Produção de bioetanol a partir de resíduos agroindustriais

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

10/12/2010

RESUMO

Concerns about global warming and the depletion of petroleum cause the search for alternative fuels from renewable sources. The current study aims at obtaining bioethanol from fermentable sugars extracted from hydrolyzed residues in situ by solid-state fermentation (SSF). The first stage was the SSF for the hydrolysis of the culture medium which is composed of malt bagasse and cassava bagasse in a 7:3 ratio, respectively. This step was conducted in Raimbault reactors, for 24 hours at 34C with aeration control in 1L/min using Rhizopus oryzae ATCC 34612. The SSF was efficient for hydrolysis of waste leading to increased glucose concentration at about 18 times. In the next step the influence of three variables on the extraction of fermentable sugars released on hydrolysis of the previous stage were evaluated: solid/liquid ratio (1:10, 1:15 and 1:20), temperature (ambient, 30C and 35C) and agitation speed (0, 100 and 150rpm). The tests were conducted in an incubator for orbital motion, for 30min. In this study, the condition in which it had the best result for the concentration of glucose (1,645g/L) was the solid/liquid ratio 1:10, ambient temperature and 150rpm agitation. To start the fermentation stage, a study was conducted to determine the mass of cells (0,05; 0,10; 0,15; 0,20g) and the most appropriate fermentation time (24h and 48h) for the process. This step was performed in an incubator for orbital motion, for 24 hours at 30C using a commercial strain of Saccharomyces cerevisiae. The most appropriate cell mass was 0,15g with a fermentation time of 24h. The testing of microbiological purity of the strains showed that both micro and macroscopic strains used in the study, commercial Saccharomyces cerevisiae and Saccharomyces cerevisiae CCT-0294, were appropriate for the process. Besides that, the growth curves of microorganisms were studied and they indicated their activity, which are viable for the use in alcoholic fermentation. Subsequently, the variables that influence the efficiency of alcoholic fermentation were studied, and these are the microbial species, Saccharomyces cerevisiae commercial and Saccharomyces cerevisiae CCT-0294, the agitation speed (0, 100 and 150rpm) and adding of the source of organic nitrogen (yeast extract) and inorganic (ammonium sulfate), in the culture medium, both in amount of 0,1% (weight/volume). This step was performed in an incubator for orbital motion, for 24 hours at constant temperature of 30C, using the extract of fermented solid medium as a base. The agitation had great influence on the alcoholic fermentation for both microbial species, and obtained the highest yield (0,01761g/L.h and 0,01584g/L.h) in the process conducted without agitation. For the yeast CCT-0294, the addition of nitrogen source had little influence, obtaining similar values of substrate conversion into product (YP/S) for the sample with addition of organic source (0,2376gethanol/gglucose), inorganic (0,2062gethanol/gglucose) and without addition of nitrogen (0,2117gethanol/gglucose). However, for commercial yeast, the addition of organic nitrogen (0,0916gethanol/gglucose) or inorganic (0,0889gethanol/gglucose) significantly reduces the value of YP/S, and without nitrogen addition, this resulted in 0,2026gethanol/gglucose. The highest yields obtained in the process were with commercial yeast (39,73%), no added nitrogen source and with yeast CCT-0294 (46,58%), using both without agitation

ASSUNTO(S)

bagaço de malte bagaço de mandioca açúcares fermentescíveis fermentação alcoólica bioetanol engenharias biocombustíveis; resíduos como combustível malt bagasse cassava bagasse fermentable sugars alcoholic fermentation bioethanol

Documentos Relacionados