Assessment of Xylanase Activity in Dry Storage as a Potential Method of Reducing Feedstock Cost

Abstract

Enzymatic preprocessing of lignocellulosic biomass in dry storage systems has the potential to improve feedstock characteristics and lower ethanol production costs. To assess the potential for endoxylanase activity at low water contents, endoxylanase activity was tested using a refined wheat arabinoxylan substrate and three commercial endoxylanases over the water activity range 0.21-1.0, corresponding to water contents of 5% to >60% (dry basis). Homogeneously mixed dry samples were prepared at a fixed enzyme to substrate ratio and incubated in chambers at a variety of fixed water activities. Replicates were sacrificed periodically, and endoxylanase activity was quantified as an increase in reducing sugar relative to desiccant-stored controls. Endoxylanase activity was observed at water activities over 0.91 in all enzyme preparations in less than 4 days and at a water activity of 0.59 in less than 1 week in two preparations. Endoxylanase activity after storage was confirmed for selected desiccant-stored controls by incubation at 100% relative humidity. Water content to water activity relationships were determined for three lignocellulosic substrates, and results indicate that two endoxylanase preparations retained limited activity as low as 7% to 13% water content (dry basis), which is well within the range of water contents representative of dry biomass storage. Future work will examine the effects of endoxylanase activity toward substrates such as corn stover, wheat straw, and switchgrass in low water content environments.

Comparison Between Water Vapor Sorption Isotherms Obtained Using The New Dynamic Dewpoint Isotherm Method and those Obtained Using The Standard Saturated Salt Slurry Method

“…To date, a few published research papers have employed the DDI method to obtain sorption isotherms, [9][10][11][12] however, no publications were found that compare the DDI method to the standard saturated salt slurry isotherm method. Thus, the objective of this research was to obtain DDIs of five diverse food materials, dent corn starch, isolated soy protein, microcrystalline cellulose, crystalline sucrose, and corn flakes, and compare them to previously obtained saturated salt slurry isotherms using a desiccator (DES) and proximity equilibration cell (PEC) chambers.…”

Direct emission of methane and nitrous oxide from switchgrass and corn stover: implications for large‐scale biomass storage

“…1). Saturated salt solutions with excess salt controlled the humidity in each container to minimize changes in biomass moisture content, as described by Smith et al (Smith et al, 2009). Sodium chloride [water activity (A w ) 0.75], potassium nitrate (A w 0.89-0.95), and potassium sulfate (A w 0.97-0.98) were used to control the relative humidity at the three target levels.…”

“…Initial bale moisture group means were close to the target moisture content for each treatment, and individual bale moisture estimates did not overlap between groups (Table 2). Target moisture contents were selected based on each crop's equilibration at a certain water activity, which was expected to correlate with the degree of microbial activity (Smith et al, 2009). The moisture content of each bale appeared consistent throughout storage.…”