Suitability of Starch-rich Lignocellulosic Feedstocks for Bioethanol Production after AFEX Pretreatment

Researchers from the Michigan State University (United States), Zhejiang Forestry University (China), and Indian Institute of Technology-Madras (India) investigated a process for bioethanol production from starch-rich lignocellulosic feedstocks. The corn-grain constitutes the starch-rich component of the crop, while the stalks, stem, and leaves ("stover") constitute the cellulosic part of the crop. Although corn is usually harvested by separating the grain from the stover, (and then separately processed into ethanol), the harvest of whole corn plants (grain plus stover) for subsequent ethanol processing by co-hydrolysis, represents an alternative. In the study, the researchers used mature whole corn plants and corn silage as the test feedstock. They subjected the material to a thermochemical pretreatment by ammona fiber expansion (AFEX), followed by co-hydrolysis by the enzymes amylase (starch hydrolysis) and cellulase (cellulose hydrolysis). Enzymatic digestibility and ethanol fermentability were evaluated after pretreatment and co-hydrolysis. The results showed that AFEX-pretreated starch-rich substrates had a 1.5-fold to 3.5-fold higher enzymatic hydrolysis compared to untreated (no AFEX pretreatment) substrates. "Sequential addition of cellulase after the hydrolysis of starch (by amylase) within whole corn plants resulted in 15% to 20% higher hydrolysis compared to simultaneous addition of both (amylase and cellulase) enzymes. Ethanol concentrations after fermentation were 28 g/L and 30 g/L, for corn silage and whole corn plants, respectively. The complete results are published in the open access journal, Biotechnology for Biofuels (URL above).

Related information of corn silage: http://www.utextension.utk.edu/publications/spfiles/sp434d.pdf