Estudo comparativo das hidrólises ácida e enzimática de matérias primas amiláceas visando a obtenção de etanol

Abstract

The work presents a comparative study about acid and enzymatic hydrolysis of starch to produce ethanol using cassava flour as raw material. Ethanol production represents an alternative to environmentally friendly replacement for fuels from petroleum derivatives. Ethanol can be produced from raw starchy and sugary. Cassava is an important agricultural product in Brazil. It‟s high starch content, which can be turned into glucose, can be used as feedstock for ethanol production. In this work the first step was to characterize the raw material, employing physical-chemical analysis in flours of three different varieties of cassava grown from Junqueiro, State of Alagoas. The second stage was a study of cell viability of three types of yeast. It was selected two selected strains of the yeast Saccharomyces cerevisiae, donated by the Biological Sciences Center of Federal University of Alagoas - CCBI, and a commercial yeast, Biological Fermix. In the last stage, tests were performed in 18 flasks, which were divided into nine trials involving acid hydrolysis and nine trial of enzymatic assays aimed producing ethanol. The musts fermented presented alcoholic strength of 7.5 º and 8.3 º GL for acid hydrolyzed while enzymatic hydrolysates achieved values between 10.7 º and 11.6 º GL. According to these results, it can observed an advantage of using enzymes in hydrolysis process. However, it is worth the cost-effectiveness in the use of acid in this stage of the fermentation process. The best variety of cassava flour was the variety-SE, despite the lower amount of starch. It‟s conversion efficiency was adequate for completion of fermentation for the three types of yeast studied. The yeast-type C3 (12) and C1 (10) were better than commercial yeast when the alcohol content was above 10%, showing more resistance to ethanol intoxication. The data obtained is a basis for further research, aiming to improve this process. The search for cheaper sources of enzymes and processes developed further decreasing the costs of hydrolysis are key to enable the production of ethanol from starchy materials.