Biomedical subjects

Denise M G Freire

Publications and source records attributed to Denise M G Freire.

8 recordsLinked to original sources

PubMed2006

Characterization of poly(3-hydroxybutyrate) produced by Cupriavidus necator in solid-state fermentation.

Solid-state fermentation (SSF) has recently been proposed as an alternative to submerged fermentation for the production of poly(hydroxyalkanoates). In the present work, X-ray diffraction, differential scanning calorimetry, nuclear magnetic resonance and infrared spectroscopy were employed to investigate the chemical structure, as well as the thermal properties and the crystalline morphology of poly(3-hydroxybutyrate) samples produced by SSF, using as raw material either soy cake or soy cake supplemented with 2.5% (m/m) sugarcane molasses. The results obtained showed that the biopolymer obtained by SSF presented the same properties as commercial PHB, except for the higher molar mass and the lower degree of crystallinity that were observed. Thus, the present data indicate that solid-state fermentation is an interesting alternative for the production of PHB, allowing the production of biopolymers with adequate properties from low-cost, renewable resources.

Culture Media↗

PubMed2006

Biosurfactant production by Rhodococcus erythropolis grown on glycerol as sole carbon source.

The production of biosurfactant by Rhodococcus erythropolis during the growth on glycerol was investigated. The process was carried out at 28 degrees C in a 1.5-L bioreactor using glycerol as carbon source. The bioprocess was monitored through measurements of biosurfactant concentration and glycerol consumption. After 51 h of cultivation, 1.7 g/L of biosurfactant, surface, and interfacial tensions values (with n-hexadecane) of 43 and 15 mN/m, respectively, 67% of Emulsifying Index (E24), and 94% of oil removal were obtained. The use of glycerol rather than what happens with hydrophobic carbon source allowed the release of the biosurfactant, originally associated to the cell wall.

Bioreactors↗

PubMed2005

Lipase production by solid-state fermentation: cultivation conditions and operation of tray and packed-bed bioreactors.

The production of lipase by Penicillium simplicissimum in solid-state fermentation was studied using babassu cake as the basal medium. Tray-type and packed-bed bioreactors were employed. In the former, the influence of temperature; content of the medium, and medium supplementation with olive oil, sugarcane molasses, corn steep liquor, and yeast hydrolysate was studied. For all combinations of supplements, a temperature of 30 degrees C, a moisture content of 70%, and a concentration of carbon source of 6.25% (m/m, dry basis) provided optimum conditions for lipase production. When used as single supplements olive oil and molasses also were able to provide high lipase activities (20 U/g). Using packed-bed bioreactors and molasses-supplemented medium, optimum conditions for enzyme production were air superficial velocities above 55 cm/min and temperatures below 28 degrees C. The lower temperature optimum found for these reactors is probably related to radial heat gradient formation inside the packed bed. Maximum lipase activities obtained in these bioreactors (26.4 U/g) were 30% higher than in tray-type reactors.

Bioreactors↗

PubMed2005

High-yield Bacillus subtilis protease production by solid-state fermentation.

A Bacillus subtilis isolate was shown to be able to produce extracellular protease in solid-state fermentations (SSF) using soy cake as culture medium. A significant effect of inoculum concentration and physiological age on pro tease production was observed. Maximum activities were obtained for inocula consisting of exponentially growing cells at inoculum concentrations in the range of 0.7-2.0 mg g(-1). A comparative study on the influence of cultivation temperature and initial medium pH on protease production in SSF and in submerged fermentation (SF) revealed that in SSF a broader pH range (5-10), but the same optimum temperature (37 degrees C), is obtained when compared to SF. A kinetic study showed that enzyme production is associated with bacterial growth and that enzyme inactivation begins before biomass reaches a maximum level for both SF and SSF. Maximum protease activity and productivity were 960 U g(-1) and 15.4 U g-1 h-1 for SSF, and 12 U mL-1 and 1.3 U mL-1 h-1 for SF. When SSF protease activity was expressed by volume of enzyme extract, the enzyme level was 10-fold higher and the enzyme productivity 45% higher than in SF. These results indicate that this bacterial strain shows a high biotechnological potential for protease production in solid-state fermentation.

Bacillus subtilis↗

PubMed2004

Effect of temperature, moisture, and carbon supplementation on lipase production by solid-state fermentation of soy cake by Penicillium simplicissimum.

The production of lipases by Penicillium simplicissimum using solid-state fermentation and soy cake as substrate was investigated. The effects of temperature, cake moisture, and carbon supplementation on lipase production were studied using a two-level experimental plan. Moisture, pH, and lipase activity were followed during fermentation. Statistical analysis of the results was performed to evaluate the effect of the studied variables on the maximum lipase activity. Incubation temperature was the variable that most affected enzyme activity, showing a negative effect. Moisture and carbon supplementation presented a positive effect on activity. It was possible to obtain lipase activity as high as 21 U/g of dry cake in the studied range of process variables.

Biotechnology↗

PubMed2003

Protease production by Streptomyces sp. isolated from Brazilian Cerrado soil: optimization of culture medium employing statistical experimental design.

Streptomyces are important microorganisms because of their capacity to produce numerous bioactive molecules. In the present work protease production, by Streptomyces sp. 594 isolated from a Brazilian Cerrado soil, was maximized by optimizing a low-cost culture medium composition (casitone and sugarcane molasses) using statistical experimental design. The final protease activity (56 U/mL) was 2.8-fold and 58-fold higher than that obtained in the beginning of this study, and in a previous work, using an actinomycete selection medium, respectively. Protease production, not growth associated, appeared to be modulated by an inducer system, whereby the C/N ratio seemed to play a significant role.

Brazil↗

PubMed2003

Synthesis of monocaprin catalyzed by lipase.

The production of monoglyceride emulsifiers commonly employed in the food, cosmetic, and pharmaceutical industries can be catalyzed by lipases, biocatalysts that are becoming increasingly attractive in the enzyme market. The aim of this study was to produce monocaprin utilizing a commercial immobilized lipase (Lipozyme IM 20) through the direct esterification of capric acid and glycerol. Experiments were performed for 6 h in an open reactor and the products were analyzed by gas chromatography. The parameters investigated were the amount of enzyme, temperature, and molar ratio between the reagents (capric acid/glycerol). The experimental runs followed an experimental design generated using Statistica software. The results showed that all the parameters were significant and that monocaprin production was enhanced at the lower ranges of the tested variables. The best conditions established were 55 degrees C, 3% (w/w) enzyme concentration, and molar ratio of 1. The final product, obtained after 6 h of reaction, was 61.3% monocaprin, 19.9% dicaprin, and 18.8% capric acid. This composition satisfies the directives of the World Health Organization food emulsifiers, which requires that these mixtures have at least 70% mono- plus diglyceride, and a minimum of 30% monoacylglycerol.

Catalysis↗

PubMed2002

Evaluation of different carbon and nitrogen sources in production of rhamnolipids by a strain of Pseudomonas aeruginosa.

Culture conditions involving variations in carbon and nitrogen sources and different C:N ratios were examined with the aim of increasing productivity in the process of rhamnolipid synthesis by Pseudomonas aeruginosa. In addition to the differences in productivity, the use of different carbon sources resulted in several proportions related to the types of rhamnolipids synthesized (monorhamnolipids and dirhamnolipids). Furthermore, the variation in nutrients, mainly the nitrogen source, resulted in different amounts of virulence factors, as phenazines and extracellular proteins. The data point out a new concern in the choice of substrate to be used for rhamnolipid production by P. aeruginosa: toxic byproducts.

Bacteriological Techniques↗