Walter A. F. de Carvalho

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The objective of this study was to evaluate the ethanol production from the sugars contained in the sugarcane bagasse hemicellulosic hydrolysate with the yeast Pichia stipitis DSM 3651. The fermentations were carried out in 250-mL Erlenmeyers with 100 mL of medium incubated at 200 rpm and 30 degrees C for 120 h. The medium was composed by raw(More)
Experiments based on a 23 central composite full factorial design were carried out in 200-ml stainless-steel containers to study the pretreatment, with dilute sulfuric acid, of a sugarcane bagasse sample obtained from a local sugar–alcohol mill. The independent variables selected for study were temperature, varied from 112.5°C to 157.5°C, residence time,(More)
BACKGROUND The recalcitrance of lignocellulosic materials is a major limitation for their conversion into fermentable sugars. Lignin depletion in new cultivars or transgenic plants has been identified as a way to diminish this recalcitrance. In this study, we assessed the success of a sugarcane breeding program in selecting sugarcane plants with low lignin(More)
This study aimed to correlate the efficiency of enzymatic hydrolysis of the cellulose contained in a sugarcane bagasse sample pretreated with dilute H2SO4 with the levels of independent variables such as initial content of solids and loadings of enzymes and surfactant (Tween 20), for two cellulolytic commercial preparations. The preparations, designated(More)
BACKGROUND Lignin and hemicelluloses are the major components limiting enzyme infiltration into cell walls. Determination of the topochemical distribution of lignin and aromatics in sugar cane might provide important data on the recalcitrance of specific cells. We used cellular ultraviolet (UV) microspectrophotometry (UMSP) to topochemically detect lignin(More)
Wheat straw hemicellulosic hydrolysate was used for xylitol bioproduction. The use of a xylose-containing medium to grow the inoculum did not favor the production of xylitol in the hydrolysate, which was submitted to a previous detoxification treatment with 2.5% activated charcoal for optimized removal of inhibitory compounds.
Candida guilliermondii cells were immobilized in Ca-alginate beads and used for xylitol production from concentrated sugarcane bagasse hydrolysate during five successive fermentation batches, each lasting 48 hours. The bioconversion efficiency of 53.2%, the productivity of 0.50 g/l x h and the final xylitol concentration of 23.8 g/l obtained in the first(More)
Candida guilliermondii cells, immobilized in Ca-alginate beads, were used for batch xylitol production from concentrated sugarcane bagasse hydrolyzate. Maximum xylitol concentration (20.6 g/L), volumetric productivity (0.43 g/L. h), and yield (0.47 g/g) obtained after 48 h of fermentation were higher than similar immobilized-cell systems but lower than(More)
Candida guilliermondii FTI 20037 cells were entrapped in Ca-alginate beads and used for xylose-to-xylitol bioconversions during five successive batches in a stirred tank reactor. Supplemented sugarcane bagasse hemicellulosic hydrolysate was used as the fermentation medium. The average volume of the Ca-alginate beads was reduced by about 30% after the 600 h(More)
Sugarcane bagasse hemicellulose was isolated in a one-step chemical extraction using hydrogen peroxide in alkaline media. The polysaccharide containing 80.9% xylose and small amounts of L-arabinose, 4-O-methyl-D-glucuronic acid and glucose, was hydrolyzed by crude enzymatic extracts from Thermoascus aurantiacus at 50 degrees C. Conditions of enzymatic(More)