Estudo da pré-hidrólise ácida da palma forrageira (Opuntia ficus indica Mill).

Abstract

Since the first petroleum crisis in 1973, ethylic alcohol has been arousing a growing interest by the Federal Government in Brazil and by researchers worldwide, and nowadays by governments of developed countries, such as the United States, Germany, and France, and by developing countries, such as índia and China. This is due to the pressure caused by the depletion of non-renewable sources of fóssil fuels, as well as to world geopolitics (greater reserves of petroleum in countries with problems of conflicts and politicai instability). The search for new sources for obtaining alcohol, such as lignocelluloses materiais, is also arising. Forage cactus was introduced in Brazil to support the raising of an insect known as cochonilha, which is responsible for the production of a dye that was of high commercial value at that time. Throughout the years, the use of this cactus has become very diversified, because aside from being used as forage, it produces fruit and greens for human consumption, biomass for energy reasons (fuels and biogas) and countless other products, such and beverages, vegetarian cheese, medicines and cosmetics. Furthermore, it is useful to shelter and feed various wild species that live in arid environments. Forage cactus has been arousing interest among many researchers because it is not only a greatly diffused culture and presents cellulose and hemicelluloses in its composition, and these substances can be used for obtaining fermentable sugars, but it is also a culture which is resistant to drought and can be produced ali year long. The purpose of this paper was to study the process of acid pre-hydrolysis of the cactus to obtain a prehydrolyzed liquor, high in pentose, thus diminishing the concentration in this raw material, which is the cladode of the giant forage cactus. The cactus cladode was received at the Biochemistry Engineering Laboratory, where its moisture content was determined and a dry matter was obtained. This matter was characterized (pH, total reducing sugars, soluble solids, ashes, hemicelluloses, cellulose, lignin, and the concentration of pentose and hexoses). Two factorial designs 23 of pre-hydrolysis were performed to verify the influence of the variables of temperature, acid concentration and dry matter/acid ratio over the responses to the sum of pentose and the percentile of pentose increase, and then a preliminary hydrolysis followed by fermentation was performed. With the results to the factorial design 23, it was verified that only the second design was statistically significant to a 95% levei of confidence for the mean and the variable ratio. Operating with the ratio below 1/10, for any value of temperature and acid concentration the sum and percentile increase in pentose is obtained above 8 g/L and 8000%, respectively. During fermentation, there wasn't production of ethylic acid, probably due to the formation of inhibitors in the hydrolysis process that was demonstrated through the strong color of the hydrolyzed liquor.