Sunday, May 3, 2009
3-86

Can endoxylanase application in wet storage preserve dry matter and reduce pretreatment severity?

William A. Smith, David N. Thompson, and Vicki S. Thompson. Biological Systems Department, Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415-2203

Is xylose more valuable as a preservative or as product? Enzymatic processing of lignocellulosics during wet storage could potentially improve dry matter stability and reduce pretreatment severity. Limited hemicellulose hydrolysis using endoxylanase would provide xylo-oligomers for ensiling–improving dry matter stability–and also reduce the amount of hemicellulose hydrolysis needed during subsequent pretreatment. To explore the cost and yield tradeoffs of this approach, a commercial endoxylanase was applied to freshly harvested corn stover at three starting water contents (36%, 51% and 68% wet basis) with and without the addition of a commercial silage amendment (lactic acid bacteria at 106 cfu g-1 dry matter). Experimental enzyme activities were high (47 to 138 U per g xylan) to identify clearly the effects of treatment. Samples were incubated anaerobically at 37° C for 4 months and were sampled for compositional analyses of both the liquid and solid fractions. Dry matter losses ranged from 12.5 to 15.3 %. pH values were lower and organic acid and total sugar concentrations were higher in the highest (68%) water content samples. Ash content was higher in the low water content samples (36% and 51%), which balanced the difference in organic acid and sugar concentrations relative to total dry matter loss. Near infrared spectrometry indicated greater loss of hemicellulose from solids subjected to a combination of high starting water content, endoxylanase addition and silage inoculant. Ongoing work will determine if this leads to a reduction in pretreatment severity, and if so to what extent relative to untreated stover.