Eficiência da hidrólise de amido de mandioca por diferentes fontes de enzimas e rendimento da fermentação alcoólica para produção de etanol

• Autor(a) principal: Santana, Nívio Batista
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2828
• topic: Enzimas amilolíticas; Etanol; Mandioca; Amilolytic enzymes; Ethanol; Cassava; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::CIENCIA DE ALIMENTOS

The objective of this work was to evaluate the alcohol production of two yeast strains from cassava starch, using cereal malts as source of amilolytic enzymes. The work was divided in two steps. In the first step, assays were carried out to determinate the best malt concentrations would be used on the hydrolysis. Four concentrations of malt in relation to starch mass, 4,0; 8,0 and 12,5% were tested, Barley, wheat, corn and rye malts were tested aiming to set if any of them of they would be most suitable for usage in this kind of process. Hidrolysated suspensions were analyzed regarding to formed sugars profile by enzymatic kits and the hydrolysis yield was calculated to determinate the best malt concentration. These tests were conduced in suspensions of 100g containing 12% of cassava starch, which was jellied and cooled until 50°C and, then, submitted to malts enzymes action for 24h at 50°C. Regressions analyses were done in order to find models that describe better the hydrolysis profile. The malts used were analyzed in relation to starch rates, sugars, moisture content, pH and amilolytic activity. The cassava starch used was characterized in relation to starch, moisture content and pH. In the second step, with the results of the first one, fermentations of the wort were done. The malt concentration used was 12,5% for all cereals. Barley malt has reached greater yield values and presented greater amilolytic activity as well as wheat. However, despite of the smaller amilolytic activity, corn malt have shown yields close to barley malt when used in the highest concentration. 1Kg suspensions containing 12% of cassava starch were jellied, hydrolyzed with malt and inoculated with the yeast. In this process were used Saccharomyces cervisiae yeast strain, traditionally used for alcohol production and Saccahromyces diastaticus yeast strain, which presents glycoamilase enzyme production and the growth using starch as substratum. Yeast were inoculated and the fermentative process was monitored by substratum consumption, product generation, pH decreasing and wort acidity increase. The largest alcohol concentrations were found in the S. cerevisiae- fermented worts and varied from 39,1 to 48,98 g of ethanol L-1. In spite of presenting smaller ethanol concentrations, the S. diastaticus fermented worts presented higher starch consumption, varying from 99,21 to 97,92%, indicating an high capacity of starch consumption by this yeast. Formed products compositions were analyzed by gas chromatography. It was observed that acetaldehyde formation was more intense in barley and rye wort fermented by S. cerevisiae. Ethyl acetate was more present in barley and rye fermented wort and there was not difference between these two yeasts for this compound. Methanol was found in greater proportions in S. cerevisiae-fermented worts, while S. diastaticus- fermented worts presented more concentrations of 1 propanol. Isobutyl and isoamyl alcohols values didn t vary among the tested treatments. The obtained data serve as basis for other researches, looking for this process improvement. The search for cheaper enzyme sources and process with higher incomes that diminish the energy costs are fundamental points to make possible the ethanol production from starch material.