Enzymatic Hydrolysis of Liquid Hot Water Pre-treated Macro-alga (Ulva lactuca) for Fermentable Sugar Production

Tri Poespowati,Ardy Riyanto,Ali Mahmudi,Hazlan Hazlan,Rini Kartika-Dewi,A.C Kumoro,Hadiyanto Hadiyanto,M.A Hussain,X Rong,S.A Roces,P.T.S Nam,M.T Phong,A.W Lothongkum,W.R.W Daud,L Yung

doi:10.1051/matecconf/201815601015

Abstract

Ulva lactucais one of green macro-algae that has a significant cellulose content. This study aims to determine the effect of variations in substrate-enzyme ratio and hydrolysis time on the enzymatic hydrolysis process of cellulose extracted fromUlva lactucato produce fermentable sugar or reducing sugar as a raw material for making bioethanol. Firstly, Liquid Hot Water (LHW) pre-treatment process was performed at the temperature of 135°C for 20 minutes; the purpose of this pre-treatment was to reduce the content of hemicellulose and to increase the cellulose content. Secondly, enzymatic hydrolysis process using cellulase enzyme was carried out, in this process citrate buffer was needed in order to stabilize the pH level during hydrolysis process. The process variables were ratio of substrate-enzyme (1:0.05; 1:0.1; 1:1.5; 1:2 and 1:2.5 w/w) and hydrolysis time (24, 48 and 72 hours) under temperature of 45°C and pH level of 5.5. The results shows that the highest reducing sugar yield is 79.7% obtained at a ratio of substrate-enzyme of 1:2.5 (w/w) for 48 hours of hydrolysis time, with the result of reducing sugar concentration is 16.2043 mg/mL.

Highlights

The world energy demand continues to increase
To replace a part of gasoline comes from fossil sources; ethanol fuel has already applied in the US as gasoline fuel additive [2]
The purpose of this research is to investigate the effect of substrate-enzyme ratio and hydrolysis time to enzymatic hydrolysis process of Liquid Hot Water (LHW) pre-treated green macro-alga (Ulva lactuca) to produce high reducing sugar content as a raw material of bioethanol alternative fuel

Summary

Introduction

The world energy demand continues to increase. This increase occurred from the requirement of 90 million barrels per day in 2012 to 100 million barrels in 2020, and raise in volume of 121 million barrels in 2014 [1]. To replace a part of gasoline comes from fossil sources; ethanol fuel has already applied in the US as gasoline fuel additive [2]. This can help to reduce the problem in the decline of fossil fuel reserves and its use as a fuel and chemical raw materials [3]. There are 3 generation types of bioethanol: first generation bioethanol produced from molasses or by-product of refining sugarcane, second generation bioethanol made from lignocellulosic agricultural waste and third generation bioethanol obtained from cellulosic biomass such as algae

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Results