Factors influencing the synthesis of an extracellular proteinase by Enterococcus faecalis subsp. liquefaciens

Studies were conducted on optimum temperature, pH and the requirement for an energy source, amino acids, casein, Zn²⁺ and Ca²⁺ during the synthesis of an extracellular acid proteinase by Enterococcus faecalis var. liquefaciens. Synthesis was monitored using cells grown to mid-logarithmic phase and resuspended at high density in fresh growth medium. Proteinase production was optimal at 30°C and pH 7.0. Proteinase synthesis, being energy-dependent, occurred only in glycolysing cells. The synthesis was high when lactose but not glucose was utilized as a source of energy, indicating that phospho-β-galactosidase gene might probably be located directly upstream the proteinase gene on a plasmid. Good induction of proteinase synthesis could be achieved by 0.2–0.5 % of either yeast extract or tryptic digested casein, perhaps due to its content of a wide variety of free amino acids. Casein was essential for preventing proteinase autolysis and sustaining the enzyme production. Zn²⁺ and Ca²⁺ were required for the formation of an active extracellular proteinase. The synthesis immediately ceased after addition of chloramphenicol or EDTA. EDTA inactivated the preformed proteinase as well. Sodium chloride at a concentration of 6.5 % inhibited both proteinase synthesis and glycolysis.     

Production of acetoin and diacetyl by lactic acid bacteria in skimmed milk with added citrate and pyruvate

Summary Thirty-two strains of starter cultures and lactic acid bacteria belonging to the genera Streptococcus, Leuconostoc and Lactobacillus were studied for their ability to produce acetoin (A) and diacetyl (D) from citrate and pyruvate added separately to skim milk and from pyruvate added to peptone-yeast extract-glucose broth (PYG).The largest amount of A + D was produced from citrate and by the citrate fermenters Streptococcus cremoris AM₂, Str. faecalis, Leuconostoc citrovorum ATCC 8082, L. Gasei ATCC 393, L. Gasei ssp. alactosus and L. xylosus. Some strains of Str. cremoris, Str. thermophilus, some strains of L. Gasei, L. plantarum and L. coryniformis on the contrary produced more A + D from pyruvate than from citrate. Str. cremoris AM₂ should be designated as Str. diaceticremoris like Str. diacetilactis.PYG was more favourable than skim milk for production of A + D from pyruvate by Str. lactis, some strains of Str. cremoris, Str. faecalis and lactobacilli. Pyruvate as a sole source of carbon gave a poor yield of A + D compared to itself in the presence of glucose in case of most of the streptococci and all of the lactobacilli.The largest amount of diacetyl was produced by 70% of the streptococci from citrate added to skim milk, and by the great most of the lactobacilli from pyruvate in PYG medium.

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Produktion von Acetoin durch Milchsäurebakterien in mit Zitrat und Pyruvat angereicherter Magermilch

Zusammenfassung Insgesamt 32 Säureweckerkulturen der Gattungen Streptococcus, Leuconostoc und Lactobacillus wurden unter Verwendung unterschiedlicher Nährsubstrate auf die Bildung von Acetoin und Diacetyl untersucht. Es zeigte sich, daß je nach Nährbodenzusammensetzung und Bakterienstamm unterschiedliche Mengen der genannten Aromastoffe gebildet wurden.

     

Rapid quantitative method for total brominated vegetable oil in soft drinks using ion chromatography

A simple, quantitative and rapid method for total brominated vegetable oil (BVO) using ion chromatography (IC) with suppressed conductivity detection was developed and successfully applied to soft drinks with results expressed as inorganic bromide anion. The procedure involves extraction of BVO with diethyl ether and treatment with zinc dust in a solution of acetic acid, giving recoveries ranging between 92.5 and 98.5%. The calibration curves obtained were linear with correlation coefficients (r (2)) of 0.998, a coefficient of variation (CV) of less than 5% and limit of detection (LOD) and limit of quantification (LOQ) of 250 and 750?μg?l(-1), respectively. The method was successfully applied to the determination of BVO in several commercial soft drinks which were found to contain BVO in the range 1.8-14.510?mg?l(-1). The method has less sources of error compared to previously published methods.     

Preparation of polyaniline and studying its electrical conductivity

Polyaniline was prepared by chemical methods. Its electrical conductivity was measured. The electrical conductivity of polyaniline salt and polyaniline base were compared with composites prepared by the hot press of polyaniline base with KBr, Co(CH₃COO)₂, and picric acid. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1658–1665, 2000     

Topography of brain sodium accumulation in progressive multiple sclerosis

Object

Sodium accumulation is involved in neuronal injury occurring in multiple sclerosis (MS). We aimed to assess sodium accumulation in progressive MS, known to suffer from severe neuronal injury.

Materials and methods

3D-²³Na-MRI was obtained on a 3T-MR-scanner in 20 progressive MS patients [11 primary-progressive (PPMS) and nine secondary-progressive (SPMS)] and 15 controls. Total sodium concentrations (TSC) within grey matter (GM), normal-appearing white matter (WM) and lesions were extracted. Statistical mapping analyses of TSC abnormalities were also performed.

Results

Progressive MS patients presented higher GM–TSC values (48.8 ± 3.1 mmol/l wet tissue vol, p < 0.001) and T₂lesions-TSC values (50.9 ± 2.2 mmol/l wet tissue vol, p = 0.01) compared to GM and WM of controls. Statistical mapping analysis showed TSC increases in PPMS patients confined to motor and somatosensory cortices, prefrontal cortices, pons and cerebellum. In SPMS, TSC increases were associated with areas involving: primary motor, premotor and somatosensory cortices; prefrontal, cingulate and visual cortices; the corpus callosum, thalami, brainstem and cerebellum. Anterior prefrontal and premotor cortices TSC were correlated with disability.

Conclusion

Sodium accumulation is present in progressive MS patients, more restricted to the motor system in PPMS and more widespread in SPMS. Local brain sodium accumulation appears as a promising marker to monitor patients with progressive MS.     

The microbial flora of Awshari cheese with special reference to lactobacilli

Thirty seven samples of Awshari cheese and 13 of Biza were examined microbiologically. Penicillia occurred in 2 samples of cheese and yeasts in 21, 3 of which contained Saccharomyces lactis. In 8 samples studied for the constitutive microflora, lactobacilli and streptococci were the most prevalent, with L. casei being the only Lactobacillus species isolated. Penicillia and yeasts occurred in all the samples of Biza, with Saccharomyces lactis being encountered in 5 out of 6 samples examined for the type of yeasts. The microbial flora consisted primarily of lactobacilli. Out of 98 lactobacilli isolated from 10 samples 55 were identified as betabacteria: 41 were attached to L. brevis, 13 L. buchneri and 1 L. pasteurianus. The remaining 43 isolates were streptobacteria: 21 belonged to L. coryniformis, 5 L. casei ssp pseudoplantarum, 3 ssp casei and 1 ssp alactosus, 2 L. plantarum ssp plantarum and 1 ssp arabinosus, 1 L. xylosus, 5 motile streptobacteria and 4 unidentifiable.     

Proteolysis and electrophoretic pattern of casein of some fermented milks

Proteolysis and electrophoretic pattern of casein were determined in Friesian cows' skim milk, buffaloes' skim milk and in these milks fermented spontaneously (leben rayeb) and by Streptococcus lactis subsp. diacetylactis DRC3 (nonfat buttermilk) or by zabadi starter (zabadi). The highest proteolysis, as evidenced by the amount of released leucine, occurred in zabadi and the lowest in leben rayeb. The highest amount of tyrosine was liberated in the nonfat buttermilk. Proteolysis seems not to depend on the kind of milk used. A band of a relatively high density appeared to be released from alpha s-casein by the cell-wall proteinase of the microflora of raw milk and by heating at 90 degrees C for 1 min. Cows' skim milk, raw or heated, showed the presence of 2 probable proteose-peptone components; buffaloes' skim milk 3 and 2. These components underwent slow or rapid degradation, depending on the type of fermented milk during skim milk coagulation.     

The Improvement of the Quality of Raffinate Obtained from Solvent Extraction of Lubricating Oils

Abstract

Vacuum distillates of an Egyptian crude oil were subjected to solvent extraction process applying N-methyl-2-pyrrolidone (NMP) and furfural as dearomatization solvents. The study shows that the extraction solvent together with the temperature and solvent-to-oil ratio have a significant effect on the yield and quality of produced lubricating oils. The optimum temperature for extracting light waxy distillates with NMP is 55°C at the solvent-to-feed ratio 2:1. These conditions are appropriate to remove the major portion of aromatics from the raffinate. The apparent activation energy (Ea), enthalpy (ΔH*), entropy (ΔS*), and free energy of activation (ΔG*) were calculated for the solvent dearomatization process.     

Multi-objective topology optimization of multi-component continuum structures via a Kriging-interpolated level set approach

This paper explores a framework for topology optimization of multi-component sheet metal structures, such as those often used in the automotive industry. The primary reason for having multiple components in a structure is to reduce the manufacturing cost, which can become prohibitively expensive otherwise. Having a multi-component structure necessitates re-joining, which often comes at sacrifices in the assembly cost, weight and structural performance. The problem of designing a multi-component structure is thus posed in a multi-objective framework. Approaches to solve the problem may be classified into single and two stage approaches. Two-stage approaches start by focusing solely on structural performance in order to obtain optimal monolithic (single piece) designs, and then the decomposition into multiple components is considered without changing the base topology (identical to the monolithic design). Single-stage approaches simultaneously attempt to optimize both the base topology and its decomposition. Decomposition is an inherently discrete problem, and as such, non-gradient methods are needed for single-stage and second stage of two-stage approaches. This paper adopts an implicit formulation (level-sets) of the design variables, which significantly reduces the number of design variables needed in either single or two stage approaches. The number of design variables in the formulation is independent from the meshing size, which enables application of non-gradient methods to realistic designs. Test results of a short cantilever and an L-shaped bracket studies show reasonable success of both single and two stage approaches, with each approach having different merits.