Production of ethanol from guava pulp by yeast strains

Guava pulp used for ethanol production by three yeast strains contained 10% (w/v) total sugars and was pH 4.1. Ethanol production at the optimum sugar concentration of 10%, at pH 4.1 and 30°C was 1.5%, 3.6% and 3.9% (w/v) by Saccharomyces cerevisiae MTCC 1972, Isolate-1 and Isolate-2, respectively, at 60 h fermentation. Higher sugar concentrations at 15 and 20% were inhibitory for ethanol production by all test cultures. The maximum production of ethanol at optimum natural sugar concentration (10%) of guava pulp, was 5.8% (w/v) at pH 5.0 by Isolate-2 over 36 h fermentation, which was only slightly more than the quantity of ethanol produced by Saccharomyces cerevisiae (5.0%) and Isolate-1 (5.3%) over 36 and 60h fermentation, respectively.     

Mitochondrial DNA sequence evolution in sharks: rates, patterns, and phylogenetic inferences

Abundant representation of sharks in the fossil record makes this group a superb system in which to investigate rates and patterns of molecular evolution and to explore the strengths and weaknesses of phylogenetic inferences from molecular data. In this report, the molecular evolution of the cytochrome b gene in sharks is described and the information related to results from phylogenetic analysis of the data evaluated in the light of a phylogeny derived independently of the molecular data. Across divergent lineages of sharks there is evidence for significant substitution rate variation, departure from compositional equilibrium, and substantial homoplasy; nevertheless, the signal of evolutionary history is evident in patterns of shared transversions and amino acid replacements.      

Metabolic rate and directional nucleotide substitution in animal mitochondrial DNA

There is marked heterogeneity of nucleotide composition in mitochondrial DNA across divergent animals. Differences in nucleotide composition presumably reflect differences in directional nucleotide substitution for A+T or G+C nucleotides. In mitochondrial DNA, there is A+T directional nucleotide substitution in most (if not all) animals surveyed, and the magnitude of directional A+T nucleotide substitution differs greatly within and among groups. Differences in directional nucleotide substitution among lineages of mammals can be explained by changes in metabolic physiology. This relationship is thought to be mediated by the effect of oxygen radicals because these toxic compounds are by-products of aerobic metabolism and are known mutagens. Association between metabolism and nucleotide composition provides additional evidence in favor of the hypothesis that rates and patterns of nucleotide substitution in mitochondrial DNA can be influenced by factors that impinge on rates of endogenous DNA damage.      

Stimulation of growth and glucose catabolite enzymes by succinate in some thermophilic fungi

Thermophilic Humicola lanuginosa, Penicillium duponti, Sporotrichum thermophile and Mucor pusillus required succinate in addition to glucose for optimal growth. The requirement for succinate was concentration-dependent and the concentration needed for one half of the maximal growth was 6.14 mM. In the presence of succinate, glucose utilization from the medium was markedly increased and this was associated with increased levels of the enzymes of the glycolytic and Krebs cycle pathways. Addition of succinate to cultures growing in glucose at any stage of growth stimulated the growth with the resulting rate of growth remaining high if the addition was made within 3 days of inoculation. Cycloheximide (71.4 M) prevented the succinate-mediated derepression of the enzymes suggesting that succinate may remove the catabolite repression in the presence of glucose.A preliminary part of this work was presented at the 17th annual meeting of the Association of Microbiologists of India at Manipal (India) held from Dec. 13 to 15, 1976     

Partial purification of a competence factor from Rhizobium japonicum

A competence factor (CF) from Rhizobium japonicum was partially purified to 43 fold on Sephadex G-100. This CF preparation was sensitive to heat, trypsin and pronase, was resistant to DNase 1, RNase A and lysozyme. It had an approximate mol. wt. of 82,000. Osmotic shock treatment of competent cells revealed that the CF is located in the periplasmic region of the cell.Abbreviations CF competence factor - BSA bovine serum albumin - YM yeast mannitol medium     

Elemental distribution in striated muscle and the effects of hypertonicity: Electron probe analysis of cryo sections

A method of rapid freezing in supercooled Freon 22 (monochlorodifluoromethane) followed by cryoultramicrotomy is described and shown to yield ultrathin sections in which both the cellular ultrastructure and the distribution of diffusible ions across the cell membrane are preserved and intracellular compartmentalization of diffusabler ions can be quantitated. Quantitative electron probe analysis (Shuman, H., A.V. Somlyo, and A.P. Somlyo. 1976. Ultramicros. 1:317-339.) of freeze-dried ultrathin cryto sections was found to provide a valid measure of the composition of cells and cellular organelles and was used to determine the ionic composition of the in situ terminal cisternae of the sarcoplasmic reticulum (SR), the distribution of CI in skeletal muscle, and the effects of hypertonic solutions on the subcellular composition if striated muscle. There was no evidence of sequestered CI in the terminal cisternae of resting muscles, although calcium (66mmol/kg dry wt +/- 4.6 SE) was detected. The values of [C1](i) determined with small (50-100 nm) diameter probes over cytoplasm excluding organelles over nuclei or terminal cisternae were not significantly different. Mitochondria partially excluded C1, with a cytoplasmic/ mitochondrial Ci ratio of 2.4 +/- 0.88 SD. The elemental concentrations (mmol/kg dry wt +/- SD) of muscle fibers measured with 0.5-9-μm diameter electron probes in normal frog striated muscle were: P, 302 +/- 4.3; S, 189 +/- 2.9;C1, 24 +/- 1.1;K, 404 +/- 4.3, and Mg, 39 +/- 2.1. It is concluded that: (a) in normal muscle the "excess CI" measured with previous bulk chemical analyses and flux studies is not compartmentalized in the SR or in other cellular organelles, and (b) the cytoplasmic C1 in low [K](0) solutions exceeds that predicted by a passive electrochemical distribution. Hypertonic 2.2 X NaCl, 2.5 X sucrose, or 2.2 X Na isethionate produced: (a) swollen vacuoles, frequently paired, adjacent to the Z lines and containing significantly higher than cytoplasmic concentrations of Na and Cl or S (isethionate), but no detectable Ca, and (b) granules of Ca, Mg, and P = approximately (6 Ca + 1 Mg)/6P in the longitudinal SR. It is concluded that hypertonicity produces compartmentalized domains of extracellular solutes within the muscle fibers and translocates Ca into the longitudinal tubules.     

Regulation of glutamine synthetase I fromRhizobium meliloti

Glutamine synthetase I fromRhizobium meliloti was found to be inhibited by adenosine 5-monophosphate, alanine, glycine, carbamyl phosphate, cytidine 5-triphosphate, tryptophan, histidine, and glucosamine-6-phosphate. Each inhibitor was independent in its action and the effect was cumulative when more than one inhibitor was added.     

Studies on transducing phage M-1 for Rhizobium japonicum D211

Phage M-1 produced clear plaques with a halo in the lawn of Rhizobium japonicum D211. A one step growth curve of phage M-1 showed a latent period of 3 h, burst size of 55 and rise period of 2 h. The inactivation of phage M-1 was found to be dependent upon the concentraion of d-glucosomanine. The neutralization kinetics of phage M-1 by antiphage serum gave a K value (velocity constant) of 83.1 min^–1. Transduction of str and kan was studied in the presence of antiphage serum and d-glucosamine. Cotransduction of different antibiotic resistance markers suggested that the system can be further explored for high resolution mapping in R. japonicum.Abbreviations YM yeast mannitol medium - PFU plaque forming unit - moi multiplicity of infection - EOP efficiency of plating     

Horseradish peroxidase catalyzed oxidation of thiocyanate by hydrogen peroxide: comparison with lactoperoxidase-catalysed oxidation and role of distal histidine

Horseradish peroxidase-catalysed oxidation of thiocyanate by hydrogen peroxide has been studied by 15N-NMR and optical spectroscopy at different concentrations of thiocyanate and hydrogen peroxide and at different pH values. The extent of the oxidation and the identity of the oxidized product of the thiocyanate has been investigated in the SCN-/H2O2/HRP system and compared with the corresponding data on the SCN-/H2O2/LPO system. The NMR studies show that (SCN)2 is the oxidation product of thiocyanate in the SCN-/H2O2/HRP system, and its formation is maximum at pH less than or equal to 4 and that the oxidation does not take place at pH greater than or equal to 6. Since thiocyanate does not bind to HRP at pH greater than or equal to 6 (Modi et al. (1989) J. Biol. Chem. 264, 19677-19684), the binding of thiocyanate to HRP is considered to be a prerequisite for the oxidation of thiocyanate. It is further observed that at [H2O2]/[SCN-] = 4, (SCN)2 decomposes very slowly back to thiocyanate. The oxidation product of thiocyanate in the SCN-/H2O2/LPO system has been shown to be HOSCN/OSCN- which shows maximum inhibition of uptake by Streptococcus cremoris 972 bacteria when hydrogen peroxide and thiocyanate are present in equimolar amounts (Modi et al. (1991) Biochemistry 30, 118-124). However, in case of HRP no inhibition of oxygen uptake by this bacteria was observed. Since thiocyanate binds to LPO at the distal histidine while to HRP near 1- and 8-CH3 heme groups, the role of distal histidine in the activity of SCN-/H2O2/(LPO, HRP) systems is indicated.