Simultaneous Saccharification and Fermentation of Switchgrass by Thermotolerant Kluyveromyces Marxianus IMB3: Effect of Enzyme Loading, Temperature and Operating Mode

Wednesday, October 19, 2011: 10:35 AM
Red Wing Room (Hilton Minneapolis)
Naveen Pessani1, Hasan K. Atiyeh1, Mark R. Wilkins1, Danielle Bellmer1 and Ibrahim M. Banat2, (1)Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK, (2)School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, United Kingdom

Hydrothermolysis-pretreated Kanlow switchgrass was used in simultaneous saccharification and fermentation (SSF) with Kluyveromyces marxianus IMB3 at various enzyme loadings and temperatures.  The pretreated switchgrass contained 57.7% glucan, 5.0% xylan and 35.1% lignin.  Various loadings (0.3, 0.5 and 0.7 mL/g glucan) of the enzyme Accellerase 1500 (Genencor, Rochester, NY) were used in the SSF at 45°C (Accellerase 1500 activity was 82.2 FPU/mL).  The highest ethanol concentration (22.3 g/L) was obtained in SSF with 8% solids and enzyme loading of 0.7 mL/g glucan.  This enzyme loading was used with 8% solids in subsequent SSFs at 37, 41 and 45°C.  The highest ethanol concentration (22.8 g/L) was obtained at 45°C after 96 h, corresponding to 83.9% of the maximum theoretical yield (MTY).  However, ethanol yield was about 79% of MTY in SSF at both 37 and 41°C.   No significant differences in the amount of ethanol produced were observed in the SSF operated in batch or fed-batch modes at 45°C and 12% solids (p > 0.05).  However, the enzyme loading in fed-batch SSF was 33% lower than in batch SSF.  About 32 g/L ethanol (81% MTY) was produced in all batch and fed-batch feeding strategies.

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