Produção de biocombustíveis a partir de glicose e manipueira

Abstract

Biofuels are produced from clean alternative energy sources and one example is biobutanol, a fuel that can be produced by fermentation of different raw materials. The production of butanol is carried out by fermentative metabolism of solvent-producing microorganisms, with acetone and ethanol as major byproducts (ABE fermentation). This work aims to produce biobutanol using strains Clostridium beijerinckii (ATCC 10132) and Clostridium acetobulylicum (ATCC 824) and four different inoculum: ES - swine effluent digester located in the Água Branca Farm in the municipality of Itu; LR - UASB sludge of sewage treatment plant from the city of Porto Feliz; ES - cattle manure; SL - Soil from sugarcane cultivation in Sorocaba region. Glucose and cassava wastewater were used as substrate. The biobutanol production efficiency was evaluated for each strain and inoculum in fermentation batch reactors in which the sole substrate was glucose or cassava wastewater. Both strains produced biofuel, and C. beijerinckii (ATCC 10132) was more efficient yielding 0.33±0.08 g L -1 butanol and 1.65±0.23 g L -1 of ethanol from 30 g L -1 of glucose. When cassava wastewater was used as substrate (10 g L -1 of reducing sugar), the production of butanol was 0.64±0.1 g L -1 and ethanol was 2.47±0.07 g L-1 in comparison to 0.27±0.13 g L -1 butanol and 1.72±0.18 g L -1 of ethanol produced when C. beijerinckii were fed with glucose 10 g L -1 as control. Fermentation inocula produced only butyric acid with concentrations of 0.31±0.04 g L -1 for cattle manure and 0.12±0.013 g L -1 for swine effluent. As the cattle manure showed higher production of butyric acid, this culture was chosen for fermentation with cassava wastewater at COD 5 g L-1 . First of all the inoculum´s DNA was amplified with the pair of primers Sj-F and Sj-R specific for the genus Clostridium. With the confirmation of the clostridia presence, the fermentation with cassava wastewater at 5 g L -1 of COD was performed. This fermentation was compared with the strain C.beijerinckii growing in medium without enrichment and cattle manure with and without medium enrichment. C. beijerinckii biofuel production was 0.02 g L -1 of butanol and 0.69 g L-1 of ethanol after 12 h of fermentation, while cattle manure fermentation yielded 0.168 g L -1 of ethanol after 106 h in enriched medium and 0.026 g L-1 of ethanol in medium without enrichment after 12 h. These results demonstrate the feasibility of using cassava as a substrate for the production of biobutanol, ethanol and the possibility of producing biobutanol by cattle manure and swine effluent since butyric acid is an intermediary product of the pathway leading to butanol synthesis.