Physical and chemical differences between one-stage and two-stage hydrothermal pretreated hardwood substrates for use in cellulosic ethanol production.

Andrew Guilliams,Deidre Willies,Matt Richards,Sindhu Kandemkavil,Erin Wiswall,Yunqiao Pu,Sivakumar Pattathil

doi:10.1186/s13068-016-0446-9

Andrew Guilliams, Deidre Willies + Show 5 more

Open Access

https://doi.org/10.1186/s13068-016-0446-9

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Abstract

BackgroundThere are many different types of pretreatment carried out to prepare cellulosic substrates for fermentation. In this study, one- and two-stage hydrothermal pretreatment were carried out to determine their effects on subsequent fermentations. The two substrates were found to behave differently during fermentation. The two substrates were then characterized using physical and chemical parameters.ResultsThe one-stage substrate was found to have higher carbohydrate content and lower lignin content. It exhibited a higher level of viscosity, a larger settled volume, and a slower settling time than the two-stage substrate. It also showed higher polarity and reduced crystallinity. Glycome profiling showed physical differences between the two substrates, specifically pointing toward higher levels of pectin and hemicellulose in the one-stage substrate (MS1112) as compared to the two-stage substrate (MS1107).ConclusionsWe hypothesize that these physical and chemical differences between the substrates contribute to the differences seen during fermentation including: ethanol yield, ethanol titer, fermentation rate, fermentation completion time, mixing, and substrate solubilization. These findings can be used in optimizing pretreatment parameters to maximize ethanol conversion and overall process yield for hardwood substrates.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0446-9) contains supplementary material, which is available to authorized users.

Highlights

There are many different types of pretreatment carried out to prepare cellulosic substrates for fermentation
The results from this study indicate that one-stage hydrothermal pretreated material performs better during fermentation that two-stage hydrothermal pretreated material under the conditions tested here
Additional fermentations were performed on one- and two-stage hot water pretreated hardwoods ranging from a severity of 3.8 to 4.6 with similar results

Summary

Introduction

There are many different types of pretreatment carried out to prepare cellulosic substrates for fermentation. Conversion of sugars in cellulosic feedstocks, an abundant and potentially sustainable source of organic complex molecules, into fuels and chemicals has drawn the interest of scientists and industry for decades [1,2,3,4]. The breakdown of these complex feedstocks into monomeric sugars that can be readily converted into fermentation products, remains a key barrier for their usage [5]. Many organisms produce enzymatic systems that can attack cellulosic biomass and break it down to its constituent monomeric sugar molecules [6,7,8], with the most

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