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Biomedical subjects

M Vitolo

Publications and source records attributed to M Vitolo.

At least 19 recordsLinked to original sources
PubMed2005

[Antibiotic prophylaxis in day surgery in dermatology].

Antibiotic prophylaxis for the prevention of surgical wounds infections is still a matter of debate in dermatology. The authors have performed an open and randomized study on the prophylactic efficacy of azithromycin, 500 mg per os 1 h prior to the procedure in a dermosurgical office. The absence of postsurgical infections when the intervention has been executed in sites without risk of contamination both in the treated and no treated group, has demonstrated that, in the presence of correct prophylactic measures, no antibiotic prophylaxis is necessary. On the other hand, when the procedure has been performed in sites under risk of infection, the antibiotic prophylaxis has instead demonstrated a significant efficacy. The study has documented that azithromycin allows to efficacely prevent bacterical suprainfection with a good compliance of the patient in the cases in which dermosurgical activity is performed in sites with risk of infection (face, scalp, genitals, perineo, feet).

Adult↗
PubMed2003

Batch xylitol production by Candida guilliermondii FTI 20037 from sugarcane bagasse hemicellulosic hydrolyzate at controlled pH values.

Batch fermentation of sugarcane bagasse hemicellulosic hydrolyzate by the yeast Candida guilliermondii FTI 20037 was performed using controlled pH values (3.5, 5.5, 7.5). The maximum values of xylitol volumetric productivity ( Q(p)=0.76 g/l h) and xylose volumetric consumption ( Q(s)=1.19 g/l h) were attained at pH 5.5. At pH 3.5 and 7.5 the Q(p) value decreased by 66 and 72%, respectively. Independently of the pH value, Y(x/s) decreased with the increase in Y(p/s) suggesting that the xylitol bioconversion improves when the cellular growth is limited. At the highest pH value (7.5), the maximum specific xylitol production value was the lowest ( q(pmax)=0.085 g/l h.), indicating that the xylose metabolism of the yeast was diverted from xylitol formation to cell growth.

Bioreactors↗
PubMed2001

Runt-related gene 2 in endothelial cells: inducible expression and specific regulation of cell migration and invasion.

Understanding the regulation of endothelial cell (EC) gene expression has important implications for angiogenesis, tumor growth, and metastasis. The transcription factor runt-related gene 2 (RUNX2)/core binding factoralpha-1/acute myeloid leukemia 3/polyoma enhancer-binding protein 2alphaA/osteoblast-specific transcription factor 2 regulates osteoblast differentiation, increases lymphomagenesis in transgenic mice, and is expressed in murine ECs. Here, we report on RUNX2 expression in human bone marrow EC (HBME-1) and its role in EC differentiation. Expression of RUNX2 occurred in HBME-1 cultured on extracellular matrix (ECM) substrates that stimulate in vitro differentiation (tube formation). Neutralizing anti-insulin-like growth factor (IGF)-I-receptor antibody inhibited tube formation as well as activation of RUNX2 expression in HBME-1 cultured on ECM. IGF-I treatment also increased both RUNX2 mRNA and protein expression. HBME-1 transfectants expressing dominant-negative (DN) RUNX were established to address the role of RUNX2 in these processes. HBME/DN cells exhibited reduced tube formation activity relative to control transfectants and less ability to growth arrest and differentiate on ECM. DNRUNX expression also inhibited HBME-1 migration and invasion, which are necessary for tube formation. The urokinase-type plasminogen activator and membrane-type MMP-1 genes were consistently down-regulated in DNRUNX transfectants. The results suggest that RUNX2 is important in IGF-I and ECM-regulated EC migration and differentiation. RUNX2 effects on HBME-1 migration and invasion may occur through activation of protease expression, events that regulate angiogenesis, and tumor growth.

Animals↗
PubMed2001

Effect of agitation and aeration on production of hexokinase by Saccharomyces cerevisiae.

A batch culture of Saccharomyces cerevisiae for the production of hexokinase was carried out in a 5-L fermentor containing 3 L of culture medium, which was inoculated with cell suspension (about 0.7 g/L), and left fermenting at 35 degrees C and pH 4.0. The aeration and agitation were adjusted to attain k(L)a values of 15, 60, 135, and 230 h(-1). The highest hexokinase productivity (754.6 U/[L x h]) and substrate-cell conversion yield (0.21 g/g) occurred for a k(L)a of 60 h(-1). Moreover, the formation of hexokinase and cell growth are coupled events, which is in accordance with the constitutive character of this enzyme. Hexokinase formation for kLa > 60 h(-1) was not enhanced probably owing to saturation of the respiratory pathway by oxygen.

Air↗
PubMed2001

Preliminary kinetic characterization of xylose reductase and xylitol dehydrogenase extracted from Candida guilliermondii FTI 20037 cultivated in sugarcane bagasse hydrolysate for xylitol production.

Candida guilliermondii FTI 20037 was cultured in sugarcane bagasse hydrolysate supplemented with 2.0 g/L of (NH4)2SO4, 0.1 g/L of CaCl2 x 2H2O, and 20.0 g/L of rice bran at 35 degrees C; pH 4.0; agitation of 300 rpm; and aeration of 0.4, 0.6, or 0.8 vvm. The high xylitol production (20.0 g/L) and xylose reductase (XR) activity (658.8 U/mg of protein) occurred at an aeration of 0.4 vvm. Under this condition, the xylitol dehydrogenase (XD) activity was low. The apparent K(M) for XR and XD against substrates and cofactors were as follows: for XR, 6.4 x 10(-2)M (xylose) and 9.5 x 10(-3) mM (NADPH); for XD, 1.6 x 10(-1)M (xylitol) and 9.9 x 10(-2) mM (NAD+). Because XR requires about 10-fold less xylose and cofactor than XD for the condition in which the reaction rate is half of the Vmax, some interference on the overall xylitol production by the yeast could be expected.

Air↗
PubMed2001

Extraction by reversed micelles of the intracellular enzyme xylose reductase.

Xylose reductase enzyme (EC 1.1.1.21) produced by Candida guilliermondii in sugarcane bagasse was extracted by reversed micelles of N-benzyl-N-dodecyl-N-bis (2-hydroxyethyl) ammonium chloride cationic surfactant. An experimental design was employed to evaluate the influences of the following factors on the enzyme extraction: temperature, cosolvent, and surfactant concentration. A model was used to represent the enzyme recovery and fit of the experimental data. The extraction yielded a total recovery of 130%, and the purity increased 4.8-fold. This study demonstrates that liquid-liquid extraction by reversed micelles is a process able to recover and increase the enzymatic activity and purity of XR produced by C. guilliermondii.

Aldehyde Reductase↗
PubMed2000

Effects of environmental conditions on xylose reductase and xylitol dehydrogenase production by Candida guilliermondii.

The effects of environmental conditions, namely initial pH (2.5-7.0) and temperature (25 and 35 degrees C), on xylose reductase and xylitol dehydrogenase levels, as well as on xylitol production, were evaluated. Although the fermentative parameter values increased with an increase in pH and temperature (the maximum Yp/s and Qp were 0.75 g/g and 0.95 g/[L.h], respectively, both attained at pH 6.0, 35 degrees C), the highest xylose reductase activities (nearly 900 IU/mg of protein) were observed at an initial pH varying from 4.0 to 6.0. Xylitol dehydrogenase was favored by an increase in both initial pH and temperature of the medium. The highest xylitol dehydrogenase specific activity was attained at pH 6.5 and 35 degrees C (577 IU/mg of protein).

Aldehyde Reductase↗
PubMed1999

A preliminary information about continuous fermentation using cell recycling for improving microbial xylitol production rates(scientific note).

Xylitol is a sugar-alcohol with important technological properties, such as anticariogenicity, low caloric value, and negative dissolution heat. It can be used successfully in food formulations and pharmaceutical industries. Its production is therefore in great demand. Biotechnological xylitol production has several economic advantages in comparison with the conventional process based on the chemical reduction of xylose. The efficiency and the productivity of this fermentation chiefly depends on the microorganism and the process conditions employed. In this article a simple continuous culture with cell recycling was evaluated to enhance the capability of Candida guilliermondii FTI 20037 to produce xylitol. The fermentation was initiated batchwise by directly inoculating the grown seed culture in a 2-L bench-scale fermentor. Continuous feeding was begun at a dilution rate (D) of 0.060/h after the xylose concentration had completely consumed and the cell concentration was about 4.0 g/L. At a dilution rate of 0.060/h the xylitol concentration was about 15 g/L and increased by about 35%, whereas the dilution rate decreased by about 58%. Furthermore, the volumetric productivity, Qp, markedly depended on the dilution rate, diminishing by about 37% as D was changed from 0.060 to 0.025/h. These preliminary results show us that continuous fermentation with cell recycling is a good way to study the xylitol production by xylose-fermenting yeasts.

Journal Article↗
PubMed1999

Characterization of invertase entrapped into calcium alginate beads.

A solution of 10 g/L of sodium alginate (Satialgine types used [Sanofi trademark]: SG800 and S1100 with manuronic/guluronic ratio of 0.5 and 1.2, respectively) containing invertase (0.08 g of protein/L) was dropped into 0.1 M CaCl2 solution buffered at pH 4.0, 7.0, or 8.0. The beads were left to harden in CaCl2 solution for 24 h. The high immobilization yield of 60% occurred with SG800 at pH 8.0. The activity of soluble and insoluble invertase was measured against pH (2.8-8.0), sucrose concentration (4.5-45 mM), and temperature (30-60 degrees C). Both forms presented an optimum pH of 4.6. However, the soluble invertase was stable at the overall pH interval studied, whereas insoluble invertase lost 30% of its original activity at pH > 5.0. At temperatures above 40 degrees C, the insoluble form was more stable than the soluble one. The kinetic constants and activation energies (Ea) for free invertase were KM = 41.2 mM, Vmax = 0.10 mg of TRS/(min.mL), and Ea 28 kJ/mol for entrapped invertase they were (KM)ap = 7.2 mM, (Vmax)ap = 0.060 mg of TRS/(min.mL), and (Ea)ap = 24 kJ/mol.

Alginates↗
PubMed1998

Adaptation and reutilization of Candida guilliermondii cells for xylitol production in bagasse hydrolysate.

The xylitol productivity increased by about 15% with the use of cells of Candida guilliermondii FTI 20037 previously recycled through four consecutive batch cultures and adapted to the sugar cane bagasse hemicellulosic hydrolysate. Furthermore, the more concentrated the hydrolysate, the more necessary was the adaptation of the cells, owing to the presence of toxic substances at high concentration which inhibited the xylose-xylitol conversion by the yeast.

Candida↗
PubMed1996

Hexokinase production from S. cerevisiae. Culture conditions.

The effects of pH (4.0, 4.5, or 5.0), temperature (T) (30, 35, or 40 degrees C) and dissolved oxygen (DO) (0.2, 2.0, 4.0,or 6.0 mg O2/L) on hexokinase and invertase formation by yeast were studied. The highest enzyme activities were attained at pH 4.0, DO = 4.0 mg O2/L, and T = 35 or 40 degrees C.

Glycoside Hydrolases↗
PubMed1995

Effect of acetic acid on xylose fermentation to xylitol by Candida guilliermondii.

The effect of acetic acid concentration on xylose-fermentation to xylitol by Candida guilliermondii FTI 20037 was evaluated in semisynthetic medium containing different concentrations of the acid. Increasing acetic acid concentration up to 1.0 g/l favored xylitol yield and productivity, with maximum values of 0.82 g/g and 0.57 g/l.h, respectively. The presence of acetic acid reduced cell production at all concentration. Furthermore, acetic acid was assimilated by the yeast together with the sugars and was depleted from the medium at concentrations of less than 3.0 g/l. The ability of this yeast to assimilate acetic acid suggests that these cells act as agents of medium detoxification. This behavior may lead to a viable microbiological process of xylitol production by C. guilliermondii FTI 20037 using xylose-rich lignocellulosic hydrolysates in which acetic acid is commonly present, causing inhibition of fermentative activity.

Acetates↗
PubMed1995

Effect of pH, aeration and sucrose feeding on the invertase activity of intact S. cerevisiae cells grown in sugarcane blackstrap molasses.

S. cerevisiae was grown in a blackstrap molasses containing medium in batch and fed-batch cultures. The following parameters were varied: pH (from 4.0 to 6.5), dissolved oxygen (DO) (from 0 to 5.0 mg O2 L-1) and sucrose feeding rate. When glucose concentration (S) was higher than 0.5 g L-1 a reduction in the specific invertase activity of intact cells (v) and an oscillatory behavior of v values during fermentation were observed. Both the invertase reduction and the oscillatory behavior of v values could be related to the glucose inhibitory effect on invertase biosynthesis. The best culture conditions for attaining S. cerevisiae cells suitable for invertase production were: temperature = 30 degrees C; pH = 5.0; DO = 3.3 mg O2 L-1; (S) = 0.5 g L-1 and sucrose added into the fermenter according to the equations: (V-Vo) = t2/16 or (V - Vo) = (Vf - Vo).(e0.6t-1)/10.

Culture Media↗
PubMed1994

Effect of moisture content on the invertase activity of freeze-dried S. cerevisiae.

The invertase activity of intact Saccharomyces cerevisiae submitted to freezing-thawing was affected by pH, the chemical nature of the buffer, and the freezing cooling rate (CR), leading in some cases to a complete invertase inactivation (acetate buffer, pH 4.0, CR = 0.5 degree C/min). Once established under adequate freezing conditions the invertase activity remained unchanged after freeze-drying. Nevertheless, in some cases the cell-growing capability after freeze-drying diminished around 70%, mainly if the frozen cell suspension was attained through freezing carried out at CR = 0.5 degree C/min. Water sorption isotherms of freeze-dried samples (freeze-dryer Edwards L-4KR; 30 degrees C and 0.1 mB) were determined at 10 and 25 degrees C. The monolayer moisture content (MMC) at each temperature (12.7 and 3.71 for 10 and 25 degrees C, respectively) was calculated from isotherms by applying BET and GAB models. Freeze-dried yeast with water activity (Aw) between 0 and 0.33 (about the MMC value) maintained at 25 degrees C for 235 days and at 89 degrees C for 15 min retained at least 85% of its original invertase activity (IA), whereas samples with Aw > MMC lost at least 60% of its IA. X ray diffraction showed that the freeze-dried cake before and after storage presented an amorphous structure.

Buffers↗
PubMed1983

Measurement of invertase activity of cells of Saccharomyces cerevisiae.

The determination of the invertase activity of intact yeast cells presents a critical point, that is, the blockage of the enzyme action at a given moment. In this paper seven blockage methods were compared: the addition of 0.010 M sodium hydroxide solution, addition of 0.010 M sodium carbonate solution, addition of 0.010 M sodium carbonate solution followed by centrifugation (9750g; 10 min), immersion of the reacting mixture in a boiling water bath, immersion of the mixture in a -15 degrees C bath, filtration through a Millipore membrane, and addition of the first Somogyi's reagent followed by immersion in a boiling water bath. Only the last two methods lead to a rapid and effective blockage of the invertase activity.

Chemical Phenomena↗
PubMedDate not supplied

Upstream parameters affecting the cell growth and xylitol production by Candida guilliermondii FTI 20037.

The effects of yeast extract (0-10 g/l), methanol (0-10% v/v), acetic acid (0-1.0 g/l), furfural (0-0.5 g/l), glucose (0-30 g/l), inoculum age (15-70 h) and product concentration (18-230 g/l) on the xylose-xylitol conversion by Candida guilliermondii FTI 20037 were studied. The xylitol specific productivity increased about 35% at a yeast extract concentration of 1.0 g/l, whereas glucose showed a strong inhibitory effect on the xylitol production and a stimulating effect on the growth of C. guilliermondii. Methanol, acetic acid and furfural under the employed concentrations did not show any positive effect neither on the growth or on the xylose-xylitol conversion by the yeast. The inoculum age showed a strong influence on xylitol formation and the best fermentative parameters were attained using a 40-h inoculum age. A xylitol concentration in the fermentation medium higher than 80 g/l inhibited markedly the xylitol productivity by the yeast C. guilliermondii.

Acetic Acid↗
PubMedDate not supplied

Use of immobilized Candida cells on xylitol production from sugarcane bagasse.

In this study we used the yeast Candida guilliermondii FTI 20037 immobilized by entrapment in Ca-alginate beads (2.5-3 mm diameter) for xylitol production from concentrated sugarcane bagasse hemicellulosic hydrolysate in a repeated batch system. The fermentation runs were carried out in 125- and 250-ml Erlenmeyer flasks placed in an orbital shaker at 30 degrees C and 200 rpm during 72 h, keeping constant the proportion between work volume and flask total volume. According to the results, cell viability was substantially high (98%) in all fermentative cycles. The values of parameters xylitol yield and volumetric productivity increased significantly with the reutilization of the immobilized biocatalysts. The highest values of xylitol final concentration (11.05 g/l), yield factor (0.47 g/g) and volumetric productivity (0.22 g/lh) were obtained in 250-ml Erlenmeyer flasks containing 80 ml of medium plus 20 ml of immobilized biocatalysts. The support used in this study (Ca-alginate) presented stability in the experimental conditions used. The results show that the use of immobilized cells is a promising approach for increasing the xylitol production rates.

Candida↗