3-86: Can endoxylanase application in wet storage preserve dry matter and reduce pretreatment severity?

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.