Retamycin production by immobilized cells of Streptomyces olindensis ICB20 in repeated-batch cultures

Repeated-batch cultures of Ca-alginate immobilized cells of Streptomyces olindensis ICB20 for retamycin production were carried out in two different bioreactors: a basket-type stirred tank reactor (BSTR) and a bubble column reactor (BCR). Higher average values of retamycin content (R) and productivity (P-R) were achieved in the BSTR cultures (about 1.7 AU and 0.031 AU h(-1), respectively) compared to those obtained in the BCR cultures (about 0.6 AU and 0.012 AU h(-1), respectively). The BCR, on the other hand, presented significantly better operation stability than the BSTR, which makes the former much more promising regarding future industrial applications. (C) 2008 Elsevier Ltd. All rights reserved.

Cephalosporin C production by immobilized Cephalosporium acremonium cells in a repeated batch tower bioreactor

The industrial production of antibiotics with filamentous fungi is usually carried out in conventional aerated and agitated tank fermentors. Highly viscous non-Newtonian broths are produced and a compromise must be found between convenient shear stress and adequate oxygen transfer. In this work, cephalosporin C production by bioparticles of immobilized cells of Cephalosporium acremonium ATCC 48272 was studied in a repeated batch tower bioreactor as an alternative to the conventional process. Also, gas-liquid oxygen transfer volumetric coefficients, k(L)a, were determined at various air flow-rates and alumina contents in the bioparticle. The bioparticles were composed of calcium alginate (2.0% w/w), alumina (<44 micra), cells, and water. A model describing the cell growth, cephalosporin C production, oxygen, glucose, and sucrose consumption was proposed. To describe the radial variation of oxygen concentration within the pellet, the reaction-diffusion model forecasting a dead core bioparticle was adopted. The k(L)a measurements with gel beads prepared with 0.0, 1.0, 1.5, and 2.0% alumina showed that a higher k(L)a value is attained with 1.5 and 2.0%. An expression relating this coefficient to particle density, liquid density, and air velocity was obtained and further utilized in the simulation of the proposed model. Batch, followed by repeated batch experiments, were accomplished by draining the spent medium, washing with saline solution, and pouring fresh medium into the bioreactor. Results showed that glucose is consumed very quickly, within 24 h, followed by sucrose consumption and cephalosporin C production. Higher productivities were attained during the second batch, as cell concentration was already high, resulting in rapid glucose consumption and an early derepression of cephalosporin C synthesizing enzymes. The model incorporated this improvement predicting higher cephalosporin C productivity. (C) 2004 Wiley Periodicals, Inc.

Efeito do polietilenoglicol e da albumina na imobilização de lipase microbiana e na catálise em meio orgânico

Poly (ethylene) glycol (PEG) and bovine serum albumin (BSA), as additive agents, were used to enhance the activity of immobilized microbial lipase in organic solvent. Controlled pore silica (CPS) was selected as matrix and different immobilization procedures were evaluated: directly lipase binding on CPS and simultaneous addition of lipase and additive agent on the same support. The highest coupling yield (59.6%) was attained when the immobilization procedure was performed at lipase loading of 150 U/g support in the presence of PEG-1.500. This immobilized system was used in esterification reactions under repeated batch cycles and the biocatalyst half-life was found to increase 2.7 times when compared with the control.

Continuous production of L-glutaminase by an immobilized marine Pseudomonas sp BTMS-51 in a packed bed reactor

A marine Pseudomonas sp BTMS-51, immobilized by Ca-alginate gel entrapment was used for the production of extracellular Lglutaminase under repeated batch process and continuous process employing a packed bed reactor (PBR). Immobilized cells could produce an average of 25 U/ml of enzyme over 20 cycles of repeated batch operation and did not show any decline in production upon reuse. The enzyme yield correlated well with the biomass content in the beads. Continuous production of the enzyme in PBR was studied at different substrate concentrations and dilution rates. In general, the volumetric productivity increased with increased dilution rate and substrate concentrations and the substrate conversion efficiency declined. The PBR operated under conditions giving maximal substrate conversion efficiency gave an average yield of 21.07 U/ml and an average productivity of 13.49 U/ml/h. The system could be operated for 120 h without any decline in productivity

Biorefinery development through utilization of biodiesel industry by-products as sole fermentation feedstock for 1,3-propanediol production

Rapeseed meal (RSM) hydrolysate was evaluated as substitute for commercial nutrient supplements in 1,3-propanediol (PDO) fermentation using the strain Clostridium butyricum VPI 1718. RSM was enzymatically converted into a generic fermentation feedstock, enriched in amino acids, peptides and various micro-nutrients, using crude enzyme consortia produced via solid state fermentation by a fungal strain of Aspergillus oryzae. Initial free amino nitrogen concentration influenced PDO production in batch cultures. RSM hydrolysates were compared with commercial nutrient supplements regarding PDO production in fed-batch cultures carried out in a bench-scale bioreactor. The utilization of RSM hydrolysates in repeated batch cultivation resulted in a PDO concentration of 65.5 g/L with an overall productivity of 1.15 g/L/h that was almost 2 times higher than the productivity achieved when yeast extract was used as nutrient supplement.

Clavulanic acid production processes in a tower bioreactor with immobilised cells

The feasibility of using Streptomyces clavuligerus ATCC 27064 bioparticles supported on alginate gel containing alumina to produce clavulanic acid (CA) was investigated. To this end, effectiveness factors for spherical bioparticles, relating respiration rates of immobilised and free cells, were experimentally determined for various dissolved oxygen (DO) levels and bioparticle radii. Monod kinetics was assumed as representative of the oxygen consuming reaction, while internal oxygen diffusion was considered the limiting step. A comparison was made of the results from a tower bioreactor operating under batch, repeated-batch and continuous conditions with immobilised bioparticles. The theoretical curve of the effectiveness factor for the zero-order reaction model, considering an inert nucleus - the dead core model - was very well fitted to the experimental data. The results of the bioprocess indicated that the batch operation was the most efficient and productive, requiring a do concentration in the reactor above 60% of the saturation value. (C) 2007 Elsevier B.V. All rights reserved.

Produção de etanol em meio sintético com recuperação de fermento entre bateladas sucessivas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Repeated fed-batch cultivation of Arthrospira (Spirulina) platensis using urea as nitrogen source

Arthospira (Spirulina) platensis (Nordstedt) Gomont was autotrophically cultivated for biomass production in repeated fed-batch process using urea as nitrogen source, with the aim of making large-scale production easier, increasing cell productivity and then reducing the production costs. It was investigated the influence or the ratio of renewed volume to total volume (R), the Urea feeding time (t(f)) and the number of successive repealed fed-batch cycles on the maximum cell concentration (X(m)), cell productivity (P(x)), nitrogen-to-cell conversion yield (Y(x/n)), maximum specific growth rate (mu(m)) and protein content of, dry biomass. The experimental results demonstrated chat R=0.80 and t(f) = 6d were the best cultivation conditions, being able to simultaneously ensure, throughout the three fed-batch cycles, the highest average values of three of the five responses (X(m) = 2101 +/- 113 mg L(-1), P(x) = 219 +/- 13 mg L(-1) d(-1) and Y(x/n) = 10.3 +/- 0.8,g g(-1)). (C) 2008 Elsevier B.V. All rights reserved.

[repeated Fine-needle Aspiration Cytology For The Diagnosis And Follow-up Of Thyroid Nodules].

The recently-proposed Bethesda reporting system has offered clinical recommendations for each category of reported thyroid cytology, including repeated fine-needle aspiration (FNA) for non-diagnostic and atypia/follicular lesions of undetermined significance, but there are no sound indications for repeated examination after an initial benign exam. To investigate the clinical validity of repeated FNA in the management of patients with thyroid nodules. The present study evaluated 412 consecutive patients who had repeated aspiration biopsies of thyroid nodules after an initial non-diagnostic, atypia/follicular lesion of undetermined significance, or benign cytology. The majority of patients were female (93.5%) ranging from 13 to 83 years. Non-diagnostic cytology was the most common indication for a repeated examination in 237 patients (57.5%), followed by benign (36.8%), and A/FLUS (5.6%) cytology. A repeated examination altered the initial diagnosis in 70.5% and 78.3% of the non-diagnostic and A/FLUS patients, respectively, whereas only 28.9% of patients with a benign cytology presented with a different diagnosis on a sequential FNA. Repeat FNA is a valuable procedure in cases with initial non-diagnostic or A/FLUS cytology, but its routine use for patients with an initial benign examination appears to not increase the expected likelihood of a malignant finding.

Effect of repeated disinfections by microwave energy on the physical and mechanical properties of denture base acrylic resins

The present study evaluated the effect of repeated simulated microwave disinfection on physical and mechanical properties of Clássico, Onda-Cryl and QC-20 denture base acrylic resins. Aluminum patterns were included in metallic or plastic flasks with dental stone following the traditional packing method. The powder/liquid mixing ratio was established according to the manufacturer's instructions. After water-bath polymerization at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling and finished. Each specimen was immersed in 150 mL of distilled water and underwent 5 disinfection cycles in a microwave oven set at 650 W for 3 min. Non-disinfected and disinfected specimens were subjected to the following tets: Knoop hardness test was performed with 25 g load for 10 s, impact strength test was done using the Charpy system with 40 kpcm, and 3-point bending test (flexural strength) was performed at a crosshead speed of 0.5 mm/min until fracture. Data were analyzed statistically by ANOVA and Tukey's test (α= 0.05%). Repeated simulated microwave disinfections decreased the Knoop hardness of Clássico and Onda-Cryl resins and had no effect on the impact strength of QC-20. The flexural strength was similar for all tested resins.

Repeated exposure of adolescent rats to oral methylphenidate does not induce behavioral sensitization or cross-sensitization to nicotine

Several lines of evidence indicate that the use of stimulant drugs, including methylphenidate (MPD), increases tobacco smoking. This has raised concerns that MPD use during adolescence could facilitate nicotine abuse. Preclinical studies have shown that repeated treatment with an addictive drug produces sensitization to that drug and usually cross-sensitization to other drugs. Behavioral sensitization has been implicated in the development of drug addiction. We examined whether repeated oral MPD administration during adolescence could induce behavioral sensitization to MPD and long-lasting cross-sensitization to nicotine. Adolescent male Wistar rats were treated orally with 10 mg/kg MPD or saline (SAL) from postnatal day (PND) 27 to 33. To evaluate behavioral sensitization to MPD in adolescent rats (PND 39), the SAL pretreated group was subdivided into two groups that received intragastric SAL (1.0 mL/kg) or MPD (10 mg/kg); MPD pretreated rats received MPD (10 mg/kg). Cross-sensitization was evaluated on PND 39 or PND 70 (adulthood). To this end, SAL- and MPD-pretreated groups received subcutaneous injections of SAL (1.0 mL/kg) or nicotine (0.4 mg/kg). All groups had 8 animals. Immediately after injections, locomotor activity was determined. The locomotor response to MPD challenge of MPD-pretreated rats was not significantly different from that of the SAL-pretreated group. Moreover, the locomotor response of MPD-pretreated rats to nicotine challenge was not significantly different from that of the SAL-pretreated group. This lack of sensitization and cross-sensitization suggests that MPD treatment during adolescence does not induce short- or long-term neuroadaptation in rats that could increase sensitivity to MPD or nicotine.

Simplified Mathematical Model for an Anaerobic Sequencing Batch Biofilm Reactor Treating Lipid-Rich Wastewater Subject to Rising Organic Loading Rates

This study proposes a simplified mathematical model to describe the processes occurring in an anaerobic sequencing batch biofilm reactor (ASBBR) treating lipid-rich wastewater. The reactor, subjected to rising organic loading rates, contained biomass immobilized cubic polyurethane foam matrices, and was operated at 32 degrees C +/- 2 degrees C, using 24-h batch cycles. In the adaptation period, the reactor was fed with synthetic substrate for 46 days and was operated without agitation. Whereas agitation was raised to 500 rpm, the organic loading rate (OLR) rose from 0.3 g chemical oxygen demand (COD) . L(-1) . day(-1) to 1.2 g COD . L(-1) . day(-1). The ASBBR was fed fat-rich wastewater (dairy wastewater), in an operation period lasting for 116 days, during which four operational conditions (OCs) were tested: 1.1 +/- 0.2 g COD . L(-1) . day(-1) (OC1), 4.5 +/- 0.4 g COD . L(-1) . day(-1) (OC2), 8.0 +/- 0.8 g COD . L(-1) . day(-1) (OC3), and 12.1 +/- 2.4 g COD . L(-1) . day(-1) (OC4). The bicarbonate alkalinity (BA)/COD supplementation ratio was 1:1 at OC1, 1:2 at OC2, and 1:3 at OC3 and OC4. Total COD removal efficiencies were higher than 90%, with a constant production of bicarbonate alkalinity, in all OCs tested. After the process reached stability, temporal profiles of substrate consumption were obtained. Based on these experimental data a simplified first-order model was fit, making possible the inference of kinetic parameters. A simplified mathematical model correlating soluble COD with volatile fatty acids (VFA) was also proposed, and through it the consumption rates of intermediate products as propionic and acetic acid were inferred. Results showed that the microbial consortium worked properly and high efficiencies were obtained, even with high initial substrate concentrations, which led to the accumulation of intermediate metabolites and caused low specific consumption rates.

The experience of repeated fatherhood during adolescence

Objective: to examine how adolescent fathers experience recurring parenthood. Design: qualitative study with a social phenomenological focus. Participants: five fathers between 16 and 19 years of age, each with two children. Findings: the participants perceived themselves as mature, responsible, worried about the care and education of their children, and desiring a secure future life. These factors made them seek employment, their own home, marital stability, construction of a family and return to school. They experienced the ambivalence of desiring one reality and living another, given that, as adolescent parents, they regretted the loss of their freedom. Key conclusions: recurring parenthood in adolescence is a complex phenomenon, with many possible perceptions. The diverse experiences depend on the social context that is defined by the wishes, plans, possibilities and meanings of each distinct social class. Implications for practice: care delivery to these adolescents should consider not only theoretical and chronobiological aspects, but also the experiences of these young people and the psychosocial and cultural factors involved in their fatherhood. (c) 2008 Elsevier Ltd. All rights reserved.

Effect of eccentric contraction velocity on muscle damage in repeated bouts of elbow flexor exercise

Eccentric exercise induces muscle damage, but controversy exists concerning the effect of contraction velocity on the magnitude of muscle damage, and little is known about the effect of contraction velocity on the repeated-bout effect. This study examined slow (60 degrees.s(-1)) and fast (180 degrees.s(-1)) velocity eccentric exercises for changes in indirect markers of muscle damage following 3 exercise bouts that were performed every 2 weeks. Fifteen young men were divided into 2 groups based on the velocity of eccentric exercise: 7 in the Ecc60 (60 degrees.s(-1)) group, and 8 in the Ecc180 (180 degrees.s(-1)) group. The exercise consisted of 30 maximal eccentric contractions of the elbow flexors at each velocity, in which the elbow joint was forcibly extended from 60 degrees to 180 degrees (full extension) on an isokinetic dynamometer. Changes in maximal voluntary isometric contraction strength, range of motion, muscle soreness, and plasma creatine kinase activity before and for 4 days after the exercise were compared in the 2 groups using a mixed-model analysis (group x bout x time). No significant differences between groups were evident for changes in any variables following exercise bouts; however, the changes were significantly smaller (p < 0.05) after the second and third bouts than after the first bout. These results indicate that the contraction velocity does not influence muscle damage or the repeated-bout effect.

Batch cooling crystallization of xylitol produced by biotechnological route

BACKGROUND: This work deals with the xylitol production by biotechnological routes emphasizing the purification process using crystallization. RESULTS: Xylitol volumetric productivity of 0.665 g L(-1) h(-1) and yield of 0.7024 g g(-1) were obtained after 92 h fermentation. The fermented broth (61.3 g L(-1) xylitol) was centrifuged, treated and concentrated obtain a syrup (745.3 g L(-1) xylitol) which was crystallized twice, xylitol crystals with 98.5-99.2% purity being obtained. CONCLUSION: The hypothetical distribution obtained permits the determination of modeling parameters, which make possible the estimation of crystal dominant size from different initial experimental conditions. (C) 2008 Society of Chemical Industry