Effect of pulp pH on solid phase fermentation of fodder beets for fuel ethanol production

Summary The pH of fodder beet pulp was varied to see how this affected solid phase fermentation by yeast. The process is for fuel ethanol production. When pulp was adjusted to a pre-inoculation pH of 3.0–3.5, ethanol yields (78–85% of theoretical, averaging 8.9% v/v) and fermentation efficiencies (97–99%) were greatest, the fermentation time was the shortest (30–39 h) and no bacterial contamination occurred.     

The metabolic sequence by which some 4,4-dimethyl sterols are converted into cholesterol

Cholest-8(14)-enol is the major radioactive component of the 4-di-demethyl sterol fraction biosynthesized from 4,4-dimethyl[2-(3)H(2)]cholest-8(14)-enol by rat liver microsomal fractions, and therefore the first steps in the biosynthesis of cholesterol from the latter compound probably involve removal of the 4-methyl groups. 4,4-Dimethylcholesta-8,14-dienol therefore is not an intermediate in this process, although its presence in the incubation medium at a concentration of 0.146mm almost completely inhibits the demethylation of 4,4-dimethyl[2-(3)H(2)]cholest-8(14)-enol. Nor is cholesta-8,14-dienol an intermediate in the conversion of cholest-8(14)-enol into cholest-7-enol and cholesterol. With 4,4-dimethyl[2-(3)H(2)]cholesta-8,14-dienol as the cholesterol precursor, 4,4-dimethylcholest-8(9)-enol becomes heavily labelled and there is very little radioactivity associated with cholesta-8,14-dienol.In this case, the most heavily labelled 4-di-demethyl sterols are cholest-7-enol and cholesterol with the former predominating. There is little or no radio-activity associated with cholest-8(14)-enol. A similar labelling pattern amongst the 4-di-demethyl sterols was observed with dihydro[(14)C]lanosterol as the precursor. The first step therefore in the synthesis of cholesterol from the 4,4-dimethyl[2-(3)H(2)]dienol is reduction of the Delta(14(15)) bond and not removal of the 4alpha-methyl group. Depending on the nature of the precursor, addition of the soluble fraction of the cell to the microsomal fraction resulted in a two- to four-fold stimulation of 4-di-demethyl sterol biosynthesis from the 4,4-dimethyl sterols studied. Under these conditions, 4,4-dimethylcholesta-8,14-dienol is the most efficient precursor of cholesterol and cholest-7-enol, and dihydrolanosterol is better than 4,4-dimethylcholest-8(14)-enol.     

Kinetic and molecular properties of citraconyl-aldolase. The reversible denaturation and hybridization of the native and modified enzymes

1. The preparation of enzymically active N-citraconyl derivatives of fructose diphosphate aldolase from rabbit muscle is described. Reaction is restricted to amino groups and the derivatives are not very heterogeneous with respect to the number of substituents. 2. Linear double-reciprocal plots of enzyme velocity against substrate concentration are found up to about 15% blocking of amino groups. With more than 15% blocking, there is a marked downward curvature in the double-reciprocal plots at high substrate concentrations. 3. Over the range 0-25% blocking of amino groups the apparent V(max.) for fructose diphosphate falls to 10% that of the native enzyme, and the apparent K(m) rises from 1 to 400mum. 4. Various pieces of evidence suggest that citraconyl-aldolase is slightly distorted in structure compared with the native enzyme. However, the kinetic properties and tetrameric structure of citraconyl-aldolase can be completely recovered after denaturation in 4m-guanidine hydrochloride. 5. After removal of the citraconyl groups in acid conditions the kinetic and molecular properties of native enzyme are restored. 6. Hybrid forms of aldolase can be constructed containing native and citraconylated subunits and the suitability of these derivatives for the study of subunit interactions in the enzyme is discussed. 7. The kinetic properties of hybridized aldolase containing native and citraconylated subunits are not exactly those predicted from the kinetic properties of the two parental forms. This result is interpreted in terms of conformational changes induced in the native and modified subunits when both are present in a hybrid molecule, evidently as a result of interactions in the tetramer.     

Dextran-induced Agglutination of Streptococcus mutans, and Its Potential Role in the Formation of Microbial Dental Plaques

Glucose-grown washed cells of streptococci similar to Streptococcus mutans, which contain cell-bound dextransucrase, have been observed to agglutinate upon the addition of high molecular weight dextran. Low molecular weight dextran or unrelated polysaccharides were ineffective. Agglutination also occurred upon addition of sucrose, which can be converted into dextran, but not with other mono- and disaccharides. Other bacteria, including species capable of synthesizing dextrans, were not observed to exhibit this phenomenon. Cells of S. mutans agglutinated upon addition of dextran over a wide pH range, but maximal sensitivity to dextran occurred at pH 8.5. At this pH, such cells can be used for a simple, specific, and exquisitely sensitive qualitative assay for high molecular weight dextran, for addition of 6 ng of dextran with a molecular weight of 2 x 10(6) (i.e., approximately three molecules per cell) caused detectable agglutination. High concentrations of glucose, levan, and dextran of molecular weight of 2 x 10(4) inhibited the reaction. Fluorescein-labeled cells of S. mutans were observed to adhere to dextran-containing plaques and dextran-treated teeth, suggesting that this phenomenon may be of importance in the formation of streptococcal dental plaques. The mechanism responsible for dextraninduced agglutination appears to involve the affinity of a receptor site, possibly dextransucrase, on the surface of several cells for common dextran molecules.     

The action of neutral hypochlorite on epithelial mucopolysaccharides

1. The uptake of dilute neutral hypochlorite by epithelial mucopolysaccharides has been compared with that of proteins, polysaccharides, amino acids and sugars. The uptake has been shown to be related to the protein content of the mucopolysaccharides rather than their polysaccharide content. 2. The destruction of the components of epithelial mucopolysaccharides, certain sugars and polysaccharides after oxidation with dilute neutral hypochlorite at 0-4 degrees has been studied. Very little destruction of the sugar components occurred and in epithelial mucopolysaccharides the only amino acid destroyed specifically was arginine. 3. Oxidation of bovine submaxillary-gland mucoprotein and ovalbumin caused very little destruction of hexosamine and no detectable liberation of this residue as a free reducing group, indicating that the O-seryl galactosaminide and the N-acyl-glycosylamine linkages reported to be present in these compounds were relatively stable to hypochlorite. 4. Depolymerization of epithelial mucopolysaccharides by neutral hypochlorite has been studied by using gel-filtration columns and compared with the depolymerization of polysaccharides and proteins under similar conditions. The polysaccharides examined were relatively resistant to oxidation whereas the proteins were extensively broken down. It is inferred that the extensive depolymerization of epithelial mucopolysaccharides by hypochlorite is related to their protein content rather than their polysaccharide content. 5. Fractionation of the products of oxidation of epithelial mucopolysaccharides by column procedures has revealed that the relative proportions of components in all fractions were similar to those in the original material. 6. Though this study does not provide unequivocal evidence from which the overall structure of this type of epithelial mucopolysaccharide may be deduced, the balance of probabilities now appears to favour a long polypeptide chain to which a large number of oligosaccharide side chains are attached via O-seryl and O-threonyl glycosidic linkages. The results, however, are also consistent with an alternating sequence of short polysaccharide and polypeptide chains and further evidence is necessary before this structure can be ruled out.     

Influence of wetland hydroperiod on diversity and abundance of metamorphosing juvenile amphibians

Numbers of successfully metamorphosing juvenile amphibians were tabulated at three wetlands in South Carolina, U.S.A. using terrestrial drift fences with pitfall traps. A relatively undisturbed Carolina bay was studied for eight years, a partially drained Carolina bay for four years, and a man-made borrow pit for three years. Annual production of juveniles at the undisturbed Carolina bay ranged from zero to 75,644 individuals of 15 species. Fewer individuals of fewer species typically metamorphosed at the borrow pit than at the undisturbed bay, with the least numbers at the partially drained Carolina bay. Both total number and species diversity of metamorphosing juveniles at each site each year showed a strong positive correlation with hydroperiod, i.e., the number of days a site contained standing water that year. Data for one common anuran species and the most common salamander species were analyzed separately by multiple regression, in addition to the community analyses. For the mole salamander, Ambystoma talpoideum, hydroperiod was a significant predictor of the number of metamorphosing juveniles, but the number of breeding females was not. For the ornate chorus frog, Pseudacris ornata, the number of breeding females was a significant predictor of the number of metamorphosing juveniles, but hydroperiod was not. Variation in the dates of wetland filling and drying interacts with other factors to determine amphibian community structure and diversity. Either increasing or decreasing the number of days a wetland holds water could increase or decrease the number and species diversity of amphibians in and around a wetland.     

IL-4 inhibits IL-2 receptor expression and IL-2-dependent proliferation of human T cells

Recent studies have shown that IL-4 can affect lymphocyte responses to IL-2. To evaluate the effects of IL-4 on T cell responses to physiologically relevant stimuli, we studied normal human T cells cultured with a low concentration of anti-CD3 mAb and IL-2 in the presence and absence of added IL-4. The addition of IL-4 to cultures of T cells stimulated with anti-CD3 mAb and IL-2 reduced the proliferative response by 49 to 59%. The inhibitory effect was observed in 3-, 5-, and 7-day cultures. Inhibition was dose-dependent with maximal inhibition at concentrations greater than or equal to 5 to 10 U/ml IL-4. IL-4-mediated inhibition occurred early during the T cell response, inasmuch as addition of IL-4 after stimulation for 24 h did not result in significant inhibition. Phenotypic analyses of cells cultured in the presence of anti-CD3 mAb, IL-2, and IL-4 suggested that the mechanism of regulation by IL-4 involves the inhibition of IL-2R expression. The proportion of both CD4+ and CD8+ cells that expressed IL-2R in response to IL-2 was diminished in the presence of IL-4, although HLA-DR levels were unaffected. Soluble IL-2R was also reduced in supernatants of cultures stimulated with anti-CD3 mAb, IL-2, and IL-4 as compared to cultures stimulated with anti-CD3 mAb and IL-2. These findings indicate that when normal human T cells are stimulated in vitro in a manner that approximates a physiologic interaction with Ag in vivo, rIL-4 provides a potent inhibitory signal to IL-2 responsive cells that is likely mediated by IL-4-induced inhibition of IL-2R expression.     

Interactions ofCandida albicans with bacteria and salivary molecules in oral biofilms

The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed.