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Title: ENZYMATIC HYDROLYSIS OF HIGH MOISTURE CORN FIBER PRETREATED BY AFEX AND RECOVERY AND RECYCLE OF THE ENZYME COMPLEX

Author
item MONIRUZZAMAN, MOHAMMED - TEXAS A&M UNIV
item DALE, BRUCE - TEXAS A&M UNIV
item Hespell, Robert
item Bothast, Rodney

Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Agricultural materials, particularly corn fiber, are available in sufficient quantities from the corn wet milling industry to serve as a low cost feedstock for production of fuel alcohol. Chemical, physical, and biological treatments are commonly used in the bioconversion of agricultural biomass to fermentable sugars. In this study, we determined the best ammonia fiber explosion (AFEX) treatment conditions with regard to moisture, particle size, ammonia to biomass ratio, temperature, and time. More than 85% of the possible sugars were obtained during subsequent recycling enzyme treatments. These sugars can then be fermented to alcohol fuel by novel microorganisms.

Technical Abstract: Corn fiber is a grain processing residue containing significant amounts of cellulose, hemicellulose and starch, which is collected in facilities where fuel ethanol is currently manufactured. Preliminary research has shown that corn fiber (30% moisture dwb) responds well to ammonia fiber explosion (AFEX) pretreatment. However, an important AFEX pretreatment variable which has not been adequately explored for corn fiber is sample moisture. In the present investigation, we determined the best AFEX operating conditions for pretreatment of corn fiber at high moisture content (150% moisture dwb). The optimized AFEX treatment conditions are defined in terms of the moisture content, particle size, ammonia to biomass ratio, temperature, and residence time using the response of the pretreated biomass to enzymatic hydrolysis as an indicator. Approximate optimal pretreatment conditions for unground corn fiber containing 150% (dwb) moisture were found to be: temperature, 90øC; ammonia: dry corn fiber mass ratio, 1:1; and residence time 30 min (the average reactor pressure under these conditions was 200 psig). More than 85% of the theoretical sugar yield was obtained during enzymatic hydrolysis after pretreatment of corn fiber under the optimized conditions described above. A simple process for enzyme recovery and reuse was demonstrated. Using this process, five batches of fresh substrate (at a concentration of 5% w/v) were successfully hydrolyzed by repeated recovery and reuse of the enzyme preparation with the addition of a small portion of fresh enzyme in each subsequent recycling step.