Effect Of Alkali Pretreatment and Enzymatic Saccharification on Bagasse Reducing Sugar For Bioethanol Production

Transcription

1 1). Technical Implementation Unit for Development of Chemical Engineering Processes GunungKidul, Yogyakarta, Indonesia. Effect Of Alkali Pretreatment and Enzymatic Saccharification on Bagasse Reducing Sugar For Bioethanol Production Kismurtono, M 1). and Sutikno 2) 1 Technical Implementation Unit for Development of Chemical Engineering Processes, The Indonesian Institution of Sciences, Indonesia. * Corresponding author: m_kismurtono@yahoo.co.id.

2 INTRODUCTION Agricultural residues and industrial wood wastes are found abundantly in the world These residues are materials that are cheap and are able to be converted to bioethanol as a biofuel Production of bioethanol from plantation materials in the form of lignocellulose which is significantly renewable and has a high economic value and also has a positive impact on the environment Lignocellulosic biomass can be converted to ethanol by microbial fermentation

3 Bagasse

4 Complex plant cell walls

5 Molecular structure of cellulose Cellulose molecule models

6 Molecular constituent of Hemicellulose H C O HO C H CH 2 OH D-glukosa H C O HO C H HO C H CH 2 OH D-manosa H C O HO C H CH 2 OH D-arabinosa H C O HO C H CH 2 OH D-xilosa H C O HO C H COOH Asam D-glukuronat

7 Molecular constituent of Lignin C H 2 O H C H C H C H 2 O H C H C H CH 2 OH CH CH O H H 3 CO OCH 3 O C H 3 OH O H p-kumaril alkohol koniferil alkohol sinapil alkohol

8 Molecular of Lignin Arilgliserol-β-aril eter Dibenzodioksosin Metoksil Hidroksil Fenolik hidroksil

9 Pretreatment

10 Saccharification and Fermentation Cellulose hydrolysis by cellulase enzymes n Endoglucanase Exoglucanase n HO OH β-glucosidase OH

11 Glucose fermentation by Saccharomyces cerevisiae C 6 H 12 O 6 Glukosa Saccharomyces cerevisiae 2CO 2 + 2C 2 H 5 OH Etanol

12 MATERIALS AND METHODS Bagasse was obtained from PT Gunung Madu Plantation, Central Lampung, Lampung, Indonesia. Before use, the bagasse was analyzed to determine its cellulose, hemicellulose, and lignin contents.

13 Chemicals Chemicals and enzymes used for these experiments were purchased from some chemistry stores in Central Lampung, Lampung, Indonesia Microorganisms Cellulase (Cellulast 1.5L) was obtained from Balai Besar Teknologi Pati (BBTP) at Sulusuban, Central Lampung, Lampung, Indonesia.All other reagents were of analytical grade.

14 Pretreatment of Baggase Bagasse was dried up to constant weight and grounded up to 40 meshes. One and half grams of grounded bagasse were put into 100 ml Erlenmeyer flask, added with 30 mlnaoh solution at concentrations of 0, 2.5, 5.0, 7.5, and 1.0 M. After mixing up to homogenize, the solutions were heated using autoclave at 121 o C for 0, 15, 30, 45, and 60 minutes.the solution was filtered with filter paper and washed with 300 ml water. The residues (holocelluloses) were dried at 105 o C for 24 hours. Bagasse delignification was measured to Misson et al method [9].

15 Saccharification using enzyme Saccharification using enzyme was conducted according Samsuriet al [8] with modification. Three gram samples of bagasseholocellulose were poured into a 100 ml Erlenmeyer flask, added with 33,6 ml citrate buffer at a ph of 4,8, added 6,4 ml of enzymes at a concentration of 0, 5, 10, 15, and 20FPU, and then incubated at a temperature of 50 o C in shaker water bath (Polyscience) at a speed of 100 rpm for 0, 6, 12, 18, 24, 30, and 36 hours.

16 After incubation, the filtrate was taken to determine its reduced sugar content. The reduced sugar was analyzed according to Nelson-Somogy method [15].

17 RESULTS AND DISCUSSION The higher NaOH concentration and the higher submersion time resulted in the higher degree of delignification (Fig. 1).Alkali can remove lignin from lignocellulose material [20]. The more concentration of alkali will remove higher lignin from the materials due to intensive reactions. The longer reaction between alkali and lignocellulosic material will also result in the higher lignin removal from the materials. Increasing NaOH concentration significantly improved lignin degradation capacity when temperature and residence time were also increased and combined [22].

18 Saccharification using enzyme After 18 hours of incubation, resulted sugar contents were relatively the same as that after 24, 30, or 36 hours of incubation when the enzyme concentration was 20 FPU (Fig. 2). It is assumed that equilibrium reactions between releasing glucose from cellulose and rejoining glucose into cellulose have occurred. During hydrolysis enzyme bound to substrate to form enzyme-substrate complex which then cleaves to form hydrolysis product such as glucose and enzyme. Glucose at a certain concentration can inhibit hydrolysis reaction; therefore, glucose content is constant although incubation is prolonged. Based on this research (Fig. 2), use of cellulase at a concentration of 20 FPU and an incubation of 18 hours was the best treatment for bagasse hydrolysis

19 CONCLUSIONS The best pretreatment of bagasse was a combination of submersion into 0,1 M NaOH solution at 121 o C for 15 minutes and hydrolysis with 20 FPU cellulase at a temperature of 50 o C, an agitation of 100 rpm, and a period of 18 hours. The pretreatment condition yielded 19,4 g/l reduced sugar.

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