Monday, April 29, 2013
Exhibit Hall
Dilute-acid pretreatment is one of the most promising methods for processing lignocellulosic biomass. However, it may produce fermentation inhibitory compounds, such as furfural and hydroxymethyl furfural (HMF). The objective of this study was to evaluate the ethanol production from the sugars contained in the sugarcane bagasse hemicellulosic hydrolysate through the simultaneous isomerization and fermentation (SIF) process. Glucose isomerase from Genencor® was covalently immobilized on chitosan and co-immobilized with baker yeast (Itaiquara®) in calcium alginate beads. The resulting biocatalyst was used for the SIF in a batch reactor. The dilute-acid hydrolysis of sugarcane bagasse provided a hydrolysate with 60.8 g.L-1 of xylose, 7.2 g.L-1 of glucose, 10.4 g.L-1 of acetic acid, 0.7 g.L-1 of furfural and 0.1 g.L-1 of HMF. The media for the SIF was composed by raw (non-detoxified) hydrolysate, or by pure xylose as a standard for comparison, both containing salts that supply nitrogen, phosphorus and trace metals (minimal media). SIF were performed with a high yeast cells concentration (50 g.L-1) at 35 °C, pH 5.6 and 150 rpm, for 24 h. Ethanol yields of baker yeast were essentially the same for both sources of carbon: non-detoxified liquid hydrolysate or pure xylose. The SIF using non-detoxified hydrolysate led to 23.1 g.L-1 of ethanol, yield of 0.33 and a productivity of 1.8 g.L-1.h-1. These results are promising and contribute to the development of a suitable process for ethanol production from xylose by S. cerevisiae.