A novel phenolic acid derivative from buds of Populus lasiocarpa

The lipophilic excretion of winter buds of Populus lasiocarpa in contrast to most other species of the genus does not contain flavonoid aglycones. One of the compounds which are excreted in this plant now could be isolated and identified by chemical methods (hydrolysis, hydrogenation) and spectral analysis (UV, IR, NMR, MS) to be 1,3-p-coumaryl-2-acetyl-glycerol.     

Anionic carbohydrate-containing cell wall polymers of <Emphasis Type="Italic">Streptomyces melanosporofaciens</Emphasis> and related species

The structures of cell wall anionic carbohydrate-containing polymers in Streptomyces melanosporofaciens VKM Ac-1864^T and phylogenetically close organisms—S. hygroscopicus subsp. hygroscopicus VKM Ac-831^T, S. violaceusniger VKM Ac-583^T, S. endus VKM Ac-1331^T, S. endus VKM Ac-129, and S. rutgersensis subsp. castelarensis VKM Ac-832^T—have been comparatively studied by chemical and NMR spectroscopic methods. The natural polymer of a new, previously unknown structure, Kdn (3-deoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid) with β-galactose residues at C-9, has been found in the cell walls of all the strains under study. The cell walls of all the studied organisms contain three teichoic acids (TA): a predominant TA (1,3-poly(glycerol phosphate) with N-acetylated α-glucosaminyl substitutes by C-2 of glycerol, and minor TAs, 1,3-and 2,3-poly(glycerol phosphate) polymers without substitution. Their chains have O-acetyl and O-lysyl groups. Microorganisms of the above-mentioned species differ in the number of α-glucosaminyl substitutes and in the degree of their acetylation in the predominant teichoic acid.     

A similarity in the O-acetylation pattern of the O-antigens of Shigellaflexneri types 1a, 1b, and 2a

Shigella flexneri type 2a is the first, and type 1b is the second, most prevalent isolates from patients with shigellosis in Russia. The O-specific polysaccharides (OPSs, O-antigens) of S. flexneri types 1-5 possess a common →2)-α-l-RhapIII-(1→2)-α-l-RhapII-(1→3)-α-l-RhapI-(1→3)-β-d-GlcpNAc-(1→ backbone and differ from each other in its glucosylation or/and O-acetylation at various positions, the modifications being responsible for various O-factors. It was suggested that O-factor 6 expressed by type 1b is associated with O-acetylation of RhaI at position 2 but more than one O-acetyl group has been detected in the type 1b OPS [Kenne, L. et al. Eur. J. Biochem.1978, 91, 279-284]. In this work, O-acetylation of RhapI in the type 1b OPS was confirmed by NMR spectroscopy and location of an additional O-acetyl group at position either 3 (major) or 4 (minor) of RhapIII was determined. Type 1a differs from type 1b in the lack of O-acetylation of RhapI only. In type 2a, in addition to two reported major O-acetyl groups at position 6 of GlcNAc and position 3 of RhapIII [Kubler-Kielb, J. et al. Carbohydr. Res.2007, 342, 643-647], a minor O-acetyl group was found at position 4 of RhaIII. Therefore, RhapIII is O-acetylated in the same manner in all three S. flexneri serotypes studied.     

Enzymatic synthesis of 1,3-dihydroxyphenylacetoyl-sn-glycerol: Optimization by response surface methodology and evaluation of its antioxidant and antibacterial activities

In this study, the enzymatic synthesis of phenylacetoyl glycerol ester was carried out as a response to the increasing consumer demand for natural compounds. 1,3-dihydroxyphenylacetoyl-sn-Glycerol (1,3-di-HPA-Gly), labeled as “natural” compound with interesting biological properties, has been successfully synthesized for the first time in good yield by a direct esterification of glycerol (Gly) with p-hydroxyphenylacetic acid (p-HPA) using immobilized Candida antarctica lipase as a biocatalyst. Spectroscopic analyses of purified esters showed that the glycerol was mono- or di-esterified on the primary hydroxyl group. These compounds were evaluated for their antioxidant activity using two different tests. The glycerol di-esters (1,3-di-HPA-Gly) showed a higher antiradical capacity than that of the butyl hydroxytoluene. Furthermore, compared to the p-HPA, synthesized ester (1,3-di-HPA-Gly) exhibited the most antibacterial effect mainly against Gram + bacteria. Among synthesized esters the 1,3-di-HPA-Gly was most effective as antioxidant and antibacterial compound. These findings could be the basis for a further exploitation of the new compound, 1,3-di-HPA-Gly, as antioxidant and antibacterial active ingredient in the cosmetic and pharmaceutical fields.     

Conformational differences between sn-3-phospholipids and sn-2-phospholipids. A neutron and x-ray diffraction investigation

Extensive work has been reported on the conformation in membranes of sn-3-phosphatidylcholines, -ethanolamines, -glycerols and -serines (sn-3-phospholipids), where the headgroup is linked to the third carbon atom in the glycerol backbone. One important feature common to all these naturally occurring phospholipids is that the glycerol moiety is oriented almost perpendicular to the membrane surface, with the sn-1 chain continuing in this direction, whereas the sn-2 chain starts first in a direction parallel to the layer and then bends sharply at the second carbon atom. We present here neutron diffraction results on 1,3-dipalmitoyl-glycero-2-phosphocholine (1,3-DPPC) in which the headgroup is attached to the second carbon atom in the middle of the glycerol part and the two other adjacent carbon atoms are linked to the paraffin chains. Two 1,3-DPPC samples. ²H-labelled at different positions, were studied. One sample was deuterated at the first methylene segment in each fatty acyl chain, and the other at the first segment in one chain and at the second segment in the other chain. The Patterson maps as well as the neutron density profiles show that both fatty acyl chains in 1,3-DPPC have the same conformation introduced by this symmetric chemical bond pattern. It is concluded from this that the C₍₁₎C₍₃₎ vector of the glycerol backbone part is oriented parallel to the bilayer surface and the ²H nuclear magnetic resonance signals indicate that both chains have a conformation similar to that observed for the bent chain in sn-3-phospholipids. These findings indirectly confirm the idea that an intramolecular energy minimum, together with the packing geometry of the lipids in the membrane, produce the characteristic conformation around the glycerol backbone as is found for all naturally occurring phospholipids that have been studied so far.     

Evolutionary and Functional Relationships of the dha Regulon by Genomic Context Analysis

3-hydroxypropionaldehyde (3-HPA) and 1,3-propanediol (1,3-PD) are subproducts of glycerol degradation and of economical interest as they are used for polymers synthesis, such as polyesters and polyurethanes. Some few characterized bacterial species (mostly from Firmicutes and Gamma-proteobacteria groups) are able to catabolize these monomers from glycerol using the gene products from the dha regulon. To expand our knowledge and direct further experimental studies on the regulon and related genes for the anaerobic glycerol metabolism, an extensive genomic screening was performed to identify the presence of the dha genes in fully sequenced prokaryotic genomes. Interestingly, this work shows that although only few bacteria species are known to produce 3-HPA or 1,3-PD, the incomplete regulon is found in more than 100 prokaryotic genomes. However, the complete pathway is found only in a few dozen species belonging to five different taxonomic groups, including one Archaea species, Halalkalicoccus jeotgali. Phylogenetic analysis and conservation of both gene synteny and primary sequence similarity reinforce the idea that these genes have a common origin and were possibly acquired by lateral gene transfer (LGT). Besides the evolutionary aspect, the identification of homologs from several different organisms may predict potential alternative targets for faster or more efficient biological synthesis of 3-HPA or 1,3-PD.     

Catabolism and disposition of exogenous 5-hydroxytryptamine in cockroach,Periplaneta americana,tissues

The concentrations of tryptophan, 5-hydroxytryptophan, 5-hydroxytryptamine, N-acetyl 5-hydroxytryptamine and N-acetyl dopamine were determined in the cerebral ganglia, haemolymph and Malpighian tubules of the cockroach Periplaneta americana, using high performance liquid chromatography with electrochemical detection. Injected 5-hydroxytryptamine was rapidly removed from the haemolymph with a concomitant elevation of circulating N-acetyl 5-hydroxytryptamine and little accumulation of 5-hydroxytryptamine in the cerebral ganglia. N-acetyl 5-hydroxytryptamine and N-acetyl dopamine were also rapidly removed from the haemolymph. Incubation of haemolymph from 5-hydroxytryptamine-injected insects and glucosidase or phosphatase, indicated that most of the injected 5-hydroxytryptamine had been converted to a sugar conjugate of N-acetyl 5-hydroxytryptamine. Whole haemolymph did not catabolize 5-hydroxytryptamine or N-acetyl 5-hydroxytryptamine whereas Malpighian tubules N-acetylated both 5-hydroxytryptamine and dopamine and metabolized N-acetyl 5-hydroxytryptamine. Injection of p-chlorophenylalanine (200 and 500 μg/g) had no effect on 5-hydroxytryptamine concentrations in the cockroach cerebral ganglia.     

Regulation of cardiolipin biosynthesis by fatty acid transport protein-1 IN HEK 293 cells

Cardiolipin (CL) is a major phospholipid involved in energy metabolism mammalian mitochondria and fatty acid transport protein-1 (FATP-1) is a fatty acid transport protein that may regulate the intracellular level of fatty acyl-Coenzyme A's. Since fatty acids are required for oxidative phosphorylation via mitochondrial oxidation, we examined the effect of altering FATP-1 levels on CL biosynthesis. HEK-293 mock- and FATP-1 siRNA transfected cells or mock and FATP-1 expressing cells were incubated for 24 h with 0.1 mM oleic acid bound to albumin (1:1 molar ratio) then incubated for 24 h with 0.1 mM [1,3-³H]glycerol and radioactivity incorporated into CL determined. FATP-1 siRNA transfected cells exhibited reduced FATP-1 mRNA and increased incorporation of [1,3-³H]glycerol into CL (2-fold, p < 0.05) compared to controls indicating elevation in de novo CL biosynthesis. The reason for this was an increase in [1,3-³H]glycerol uptake and increase in activity and mRNA expression of the CL biosynthetic enzymes. In contrast, expression of FATP-1 resulted a reduction in incorporation of [1,3-³H]glycerol into CL (65%, p < 0.05) indicating reduced CL synthesis. [1,3-³H]Glycerol uptake was unaltered whereas activity of cytidine-5′-diphosphate-1,2-diacyl-sn-glycerol synthetase (CDS) and CDS-2 mRNA expression were reduced in FATP-1 expressing cells compared to control. In addition, in vitro CDS activity was reduced by exogenous addition of oleoyl-Coenzyme A. The data indicate that CL de novo biosynthesis may be regulated by FATP-1 through CDS-2 expression in HEK 293 cells.     

Construction of glycerol synthesis pathway in <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> for bioconversion of glucose into 1,3-propanediol

1,3-Propanediol (1,3-PDO) is an important three-carbon compound widely used in new polyester polymer materials. Natural organisms that can produce 1,3-PDO from glycerol were well studied. However, no natural microorganisms found could directly convert glucose to 1,3-PDO due to its insufficient glycerol synthesis pathway. In this study, two essential glycerol synthesis genes, CgGPD gene (encoding glycerol-3-phosphate dehydrogenase from Candida glycerinogenes) and ScGPP2 gene (encoding glycerol-3-phosphatase from Saccharomyces cerevisiae), were expressed in wild-type Klebsiella pneumoniae, a natural 1,3-PDO producers with reduction pathway for 1,3-PDO synthesis from glycerol. The results of fermentation, key enzyme activities, and metabolites analysis confirmed that recombinant K. pneumoniae now possessed a metabolic pathway capable of converting glucose to 1,3-PDO. The strain could produce 1,3-PDO from glucose with a final titer of 17.27 g/L with 40 g/L glucose in the medium, showing a 1.26-fold increase compared with 30 g/L glucose. Also, adding certain concentrations of glycerol could quickly initiate the 1,3-PDO synthetic pathway and promote the accumulation of 1,3-PDO, which could shorten the fermentation cycle. These results have important implications for further studies involving the use of one strain for bioconversion of glucose to 1,3-PDO.     

System Development for Linked-Fermentation Production of Solvents from Algal Biomass

Five species of the genus Dunaliella (D. tertiolecta, D. primolecta, D. parva, D. bardawil, and D. salina) were examined for glycerol accumulation, growth rate, cell density, and protein and chlorophyll content. The suitability of each algal species for use as a fermentation substrate was judged according to glycerol accumulation and quantities of neutral solvents produced after sequential bacterial fermentations. When grown in 2 M NaCl, with 24 mM NaHCO₃ or 3% CO₂ at 28°C and with 10,000 to 15,000 lx of incident light on two sides of a glass aquarium, four of the five species tested produced ca. 10 to 20 mg of glycerol per liter of culture. Clostridium pasteurianum was found to convert an algal biomass mixture supplemented with 4% glycerol to ca. 16 g of mixed solvents (n-butanol, 1,3-propanediol, and ethanol) per liter. Acetone was not detected. Additionally, it has been demonstrated that Dunaliella concentrates of up to 300-fold can be directly fermented to an identical pattern of mixed solvents. Overall solvent yields were reduced by >50% when fermentations were performed in the presence of 2% NaCl. These results are discussed in terms of practical application in tropical coastal zones.     

Sensitivity to vinyl phenol derivatives produced by phenolic acid decarboxylase activity in Escherichia coli and several food-borne Gram-negative species

Ferulic, p-coumaric, and caffeic acids are phenolic acids present in soil, food, and gut, which have antimicrobial effects. Some Gram (+) bacteria metabolize these phenolic acids into vinyl derivatives due to phenolic acid decarboxylase activity (PAD) involved in the phenolic acid stress response (PASR). In this study, the antimicrobial activity of phenolic acids and their vinyl derivatives was tested on a panel of desirable and undesirable food-borne bacteria, especially Gram (?) species of Salmonella, Enterobacter, Klebsiella, and Pseudomonas, most of them without PAD activity. Native and engineered Escherichia coli strains either expressing or not PAD activity were included. Gram (?) bacteria of the panel were not significantly inhibited by phenolic acids at 3 mM, but were dramatically inhibited by the corresponding vinyl derivatives. On the contrary, Gram (+) bacteria displaying the PASR face the toxicity of phenolic acids by PAD activity and are not inhibited by vinyl phenols. In E. coli, the genes aaeB and marA, encoding efflux pumps for antimicrobial compounds, are upregulated by the addition of p-coumaric acid, but not by its derivative 4-vinyl phenol (p-hydroxystyrene). These results suggest that phenolic acids and their vinyl phenol derivatives produced by PAD (+) species could have a significant impact on undesirable or pathogenic food-borne Gram (?) bacteria in complex microbial ecosystems.     

New structures and composition of cell wall teichoic acids from Nocardiopsis synnemataformans,Nocardiopsis halotolerans,Nocardiopsis composta and Nocardiopsis metallicus: a chemotaxonomic value

The structures of the cell wall teichoic acids (TA) from some species of the genus Nocardiopsis were established by chemical and NMR spectroscopic methods. The cell walls of Nocardiopsis synnemataformans VKM Ac-2518^T and Nocardiopsis halotolerans VKM Ac-2519^T both contain two TA with unique structures—poly(polyol phosphate-glycosylpolyol phosphate)—belonging to the type IV TA. In both organisms, the minor TA have identical structures: poly(glycerol phosphate-N-acetyl-β-galactosaminylglycerol phosphate) with the phosphodiester bond between C-3 of glycerol and C-4 of the amino sugar. This structure is found for the first time. The major TA of N. halotolerans has a hitherto unknown structure: poly(glycerol phosphate-N-acetyl-β-galactosaminylglycerol phosphate), the N-acetyl-β-galactosamine being acetalated with pyruvic acid at positions 4 and 6. The major TA of N. synnemataformans is a poly(glycerol phosphate-N-acetyl-β-galactosaminylglycerol phosphate) with the phosphodiester bond between C-3 of glycerol and C-3 of the amino sugar. The cell walls of Nocardiopsis composta VKM Ac-2520 and N. composta VKM Ac-2521^T contain only one TA, namely 1,3-poly(glycerol phosphate) partially substituted with N-acetyl-α-glucosamine. The cell wall of Nocardiopsis metallicus VKM Ac-2522^T contains two TA. The major TA is 1,5-poly(ribitol phosphate), each ribitol unit carrying a pyruvate ketal group at positions 2 and 4. The structure of the minor TA is the same as that of N. composta. The results presented correlate well with the phylogenetic grouping of strains and confirm the species and strain specific features of cell wall TA in members of the genus Nocardiopsis.     

Microbial Conversion of Glycerol to 1,3-Propanediol: Physiological Comparison of a Natural Producer, Clostridium butyricum VPI 3266, and an Engineered Strain, Clostridium acetobutylicum DG1(pSPD5)

Clostridium acetobutylicum is not able to grow on glycerol as the sole carbon source since it cannot reoxidize the excess of NADH generated by glycerol catabolism. Nevertheless, when the pSPD5 plasmid, carrying the NADH-consuming 1,3-propanediol pathway from C. butyricum VPI 3266, was introduced into C. acetobutylicum DG1, growth on glycerol was achieved, and 1,3-propanediol was produced. In order to compare the physiological behavior of the recombinant C. acetobutylicum DG1(pSPD5) strain with that of the natural 1,3-propanediol producer C. butyricum VPI 3266, both strains were grown in chemostat cultures with glycerol as the sole carbon source. The same “global behavior” was observed for both strains: 1,3-propanediol was the main fermentation product, and the qH₂ flux was very low. However, when looking at key intracellular enzyme levels, significant differences were observed. Firstly, the pathway for glycerol oxidation was different: C. butyricum uses a glycerol dehydrogenase and a dihydroxyacetone kinase, while C. acetobutylicum uses a glycerol kinase and a glycerol-3-phosphate dehydrogenase. Secondly, the electron flow is differentially regulated: (i) in C. butyricum VPI 3266, the in vitro hydrogenase activity is 10-fold lower than that in C. acetobutylicum DG1(pSPD5), and (ii) while the ferredoxin-NAD⁺ reductase activity is high and the NADH-ferredoxin reductase activity is low in C. acetobutylicum DG1(pSPD5), the reverse is observed for C. butyricum VPI 3266. Thirdly, lactate dehydrogenase activity is only detected in the C. acetobutylicum DG1(pSPD5) culture, explaining why this microorganism produces lactate.     

Chemotaxonomic contribution to the Sideritis species dilemma on the Balkans

Forty-two samples of Sideritis species (Sideritis scardica, Sideritis raeseri, Sideritis syriaca, Sideritis taurica and Sideritis lanata) from the Balkan Peninsula were evaluated for their polyphenolic profiles in order to establish a correlation between the taxonomy, geographical location and nature and content of phenolic compounds.Eight compounds were detected in all analyzed Sideritis samples: 5-caffeoylquinic acid, lavandulifolioside, verbascoside, isoscutellarein 7-O-allosyl(1→2)glucoside, hypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside, isoscutellarein 7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside, 3′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl(1→2)glucoside and 4′-O-methylhypolaetin 7-O-[6‴-O-acetyl]-allosyl-(1→2)-[6″-O-acetyl]-glucoside). They present from 50 to 80% of total phenolic content in S. scardica, S. raeseri, S. syriaca and S. taurica and up to 90% in S. lanata and the similarity of their polyphenolic profiles implies that they are systematically very closely related.Based on their polyphenolic patterns, very good differentiation between the samples of S. lanata (sect. Hesiodia) and S. scardica, S. syriaca and S. raeseri (sect. Empedoclia) was observed, that is mainly due to the very high content of 5-cafeoylquinic acid and very low amount of phenylethanoid glycosides and flavonoid glycosides.The obtained results demonstrate considerable degree of similarity between S. scardica, S. raeseri and Bulgarian S. syriaca that give contribution to the dilemma that Bulgarian S. syriaca is very similar to Turkish S. taurica and suggest further verification of its taxonomic status.     

Synthesis of two isomeric methyl β-D-xylotriosides containing a (1→2)-β-linkage

Partial hydrolysis with acid, methylation analysis (including uronic acid degradation), Smith degradation, and p.m.r. spectroscopy have been used to determine the primary structure of the capsular polysaccharide of Klebsiella serotype k64. The hexasaccharide repeating-unit, which also contains one O-acetyl substituent, comprises a 4)-α-d-GlcpA-(1 → 3)-α-d-Manp-(1 → 3)-β-d-Glcp-(1 → 4)-α-d-Manp-(1 → chain with a 4,6-O-(l-carboxyethylidene)-β-d-glucopyranosyl and an l-rhamnosyl group attached to the 4-linked d-mannosyl residue at O-2 and O-3, respectively.     

Identification of 2-O (indole-3-acetyl)-D-glucopyranose, 4-O-(indole-3-acetyl)-D-glucopyranose and 6-O-(indole-3-acetyl)-D-glucopyranose from kernels of Zea mays by gas-liquid chromatography-mass spectrometry

New esters of indole-3-acetic acid and d-glucose have been isolated from mature sweet-corn kernels of Zea mays. The esters were resolved by t.l.c. into two fractions having R_F values distinct from that of authentic 1-O-(indole-3-acetyl)-β-d-glucopyranose. Analysis of the trimethylsilyl ethers of the two fractions by combined gas-liquid chromatography-mass spectrometry (g.l.c.-m.s.) showed that the esters have a free carbonyl group. Labeling of the carbonyl carbon atom with an O-methyloxime group, and analysis of the O-trimethylsilyl O-methyloxime derivatives by g.l.c.-m.s. permitted the new compounds to be identified as a mixture of 2-O-(indole-3-acetyl)-d-glucopyranose, 4-O-(indole-3-acetyl)-d-glucopyranose, and 6-O-(indole-3-acetyl)-d-glucopyranose.     

Cell wall teichoic acids of Bacillus licheniformis VKM B-511T, Bacillus pumilus VKM B-508T, and other strains previously assigned to Bacillus pumilus

The teichoic acids (TAs) of type strains, viz. Bacillus licheniformis VKM B-511^T and Bacillus pumilus VKM B-508^T, as well as phylogenetically close bacteria VKM B-424, VKM B-1554, and VKM B-711 previously assigned to Bacillus pumilus on the basis of morphological, physiological, and biochemical properties, were investigated. Three polymers were found in the cell wall of each of the 5 strains under study. Strains VKM B-508^T, VKM B-424, and VKM B-1554 contained polymers of the same core: unsubstituted 1,3-poly(glycerol phosphate) (TA I) and 1,3-poly(glycerol phosphate) with O-D-Ala and N-acetyl-??-D-glucosamine substituents (TA II and TA III??, respectively). The cell walls of two remaining strains contained TA I, TA II, and a poly(glycosylpolyol phosphate) with the following structure of repeating units: -6)-??-D-GlcpNAc(1??1)-snGro-(3-P-(TA III?) in ??Bacillus pumilus?? VKM B-711 (100% 16S rRNA gene similarity with the type strain of Bacillus safensis) and -6)-??-D-Galp-(1??2)-snGro-(3-P-(TA III?) in Bacillus licheniformis VKM B-511^T. The simultaneous presence of three different TAs in the cell walls was confirmed by the NMR spectroscopic DOSY methods. The structure of the polymers and localization of O-D-Ala residues were investigated by the chemical and NMR spectroscopic methods.     

Isolation of 2,5-anhydro-1,3-O-isopropylidene-6-O-trityl-D-glucitol and conformations of its 4-O-substituted and deprotected,acylated derivatives

Acidic dehydration of D-mannitol (1) gave a mixture of anhydrides (2) that was isopropylidenated and subsequently tritylated. A single component crystallized from the resulting mixture and was shown to be the novel 2,5-anhydro-1,3-O-isopropylidene-6-O-trityl-D-glucitol (4) by chemical and physical analysis and by comparison of its deprotected, dibenzoylated derivative (10) with authentic 2,5-anhydro-1,6-di-O-benzoyl-D-glucitol. Acid hydrolysis of 4 afforded pure 2,5-anhydro-D-glucitol (9) in better yield than by the previously reported route. The 4-O-acetyl (5), 4-O-chloro-acetyl (6), 4-O-methyl (7), and 4-O-(methylsulfonyl) (8) derivatives of 4, the tetra-O-acetyl (11) derivative of 9, and the 3,4-di-O-acetyl (12) derivative of 10, have been prepared and spectrally characterized. Complete proton-n.m.r. analysis yields first-order coupling constants that indicate the E₁ (D) conformation for the tetrahydrofuran ring and the chair conformation for the 1,3-dioxane ring of 4-2-8. Obtainable coupling constants suggest that 11 and 12 exist in the ^oE and/or ^oT₁, conformations.     

Production of 1,3-Propanediol from Glucose by Recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis> BL21(DE3)

A range of recombinant strains of Escherichia coli were developed to produce 1,3-propanediol (1,3-PDO), an important C3 diol, from glucose. Two modules, the glycerol-producing pathway converting dihydroxyacetone phosphate to glycerol and the 1,3-PDO-producing pathway converting glycerol to 1,3-PDO, were introduced into E. coli. In addition, to avoid oxidative assimilation of the produced glycerol, glycerol oxidative pathway was deleted. Furthermore, to enhance the carbon flow to the Embden- Meyerhof-Parnas pathway, the Entner-Doudoroff pathway was disrupted by deleting 6-phosphogluconate dehydratase and 2-keto-3-deoxy-6-phosphogluconate aldolase. Finally, the acetate production pathway was removed to minimize the production of acetate, a major and toxic by-product. Flask experiments were carried out to examine the performance of the developed recombinant E. coli. The best strain could produce 1,3-PDO with a yield of 0.47 mol/mol glucose. Along with 1,3-PDO, glycerol was produced with a yield of 0.33 mol/mol glucose.     

Structural studies on an antitumor polysaccharide from Microellobosporia grisea

The structure of the antitumor polysaccharide from the actinomycete Microellobosporia grisea has been investigated. By methylation and periodate-oxidation studies, the polysaccharide was shown to consist of (nonreducing)d-mannosyl groups, (1→4)-linkedd-glucosyl residues, and 3,6-branched, (1→4)-linkedd-glucosyl residues in the approximate molar ratios of 2:1:1. Periodate oxidation of the polysaccharide, followed by borohydride reduction and mild hydrolysis with acid yielded glycerol, erythritol, 2-O-β-d-glucopyranosyl-d-erythritol, and 5-O-β-d-glucopyranosyl-2,4-bis(hydroxymethyl)-1,3-dioxane, which were isolated in the molar ratios of 2.0:0.14:0.74:0.35. Partial hydrolysis of the polysaccharide gave α-d-Man p-(1→6)-d-Glcp, β-d-Glcp-(1→4)-d-Glcp, α-d-Man p-(1→3)-d-Glcp, and β-d-Glcp-(1→4)-[α-d-Man p-(1→3)-]-d-Glcp. From these results, it is proposed that the polysaccharide is mainly composed of tetrasaccharide repeating-units having the following structure.