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This study investigated the conversion of Lemna minor biomass to bioethanol. The biomass was pre-treated by steam explosion (SE, 210 °C, 10 min) and then subjected to simultaneous saccharification and fermentation (SSF) using Cellic® CTec 2 (20 U or 0.87 FPU g −1 substrate) cellulase plus β-glucosidase (2 U g −1 substrate) and a yeast inoculum of 10% (v/v or 8.0 × 10 7 cells mL −1 ). At a substrate concentration of 1% (w/v) an ethanol yield of 80% (w/w, theoretical) was achieved. However at a substrate concentration of 20% (w/v), the ethanol yield was lowered to 18.8% (w/w, theoretical). Yields were considerably improved by increasing the yeast titre in the inoculum or preconditioning the yeast on steam exploded liquor. These approaches enhanced the ethanol yield up to 70% (w/w, theoretical) at a substrate concentration of 20% (w/v) by metabolising fermentation inhibitors. [ABSTRACT FROM AUTHOR]

Abstract: Duckweed is a rapidly replicating aquatic plant that has the potential to decontaminate effluent streams from food processing and also has a low-lignin content. Hence it could provide a more suitable source of cellulose for conversion to biofuels. This paper reports that duckweed biomass has the potential to be enzymatically saccharified to produce glucose and other cell-wall-derived sugars which might be converted to ethanol by fermentation or exploited as industrial platform chemicals. The enzymatic digestibility has been studied on alcohol-extracted, water-insoluble preparations of duckweed cell walls. Within these, glucose accounts for w = 25.4% (dry wt), which has arisen from cellulose and non-cellulosic glucans including starch. Several commercial cell-wall degrading enzymes and cocktails have been evaluated. Saccharification can be achieved within about 8 h using commercial cellulase at 4.35 FPU g−1 substrate in conjunction with added beta-glucosidase at 100 U g−1 substrate. The potential for exploiting duckweed is discussed. [Copyright &y& Elsevier]