Cellulase Synergetic Experiment And The SSF Of Recombinant Yeast

It is economic and environmental to product ethanol by cellulose, which is the most abundant regenerated resources in the world. Cellulosic saccharification and ethanol fermentation are two important research parts in the bioconversion of cellulose to ethanol currently. This research was about cellulase activities, cellulose composing and SSF as follows for enhancing hydrolytic efficience and ethanol yeild.1) In order to enhance cellulase activity, we carried out synergetic experiment to find a protein which can promote cellulase hydrolyzing. The research was carried using 15 fungus in our lab, with Trichoderma sp.9414 cellulase as the control. The fungus which can increase the cellulase activity all have higherβ- glucosidases activity than 9414. According to their DS, the promote effect is probably caused byβ-glucosidase.2) We optimized SSF condition of JU-A10 via gradual tests of temperature, yeast inoculation, substrate and enzyme concentration. The best condition is SSF with 20 IU/g enzyme concentration, 15%acid- pretreated corncob using 0.2% yeast inocu- lation in 35℃. The optimization provide important value for bioethanol industry progress.3) Theβ-glucosidase gene—BGL1 of Saccharomycopsis fibuligera was isolated and expressed in Saccharomyces cerevisiae NAN-27 using the standard yeast trans- formation method we set up in the past. The recombinant yeast with the highestβ-glucosidase activity—1.02 IU/mg was named NAN-227, and was approved to utilizing cellobiose effectively on cellobiose as the sole carbon source. Its ethanol yield ability using cellobiose is 0.533 g/g, approach to the theoretical value. The SSF of NAN-27 and NAN-227 using Celluclast 1.5 L and JU-A10 as cellulase indicated that recombinant yeast could utilize cellobiose much quickly and the ethanol yield increased. Nevertheless, it had a gap between the SSF using NAN-227 and the one using NAN-27 addedβ-glucosidase. The expression of BGL1 in industrial yeast NAN-27 decreased the prevence of cellobiose for cellulose degradation in SSF and was able to decrease, even instead of addingβ-glucosidase in ethanol industry.