Anaerobic fermentation of products from acidogenic digestion of sugarcane bagasse pentose liquor for ethanol and butanol production

Abstract

Pentoses liquor is a liquid residue from sugarcane bagasse preprocessing for its hydrolysis towards second generation ethanol production. The composition of this residue varies with the kind of pretreatment process used, but the most common constituents are lignin, mono- and oligosaccharides from hemicellulose, which xylose is the major constituent carbohydrate. The ongoing research which this project is directly linked (FAPESP process 2010/18.463-9) is showing the viability in production of VFAs by anaerobic digestion of pentoses liquor and xylose as carbon sources. Although the main focus of research is hydrogen (as fuel) production throughout acidogenic processes, the search of an alternative processing leading into a more attractive energy carrier like ethanol or butanol is desirable due the instability on hydrogen production by anaerobic means. Also, ethanol and butanol are fuels which are more integrated to the actual energy matrix, considering the amount of combustion engines which works with such fuels, thus, there are no need a drastic changing of energy matrix used nowadays.Conversion of acetate and butyrate in ethanol and butanol could be carried out through another anaerobic step known by solventogenesis. In spite of many papers focuses direct ABE fermentation from raw materials and residues, acidogenisis seems to be crucial step to a well-succeeded solventogenisis. Also, some acidogenic and acetogenic microorganisms could metabolize the produced ABE solvents into CO2 (solvolysis). Thus, a two-step approach (acidogenic and acetogenic - solventogenic processes performed separately) could be an interesting alternative to a single step solventogenic process.In this sense, present project proposes the investigation of the influence of environmental factors as temperature, pH and hydrogen partial pressure over metabolism of both acetate and butyrate, in the same ratio than obtained by acidogenic processing of xylose, into ethanol and butanol throughout an anaerobic solventogenic process. (AU)