Comparison of digestibility of wood pulps produced by the sulfate and TMP methods and woodchips of various botanical origins and sizes

Kamila Buzała,Justyna Rosicka-Kaczmarek,Piotr Przybysz,Halina Kalinowska

doi:10.1007/s10570-015-0644-9

Kamila Buzała, Justyna Rosicka-Kaczmarek + Show 2 more

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https://doi.org/10.1007/s10570-015-0644-9

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Journal: Cellulose	Publication Date: May 12, 2015
Citations: 24	License type: CC BY 4.0

Affiliation: Lodz University of Technology

Abstract

Poplar and pine cellulosic pulps derived by the sulfate process (Kappa numbers of 15.4 and 31.4, respectively) and a poplar thermomechanical pulp (TMP, Kappa number of 124.7) as well as 0.43–0.8 mm woodchips of various botanical origins (poplar, birch, lime, oak, beech, pine, and spruce) and poplar chips of five different average particle sizes, ranging from 1.6–2.0 to <0.43 mm, were digested by a commercial preparation of cellulases and xylanases (NS-22086 from Novozymes). Yields of reducing sugars derived by enzymatic hydrolysis of the poplar and pine pulps that were obtained by the sulfate method achieved 100 and 89 % on a dry weight basis (52.3 and 35.9 % d.w. wood, respectively) while glucose yields reached 79 and 70.7 % d.w. pulp (41.3 and 28.6 % d.w. wood), respectively. Enzymatic hydrolysis of the pine TMP resulted in glucose and reducing sugars yields of only 14.0 and 36.7 % d.w. pulp (around 13 and 34 % d.w. wood, respectively). Yields of glucose and soluble reducing sugars released from the poplar chips were inversely proportional to their size and varied between around 5.3–7.8, and 15.7–22.4 % d.w., respectively. Reducing sugars yields from beech, birch and lime chips were slightly higher than from the poplar chips of the same size while pine, spruce and oak chips were less susceptible to enzymatic digestion. The dominating sugars in the hydrolysates of woodchips were glucose and cellobiose (70–90 % w/w of the sum of 5 detected sugars) while mannose, xylose and arabinose concentrations were relatively low.

Highlights

A sustainable production of biofuels and valuable chemicals from renewable lignocellulosic biomass has been considered a safe and ethical alternative to consumption of fossil resources that will be soon exhausted
The multienzyme preparation NS-22086, which was used in this study for digestion of the woodchips, kraft pulps and thermomechanical pulp (TMP), was selected as described by Buzała et al (2015)
The highest glucose and total reducing sugars yields were obtained from the poplar kraft pulp, which had the lowest Kappa number (15.4) among substrates used in this study

Summary

Introduction

A sustainable production of biofuels and valuable chemicals from renewable lignocellulosic biomass has been considered a safe and ethical alternative to consumption of fossil resources that will be soon exhausted. The harsh thermal pretreatment leads to losses in sugars and generates fermentation inhibitors like furfural, 5-hydroxymethylfurfural (5HMF), and phenolic acids (Stoutenburg et al 2011). These harmful compounds, reducing productivity of fermentation processes, need to be removed from biomass hydrolysates that increases overall costs of lignocellulose conversions. Xylose and other pentoses, derived from hemicelluloses, are usually less efficiently converted to fermentation products than glucose (Stoutenburg et al 2011). Their content in enzymatic hydrolysates depends on conditions of biomass pretreatment. Enzymatic hydrolysates of hardwood and softwood cellulosic pulps derived by kraft pulping are rich in glucose, constituting above 73 % soluble sugars (Buzała et al 2015)

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