| Although the process of cellulosic ethanol production was well known, the high production cost hindered the commercial development of cellulosic ethanol seriously. Not getting the “THREE-HIGH” technical levels like starch-based ethanol production was considered as one of the main reasons for the high cost of cellulosic ethanol production. The key of solving that problem was making cellulosic ethanol fermentation at high-gravity. Therefore, the different treatment methods for steam-exploded corn stover and semi-siultaneous saccharification and fermentation process of pretreated steam-exploded corn stover were conducted, which were as follows:?1? In order to increase the enzymatic feasibility of steam-exploded corn stover, the treatment conditions of two kinds of treatment were studied. The results were as follows: the optimum treatment conditions of glycerol organosolv treatment were as follows: temperature 110 oC, time 2 h, concentration of glycerol solution 70%(w·w-1), NaOH amounts 0.1 g·?g material?-1. Under the optimal conditions, the cellulose content of the pretreated steam-exploded corn stover increased to 57.4%, meanwhile the lignin content decreased to 15.5%. The optimum treatment conditions of alkaline hydrogen peroxide treatment were as follows: hydrogen peroxide concentration 2%, solid/liquid(w·w-1) 10/110, temperature 110 oC and time 2 h. Under the optimal conditions, the cellulose content of the pretreated steam-exploded corn stover was 61%, meanwhile the lignin content was 7.0%. Glucose yields of 515 mg·g-1, 620 mg·g-1 and 265 mg·g-1 were obtained from steam-exploded corn stover preteated with glycerol organosolv treatment?GOT-SECS?, SECS pretreated with alkaline hydrogen peroxide treatment?AHT-SECS? and untreated SECS, respectively, when the tree samples were hydrolysed at cellulase loading of 15 FPU·?g biomass? and substrate concentration of 2% after the enzymatic hydrolysis of 48 h. So AHT was chosen as the treatment method for SECS.?2? The optimization of Semi-simultaneous saccharification and fermentation for high-titer ethanol from AHT-SECS was carried out on pre-hydrolysis process, culture medium and fermentation conditions. Under the optimum s-SSF process(enzyme loading 30 FPU·?g dry mass?-1,?15.6+20?%(w·v-1) substrate concentration(20%(w·v-1) fresh dry biomass was fed at 12 h of pre-hydrolysis process), 36 h of pre-hydrolysis time, inoculation of age 20 h, inoculum size 0.6 g dry cell·L-1, 39 oC of fermentation temperature and PEG4000 additive amounts 0.01 g·?g dry mass?-1), the ethanol yield, fermentation productivity and cellulose conversion ratio achieved were 73.7 g·L-1, 3.07 g·?L·h?-1 and 61% respectively at 24 h of fermentation.?3? In order to increase the ethanol yield, the intensification of fed-batch pro-hydrolysis process was conducted. The intensified pre-hydrolysis process was initiated with 14.5%(w·v-1) solid loading in 250 m L flasks, where 5%, 7% and 9% fresh solid were fed at 4 h, 10 h and 16 h respectively to get a final solids loading of 35.5%, meanwhile all cellulase and four beads of 9 mm were added at the beginning. Under the same fermentation medium and conditions as?2?, the ethanol yield, fermentation productivity and cellulose-ethanol conversion ratio were increased to 81.2 g·L-1, 3.38 g·?L·h?-1 and 67.2%, respectively. |
PDF Full Text Request