Produção de bioetanol a partir da hidrólise ácida e enzimática da palma forrageira.

Abstract

The pursuit for alternatives to ethanol production in order to meet the current demand raises as raw materials, besides the sugarcane broth (first generation ethanol), the lignocellulosic materials (second generation ethanol), which have in their composition cellulose, hemicellulose and lignin, that through chemicals and biochemical processes (acid and enzymatic hydrolysis) can be converted into fermentable sugar and, after, into biofuel. As an example the lignocellulosic material, there is the cactus pear, with a widespread cropping of easy handling and cultivated in all periods of the year. Therefore, the main goal of this paper was to study the cactus pear process of acid/enzymatic hydrolysis for cellulose saccharification aiming ethanol production, characterizing it physic chemically and morphologically, besides perform chemical and biochemical processes of cellulose conversion, as well for the hemicelulose into directly fermentable sugars, verifying by the experimental design, the influence of the variables: temperature and sulfuric acid concentrations and the relation dry mass of cactus pear/acid concentration (acid hydrolysis) over the glucose concentration. It was also studied the enzyme load and the relation dry mass of cactus pear/extract (enzymatic hydrolysis) over the conversion of cellulose into glucose efficiency, ending with the fermentation of the hydrolyzed liquor, gathered in the best experimental design conditions, setting then the process parameters. The results indicated that the cactus pear presents a considerable cellulose content (37.34%) compared to other studied sources and low contents of hemicellulose (10.88%) and lignin (3.36%), dismissing the execution of a pre-treatment in this material. The low contents of hemicellulose and lignin also were verified by the Scanning Electron Microscopy (SEM), which shows a high disorder level for the cactus pear. The statistic models obtained for the acid and enzymatic hydrolysis were statically significant with 95% reliability. The results showed that, for the acid hydrolysis, raising the acid concentration and lowering the relation dry mass of cactus pear/acid it is obtained glucose concentrations in the liquor above 7500 mg/L, while for the enzymatic hydrolysis, raising de enzymatic load and lowering the relation dry mass of cactus pear/extract it is obtained conversion. efficiency above 60%. The hydrolyzate fermentation parameters calculated showed that cactus pear presents itself as a potential source for ethanol production, with conversion of fermentable sugars around 98%.