Sesquiterpenoid phytoalexins from suspended callus cultures of Nicotiana tabacum

Treatment of suspended callus cultures of Nicotiana tabacum with commercial cellulase elicited four principal stress metabolites including the phytoalexin capsidiol and a second eremophilane-type diol, shown on the basis of chemical and spectroscopic evidence to be 4-epieremophil-9-ene-11 /gx, 12-diol (without assignment of absolute configuration). This diol appears to be structurally identical with debneyol isolated from N. debneyi (see accompanying paper). Among minor metabolites were an isomer and a dehydro-analogue of the diol. GC/MS of cyclic derivatives (boronates and di-t-butylsilylene derivatives) of vicinal diols was useful for their detection and characterisation. The remaining two major metabolites appeared to be phytuberol and phytuberin.     

Growth Characteristics of a Novel Nitrogen-Fixing Cellulolytic Bacterium

Growth characteristics of a cellulolytic nitrogen-fixing bacterium isolated from a marine shipworm by Waterbury et al. (J. B. Waterbury, C. B. Calloway, and R. D. Turner, Science 221:1401-1403, 1983) are described. When grown microaerobically, the bacterium exhibited doubling times of about 2 days in cellulose-supplemented synthetic medium devoid of combined nitrogen. Maximum growth was reached 12 to 16 days after inoculation. Growth optima for pH, temperature, and NaCl concentration were 8.5, 30 to 35°C, and 0.3 M, respectively. During growth the bacterium produced succinic acid (0.026%) and acetic acid (0.010%). Formic acid (0.010%) was produced during the stationary growth phase. No growth was observed when glucose was the sole carbon source. Cellobiose supported weak growth, while longer-chain-length cellodextrins supported extensive growth. Analysis of residual carbohydrates in the medium during growth indicated that the bacterium catabolized a terminal glucose moiety from the cellodextrin chain.     

Affinity Purifications of Aldose Reductase and Xylitol Dehydrogenase from the Xylose-Fermenting Yeast Pachysolen tannophilus

Although xylose is a major product of hydrolysis of lignocellulosic materials, few yeasts are able to convert it to ethanol. In Pachysolen tannophilus, one of the few xylose-fermenting yeasts found, aldose reductase and xylitol dehydrogenase were found to be key enzymes in the metabolic pathway for xylose fermentation. This paper presents a method for the rapid and simultaneous purification of both aldose reductase and xylitol dehydrogenase from P. tannophilus. Preliminary studies indicate that this method may be easily adapted to purify similar enzymes from other xylose-fermenting yeasts.     

Regulation of β-1, 4-Glucosidase Expression by Candida wickerhamii

Candida wickerhamii NRRL Y-2563 expressed β-glucosidase activity (3 to 8 U/ml) constitutively when grown aerobically in complex medium containing either glycerol, succinate, xylose, galactose, or cellobiose as the carbon source. The addition of a high concentration of glucose (>75 g/liter) repressed β-glucosidase expression (<0.3 U/ml); however, this yeast did produce β-glucosidase when the initial glucose concentration was ≤50 g/liter. When grown aerobically in medium containing glucose plus the above-listed carbon sources, diauxic utilization of the carbon source was observed and the expression of β-glucosidase was glucose repressed. Surprisingly, glucose repression did not occur when the cells were grown anaerobically. When grown anaerobically in medium containing 100 g of glucose per liter, C. wickerhamii produced 6 to 9 U of enzyme per ml and did not demonstrate diauxic utilization of glucose-cellobiose mixtures. To our knowledge, this is the first report of apparent derepression of a glucose-repressed enzyme by anaerobiosis.     

Fermentation of cellodextrins to ethanol using mixed-culture fermentations

The potential for enhancing ethanol production from cellodextrins by employing mixed-culture (Candida wickerhamii-Saccharomyces cerevisiae) fermentations was investigated. Initially, ethanol production was monitored in fermentation medium containing 50 g/L glucose plus 45 g/L cellobiose. Inoculum levels and times of inoculum addition were varied. Of the conditions tested, the most rapid rates of ethanol formation occurred in fermentations in which either C. wickerhamii and S. cerevisiae were coinoculated at a ratio of 57 : 1 cell/mL or in fermentations in which a 10-fold-greater S. cerevisiae inoculum was added to a pure culture C. wickerhamii fermentation after 1 day incubation. These conditions were used to attempt to enhance fermentations in which cellodextrins produced by trifluoroacetic acid hydrolysis of cellulose served as the sole carbon source. Cellodextrins that were not further purified after cellulose hydrolysis contained compounds that were slightly inhibitory to C. wickerhamii. In this case the mixed-culture fermentations produced 12-45% more ethanol than a pure culture C. wickerhamii fermentation. However, if the substrate was treated with Darco G-60 charcoal, the toxic materials were apparently removed and the pure culture C. wickerhamii fermentations performed as well as the mixed-culture fermentations.     

Production of L-lactic acid by Rhizopus oryzae under oxygen limiting conditions

Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.During aerobic growth, Rhizopus oryzae produces L-lactic acid from lactate dehydrogenase mediated reduction of pyruvate, while O2 limiting conditions yield primarily ethanol. A mutant was isolated that expressed only 5% of the wild type alcohol dehydrogenase activity under O2 limiting conditions and produced nearly 40 g lactic acid/l in 70 h. This is almost a ten-fold increase in lactic acid production when compared to the parent strain.     

Factors influencing the activity of succinate dehydrogenase in membrane preparations from Micrococcus lysodeikticus

1. Some properties of succinate dehydrogenase [succinate-(acceptor) oxidoreductase, EC 1.3.99.1] in membrane preparations from Micrococcus lysodeikticus (N.C.T.C. 2665) were investigated. 2. In the spectrophotometric assay system adopted the reaction velocity was shown to be proportional to the amount of membrane added. Dichlorophenol-indophenol, reduced photochemically in the presence of phenazine methosulphate, or enzymically by the membrane-bound enzyme, was shown to undergo reoxidation in the dark. 3. The membrane-bound enzyme was found to be inactivated at temperatures above 10 degrees C. 4. The specific activity of membrane-bound succinate dehydrogenase was found to increase between two- and three-fold in diluted membrane preparations equilibrated at 0 degrees C for 6h. Membranes treated with sodium deoxycholate showed no enzyme activation on dilution but displayed maximal activity, all activity being sedimentable at 103000g. The increase in specific activity observed on dilution could be partially inhibited by fixation with glutaraldehyde, or by the presence of bovine serum albumin. 5. The addition of Mg(2+) or Ca(2+) ions to membrane suspensions caused an overall depression of enzyme activity. 6. The results suggest the presence of an ;inhibitor' that affects the expression of membrane bound succinate dehydrogenase activity.