Carlos Edison Lopes

Continuous ethanol production using yeast immobilized on sugar-cane stalks

Sugar-cane stalks, 2.0 cm long, were used as a support for yeast immobilization envisaging ethanol production. The assays were conducted in 38.5 L fermenters containing a bed of stalks with 50% porosity. The operational stability of the immobilized yeast, the efficiency and stability of the process, as well as the best dilution rate were evaluated. Molasses from demerara sugar production was used in the medium formulation. It was diluted to obtain 111.75 ± 1.51 g/L without any further treatment. Sulfuric acid was used to adjust the pH value to around 4.2. Every two days Kamoran HJ (10 ppm) or with a mixture containing penicillin (10 ppm) and tetracycline (10 ppm), was added to the medium. Ethanol yield and efficiency were 29.64 g/L.h and 86.40%, respectively, and the total reducing sugars (TRS) conversion was 74.61% at a dilution rate of 0.83 h-1. The yeast-stalk system was shown to be stable for over a 60 day period at extremely variable dilution rates ranging from 0.05 h-1 to 3.00 h-1. The concentration of immobilized cell reached around 109 cells/gram of dry sugar-cane stalk when the fermenter was operating at the highest dilution rate (3.00 h-1).

Biodegradation of diesel oil by yeasts isolated from the vicinity of suape port in the state of Pernambuco - Brazil

The aim of this work was to investigate the potential of the diesel oil degrading yeasts to use them in bioremediation of areas contaminated by this pollutant. The cultures, identified as Rhodotorula aurantiaca UFPEDA 845 and Candida ernobii UFPEDA 862, were selected at the initial stage. In the course of the biodegradation assays, C. ernobii degraded tetradecane, 5 methyl-octane and octadecane completely and decane (60.8%) and nonane (21.4%) partially whilst R. aurantiaca presented degradation percentages of 93% for decane, 38.4% for nonane and 22.9% for dodecane.

Three-phase partitioning of hydrolyzed Levan

During the fructose and polymerization to synthesize levan, smaller fructooligosaccharide (FOS) molecules are produced. FOS can also be obtained by levan hydrolysis. Three-phase partitioning (TPP) is a separation technique that has been used for polysaccharide precipitation and gathers t-butanol and ammonium sulphate to exclude the polymer from the aqueous solution. In this work TPP was tested to separate levan and FOS from aqueous solution. The FOS used was obtained from Zymomonas mobilis levan acid hydrolysis and fractionation with ethanol. The yield of low TPP fractions was higher than those obtained from the native levan. The F-90 exhibited a higher yield than other fractions. However, when applying the TPP technique to lightest fraction not precipitated by ethanol at 90% (F>90), the intermediate phase was not possible to be visualize. These results have potential application because they show that by using the levan TPP separation it is possible to separate low-molecular weight sugar.

A chemically defined medium for production of actinomycin D by Streptomyces parvulus

A chemically defined medium consisting of D(+)fructose, L(-)threonine, K2HPO4, MgSO4.7H2O, ZnSO4.7H2O, CaCl2.2H2O, FeSO4.7H2O and deionized water, was developed to maximize the synthesis of actinomycin D by the Streptomyces parvulus DAUFPE 3124 strain. This medium resulted in the maximum antibiotic concentration of 133mg/L while using the original medium the production of actinomycin D was poor not surpassing 43mg/L.

Recovery of Bacillus sphaericus spores by flocculation/sedimentation and flotation

The aim of this work was use flocculation/sedimentation and flotation for recovery of spores of the Bacillus sphaericus. Microorganism was produced batchwise using culture medium based skimmed milk, corn steep liquor and mineral salts. The best results of flocculation were obtained using CaCl2.2H2O, FeCl3.6H2O, Al2(SO4)3 and tannin as flocculating agents, with optimal flocculation concentrations of 1,500, 3,000, 2,000 and 1,700ppm, respectively. Flocculent suspensions were characterized based on floc diameter and density. Settling tests were performed in batch at different concentrations of the cellular suspensions and revealed high recovery of the solids in suspension in all cases. Flotation tests were accomplished using a mechanical agitated flotation cell and the process was favoured by the increase of the system agitation and for the presence of a cationic collector.

On the dynamics of nonequilibrium simple batch distillation processes

Abstract The study of the dynamics of a simple batch distillation usually assumes the equilibrium between the liquid and vapour phases. In contrast to that approach, this work considers the analysis of the dynamic behaviour of a nonequilibrium simple batch distillation. A simple batch distillation device is similar to an evapouration unit because no reflux is employed. A mathematical model and their singular points are analysed through the usual technique of linearization followed by the eigenvalues analysis. The stability nature of those points is presented for ideal solutions. Phase plane plots are made to show the occurrence of some unexpected behaviours such as ‘dynamic azeotropic points’ and ‘inversion of the distillation order’. The dependence of these phenomena on the vapour withdrawal flowrate is established for simple batch distillation.

The influence of centrifugation on Zymomonas mobilis aggregation

Flocculent Zymomonas mobilis breaks down in smaller flocs and individual cells when centrifuged. The main consequence of it is an increase in the dispersion of the sample, suggesting that the influence of the centrifugal force on the aggregation of cells is worth to study. The experiments showed that the degree of dispersion varied between 30% and 100% when the centrifugal acceleration changed from 25 g to 2500 g. Observation under the electronic microscope showed that a slimy material covered the cells recovered by gentle gravitational settling and, that the centrifuged cells presented a bare cell wall.