PRETREATMENT OF CELLULOSIC WASTE SAWDUST INTO REDUCING SUGARS USING MERCERIZATION AND ETHERIFICATION

Beomsoo Kim, Ishan Gulati, Jinwon Park, Jong-Shik Shin

Abstract


Pretreatment of sawdust using a combination of sodium hydroxide (NaOH) and monochloroacetic acid (MCA) was investigated for the formation of reducing sugars. Optimum conditions for the pretreatment process were determined by the amount of reducing sugars formed during the enzymatic hydrolysis of the pretreated substrate. It was found that mercerization by NaOH played an important role in increasing the degree of substitution (DS) and that the maximum solubility was achieved during the etherification by MCA. A maximum amount of 34.2% lignin was removed in the process. As the DS of the substrate was increased, the efficiency of the hydrolysis process increased, leading to the higher yield of reducing sugars. The optimum operating conditions for the pretreatment process were determined to be 75 °C at 90 rpm for 4 hours (2 hours for mercerization plus 2 hours for etherification). Under these operating conditions, with 1% (w/v) NaOH and 2% (w/w) MCA loading, a maximum DS of 0.2 and a solubility of 10.3% was attained. At 75 °C and after 48 hours of the hydrolysis process, cellulases from Aspergillus niger resulted in the production of 2.88 g/L of glucose with a yield of 62.72% reducing sugars. X-ray diffraction (XRD) revealed reduced crystallinity of the sawdust and Scanning Electron Microscopy (SEM) showed distortion of the structure after pretreatment.

Keywords


Lignocellulosic biomass; Mercerization; Etherification; Lignin removal; Enzymatic hydrolysis

Full Text: PDF

Welcome to BioResources! This online, peer-reviewed journal is devoted to the science and engineering of biomaterials and chemicals from lignocellulosic sources for new end uses and new capabilities. The editors of BioResources would be very happy to assist you during the process of submitting or reviewing articles. Please note that logging in is required in order to submit or review articles. Martin A. Hubbe, (919) 513-3022, hubbe@ncsu.edu; Lucian A. Lucia, (919) 515-7707, lucian.lucia@gmail.com URLs: bioresourcesjournal.com; http://ncsu.edu/bioresources ISSN: 1930-2126