Production of simple sugars from olive grove pruning using acid pretreatment and enzymatic hydrolysis

N. Pedro¹²*, R. Bezerra³⁴, I. Fraga³⁴ and A.P. Duarte⁵⁶

¹Polytechnic University of Castelo Branco, Faculty of Agriculture, Department of Natural Resources and Sustainable Development, Quinta da Sra. de Miércoles, apartado 119, PT6001-909 Castelo Branco, Portugal
²QRural - Qualidade De Vida No Mundo Rural, Av. Pedro Álvares Cabral, n.º12, PT6000-084 Castelo Branco, Portugal
³UTAD - University of Trás-os-Montes and Alto Douro, Quinta de Prados, PT5000-801 Vila Real, Portugal
⁴CITAB - Centre for the Research and Technology of Agro-Environmental and Biological Sciences. UTAD, Quinta de Prados, PT5000-801 Vila Real, Portugal
⁵UBI - University Beira Interior. Convento de Sto. António, PT6201-001 Covilhã, Portugal
⁶CICS-UBI - Health Sciences Research Centre, University Beira Interior,
Av. Infante D. Henrique, PT6200-506 Covilhã, Portugal
*Correspondence: npedro@ipcb.pt; lnova@ipcb.pt

Abstract:

The purpose of this paper was to optimize the production of simple sugars from olive grove pruning (OGP) using acid pretreatment and enzymatic hydrolysis. This study was based on a model composition corresponding to a 34 orthogonal factorial design and employed the response surface methodology (RSM) to optimize the pretreatment and hydrolysis conditions, aiming to attain maximum glucose, xylose and arabinose extraction from cellulose and hemicellulose of biomass. The pretreatment operating conditions considered for optimization, were temperature (60–180 °C), residence time (30–120 min) and sulphuric acid concentration (0.5–5% w w^-1). Enzymatic hydrolysis experiments on solid fraction pretreated with diluted acid were performed at a solid concentration of 5% (w v^-1, based on dry weight), using 50 mM citrate buffer pH 4.8 with BSA at a concentration of 60 mg g^-1 dry biomass. The reaction mixture was incubated at 50 °C for 174 h on an orbital shaker at 150 rpm. Three commercial enzyme preparations (cellulase complex, b-glucosidase and xylanase) were used in enzymatic saccharification. Total carbohydrate content of the initial biomass was 51.25% (in dry mass), of which glucose was the major constituent with 33.59%. Contents of lignin and extractable found in biomass were 24.96% and 15.84%, respectively. In this work, it was possible to extract 93.1% of the sugars present in the olive grove pruning, with pretreatments carried out for 102 min at 156 °C with a sulfuric acid load of 4.09% (w w^-1), followed by enzymatic hydrolysis performed for 174 h, with an enzyme loading of 18 PFU, 36 p-NPGU and 36 IU per gram of substrate.

Key words:

acid hydrolysis, enzymatic hydrolysis, olive pruning, pretreatment, RSM, sugars

Production of cellulose nanostructures from Chilean bamboo, Chusquea quila

P.E. Oliveira¹*, X. Petit-Breuilh², O.J. Rojas³ and W. Gacitúa⁴

¹Department of Industrial Process Engineering, Nucleus of Research in Bioproducts and Advanced Materials, Catholic University of Temuco, Manuel Montt Street, Postal Code CL4813302 Temuco, Chile
²School of Engineering and Business, Viña del Mar University, Diego Portales Street, Postal Code CL2580022, Chile
³Department of Bioproducts and Biosystems, Aalto University School of Chemical Engineering, P.O. Box 16300, 00076 Aalto, Finland
⁴Postgraduate Department of Wood Engineering, Biomaterials and Nanotechnology Center, Bío-Bío University, Collao Avenue 1202, Postal Code CL4051381 Concepción, Chile
*Correspondence: poliveira@uct.cl

Abstract:

In Chile, bamboo bushes of Chusquea quila genus (or popularly known as ‘quila’) have brought economic and ecological problems for decades in the south-central part of this country. On the other hand, this plant species was studied as a raw material for the production of nanofibrillated cellulose (CNF) and nanocrystalline cellulose (CNC), presenting an opportunity for sustainable and environmentally friendly management, positioning Chile as a Latin American country at the forefront of studies with nanotechnological approaches. The methodology applied to generate these nanostructures contemplated hydrolysis with sulfuric acid and oxalic acid, in addition to an intermediate stage of microfluidization to generate nanofibrillated cellulose. The products obtained showed morphological and topographic homogeneity in the scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. The diameter values of the particles ranged from 10 to 20 nanometers for the CNCs. Through Fourier transformed spectrophotometry (FTIR) it was found that the processes of microfluidization and acid hydrolysis did not affect the molecular shape of the nanostructures and X-ray diffraction (XRD) was important to determine crystallinity index (IC), presenting values higher than 80%.

Key words: