Relation between Citric Acid Production and Respiration Rate of Aspergillus niger in Solid‐State Fermentation

Among the organic acids produced industrially, citric acid is the most important in quantitative terms. Solid‐state fermentation (SSF) has been an alternative method for citric acid production using agro‐industrial residues such as cassava bagasse (CB). The use of CB as a substrate can avoid environmental problems caused by its disposal into the environment. This study was developed to verify the influence of the treated bagasse amount, and consequently, the influence of the gelatinization degree of CB starch on citric acid production by SSF in Erlenmeyer flasks, horizontal drums, and trays. The best results were obtained in a horizontal drum bioreactor using 100 % of treated CB. However, trays showed advantages and good perspectives for large‐scale citric acid production due to economic reasons such as energy costs. A kinetic study was also carried out in order to compare citric acid production in glass columns (laboratory scale) and horizontal drum bioreactors (semi‐pilot scale). This study was accomplished in order to follow the influence of aeration on citric acid accumulation. In addition, the production of CO₂ was evaluated as an indirect method of biomass estimation. Citric acid production was higher in glass columns (309.70 g/kg of dry CB) than in HD bioreactors (268.94 g/kg of dry CB). Finally, it was possible to show that citric acid production was favored by a limited biomass production, which occurred with low aeration rates. Biomass production is related to CO₂ production and as a result, a respirometry analysis could be used for biomass estimation.     

Murein Hydrolase Activity in the Surface Layer of Lactobacillus acidophilus ATCC 4356

We describe a new enzymatic functionality for the surface layer (S-layer) of Lactobacillus acidophilus ATCC 4356, namely, an endopeptidase activity against the cell wall of Salmonella enterica serovar Newport, assayed via zymograms and identified by Western blotting. Based on amino acid sequence comparisons, the hydrolase activity was predicted to be located at the C terminus. Subsequent cloning and expression of the C-terminal domain in Bacillus subtilis resulted in the functional verification of the enzymatic activity.     

Numerical Taxonomy of Microorganisms Isolated from Goat Cheese Made in Chile

118 strains of heterotrophic microorganisms were isolated from goat cheese produced domestically in the IV Region of Northern Chile (Serene, Ovalle, and Illapel) and sold in supermarkets in Valparaíso, Chile. The results of 89 phenotypic tests were numerically analyzed against 17 reference strains, using the simple matching coefficient (S_SM). Thirteen phena were found at a 78% similarity level. Five of them (A, B, C, D, and E) were assigned to the family Enterobacteriaceae, phenon F was identified as belonging to the genus Aeromonas and strains of phenon G were assigned to the genus Acinetobacter. The other phena were identified as being members of the genera Bacillus (H, I, and J), Staphylococcus (K), Enterococcus (L), and Micrococcus (M). Approximately 19% of the isolates were Escherichia coli and 27%, Staphylococcus aureus. Received: 20 February 2001 / Accepted: 12 April 2001     

KCNE1 is an auxiliary subunit of two distinct ion channel superfamilies

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Quantification of Inter-particle Spacing Caused by Thiol Self-Assembled Monolayers Using Transmission Electron Microscopy

Plasmonics - Nano-surface modification techniques have been increasingly reported in a multitude of applications. However, the metal-ligand interface can be difficult to characterize, mainly due to...     

Menarcheal age in medio-altitude sample. Comparison with another populations of same province. Cuenca (Spain)

Environmental contributions to variation on menarcheal age were studied in 2018 Spanish girls and women from de Province of Cuenca. (Spain). This province has a big variation in altitude and is one of the most representative as middle-altitude population in Spain. Maturation's delay in high populations is well referenced but there are less studies in European middle-altitude populations. To give news about this topic is the main objective of this paper. Retrospective Method was employed in adult sample and Status-Quo in young population (9 to 15 years old) Another social, nutritional, somatic and educational levels was recording to give a variation contest. Our study shows a significantly variation between the provincial areas. In effect, the population of “Sierra”, the mountain region has the last maturation in the adults (13.45±0.73) as well as in girls (13.26±1.07). Secular change was observed in relation with this parameter., but less intense that in total, of province. We can confirm the utility of the age of menarche as evaluator of human variation in time and ecological situations.     

A study of the mating system in Dolichandra cynanchoides (Bignoniaceae): an Argentinian Chaco woodlands liane with a late-acting self-incompatibility

We estimated the outcrossing rate in a population of 14 individuals of Dolichandra cynanchoides (Bignoniaceae), a species with late-acting self-incompatibility (LSI), at a site in Chaco woodland in Santa Fe province, Argentina. A subsample of five arbitrarily chosen loci from a total of 16 allozyme loci gave mating system parameters of t_m=0.881 (SD 0.039) and t_s=0.749 (SD 0.048), thus indicating that although predominantly outcrossing, D. cynanchoides has a mixed mating system. We draw attention to the fact that mixed mating in species with LSI is a very likely scenario, given that previous studies with diverse LSI taxa have shown that mixed cross-self pollen loads on the stigma, which is probably a common occurrence with natural pollinators, result in fruits with a proportion of selfed seeds.     

The sweet jelly of Combretum lanceolatum flowers (Combretaceae): a cornucopia resource for bird pollinators in the Pantanal, western Brazil

 The pollination biology of the neotropical scandent shrub Combretum lanceolatum was studied in the seasonally-flooded Pantanal region in western Brazil. This plant bears horizontally oriented inflorescences, whose yellowish green flowers begin to expand at dusk and are fully open at dawn. Instead of fluid nectar the flowers produce sweet gelatinous secretion in form of pellets. The glandular complex of the flower is composed of the inner wall of the receptacle and its tubular extension, being equivalent to the nectariferous disk of the nectar-producing species within the genus. The jelly is produced at night, contains mannan and is imbibed by free hexoses. It originates by swelling and disintegration of the inner wall, after contact with the nectar generated concomitantly in the mesophyll. Combretum lanceolatum is unique within the genus in its production of jelly pellets instead of liquid nectar. A new term, the jelly-flower, is proposed for flowers with this kind of reward. The pellet is not replaced once removed by a bird, and thus resembles a fruit in its availability to consumers, another unique feature that distinguishes this species within the genus. The jelly pellets offered by the many flowered branches attract a great diversity of bird visitors (28 species from eight families), which feed on this copious food resource and pollinate the flowers. The most effective pollinators probably are thrushes, tanagers, and orioles. Flocking parakeets and macaws sometimes feed on the petals, thus acting as flower plunderers. Combretum lanceolatum presents a high fruit set under natural conditions, which likely favours its spreading and becoming a weed species. Received July 11, 2000 Accepted November 18, 2000     

Pyridostigmine Restores Cardiac Autonomic Balance after Small Myocardial Infarction in Mice

The effect of pyridostigmine (PYR) - an acetylcholinesterase inhibitor - on hemodynamics and cardiac autonomic control, was never studied in conscious myocardial infarcted mice. Telemetry transmitters were implanted into the carotid artery under isoflurane anesthesia. Seven to ten days after recovery from the surgery, basal arterial pressure and heart rate were recorded, while parasympathetic and sympathetic tone (ΔHR) was evaluated by means of methyl atropine and propranolol. After the basal hemodynamic recording the mice were subjected to left coronary artery ligation for producing myocardial infarction (MI), or sham operation, and implantation of minipumps filled with PYR or saline. Separate groups of anesthetized (isoflurane) mice previously (4 weeks) subjected to MI, or sham coronary artery ligation, were submitted to cardiac function examination. The mice exhibited an infarct length of approximately 12%, no change in arterial pressure and increased heart rate only in the 1st week after MI. Vagal tone decreased in the 1^st week, while the sympathetic tone was increased in the 1^st and 4^th week after MI. PYR prevented the increase in heart rate but did not affect the arterial pressure. Moreover, PYR prevented the increase in sympathetic tone throughout the 4 weeks. Concerning the parasympathetic tone, PYR not only impaired its attenuation in the 1^st week, but enhanced it in the 4^th week. MI decreased ejection fraction and increased diastolic and systolic volume. Therefore, the pharmacological increase of peripheral acetylcholine availability by means of PYR prevented tachycardia, increased parasympathetic and decreased sympathetic tone after MI in mice.     

Biodegradation by activated sludge and toxicity of tetracycline into a semi-industrial membrane bioreactor

Much attention has been devoted recently to the fate of pharmaceutically active compounds such as tetracycline antibiotics in soil and water. Tetracycline (TC) biodegradability by activated sludge derived from membrane bioreactor (MBR) treating swine wastewater via CO₂-evolution was evaluated by means of modified Sturm test, which was also used to evaluate its toxicity on carbon degradation. The impact of tetracycline on a semi-industrial MBR process was also examined and confronted to lab-scale experiments. After tetracycline injection in the pilot, no disturbance was detected on the elimination of organic matters and ammonium (nitrification), reaching after injection 88% and 99% respectively; only denitrification was slightly affected. Confirming the ruggedness and the superiority of membrane bioreactors over conventional bioreactors, no toxicity was observed at the considered level of TC in the pilot (20 mg TOC L⁻¹), while at lab-scale sodium benzoate biodegradation was completely inhibited from 10 mg TOC L⁻¹ TC. The origin of the activated sludge showed a significant impact on the performances, since the ultimate biodegradation was in the range −50% to −53% for TC concentrations in the range 10–20 mg TOC L⁻¹ with conventional bioreactor sludge and increased to 18% for 40 mg TOC L⁻¹ of TC with activated sludge derived from the MBR pilot. This confirmed the higher resistance of activated sludge arising from membrane bioreactor.