Obtaining Fermentable Sugars from a Highly Productive Elm Clone Using Different Pretreatments

David Ibarra,Juan A Martín,Manuel J Díaz,María E Eugenio,Raquel Martín-Sampedro,Laura Jiménez-López

doi:10.3390/en14092415

Abstract

The interest of supplying lignocellulosic materials for producing fermentable sugars has recently emerged in order to diminish the negative environmental effects of fossil fuels. In this study, the Ulmus minor clone Ademuz, characterized for its tolerance to Dutch elm disease and its rapid growth, was evaluated as a source of fermentable sugars. For that, different pretreatments, comprising autohydrolysis, dilute acid hydrolysis, acid catalyzed organosolv, and alkaline extraction, were evaluated at two levels of severity (pretreatment temperatures at 160 °C and 180 °C, except for alkaline extraction at 80 °C and 160 °C); and the resulting pretreated materials were enzymatically hydrolyzed for fermentable sugars production. The major extraction of lignin and hemicellulose was achieved during organosolv (48.9%, lignin; 77.9%, hemicellulose) and acid hydrolysis (39.2%, lignin; 95.0%, hemicellulose) at 180 °C, resulting in the major enzymatic digestibility (67.7%, organosolv; 53.5% acid hydrolysis). Contrarily, under the most favorable conditions for autohydrolysis (180 °C) and alkaline extraction (160 °C), lower extraction of lignin and hemicellulose was produced (4.8%, lignin; 67.2%, hemicellulose, autohydrolysis; 22.6%, lignin; 33.1%, hemicellulose, alkaline extraction), leading to lower enzymatic digestibility (32.1%, autohydrolysis; 39.2%, alkaline extraction). Taking into account the sugars produced during enzymatic hydrolysis of pretreated materials and the solubilized sugars from pretreatment liquors, the highest sugars (glucose and xylose) yield production (28.1%) per gram of biomass from U. minor clone Ademuz was achieved with acid catalyzed organosolv at 180 °C.

Highlights

The use of biomass as a basic and renewable raw material implies a transition from an economy based on fossil fuels to one based on biomass, which has been called “bioeconomy”
The aim of this study is to evaluate the effect of four different pretreatments at two severity levels on the production of fermentable sugars from U. minor clone Ademuz, which can be transformed into different biofuels or bioproducts, and to select the most efficient one
The U. minor clone Ademuz was supplied by the Spanish elm breeding program. This clone eligible for the production of forest reproductive materials and tolerant to Dutch elm disease was registered in Spain

Summary

Introduction

The urgency of identifying and developing sustainable solutions that respond to society’s current and future needs has been clearly demonstrated by the alarming escalation in global energy demand, the need to reduce greenhouse gas emissions, and the exhaustion of fossil fuel reserves In this scenario, the use of biomass as a basic and renewable raw material implies a transition from an economy based on fossil fuels to one based on biomass, which has been called “bioeconomy”. From there arises the biorefinery concept, defined as the use of biomass to produce energy together with a great variety of bioproducts including materials, chemicals, feed, and food [1] Unlike other biomasses, such as sugar or starch, the lignocellulosic materials are abundant, low cost, and not destined for food. All of these advantages make lignocellulosic biomass the most suitable raw material for the development of lignocellulosic biorefineries [2]

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Conclusion