Multigram-scale production of aliphatic carboxylic acids by oxidation of alcohols with Acetobacter pasteurianus NCIMB 11664

Acetobacter pasteurianus NCIMB 11664 was selected for multigram-scale production of different aliphatic carboxylic acids through oxidation of the corresponding alcohols after screening different acetic acid bacteria. Continuous production was carried out using an air-lift reactor, with overall yields of 1-propionic, 1-butyric, 2-methyl-1-butyric and 3-methyl-1-butyric acids ranging from 45 to 61 g dm⁻³. ©1997 SCI     

Analysis of the Structure and Biosynthesis of the Lipopolysaccharide Core Oligosaccharide of Pseudomonas syringae pv. tomato DC3000

Lipopolysaccharide (LPS), the major component of the outer membrane of Gram-negative bacteria, is important for bacterial viability in general and host–pathogen interactions in particular. Negative charges at its core oligosaccharide (core-OS) contribute to membrane integrity through bridging interactions with divalent cations. The molecular structure and synthesis of the core-OS have been resolved in various bacteria including the mammalian pathogen Pseudomonas aeruginosa. A few core-OS structures of plant-associated Pseudomonas strains have been solved to date, but the genetic components of the underlying biosynthesis remained unclear. We conducted a comparative genome analysis of the core-OS gene cluster in Pseudomonas syringae pv. tomato (Pst) DC3000, a widely used model pathogen in plant–microbe interactions, within the P. syringae species complex and to other plant-associated Pseudomonas strains. Our results suggest a genetic and structural conservation of the inner core-OS but variation in outer core-OS composition within the P. syringae species complex. Structural analysis of the core-OS of Pst DC3000 shows an uncommonly high phosphorylation and presence of an O-acetylated sugar. Finally, we combined the results of our genomic survey with available structure information to estimate the core-OS composition of other Pseudomonas species.     

有机酸对木醋杆菌合成细菌纤维素的影响规律

木醋杆菌(Acetobacter xylinum)在静止培养条件下,在基本培养基中添加醋酸、柠檬酸和乳酸,可以提高细菌纤维素的产量。但各种增效因子的添加量均有一最适宜的浓度。其中,添加0.1%的醋酸,细菌纤维素的产量为2.75 g/L;加入0.2%的柠檬酸时细菌纤维素产量为2.15 g/L;加入0.1%的乳酸,细菌纤维素的产量为2.76 g/L。     

Complete Characterization of the O-Antigen from the LPS of Aeromonas bivalvium

Aeromonas species are found in the aquatic environment, drinking water, bottled mineral water, and different types of foods, such as meat, fish, seafood, or vegetables. Some of these species are primary or opportunistic pathogens for invertebrates and vertebrates, including humans. Among the pathogenic factors associated with these species, there are the lipopolysaccharides (LPSs). LPSs are the major components of the external leaflet of Gram-negative bacterial outer membrane. LPS is a glycoconjugate, generally composed of three portions: lipid A, core oligosaccharide, and O-specific polysaccharide or O-antigen. The latter, which may be present (smooth LPS) or not (rough LPS), is the most exposed part of the LPS and is involved in the pathogenicity by protecting infecting bacteria from serum complement killing and phagocytosis. The O-antigen is a polymer of repeating oligosaccharide units with high structural variability, particularly the terminal sugar, that confers the immunological specificity to the O-antigen. In this study, we established the structure of the O-chain repeating unit of the LPS from Aeromonas bivalvium strain 868 E^T (=CECT 7113^T = LMG 23376^T), a mesophilic bacterium isolated from cockles (Cardium sp.) and obtained from a retail market in Barcelona (Spain), whose biosynthesis core LPS cluster does not contain the waaE gene as most of Aeromonas species. After mild acid hydrolysis, the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by chemical analysis and NMR spectroscopy. The polymer consists of a heptasaccharide repeating unit containing D-GalNAc, L-Rha, D-GlcNAc, and D-FucNAc residues.     

皮革涂料用丙烯酸酯核-壳乳液的研制

采用种子乳液聚合法，以交联型软性聚合物为核，交联型硬性高聚物为壳，合成了具有优异耐寒性及高温抗回粘性聚合物。讨论了乳化剂种类及应用、核／壳比等对聚合物性能的影响。     

Heterogenicity within the LPS Structure in Relation to the Chosen Genomic and Physiological Features of the Plant Pathogen Pectobacterium parmentieri

Pectobacterium parmentieri is a pectinolytic plant pathogenic bacterium causing high economic losses of cultivated plants. The highly devastating potential of this phytopathogen results from the efficient production of plant cell wall-degrading enzymes, i.e., pectinases, cellulases and proteases, in addition to the impact of accessory virulence factors such as motility, siderophores, biofilm and lipopolysaccharide (LPS). LPS belongs to pathogen-associated molecular patterns (PAMPs) and plays an important role in plant colonization and interaction with the defense systems of the host. Therefore, we decided to investigate the heterogeneity of O-polysaccharides (OPS) of LPS of different strains of P. parmentieri, in search of an association between the selected genomic and phenotypic features of the strains that share an identical structure of the OPS molecule. In the current study, OPS were isolated from the LPS of two P. parmentieri strains obtained either in Finland in the 1980s (SCC3193) or in Poland in 2013 (IFB5432). The purified polysaccharides were analyzed by utilizing 1D and 2D NMR spectroscopy (¹H, DQF-COSY, TOCSY, ROESY, HSQC, HSQC-TOCSY and HMBC) in addition to chemical methods. Sugar and methylation analyses of native polysaccharides, absolute configuration assignment of constituent monosaccharides and NMR spectroscopy data revealed that these two P. parmentieri strains isolated in different countries possess the same structure of OPS with a very rare residue of 5,7-diamino-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid (pseudaminic acid) substituted in the position C-8: →3)-β-d-Galf-(1→3)-α-d-Galp-(1→8)-β-Pse4Ac5Ac7Ac-(2→6)-α-d-Glcp-(1→6)-β-d-Glcp-(1→. The previous study indicated that three other P. parmentieri strains, namely IFB5427, IFB5408 and IFB5443, exhibit a different OPS molecule than SCC3193 and IFB5432. The conducted biodiversity-oriented assays revealed that the P. parmentieri IFB5427 and IFB5408 strains possessing the same OPS structure yielded the highest genome-wide similarity, according to average nucleotide identity analyses, in addition to the greatest ability to macerate chicory tissue among the studied P. parmentieri strains. The current research demonstrated a novel OPS structure, characteristic of at least two P. parmentieri strains (SCC3193 and IFB5432), and discussed the observed heterogenicity in the OPS of P. parmentieri in a broad genomic and phenotype-related context.     

醋酸反应釜的基本结构和日常维护

醋酸反应釜是醋酸系统的重点设备,反应釜由锆/钢复合材料焊接而成,主要由7个部件组成：电机、变速箱、机械密封、机轴、导流板、叶轮和轴套等。由于反应釜控制的温度和压力较高,所以对于特材设备的日常维护就显得尤为重要。根据不同部件的工作特点,重点阐述了反应釜顶部密封垫片的更换和变速箱的拆检以及回装时的注意事项等。     

The Lipid A from the Lipopolysaccharide of the Phototrophic Bacterium Rhodomicrobium vannielii ATCC 17100 Revisited

The structure of lipid A from lipopolysaccharide (LPS) of Rhodomicrobium vannielii ATCC 17100 (Rv) a phototrophic, budding bacterium was re-investigated using high-resolution mass spectrometry, NMR, and chemical degradation protocols. It was found that the (GlcpN)-disaccharide lipid A backbone was substituted by a GalpA residue that was connected to C-1 of proximal GlcpN. Some of this GalpA residue was β-eliminated by alkaline de-acylation, which indicated the possibility of the presence of another so far unidentified substituent at C-4 in non-stoichiometric amounts. One Manp residue substituted C-4′ of distal GlcpN. The lipid A backbone was acylated by 16:0(3-OH) at C-2 of proximal GlcpN, and by 16:0(3-OH), i17:0(3-OH), or 18:0(3-OH) at C-2′ of distal GlcpN. Two acyloxy-acyl moieties that were mainly formed by 14:0(3-O-14:0) and 16:0(3-O-22:1) occupied the distal GlcpN of lipid A. Genes that were possibly involved in the modification of Rv lipid A were compared with bacterial genes of known function. The biological activity was tested at the model of human mononuclear cells (MNC), showing that Rv lipid A alone does not significantly stimulate MNC. At low concentrations of toxic Escherichia coli O111:B4 LPS, pre-incubation with Rv lipid A resulted in a substantial reduction of activity, but, when higher concentrations of E. coli LPS were used, the stimulatory effect was increased.     

The Topology,in Model Membranes,of the Core Peptide Derived from the T‐Cell Receptor Transmembrane Domain

The T‐cell receptor–CD3 complex (TCR–CD3) serves a critical role in protecting organisms from infectious agents. The TCR is a heterodimer composed of α‐ and β‐chains, which are responsible for antigen recognition. Within the transmembrane domain of the α‐subunit, a region has been identified to be crucial for the assembly and function of the TCR. This region, termed core peptide (CP), consists of nine amino acids (GLRILLLKV), two of which are charged (lysine and arginine) and are crucial for the interaction with CD3. Earlier studies have shown that a synthetic peptide corresponding to the CP sequence can suppress the immune response in animal models of T‐cell‐mediated inflammation, by disrupting proper assembly of the TCR. As a step towards the understanding of the source of the CP activity, we focused on CP in egg phosphatidylcholine/cholesterol (9:1, mol/mol) model membranes and determined its secondary structure, oligomerization state, and orientation with respect to the membrane. To achieve this goal, 15‐residue segments of TCRα, containing the CP, were synthesized and spin‐labeled at different locations with a nitroxide derivative. Electron spin‐echo envelope modulation spectroscopy was used to probe the position and orientation of the peptides within the membrane, and double electron–electron resonance measurements were used to probe its conformation and oligomerization state. We found that the peptide is predominantly helical in a membrane environment and tends to form oligomers (mostly dimers) that are parallel to the membrane plane.     

Structure of the O-Antigen and the Lipid A from the Lipopolysaccharide of Fusobacterium nucleatum ATCC 51191

Fusobacterium nucleatum is a common member of the oral microbiota. However, this symbiont has been found to play an active role in disease development. As a Gram-negative bacterium, F. nucleatum has a protective outer membrane layer whose external leaflet is mainly composed of lipopolysaccharides (LPSs). LPSs play a crucial role in the interaction between bacteria and the host immune system. Here, we characterised the structure of the O-antigen and lipid A from F. nucleatum ssp. animalis ATCC 51191 by using a combination of GC-MS, MALDI and NMR techniques. The results revealed a novel repeat of the O-antigen structure of the LPS, [→4)-β-d -GlcpNAcA-(1→4)-β-d -GlcpNAc3NAlaA-(1→3)-α-d -FucpNAc4NR-(1→], (R=acetylated 60 %), and a bis-phosphorylated hexa-acylated lipid A moiety. Taken together these data showed that F. nucleatum ATCC 51191 has a distinct LPS which might differentially influence recognition by immune cells.     

The High Resolution NMR Structure of Parvulustat (Z‐2685) from Streptomyces parvulus FH‐1641: Comparison with Tendamistat from Streptomyces tendae 4158

The protein parvulustat (Z‐2685) from Streptomyces parvulus comprises 78 amino acids and functions as a highly efficient α‐amylase inhibitor. Parvulustat shares 29.6 % overall amino acid sequence identity to the well‐known α‐amylase inhibitor tendamistat. Among the conserved residues are the two disulfide bridges (C9–C25, C43–C70) and the active‐site motif (W16, R17, Y18). Here, we report the high‐resolution NMR structure of parvulustat based on NOEs, J couplings, chemical shifts and hydrogen‐exchange data. In addition, we studied the dynamical properties of parvulustat by heteronuclear relaxation measurements. We compare the structure of parvulustat with the structure of tendamistat in terms of secondary structure elements, charges and hydrophobicity. The overall structural composition is very similar, but there are distinct differences including the active‐site region. These structural and dynamical differences indicate that for parvulustat an induced‐fit mechanism for binding to α‐amylase might take place, since the structure of tendamistat does not change upon binding to α‐amylase.     

The Oxidative Fermentation of Ethanol in Gluconacetobacter diazotrophicus Is a Two-Step Pathway Catalyzed by a Single Enzyme: Alcohol-Aldehyde Dehydrogenase (ADHa)

Gluconacetobacter diazotrophicus is a N₂-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2–C6) and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.