Second generation bioethanol from municipal organic waste, barley straw and fiber sorghum

In this study municipal organic waste (MOW), barley straw (BS) and fibre sorghum (Sorghum bicolor (L.) Moench) B133 hybrid were compared as sources for bioethanol production, through simultaneous saccharification and fermentation (SSF) process. Kluyveromyces marxianus DSM 4906 and Saccharomyces cerevisiae DSM 70449 were employed for fermentation at 45 °C and 37 °C, respectively. Experiments were conducted for 96 hours in 500 mL flasks with a total solid load of 50 g L-1, in anaerobic condition and constant orbital shaking (120 rpm). The analysis of variance of ethanol production showed significant differences among sources, and MOW resulted the most productive one (12.2 g L-1) compared to B133 (5.8 g L-1) and BS (2.5 g L-1). Also the efficiency in the conversion of cellulose to ethanol (CCE) was only significantly influenced by biomass source. BS exhibited the lowest CCE (32.2 %), compared to BS, B133 (67.4%) and MOW (84.3%). The difference in CCE observed for B133 and BS, suggests that the spatial disposition of structural components (cellulose, hemicellulose and lignin), and perhaps also soluble glucose, are major factors in second generation ethanol production.