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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Chem. | doi: 10.3389/fchem.2019.00585

Wheat bran pretreatment by Room Temperature Ionic Liquid-Water mixture: Optimization of process conditions by PLS-Surface Response Design

 Catherine Sarazin1, 2*,  Monica Araya Farias1, 2, Eric Husson1, 2,  Jorge Saavedra3,  Doriane Gérard4, 5, 6, Romain Roulard2,  Isabelle Gosselin1, 2, Harivony Rakotoarivonina4, 5, 6, Virginie Lambertyn1, 2 and  Caroline REMOND4, 5, 6
  • 1UMR CNRS 7025 Génie Enzymatique et Cellulaire (GEC), France
  • 2University of Picardie Jules Verne, France
  • 3Pontificia Universidad Católica de Valparaíso, Chile
  • 4Independent researcher, France
  • 5Fractionnation of AgroResources and Environment (INRA), France
  • 6Université de Reims Champagne-Ardenne, France

Room Temperature Ionic Liquids (RTILs) pretreatment are well-recognized to improve the enzymatic production of platform molecules such as sugar monomers from lignocellulosic biomass. The conditions for implementing this key step requires henceforth optimization to reach a satisfactory compromise between energy saving, required RTIL amount and hydrolysis yields. Wheat bran (WB) and destarched wheat bran (DWB), which constitute relevant sugar-rich feedstocks were selected for this present study. Pretreatments of these two distinct biomasses with various 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc])-water mixtures prior to hydrolysis catalyzed by hemicellulolytic cocktail (Cellic Ctec2) were finely investigated. The main operating conditions such as pretreatment temperature (25-150°C), time (40-180 min), WB and DWB loading (2-5% w/v) and concentration of [C2mim][OAc] in water (10-100% (v/v)) were screened through glucose and xylose yields and then optimized through a Partial Least Square (PLS) - Second Order Design. In an innovative way, the PLS results showed that the four factors and their interactions could be well fitted by a second-order model (p<0.05). The quadratic PLS models were used to predict optimal pretreatment conditions. Thus, maximum glucose (83%) and xylose (95%) yields were obtained from enzymatic hydrolysis of WB pretreated at 150°C for 40 min with 10 % of [C2mim][OAc] in water and 5% of WB loading. For DWB, maximum glucose (100%) and xylose (57%) yields were achieved for pretreatment temperatures of 150°C and 25°C respectively. The required duration was still 40 min, with 20 % of [C2mim][OAc] in water and a 5% DWB loading. Then, Multiple Response Optimization performed by Nelder-Mead Simplex Method displayed sugar yields similar to those obtained by individual PLS optimization. This complete statistical study confirmed that the established models were appropriate to predict the sugar yields achieved after different pretreatment conditions from WB and DWB biomasses. Finally, Scanning Electron microscopy (SEM) studies allowed us to establish clearer link between structural changes induced by pretreatment and the best enzymatic performances obtained

Keywords: Wheat bran (WB), Room temperature ionic liquid (RTIL), pretreatment, Ionic liquid-water mixture, hemicellulolytic cocktail, Enzymatic hydrolysis, Partial Least Square surface response design

Received: 14 May 2019; Accepted: 05 Aug 2019.

Copyright: © 2019 Sarazin, Araya Farias, Husson, Saavedra, Gérard, Roulard, Gosselin, Rakotoarivonina, Lambertyn and REMOND. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Catherine Sarazin, UMR CNRS 7025 Génie Enzymatique et Cellulaire (GEC), Compiegne, Picardy, France,