Pré-tratamento alcalino (NaOH) do bagaço de cana-de açúcar para a produção de etanol e obtenção de xilooligômeros

Abstract

The aim of this study was to optimize the pretreatment of sugarcane bagasse raw and exploded with diluted sulfuric acid, water and sodium hydroxide in order to obtain Xylooligosaccharides in hemicellulose and production of second generation ethanol. The experiments with sugarcane bagasse and exploded with diluted acid and water respectively were performed according to the methodology CCRD (Central Composite Rotatable Design) with two replications at the center point response variables were: amount of xylose (g), acid concentration acetic acid and furfural (g / l) and xyllo-oligomers yield (%). Pretreatment with sodium hydroxide was carried out with sugarcane bagasse according to the methodology of factorial design with two replications at the central point in order to evaluate the influence of time of pretreatment (t), and hydroxide concentration sodium in the release of sugars after hydrolysis. The pretreatment of sugarcane bagasse with fresh H2SO4 concentration 0.8% v / v, 13 minutes at 100 º C allowed 94% extraction of xylan in the form of scyllo-oligomers, with a minimum of xylose, furfural and acetic acid showing as a condition favorable for the extraction of XOS production. The pretreatment of sugarcane bagasse was used only blown hot water already there due to acetic acid, due to the fact that exploded bagasse have already undergone a process of pre-treatment self-hydrolysis at the plant. Provided by washing with water in the ratio 1:5 (w / v) for 5 minutes at 70 ° C allowed the extraction of 80% xylose from bagasse which was already dissolved in the material, this fraction was 62.5% in the form oligomers. If this condition is unfavorable for the production of XOS is great because the production of monomer (xylose), which required a purification step which is very costly. If ethanol is the desired end product is a slight increase in the need of pretreatment conditions for improved xylose production by hydrolysis step by the enzyme xylanase or using acid as catalyst. For the pretreatment of sugarcane bagasse early experiments proved inconclusive for obtaining a correlation between the length, amount of NaOH used in the hydrolysis and fermentation yields. With the experimental design was obtained for 7% NaOH, 30 minutes (min.) 76% of hydrolysis efficiency with a maximum production of glucose 62 g / l and 90% efficiency of fermentation with an average yield of 20g / L ethanol. The materials were characterized chemically and physically before and after the stages of pretreatment showing the openness and better availability of fibers for the enzymatic process.