Conversion of Fruit wastes and Agricultural Residues into Value-Added Products for Circular Bio Economy = 통합 과일 폐기물과 농업 부산물의 고도화 기술 개발

다국어 초록 (Multilingual Abstract)

To replace non-renewable resources such as fossil fuels, the demand for sustainable and renewable alternative resources has increased recently. Fruit wastes and agricultural residues produced as a result of agricultural activities can be fermented to obtain biofuels or biochemicals. However, the high cost of feedstock and catalytic process for biofuel production hinders the practical use of biofuels. This study aimed to establish an efficient and direct enzymatic saccharification process that omits pretreatment to produce high-value bioproducts from fruit wastes and agricultural residues. Herein, we developed a novel approach for the bioconversion of fruit wastes and agricultural residues to biofuel and biochemicals. In our study, the conversion rate of mixed agricultural wastes to produce fermentable sugars following enzymatic hydrolysis was approximately 91% after 24 h. After successfully removing D-limonene using the D-limonene removal column, the yield of ethanol from the mixed agricultural waste increased by 4.5%. D-Allulose yield from mixed hydrolysates was 4.6 mg/mL at 4 °C. Lactic acid and succinic acid were produced from agricultural hydrolysate at a conversion rate of approximately 67.4% and 37.1% using Actinobacillus succinogenes and Corynebacterium glutamicum Δldh, respectively, under facultative anaerobic condition. Altogether, we describe a strategy for the biosynthesis of high-value functional sugars and value-added chemicals from low-cost waste biomass.

국문 초록 (Abstract)

현재 전 세계적으로 화석연료를 대신할 지속가능한 재생에너지의 개발 및 보급의 필요성이 강조되고 있으며 바이오연료는 그 대체제로 주목받고 있다. 바이오 연료는 생산 공정 중 공급원료, 전처리 및 효소당화 공정에 들어가는 고비용으로 인해 실용성과 경제성을 향상시킬 필요가 있다. 본 연구에서는 농업 부산물로 매년 발생하는 과일 폐기물 및 농업잔류물을 바이오매스 원료 물질로 선택하여 고부가가치 바이오 케미컬을 생산하기 위해 전처리 공정을 생략한 직접적인 효소 당화 공정만으로 비용 효율적이고 효과적인 바이오공정 시스템을 개발하였다.
혼합 농업 폐기물은 효소적 가수분해만을 통해 91%가 발효 가능한 당으로 전환되었다. 또한 LRC 칼럼을 사용하여 과일 폐기물에 존재하는 발효 억제제, ​​리모넨도 성공적으로 제거하였다. 리모넨의 제거는 혼합농업폐기물에서 에탄올 발효 수율은 4.5% 증가시켰다. 바이오 공정의 고도화를 위하여 D-알룰로스는 혼합된 가수분해물로부터 저온인 4°C에서 52.2%로 효율적으로 전환되었다. 가수분해물에서 생산된 젖산과 숙신산은 통성혐기성 조건에서 Actinobacillus succinogenes와 Corynebacterium glutamicum Δldh를 통해 각각 약 67.4%와 37.1%로 각각 생산되었다.

목차 (Table of Contents)

• 1. Introduction 4
• 2. Material and methods 7
• A. Preparation of raw materials 7
• B. Chemical composition analysis of different agricultural waste materials 8
• C. Enzymatic hydrolysis and optimization of enzyme loading 9
• D. D-Limonene removal 10
• 1) D-Psicose 3-epimerase gene cloning, enzyme expression, and enzyme purification 10
• E. Bioethanol production by yeast fermentation (from hydrolysate of multiple agricultural waste) 12
• F. D-Allulose production 13
• G. Microbial metabolic engineering for platform chemical production 14
• 1) Strain and seed culture 14
• 2) Production of lactic acid and succinic acid from hydrolylsate 14
• 3. Results and discussion 16
• A. Monosaccharide composition of multiple agricultural wastes 16
• B. Optimization of cellulase and pectinase treatment of multiple agricultural waste 18
• C. D-Limonene recovery and ethanol production 21
• D. D-Allulose production 24
• E. Production of lactic acid and succinic acid from multiple agricultural waste hydrolysate 29
• 1) Lactic acid production 29
• 2) Succinic acid production with Δldh1 mutant in 5% agricultural waste hydrolysate 32
• F. Overall mass balance 36
• 4. Conclusion 38