Ana Maria Souto-Maior

Validação de metodologia para a caracterização química de bagaço de cana-de-açúcar

In this work, a methodology for the characterization of sugar cane bagasse was validated. Bagasse pre-treated with steam in a 5000 L reactor at a pressure of 15.3 kgf/cm2, during 7 min, was used to test the methodology. The methodology consisted of the hydrolysis of the material with H2SO4 at 72% v/v, for the quantification of carbohydrates, organic acid, furfural and hydroxymethylfurfural by HPLC; insoluble lignin and ash by gravimetry; and soluble lignin by spectrophotometry. Linearity, repeatability, reproducibility and accuracy of the results obtained in two Research Laboratories were determined, and were considered to be suitable for the validation of the methodology.

Industrial-scale steam explosion pretreatment of sugarcane straw for enzymatic hydrolysis of cellulose for production of second generation ethanol and value-added products

Steam explosion at 180, 190 and 200°C for 15min was applied to sugarcane straw in an industrial sugar/ethanol reactor (2.5m(3)). The pretreated straw was delignificated by sodium hydroxide and hydrolyzed with cellulases, or submitted directly to enzymatic hydrolysis after the pretreatment. The pretreatments led to remarkable hemicellulose solubilization, with the maximum (92.7%) for pretreatment performed at 200°C. Alkaline treatment of the pretreated materials led to lignin solubilization of 86.7% at 180°C, and only to 81.3% in the material pretreated at 200°C. All pretreatment conditions led to high hydrolysis conversion of cellulose, with the maximum (80.0%) achieved at 200°C. Delignification increase the enzymatic conversion (from 58.8% in the cellulignin to 85.1% in the delignificated pulp) of the material pretreated at 180°C, but for the material pretreated at 190°C, the improvement was less remarkable, while for the pretreated at 200°C the hydrolysis conversion decreased after the alkaline treatment.

Diluted phosphoric acid pretreatment for production of fermentable sugars in a sugarcane-based biorefinery

The influence of time (8-24 min), temperature (144-186 °C) and phosphoric acid concentration (0.05-0.20%, w/v) on the pretreatment of sugarcane bagasse in a 20 L batch rotary reactor was investigated. The efficiency of the pretreatment was verified by chemical characterization of the solid fraction of the pretreated bagasse and the conversion of cellulose to glucose by enzymatic hydrolysis. Models representing the percentage of cellulose, hemicelluloses, lignin, solubilized hemicellulose and the enzymatic conversion of cellulose to glucose were predictive and significant. Phosphoric acid concentration of 0.20% at temperature of 186 °C, during 8 and 24 min, was shown to be very effective in solubilizing hemicellulose from sugarcane bagasse, reaching solubilization of 96% and 98%, respectively. Relatively low amounts of inhibitors were produced, and the phosphoric acid remaining in the hemicellulosic hydrolysate is at adequate levels for supplying phosphorous requirement during subsequent fermentation.

Antagonism of Bacillus spp. against Xanthomonas campestris pv. campestris

The antagonism of eight Bacillus isolates was investigated against nine strains of Xanthomonas campestris pv. campestris (causal agent of crucifers black rot) to assess the role of lipopeptides in this process. Antimicrobial and hemolytic (surfactant) activity tests were performed in vitro using agar diffusion methods. Antibiosis and hemolysis were positive for four Bacillus isolates against all X. campestris pv. campestris strains. The correlation observed between antimicrobial and hemolytic activities indicated that lipopeptides were involved in the antibiosis mechanism of the studied antagonists. Fermentation studies were carried out with the isolates that showed highest antimicrobial and hemolytic activities, to follow up growth and production of bioactive and surfactant compounds. Production of bioactive and surfactant compounds was observed during the late growth phase of the Bacillus isolates.

Comparison of SHF and SSF processes from sugar cane bagasse for ethanol production by Saccharomyces cerevisiae.

In this work, four different process configurations, including three simultaneous saccharification and fermentation (SSF) schemes and one separate hydrolysis and fermentation (SHF) scheme, were compared, at 8% water-insoluble solids, regarding ethanol production from steam-pretreated and alkali-delignified sugar cane bagasse. Two configurations included a 16 h lasting enzymatic presaccharification prior to SSF, and the third one was a classical SSF without presaccharification. Cellulose conversion was higher for the delignified bagasse, and higher in SSF experiments than in SHF. The highest cellulose-to-ethanol conversion (around 60% in 24 h) and maximum ethanol volumetric productivities (0.29-0.30 g/L.h) were achieved in the presaccharification-assisted SSF.

Controle biológico da mancha-aquosa do melão por compostos bioativos produzidos por Bacillus spp.

ABSTRACT The bacterial fruit blotch, caused by the bacterium Acidovoraxavenae subsp. citrulli (Aac), is responsible for great losses in melonproduction. The control of this disease was investigated in vivo by treatinginfected yellow melon seeds with fermented broths of B. subtilis R14, B.megaterium pv . cerealis RAB7, B. pumilus C116 and Bacillus sp. MEN2,with and without bacterial cells. The mechanism of action of the strainswas studied in vitro by the agar diffusion technique. The bioactivecompounds produced were partially characterized by hemolysis test andsurfactant activity. Regarding the tests conducted in vivo there was no Santos, E.R.; Gouveia, E.R.; Mariano, R.L.R.; Souto-Maior, A.M. Biocontrol of bacterial fruit blotch of melon by bioactive compoundsproduced by Bacillus spp. Summa Phytopathologica , v.32, n.4, p.376-378, 2006. RESUMO A mancha-aquosa, causada por Acidovorax avenae subsp. citrulli (Aac) causa grandes prejuizos a cultura do melao. O controle dessa doencafoi estudado

Anthracycline production by Streptomyces capoamus in batch fermentation

Anthracyclines have been intensely studied worldwide due to their importance as anticancer agents. In this work investigation was made on the production of ciclamycin, an antitumour complex of the anthracycline class, produced by Streptomyces capoamus. The fermentation medium consisted of glucose, as the main carbon source, and soymilk, as the sole nitrogen source. Experiments were performed in a 5-liter batch bioreactor under nitrogen and carbon-limiting conditions. Increasing antibiotic activity was observed both intra and extracellularly during growth under the two conditions used. Progressive loss of activity occurred in both cases after glucose was depleted from the medium. The results obtained showed that harvest of ciclamycin in a batch process should be controlled by the level of glucose in the reactor and that nitrogen should preferably be the limiting substrate. Alternatively, results indicate that extended production might be achieved in a fed-batch process where nitrogen was the limiting substrate.

Determinação da concentração de paclobutrazol por cromatografia líquida de alta eficiência e espectroscopia

Paclobutrazol is a plant growth retardant which is used world-wide for increasing the yield of cereal crops. However, this compound remains active in the soil for several years and can severely affect the growth and development of subsequent crops, mainly by reducing vegetative vigor. The aim of this work was to develop and validate methods for the determination of paclobutrazol concentrations by both high performance liquid chromatography and spectroscopy. Both methods were satisfactory and showed appropriately low quantification limits. The determination by spectroscopy has, however, the advantage of being a method significantly less expensive than high performance liquid chromatography.