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Cellulose conversion of corn pericarp without pretreatment

Kim, Daehwan, Orrego, David, Ximenes, Eduardo A., Ladisch, Michael R.
Bioresource technology 2017 v.245 pp. 511-517
Aspergillus niger, Trichoderma reesei, cellulose, corn, endo-1,4-beta-glucanase, enzymatic hydrolysis, enzyme activity, ethanol, hydrolysis, pericarp, phenols, polygalacturonase
We report enzyme hydrolysis of cellulose in unpretreated pericarp at a cellulase loading of 0.25FPU/g pericarp solids using a phenol tolerant Aspergillus niger pectinase preparation. The overall protein added was 5mg/g and gave 98% cellulose conversion in 72h. However, for double the amount of enzyme from Trichoderma reesei, which is significantly less tolerant to phenols, conversion was only 16%. The key to achieving high conversion without pretreatment is combining phenol inhibition-resistant enzymes (such as from A. niger) with unground pericarp from which release of phenols is minimal. Size reduction of the pericarp, which is typically carried out in a corn-to-ethanol process, where corn is first ground to a fine powder, causes release of highly inhibitory phenols that interfere with cellulase enzyme activity. This work demonstrates hydrolysis without pretreatment of large particulate pericarp is a viable pathway for directly producing cellulose ethanol in corn ethanol plants.