Rapid and stable production of 2,3-butanediol by an engineered <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> strain in a continuous airlift bioreactor

Utilization of renewable feedstocks for the production of bio-based bulk chemicals, such as 2,3-butanediol (2,3-BDO), by engineered strains of the non-pathogenic yeast, Saccharomyces cerevisiae, has recently become an attractive option. In this study, to realize rapid production of 2,3-BDO, a flocculent, 2,3-BDO-producing S. cerevisiae strain YPH499/dPdAdG/BDN6-10/FLO1 was constructed from a previously developed 2,3-BDO-producing strain. Continuous 2,3-BDO fermentation was carried out by the flocculent strain in an airlift bioreactor. The strain consumed more than 90 g/L of glucose, which corresponded to 90% of the input, and stably produced more than 30 g/L of 2,3-BDO over 380 h. The maximum 2,3-BDO productivity was 7.64 g/L/h at a dilution rate of 0.200/h, which was higher than the values achieved by continuous fermentation using pathogenic bacteria in the previous reports. These results demonstrate that continuous 2,3-BDO fermentation with flocculent 2,3-BDO-producing S. cerevisiae is a promising strategy for practical 2,3-BDO production.     

Intramolecular photoredox reactions of 1,2-naphthoquinone derivatives

Photoirraditation of substituted 1,2-naphthoquinones gives the corresponding oxacycle via intramolecular redox reaction, which enabled net CH functionalization of the proximal position to the excited carbonyl group of the quinones. The substrate scope and mechanistic insights are described.     

The local structure of solid diorganotin(IV) complexes formed with carbohydrates by X-ray absorption spectroscopy

Diethyltin(IV) complexes formed with carbohydrate ligands (aldoses, polyalcohols, sugar acids and disaccharides) containing the diethyltin(IV) moiety and the carbohydrate ligand in a 1:1 ratio were prepared. Their local structures were determined by extended X-ray absorption fine structure (EXAFS) in the solid state. The results showed that the dioxastannolane units are associated into an infinite chain polymer, in which tin(IV) is bound by two carbon atoms and three or four oxygen atoms either in highly distorted octahedral and trigonal bipyramidal arrangements or in a purely trigonal bipyramidal arrangement. The present structure models are consistent with the results of previous Mössbauer studies, proving the advantages of the use of the partial quadrupole splitting concept for the determination of the symmetry of the coordination sphere in tin(IV) organic complexes.     

Regional heterogeneity of bacteria and their glycosidase activities across and along the colonic segments of rats

Numbers of Bacteroidaceae, Enterobacteriaceae and staphylococci were higher in the periphery of the colonic contents of rats than in the core. Numbers of total anaerobic bacteria, lactobacilli and enterococci did not differ among these regions. Activities of glycosidases were higher in the periphery than in the core.     

Microbial diversity in ostrich ceca as revealed by 16S ribosomal RNA gene clone library and detection of novel Fibrobacter species

The ostrich (Struthio camelus) is a herbivorous bird and although the hindgut is known as the site for fiber digestion, little is known about the microbial diversity in the ostrich hindgut. Our aim was to analyze the microbial diversity in ostrich ceca using a 16S ribosomal RNA gene (rDNA) clone library approach. A total of 310 clones were sequenced and phylogenetically analyzed and were classified into 110 operational taxonomy units (OTUs) based on a 98% similarity criterion. The similarity of the sequences ranged from 86 to 99% and 95 OTUs had less than 98% similarity to the sequences in the public databases. Coverage and the Shannon–Wiener index (H′) of the library were 83.9% and 4.29, respectively. The sequences were assigned to the following 6 phyla: Firmicutes (50.9% of the total number of sequences), Bacteroidetes (39.4%), Fibrobacteres (6.5%), Euryarchaeota (1.9%), Spirochaetes (1.0%), and Verrucomicrobia (0.3%); approximately 90% of the sequences were affiliated with Firmicutes and Bacteroidetes. The only OTU of Fibrobacteres (OTU 107), had 93 and 90% similarity to Fibrobacter succinogenes and F. intestinalis, respectively, suggesting a new species of Fibrobacter in ostrich ceca. Clostridium coccoides and C. leptum formed major groups within the Firmicutes. There was no OTU with high similarity (≥98%) to the 16S rDNA of cultivated fibrolytic bacteria in our library. Although two OTUs were affiliated with Euryarchaeota, no sequence was affiliated with methanogenic Archaea. This study presents the very complex ostrich cecal microbial community, in which the majority of the bacterial species have not yet been cultivated.     

Nucleotide sequence of the structural gene for the penicillin-binding protein 2 of Staphylococcus aureus and the presence of a homologous gene in other staphylococci

Abstract During growth of Streptomyces niveus wild-type in the novobiocin production medium CDM the resistance of mycelia to novobiocin rises from about 25 μg/ml to over 200 μg/ml. ( S. lividans , a novobiocin-sensitive strain, is resistant to approx. 10 μg/ml novobiocin.) The initial period of low level resistance extends from the time of inoculation of the culture until approx. 70 h when the culture is still in the growth phase. High level resistance is initiated before the start of novobiocin production and rises rapidly to a maximum level beyond the end of the growth phase. The rise in pH of the unbuffered CDM medium which occurs during S. niveus fermentation was shown not to be the cause of the change in novobiocin resistance. However, mycelia-free CDM from S. niveus cultures expressing high level novobiocin resistance was shown to contain a factor which induced high level novobiocin resistance in germinating S. niveus spores. Kinetic studies revealed that the inducer first appears in the culture medium before the switch to high level resistance begins and reaches its highest concentration before resistance reaches its maximum level.     

Potent inhibitors of amyloid β fibrillization, 4,5-dianilinophthalimide and staurosporine aglycone, enhance degradation of preformed aggregates of mutant Notch3

Cytotoxic T lymphocytes (CTL) are critical effector cells in tumor immunity. Adoptive transfer therapy with in vitro-expanded tumor-specific CTL is a promising approach for preventing cancer metastasis and recurrence. Transferred CTL are not effective in clinical trials, however, due to inadequate tumor-infiltration. Therefore, the development of functionally modified CTL, such as tumor-targeting CTL, is widely desired. Here, we designed the tumor-targeting CTL expressing a single-chain antibody fragment (scFv-CTL) specific for vascular endothelial growth factor receptor 2 (VEGFR2/flk1) by transducing the CTL with a retroviral vector. The scFv-CTL bound to VEGFR2/flk1-expressing cells and retained their cytotoxic activity against tumor cells. In addition, adoptive transfer of scFv-CTL into tumor-bearing mice effectively suppressed tumor growth due to the augmented accumulation of the transferred CTL in the tumor tissue. These findings indicate that the creation of CTL capable of targeting tumor vascular endothelial cells by scFv-expression technique is considerably promising for improvement of efficacy in adoptive immunotherapy.     

Geological and geochemical aspects of a Devonian siliceous succession in northern Thailand: Implications for the opening of the Paleo-Tethys

The opening of the Paleo-Tethys are reconstructed, including the depositional setting and redox conditions, based on an analysis of radiolarian fossils and the geochemistry of a Devonian siliceous succession in the Chiang Dao area of northern Thailand. The succession is subdivided into the following five rock types (in ascending stratigraphic order): black shale (Lower Devonian), siliceous shale (Middle Devonian), tuffaceous chert and tuff (Middle/Upper Devonian), and chert (Upper Devonian). The succession was deposited in continental margin and pelagic environments between the Sibumasu Block and the Indochina-North China blocks. The concentrations of terrestrial-derived elements (Al₂O₃, TiO₂, Rb, and Zr) suggest that the succession (except for the chert) was supplied with terrigenous material and volcanic ash from the adjacent continent, deposited within a SiO₂-rich environment. Geochemical indicators of redox conditions (total organic carbon and the Th/U ratio) reveal a gradual change from anoxic to oxic oceanic conditions between the black shale and chert. Taking into account the interpreted depositional setting and redox conditions, the initial Paleo-Tethys developed as a small, closed anoxic-suboxic oceanic basin during the Early to Middle Devonian, located close to the continental margin. Black shale and siliceous shale were deposited in the basin at this time. Opening of the Paleo-Tethys started around the Middle and Upper Devonian boundary, marked by voluminous volcanic activity. The tuffaceous chert was deposited under oxic conditions, suggesting that ash and pumice within the chert were derived from a continental source. After the Late Devonian, the Paleo-Tethys developed as a deep, broad ocean in which pelagic chert was deposited.