COSLIF법에 의한 바이오매스의 전처리 특성 및 가수분해 효율 향상에 관한 연구

다국어 초록 (Multilingual Abstract)

Ethanol produced from renewable lignocellulosic biomass, being a 2nd-generation biomass, has a potential to play a leading role in transforming the current fossil-fuel-based economy to a renewable-carbon-based economy. Cellulose-derived ethanol has a strength over the ethanol produced otherwise in that it can be produced from various and abundant raw materials. In particular, cellulose-derived ethanol can reduce more than 85% of the global warming gas emissions from fossil fuel. The lignocellulosic biomass composed of cellulose, hemicellulose and lignin, however, has an important drawback; it is difficult to separate cellulose, which is the source material for the production of bio-ethanol, from hemicellulose and lignin, which act as interfering substances. This has caused high cost of pretreatment for the removal of hemicellulose and lignin and low productivity, leading to low economic feasibility compared to first-generation biomass materials.
In this study, an efficient and economical method for pretreatment of various lignocellulosic biomass materials was evaluatead against a conventional pretreatment method. Waste biomass materials, such as rice straw, corn stalk, reed, and herbal medicine residue, were used as raw material samples. Two pretreatment methods, the dilute acid (DA) method and the cellulose solvent- and organic solvent-based lignocellulose fractionation (COSLIF) method were used to extract cellulose from lignocellulosic biomass and their efficiencies were compared.
The composition analysis of the lignocellulose samples showed that the content of cellulose was in the order of corn stalk (37.5%), rice straw (35.1%), reed (31.0%), and herbal medicine residue (16.4%), that of hemicellulose was in the order of rice straw (25%), corn stalk (22.4%), reed (20.4%), and herbal medicine residue (8.8%), and that of lignin was in the order of herbal medicine residue (39.8%), reed (25%), corn stalk (17.6%), and rice straw (12.0%). The ash content was in the order of reed (18.9%), rice straw (16.1%), herbal medicine residue (6.6%), and corn stalk (5.59%).
When dried samples of rice straw, corn stalk, reed, and herbal medicine residue were hydrolyzed using dilute H2SO4, the cellulose yield obtained was 35.1%, 37.5%, 31.0%, and 16.4%, respectively. On the other hand, when they were hydrolyzed using the COSLIF method, the cellulose yield was 40.5%, 41.8%, 32.1%, 22.6%, respectively. The COSLIF method provided higher cellulose yields than the DA method by 5.4% (rice straw), 4.3% (corn stalk), 1.1% (reed), and 6.2% (herbal medicine residue). The COSLIF method also showed a higher lignin removal efficiency than the DA method. For example, in the case of corn stalk, the lignin removal efficiency of the COSLIF method was 18.4%, whereas that of the DA method was 17.6%. Hemicellulose was also removed more efficiently by the COSLIF method than by the DA method; 23.5% of hemicellulose remained after the COSLIF pretreatment, whereas 22.4% remained after the DA pretreatment. Overall, the COSLIF method showed a better pretreatment performance than the DA method.
During the COSLIF pretreatment, the following conditions must be satisfied: (1) phosphoric acid with a concentration higher than the threshold value (~83%) must play a role as a solvent for cellulose; ​​(2) reaction time must be long enough to dissolve biomass and must not be too long to prevent complete hydrolysis; and (3) reaction temperature must be lower than 60 ℃ to prevent the decomposition of xylose. The optimum reaction conditions for the COSLIF pretreatment of biomass found in this study were phosphoric acid concentration of 84%, reaction temperature of 50℃, and reaction time of 45 min.
The digestion efficiency of glucan of corn stalk pretreated by the COSLIF method with a high enzyme dose was > 90% at 12 h and 94% at 24 h. When the COSLIF pretreatment time was reduced to 20 min, the hydrolysis rate and the digestion efficiency decreased. The hydrolysis rate of DA-pretreated corn stalk was lower than that of COSLIF-pretreated corn stalk and the digestion efficiency of glucan was 82% at 24 h. With a small enzyme dose (5 FPUs per gram of glucan), the final glucan digestion efficiencies of the COSLIF-treated and DA-treated biomass were 92% and 53% at 24 h, respectively. The results of this study indicates that the COSLIF method is a superior pretreatment method than the conventional DA method. Finally, Spirogyra. sp, one of algae from ocean is very enough to make bioethanol by COSLIF-pretreated and even better than that of corn stalk.

목차 (Table of Contents)

• Ⅰ. 서론 1
• 1.1 연구 배경 및 필요성 1
• 1.1.1 연구 배경 1
• 1.1.2 연구의 필요성 5
• 1.2 연구 내용 및 범위 8
• 1.2.1 Lignocellulose계 바이오에탄올의 기술 요소 분석 8
• 1.2.2 Lignocellulose계 biomass 전처리기술 연구 9
• 1.2.3 차세대 바이오매스인 조류의 COSLIF 전저리에 의한 바이오에탄올 생산효율 증대 가능성 검토 11
• Ⅱ. 이론 및 연구동향 12
• 2.1 Lignocellulose계 바이오에탄올의 기술요소 분석 12
• 2.1.1 바이오매스(Biomass) 정의 및 특성 12
• 2.1.2 Lignocellulose계 바이오에탄올 생산 기술 요소 18
• 2.1.3 Lignocellulose 바이오매스 전처리 및 효소 가수분해 공정 기술 32
• 2.2 바이오에탄올의 생산 기술 58
• 2.2.1 바이오에탄올 생산을 있어 당면과제 58
• 2.2.2. 바이오에탄올 생산에 위한 조류의 이용 61
• 2.2.3 바이오에탄올 잠재 원료로서의 조류 64
• 2.3 조류 배양과 수확 74
• 2.4 조류 바이오매스의 바이오에탄올화 방법 82
• 2.4.1 조류 대사 물질에서 에탄올 생산 82
• 2.4.2 혐기성 조건에서 조류에탄올 생산 (Dark fermentation) 87
• 2.4.3 조작된 미세조류에 의한 에탄올의 직접생산 90
• Ⅲ. 실험내용 및 방법 93
• 3.1. COSLIF법에 의한 lignocellulose 바이오매스 전처리법 93
• 3.1.1 실험 대상시료의 준비 및 성분분석 94
• 3.1.2 Lignocellulose 대상 시료의 성분 분석 96
• 3.1.3 Lignocellulose 대상 시료의 COSLIF법에 의한 전처리 102
• 3.1.4 전처리된 시료의 효소 가수분해 108
• 3.2. 에탄올 생산을 위한 조류 바이오매스 전처리법 연구 111
• 3.2.1 Spirogyra .sp(해캄, 녹조류)의 셀룰로오스 성분 분석 111
• 3.2.2 시료 채취 및 전처리 111
• 3.2.3 Spirogyra .sp의 셀룰로오스 성분분석 방법 112
• Ⅳ. 실험 결과 및 고찰 113
• 4.1. COSLIF법에 의한 lignocellulose 바이오매스 전처리 113
• 4.1.1 Lignocellulose 대상 시료의 성분분석 113
• 4.1.2 COSLIF에 의한 바이오매스의 전처리 114
• 4.1.3 DA(Diluted Acid)에 의한 전처리 118
• 4.2. 조류의 바이에탄올 생산 가능성과 COSLIF 전처리 효과 131
• 4.2.1 바이오에탄올 생산을 위한 최적 조류종의 도출 131
• 4.2.2 조류의 바이오에탄올 생산 가능성 검토 135
• 4.2.3 COSLIF법과 DA 법에 의한 Spirogyra .sp의 전처리효율 비교 140
• 4.2.4 COSLIF 및 DA 전처리 Spirogyra.sp의 효소 가수분해 특성 144
• Ⅴ. 결론 146
• Ⅵ. 참고 문헌 151