japanese tea, BUB46 germinated effectively at an acidic pH in a mixture of D-glucose plus KNO3 (G+K), and in a mixture of L-asparagine, D-glucose, D-fructose and KCI (AGFK) at 45 or 53°C, but not by L-alanine. The spores of BUB130 germinated in a mixture containing G+K, AGFK or L-alanine, and BUB44 spores also germinated most effectively in an acidic solution of AGFK. Pretreatment of the BUB44 spores with 1/16N NaOH stimulated germination, but that with 1% sodium dodecyl sulfate plus 5 mM dithiothreitol did not. The spores of an acidophile Bacillus spp. isolated from fruit juice germinated at pH 3.0 in a mixture containing G + K, AGFK, L-alanine or potato dextrose.

Structure-activity relationship of lepidimoide and its analogues

The structure-activity relationship of lepidimoide and its analogues was investigated by means of the Amaranthus caudatus L. hypocotyl elongation test. In addition, the activities of α- d-galacturonic acid and l-(+)-rhamnose, which are component sugars of lepidimoide, were also studied. The carboxylic acid free type of lepidimoide showed growth-promoting activity as high as the original lepidimoide (sodium type). The acetylated compound showed considerably higher activity than lepidimoide, whereas the methylated lepidimoide did not show any activity. The hydroxylated lepidimoide without a double bond in the C-4,5 position showed lower activity. The sugar alcohol type of lepidimoide [ 2-O-(α- d-glucopyranosyl )- l-rhamnose ] showed the highest activity in all the compounds studied. α- d-Galacturonic acid, l-(+)-rhamnose and their mixtures, which are component sugars of lepidimoide, exhibited only slight or no activity, respectively. d-Glucose and the mixture of d-glucose and l-(+)-rhamnose were also slightly active or inactive. These data suggest that the active sites in the chemical structure of the lepidimoide are the uronic acid derivative bearing an α,β-unsaturated carboxylate bonded to rhamnose via an α-glucoside linkage and a double bond in the C-4,5 position in the uronic acid.

Synthesis of membranes having a saccharide side chain and their optical resolution properties for d-/l- glucose mixtures

The objective of the present investigation is to synthesize new polymeric membranes having a saccharide in the side chain and to clarify the specific affinity of the saccharide chains. During this study chloromethylated polysulfone (CM-PSF), poly(chloromethylated styrene) (P-CM-St), poly(methyl methacrylate) (PMMA), and chlororethylated poly(γ -methyl L-glutamate) (CE-PMLG) as synthetic polymers along with an equal mixture of α-D-2-deoxy-2-aminoglucopyranosyl-(1'6) -D-sorbitol and mannitol (AGP) as saccharides were used. PMMA+AGP and CE-PMLG+AGP membranes showed the highest permeability of D-glucose in sugars (molecular weight = 180.16), although the CM-PSP+AGP and P-CM-St+AGP membranes showed less permeability. The reason for the high permeability of D-glucose is the high partition coefficient of D-glucose, which may come from an interaction between the AGP terminating D-glucose structure and D-glucose as the solute. The optical resolution could be done by the difference between the D- and L-glucose permeation rates from an equimolar mixture of D-glucose and L-glucose.

D-Xylose Utilization by Saccharomyces cerevisiae

Although it is generally accepted that Saccharomyces cerevisiae is unable to assimilate D-xylose, four strains were found to utilize xylose aerobically at different efficiencies in the presence of a mixture of substrates. The degree of D-xylose utilization by S. cerevisiae ATCC 26602 depended upon the presence of other substrates or yeast extract. The greatest amount of xylose (up to 69% over 7 d) was utilized when sugar substrates such as D-ribose were co-metabolized. Much lower degrees of utilization occurred with co-metabolism of organic acids, polyols or ethanol. A mixture of D-glucose, D-ribose, D-raffinose, glycerol and D-xylose resulted in greater xylose utilization than the presence of a single substrate and xylose. The absence of growth on a co-substrate alone did not prevent the utilization of xylose in its presence. Xylose was co-metabolized with ribose under anaerobic conditions but at a much slower rate than under aerobic conditions. When [14C]xylose was utilized in the presence of ribose under anaerobic conditions, the radioactive label was detected mainly in xylitol and not in the small amounts of ethanol produced. Under aerobic conditions the radioactive label was distributed between xylitol (91.3 +/- 0.8%), CO2 (2.6 +/- 2.3%) and biomass (1.7 +/- 0.6%). No other metabolic products were detected. Whereas most xylose was dissimilated rather than assimilated by S. cerevisiae, the organism apparently possesses a pathway which completely oxidizes xylose in the presence of another substrate.

Molecular Recognition of Aldoses Using [Ni(R, R- or S, S-cxhn)3]Br2. 3H20 (chxn=1, 2-cyclohexanediamine)

[Ni(R, R- or S, S- chxn)2]Br2.3 H20(abbreviated to [R, R] or [S, S]) reacts with certain aldoses in methanol to yield octahedral Ni(II) paramagnetic complexes [Ni(aldose-chxn)2]Br2containing two N-glycosides, where chxn is 1, 2-cyclohexanediamine. This reaction is sensitive to the absolute configuration on C2 of aldoses. In most cases, [R, R] reacts preferentially with aldoses having S configuration on their C2 atom, and [S, S] with corresponding C2-epimer having R configuration. Aldoses are easily recovered from the complexes by the treatment of slightly acidic aqueous solutions. Therefore, this reaction can be utilized for molecular recognition and separation of certain sugars. The 1:1 mixture of D-glucose and D-mannose which are mutual C2-epimers reacted with [R, R] in methanol to yield blue complex which contained only D-mannose. In other cases there occurred partial separation in a mixture of C2-epimers. This selectivity was discussed in terms of the stereochemical features of these complexes. As previously observed in N-glycoside complexes derived from en or tn (en=ethylenediamine, tn=trimethylenediamine), these N-glycosides which have been derived from chxn is also expected to coordinate with a Ni(II) ion stably as a tridentate ligand in meridional form. When the coordination was achieved in meridional form, these tridentate ligands containing two five-membered chelate rings linked with a glycoside nitrogen, will take its most stable form in such a way as one chelate ring is δ-gauche, and the other is λ. These stereochemical features seem to be very important to the molecular recognition of aldoses.

Hydrogenation of d-fructose and d-fructose/ d-glucose mixtures

d-Fructose and d-fructose/ d-glucose mixtures have been hydrogenated in water at 60–80° and 20–75 atm. of hydrogen with Ni, Cu, Ru, Rh, Pd, Os, Ir, and Pt severally as catalysts. The selectivity for the formation of d-mannitol from d-fructose as well as the selectivity for the hydrogenation of d-fructose in the presence of d-glucose with Cu/silica as the catalyst are substantially higher than those for the other catalysts. With Cu/silica as the catalyst, the hydrogenation of d-fructose is first order with respect to the amount of catalyst and the hydrogen pressure, whereas a shift from first- to zero-order kinetics occurs on going from low (<0.3 m) to high (0.8 m) concentrations of d-fructose. d-Fructose is preferentially hydrogenated via its furanose forms, presumably by attack of a copper hydride-like species at the anomeric carbon atom with inversion of configuration. Preferential adsorption of pyranose with respect to furanose forms occurs, whereas the furanose forms show a much higher reactivity. The mechanism proposed for the copper-catalysed hydrogenation reaction explains both the enhanced yield of d-mannitol from boric esters of d-fructose and the diastereoselectivity of the hydrogenation of seven other ketoses.

A cybernetic view of microbial growth: Modeling of cells as optimal strategists

A cybernetic framework is presented which views microbial response in multiple substrate environments as a judicious investment of cellular resources in synthesizing different key proteins according to an optimal regulatory strategy. A mathematical model is developed within the cybernetic framework for the diauxic growth of Klebsiella pneumoniae on a mixture of D-glucose and D-xylose. The "bang-bang" optimal policy describes well the experimental observations obtained using a fermenter coupled to an Apple II microcomputer. Striking variations in respiratory levels are observed experimentally during the switching of the cell's adaptive machinery for the utilization of the less preferred substrate.

Complexes of carbohydrates with aluminate ion. Chromatography of carbohydrates on columns of anion-exchange resin (aluminate form)

With water as sole eluant, the retention volumes for carbohydrates on an aluminate-resin column generally decrease in the order: ketoses>aldoses>alditols>methyl glycosides; retention increases with molecular size. Both aluminate ion and hydroxide ion contribute to the chromatographic properties of an aluminate resin. To avoid alkaline degradation and interconversion, which can occur extensively at 25°, chromatography of reducing sugars must be performed both rapidly and at low temperature. A mixture of d-glucose and d-fructose can be completely separated on a short aluminate column.