Optimization of Sulphuric Acid Hydrolysis Process for Fermentable Sugars from Lignocellulosic Content of Wood Sawdust for Production of Cellulosic Ethanol

Gebreyohannes Gebrehiwot; Kiros Birhane; Tsegay Gebrekidan

Abstract

The aim of this study was to investigate the optimization of acid hydrolysis process for fermentable sugars from the lignocellulosic content of wood sawdust for cellulosic ethanol production. In this study, four process parameters were investigated; acid concentration (3-7%), solid fraction (8-12ml/gm), temperature (100-120oC) and time (90-150minutes). The total reducing sugar content of hydrolyzed solutions was analyzed using Phenol-Sulfuric Acid method. The result of the statically analysis 2mm particle size of wood sawdust showed that maximum sugar content of 75.88% (w/w) was achieved at 5% (v/v) sulfuric acid concentration, 10ml/gm solid fraction, 110oC and 120minutes. Furthermore, the minimum yield of 44.45% (w/w) was achieved at 3% (v/v) sulfuric acid concentration, 8ml/gm solid fraction, 90oC and 120minutes. The reducing sugars were fermented using Saccharomyces cerevisiae in anaerobic condition at 30°C, 4.5-5.3 pH and 72hours and the residual solutions were distilled every 150minutes by rotary evaporator. The concentrations of cellulosic ethanol were measured by Alcoholmeter. Moreover, the maximum and minimum cellulosic ethanol concentrations of 80.41% (v/v) with 94% (0.48g/g) and 38.72% (v/v) with 45.26% (0.23g/g) of the theoretical conversion of (0.51g/g) were achieved respectively. Response surface methodology (RSM) using Design expert® 7.0 was used to optimize the total reducing sugar yield. The optimum result was obtained at 5.87% (v/v) acid concentration, solid fraction 9.45ml/gm, 109.87oC and 132.11minutes. The yield of total reducing sugar is 72.28% (w/w) was achieved under these conditions. Keywords: Optimization, Phenol-Sulphuric Acid Method, Wood Sawdust, Saccharomyces cerevisiae, Total Reducing Sugars.