Poster Presentation 1B-42

Utilisation of Separated Liquid Stream from Wet Oxidisation of Corn Stover for Cellulase Enzyme Production

Nóra Szijártó,¹ Enikő Varga,² Zsolt Szengyel,¹ Anne Belinda Thomsen² and Kati Réczey¹*

¹ Department of Agricultural Chemical Technology

Budapest University of Technology and Economics

Szent Gellért tér 4

H-1521, Budapest, Hungary

Phone: +36 1 463 28 43

Fax: +36 1 463 25 98

E-mail: kati_reczey@mkt.bme.hu

^2.Plant Research Department, Risø National Laboratory

P.O. Box 49, DK-4000, Roskilde, Denmark

For the conversion of biomass to liquid fuels, such as ethanol, the cellulose content of the raw material must be hydrolysed to glucose, which is then fermented to ethanol. In order to make cellulosic raw materials accessible to enzymatic attack by cellulases, they must be pretreated. Among the available pretreatment methods, wet oxidisation is a promising alternative, which was applied to corn stover in this study.

Enzymatic hydrolysis of separated fibre fraction gained after the wet oxidisation of corn stover performs better than that of whole slurry. Therefore, pretreated fibres must be separated and effective utilisation of the side fraction rich in hemicellulose derivatives is required. This liquid fraction can be utilised for ethanol production by pentose fermenting yeasts; however, these microorganisms are known to be sensitive to inhibitors potentially generated during pretreatment. Furthermore, inhibitory compounds might accumulate in the process due to recirculation of process streams, which is required to minimise the need for freshwater - as an important economical aspect. Consequently, pentose stream must be detoxified prior to further processing. Due to its ability to metabolise pentoses while being able to degrade certain inhibitory compounds, the cellulolytic fungus Trichoderma reesei is of major importance in the detoxification of pentose fraction, which thus can be coupled with the production of high quality cellulose degrading enzymes.

In the present study, applicability of liquid streams generated during wet oxidisation of corn stover under different circumstances was tested for cellulase enzyme production by T. reesei RUT C30. Shake flask cultures were run to investigate the highest ratio in which pentose streams can be included in the fermentation medium together with Mandels nutrients and 10 g/l Solka floc as the carbon source. Applicability of an inert buffer system at desired pH was also studied with special emphasis on the effect of alterations in pH.