Microflora participating in the decomposition of carboxymethyl cellulose continuously added to the soil

The microbial community in the soil was analyzed during four weeks of a continuous enrichment of structural chernozem soil samples with a 0.1% solution of carboxymethyl cellulose (CMC) under aerobic and semianaerobic conditions. During the first 14 d, the total amount of the aerobic and anaerobic, cellulose-degrading microorganisms increased significantly. Various metabolic pathways were u‘ed te decompose the substrate: diverse metabolic systems were activated and different groups of microorganisms preferred in dependence on the presence of oxygen or the source of mineral nitrogen. In the later phases of cultivation, a decrease in the concentration of zymogenous microflora and in the level of substrate mineralization was observed ovon though CM-cellulase activity remained high. During the fourth week of cultivation, a conspicuous increase in the numbers of oligothropic bacteria occurring in the colcnies of the microorganisms degrading cellulose was found. The representatives of prosthecobacteria (Caulobacter, Hyphomicrobium, Prosthecomicrobium spp.) andSeliberia sp. were thus identified. This “microflora of dispersion” attends the zymogenous microbes degrading CMC and indicates later phases of the process of decomposition.     

Effect of detergents on aspartate ammonia-lyase activity inEscherichia alcalescens

The effect of twelve detergents on aspartate ammonia-lyase activity of Escherichia alcalescens used for the production of L-aspartic acid was tested. Best permeabilization was found with Triton X-100, Slovafol 910 and Corona, a mixed commercial preparation. In contrast to Triton X-100 and Slovafol 910, a much narrower range of suitable concentrations was observed with Corona.     

Uptake of L-lysine by a double mutant ofSaccharomyces cerevisiae

A gap1 can1 mutant of Saccharomyces cerevisiae with a single lysine transport system remaining was used to study detailed kinetics of this transport. Its half-saturation constant was 78 mumol per litre, its maximum rate of transport was 0.29 mumol L-lysine per g dry matter per minute, both parameters being lower by more than an order of magnitude in comparison with the GAP system. The pH optimum lay at very acid values of about 3, the temperature dependence without any transition point showed an activation energy of 48 kJ/mol. The transport was inhibited by common metabolic inhibitors (3'-chlorophenylhydrazonomalononitrile, antimycin, 2-deoxy-D-glucose, sodium arsenate) as well as by a membrane-active one (uranyl nitrate). The specificity of the system was extremely high, none of the natural amino acids acting as competitor to L-lysine. The maximum accumulation ratio attained (at about 5 mg dry matter per mL) was 100: 1-120: 1, in agreement with the measured protonmotive force under the assumption of 1 H+ ion being transported with 1 lysine molecule. The ratio decreased with increasing external concentration of lysine to as little as 4: 1 at 1 mmol lysine per litre. It also decreased with increasing suspension density and it was at extremely low suspension densities (0.2 mg dry matter per mL) that ratios of as much as 500: 1 were reached. Application of group-specific inhibitors showed that the active site of the carrier contains an essential histidine residue.     

Selection of Ethanol-Tolerant Yeast Hybrids in pH-Regulated Continuous Culture

Hybrids between naturally occurring wine yeast strains and laboratory strains were formed as a method of increasing genetic variability to improve the ethanol tolerance of yeast strains. The hybrids were subjected to competition experiments under continuous culture controlled by pH with increasing ethanol concentrations over a wide range to select the fastest-growing strain at any concentration of ethanol. The continuous culture system was obtained by controlling the dilution rate of a chemostat connected to a pH-meter. The nutrient pump of the chemostat was switched on and off in response to the pH of the culture, which was thereby kept near a critical value (pH_c). Under these conditions, when the medium was supplemented with ethanol, the ethanol concentration of the culture increased with each pulse of dilution. A hybrid strain was selected by this procedure that was more tolerant than any of the highly ethanol-tolerant wine yeast strains at any concentration of ethanol and was able to grow at up to 16% (vol/vol) ethanol. This improvement in ethanol tolerance led to an increase in both the ethanol production rate and the total amount of ethanol produced.     

Presence of aflatoxin M1 in commercial ultra-high-temperature-treated milk.

Forty-seven samples of commercial ultra-high-temperature-treated milk from a dairy facility in the northwest part of Spain were analyzed for the presence of aflatoxin M1. A total of 14 samples (29.8%) were positive for aflatoxin M1 (4 in May, 3 in November, 3 in December, 1 in January, 1 in April, 1 in July, and 1 in August), 29 (61.7%) were negative, and 4 (8.5%) were doubtful, i.e., they showed trace quantities of aflatoxin M1. The range of aflatoxin M1 content was 0.02 to 0.1 ng/ml.     

Effect of glycerol on gluconeogenesis in isolated rabbit kidney cortex tubules

In renal tubules isolated from fed rabbits glycerol is not utilized as a glucose precursor, probably due to the rate-limiting transfer of reducing equivalents from cytosol to mitochondria. Pyruvate and glutamate stimulated an incorporation of [14C]glycerol to glucose by 50- and 10-fold, respectively, indicating that glycerol is utilized as a gluconeogenic substrate under these conditions. Glycerol at concentration of 1.5 mM resulted in an acceleration of both glucose formation and incorporation of [14C]pyruvate and [14C]glutamate into glucose by 2- and 9-fold, respectively, while it decreased the rates of these processes from lactate as a substrate. In the presence of fructose, glycerol decreased the ATP level, limiting the rate of fructose phosphorylation and glucose synthesis. As concluded from the 'cross-over' plots, the ratios of both 3-hydroxybutyrate/acetoacetate and glycerol 3-phosphate/dihydroxyacetone phosphate, as well as from experiments performed with methylene blue and acetoacetate, the stimulatory effect of glycerol on glucose formation from pyruvate and glutamate may result from an acceleration of fluxes through the first steps of gluconeogenesis as well as glyceraldehyde-3-phosphate dehydrogenase. As inhibition by glycerol of gluconeogenesis from lactate is probably due to a marked elevation of the cytosolic NADH/NAD+ ratio resulting in a decline of flux through lactate dehydrogenase.     

Osmotic adjustment in tobacco plantlets

UsingNicotiana tabacum L. plantlets cultivatedin vitro as a model system it was proved that osmotic adjustment may be caused by a decrease in water potential of substrate as well as by a decrease in air humidity.     

Content of phenolic acids in callus culture of alfalfa (Medicago sativa): The effect of age and biochemical differentiation

Phenolic acids were separated into three fractions and determined by HPLC inMedicago sativa callus culture at the age of two, three and four weeks. The contents of free and especially of predominating ester-bound phenolic acids decreased with callus age to approx. 80 % while the content of phenolic acids nonextractable by methanol increased byca. 90 %. The proportion of benzoic acid derivatives rose from 15 to 21 % within four weeks. The determined difference in the contents of phenolic acids in the upper and lower parts of callus diminished with age. The content of bound forms was higher in the lower part regardless of the callus age. The content of free acids in two weeks old callus was half as high as in the upper part.