Chemical and Structural Changes in Corn Stover After Ensiling: Influence on Bioconversion.

Nick J. Nagle,Thomas J. Haas,Bryon S. Donohoe,Noah D. Weiss,Lynn M. Wendt,Erik M. Kuhn,Mark E. Delwiche,Edward J. Wolfrum,Allison E. Ray,Corey Radtke

doi:10.3389/fbioe.2020.00739

Abstract

Production of biofuels, bioproducts, and bioenergy requires a well-characterized, stable, and reasonably uniform biomass supply and well-established supply chains for shipping biomass from farm fields to biorefineries, while achieving year-round production targets. Preserving and stabilizing biomass feedstock during storage is a necessity for cost-effective and sustainable biofuel production. Ensiling is a common storage method used to preserve and even improve forage quality; however, the impact of ensiling on biomass physical and chemical properties that influence bioconversion processes has been variable. Our objective in this work was to determine the effects of ensiling on lignocellulosic feedstock physicochemical properties and how that influences bioconversion requirements. We observed statistically significant decreases (p < 0.05) in the content of two major structural carbohydrates (glucan and xylan) of 5 and 8%, respectively, between the ensiled and non-ensiled materials. We were unable to detect differences in sugar yields from structural carbohydrates after pretreatment and enzymatic hydrolysis of the ensiled materials compared to non-ensiled controls. Based on this work, we conclude that ensiling the corn stover did not change the bioconversion requirements compared to the control samples and incurred losses of structural carbohydrates. At the light microscopy level, ensiled corn stover exhibited little structural change or relocation of cell wall components as detected by immunocytochemistry. However, more subtle structural changes were revealed by electron microscopy, as ensiled cell walls exhibit ultrastructural characteristics such as wall delimitation intermediate between non-ensiled and dilute-acid-pretreated cell walls. These findings suggest that alternative methods of conversion, such as deacetylation and mechanical refining, could take advantage of lamellar defects and may be more effective than dilute acid or hot water pretreatment for biomass conversion of ensiled materials.

Highlights

IntroductionConversion of the 1.2 billion metric tons of biomass could result in the production of 50 billion gallons of biofuels, 50 billion pounds of bio-based chemicals and bioproducts, and 85 billion kilowatthours of electricity to power 7 million households (Rogers et al, 2016)
The United States Department of Energy’s 2016 Billion-Ton Report: Advancing Domestic Resources for a Thriving Bioeconomy (Langholtz et al, 2016) projects that 1.0 billion tons of biomass will be available by 2030 and 1.2 billion tons by 2040
The ensiling storage reactors were monitored for the duration of the study and showed no evidence of gas-seal failure on the reactor bodies and no indication of spoilage, this biomass was not included in the conversion study

Summary

Introduction

Conversion of the 1.2 billion metric tons of biomass could result in the production of 50 billion gallons of biofuels, 50 billion pounds of bio-based chemicals and bioproducts, and 85 billion kilowatthours of electricity to power 7 million households (Rogers et al, 2016) This resource would contribute 1.1 million jobs to the U.S economy and keep $260 billion in the United States. Regardless, the most common practice is to aggregate biomass prior to delivery to the biorefinery These practices have shown dry-matter losses (DML) of

Methods

Results

Conclusion