Bioethanol production pretreatment

Corn stover, a well-known example of lignocellulosic biomass, is a potential renewable feed for bioethanol production. Dilute sulfuric acid pretreatment removes hemicellulose and makes the cellulose more susceptible to bacterial digestion. The rheologic properties of corn stover pretreated in such a manner were studied. The Power Law parameters were sensitive to corn stover suspension concentration becoming more non-Newtonian with slope n, ranging from 0.92 to 0.05 between 5 and 30% solids. The Casson and the Power Law models described the experimental data with correlation coefficients ranging from 0.90 to 0.99 and 0.85 to 0.99, respectively. The yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of corn stover tested. 

The use of recombinant microorganisms for cofermentation is one of the most promising approaches in the field of bioethanol production, though their use for large-scale industrial processes still requires fine-tuning of the reliability of the entire process (2). The technical hurdles of cofermentation increase when real biomass hydrolysates have to be fermented. In fact, whatever the biomass pretreatment, the formation of degradation byproducts that could inhibit the fermentation usually requires the addition of a further detoxification step. Therefore, the production of ethanol from hydrolysates should be considered in its entirety, from the optimal pretreatment to the choice of the proper fermentation process. 

Hsu, T.-A. (1996) Pretreatment of Biomass, in Handbook on Bioethanol Production and Utilisation, C.E. Wyman (Ed.), Taylor Francis, London. 

The results presented in this paper were only a very preliminary study of pretreatment of maize silage. Trials should be made at lower temperatures to examine if more energy could be saved in the process. It would also be interesting to determine the content of starch and cellulose separately by enzymatic hydrolysis, instead of total glucan as is the case in this study. Also, enzymatic hydrolysis and SSF using low enzyme loadings (of both cellulases and amylases) should be made to fully see the potential of this promising raw material for bioethanol production. 

Alvira P, Tomas-Pejo E, Ballesteros M, Negro MJ. (2010). Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis a review. Bioresour Technol, 101,4851 861. 

Chaudhary G, Singh LK, Ghosh S. (2012). AlkaUne pretreatment methods followed by acid hydrolysis of saccharum spontaneum for bioethanol production. Bioresour Technol, 124, 111-118. 

Galbe M, Zacchi G. (2007). Pretreatment of lignocellulosic materials for efficient bioethanol production. Biofuels, 108, 41-65. 

Rabelo SC, Filho RM, Costa AC. (2009). Lime pretreatment of sugarcane bagasse for bioethanol production. Appl Biochem Biotechnol, 153, 139-153. 

The search for new and cheap substrates for the production of bioenergy and other biotechnological products is continuously demanded. Pal et al. reported that the mustard stalk and straw served as an alternative substrate for the production of lignocellulolytic enzymes and as a source for saccharification. The biomass from halophyte plants such as Retama retam and Juncus maritimus were used as the substrate for bioethanol production. The combined effect of thermochemical pretreatment and enzymatic hydrolysis of kitchen wastes for maximizing the production of fermentable soluble sugars has been described previously. ... 

Han, M. H., Kim, Y, Kim, S. W., Choi, G. W. High efficiency bioethanol production from OPEFB using pilot pretreatment reactor. Journal of Chemical Technology end Biotechnology lOW, 86,1527-1534. 

Kim, S., Kim, C. H. Bioethanol production using the sequential acid/alkali-pretreated empty pakn fruit bunch fiber. Renewable Energy 2013,54,150-155. 

Conde-Mejia, C., A. Jimdnez-Gutidrrez and M. El-Halwagi (2012). A comparison of pretreatment methods for bioethanol production from hgnocellulosic materials. Process Safety and Environmental Protection 90(3) 189-202. 

TABLE 22.4 Pretreatment Techniques for Bioethanol Production (Taherzadeh and Karimi, 2008)... 

Bioethanol production routes from different biomasses are show in Fig. 9.1. It typically contains foiu major steps, ie, feedstock pretreatment, hydrolysis (or saccharification). 

Currently, cellulosic biomass use is very hmited due to the expensive pretreatment required for breaking the crystalline stractnre of cellnlose. Bioethanol is already an established commodity due to its ongoing non-fuel uses in beverages, and in the manufactnre of pharmaceuticals and cosmetics. In facf ethanol is the oldest synthetic organic chemical used by mankind. Table 3.3 shows ethanol production in different continents (Demirbas, 2008b). 

The production of fuel ethanol from renewable lignocellulosic material ("bioethanol") has the potential to reduce world dependence on petroleum and to decrease net emissions of carbon dioxide. The lignin-hemicellulose network of biomass retards cellulose biodegradationby cellulolytic enzymes. To remove the protecting shield of lignin-hemicellulose and make the cellulose more readily available for enzymatic hydrolysis, biomass must be pretreated (1). 

---