Title Page
Contents
Abstract 14
Chapter 1. Overall Introduction 16
1.1. Biorefinery 16
1.2. Food processing residue 18
1.3. Chemical pretreatment 19
1.4. Bacterial cellulose 22
1.5. Objectives 24
Chapter 2. Improved Bacterial Cellulose Production in the Mutant Strain Gluconacetobacter sp. LYP25 Through UVC-Induced Random Mutagenesis 26
2.1. Introduction 26
2.2. Materials and methods 28
2.2.1. Materials 28
2.2.2. Preculture procedure 28
2.2.3. UVC mutagenesis procedure 29
2.2.4. Analytical methods 33
2.2.5. Characterization of BC 33
2.3. Results and discussion 34
2.3.1. Determination of UVC dose followed by random mutagenesis 34
2.3.2. Screening of G. xylinus mutants based on the BC production 36
2.3.3. Fermentation performance of the selected mutants 39
2.3.4. Characterization of BC synthesized by Gluconacetobacter xylinus ATCC 53524 and Gluconacetobacter sp. LYP25 44
2.4. Conclusions 47
Chapter 3. Process Optimization of Glucose Conversion from Chestnut Shells 48
3.1. Introduction 48
3.2. Optimization of KOH pretreatment to improve the glucose conversion from chestnut shells 51
3.2.1. Materials and methods 51
3.2.2. Results and discussion 56
3.3. Optimization of NaOH pretreatment to improve the glucose conversion from chestnut shells 72
3.3.1. Materials and methods 72
3.3.2. Results and discussion 75
3.4. Process evaluation of glucose conversion from chestnut shells 86
3.5. Conclusions 90
Chapter 4. Production of BC Using Enzymatic Hydrolysates from Chestnut Shells and Its Physicochemical Characterization 91
4.1. Introduction 91
4.2. Materials and methods 93
4.2.1. Materials 93
4.2.2. Preparation of CS hydrolysates 93
4.2.3. Seed culture procedure 94
4.2.4. Main culture procedure for BC production 94
4.2.5. Analytical methods 95
4.3. Results and discussion 96
4.3.1. Identification of fermentation inhibitors in CS hydrolysates 96
4.3.2. BC production using CS hydrolysates 98
4.3.3. Characterization of the BCs 103
4.4. Conclusions 107
Chapter 5. Overall Conclusions 108
References 113
Achievements 124
국문요약 129
Table 2.1. Summary of strain improvement study for Gluconacetobacter xylinus to enhance bacterial cellulose production 43
Table 3.1. Variables and their coded levels for the central composite design of response surface methodology in KOH pretreatment optimization. 52
Table 3.2. Analysis result of the chemical composition of chestnut shells. 57
Table 3.3. Predicted and experimental results of the biomass to glucose conversion (BtGC) of chestnut shell based on the designed KOH pretreatment conditions. 61
Table 3.4. ANOVA results for the quadratic regression model of the biomass to glucose conversion (BtGC) of chestnut shells in KOH pretreatment process. 64
Table 3.5. Predicted and experimental biomass to glucose conversion (BtGC) of chestnut shells under the optimal conditions (for KOH pretreatment) suggested by the BtGC predictive model through numerical optimization. 68
Table 3.6. Variables and their coded levels for the central composite design of response surface methodology in NaOH pretreatment optimization. 73
Table 3.7. Predicted and experimental results of the biomass to glucose conversion (BtGC) of chestnut shell based on the designed NaOH pretreatment conditions. 79
Table 3.8. ANOVA results for the quadratic regression model of the biomass to glucose conversion of chestnut shells in NaOH pretreatment process. 81
Table 3.9. Predicted and experimental biomass to glucose conversion (BtGC) of chestnut shells under the optimal conditions (for NaOH pretreatment) suggested by the BtGC predictive model through numerical optimization. 85
Table 3.10. Summary of alkali pretreatment studies for efficient glucose recovery from food processing residues. 89
Table 4.1. The composition of fermentation inhibitors in chestnut shell hydrolysates. 97
Figure 1.1. Global bioproducts market. 17
Figure 1.2. Effect of alkali pretreatment on biomass. 21
Figure 1.3. A simplified biosynthesis pathway for BC production in Gluconacetobacter xylinus. Glucose-6-P, glucose-6-phosphate; glucose-1-P,... 23
Figure 1.4. Schematic diagram of the overall process. 25
Figure 2.1. UVC mutagenesis procedure for Gluconacetobacter xylinus ATCC 53524 designed in this study. 30
Figure 2.2. The correlation between UVC fluence and viable cells of Gluconacetobacter xylinus ATCC 53524. 35
Figure 2.3. Relative changes in BC production in 60 UVC-induced mutants of Gluconacetobacter xylinus ATCC 53524 (control). Data are expressed as... 38
Figure 2.4. Profiles of glucose concentration (filled symbols) and bacterial cellulose production (hollow symbols) for 10 days fermentation by... 41
Figure 2.5. SEM images of bacterial cellulose synthesized by Gluconacetobacter xylinus ATCC 53524 (a) and Gluconacetobacter sp. LYP25 (b). 45
Figure 2.6. FTIR spectra of bacterial cellulose synthesized by Gluconacetobacter xylinus ATCC 53524 (black straight line),... 46
Figure 3.1. Effect of KOH concentration on biomass-to-glucose conversion of chestnut shells in the pretreatment process. 59
Figure 3.2. 3D plots showing correlations between variables with respect to the biomass to glucose conversion of chestnut shells (KOH pretreatment): (a) effects of temperature and time at a fixed biomass loading of 100 g/L; (b) effects of... 66
Figure 3.3. Profiles of enzymatic digestibility of pretreated chestnut shells (ptCSs) in enzymatic saccharification reactions using various enzyme cocktails. 71
Figure 3.4. Effect of NaOH concentration on biomass-to-glucose conversion of chestnut shells in the pretreatment process. 77
Figure 3.5. 3D plots showing correlations between variables with respect to the biomass to glucose conversion of chestnut shells (NaOH pretreatment): (a) effects of temperature and reaction time at a fixed NaOH concentration of 1.0%; (b)... 83
Figure 3.6. Mass balance according to scenarios for glucose conversion from chestnut shell. 87
Figure 4.1. Profiles of BC production during fermentation by Gluconacetobacter sp. LYP25. 100
Figure 4.2. Mass balance for BC production from 1000 g chestnut shells. 102
Figure 4.3. Scanning electron microscopy (SEM) images of bacterial cellulose synthesized from commercial glucose (a) and chestnut shell hydrolysates (b). 105
Figure 4.4. Fourier transform infrared (FTIR) spectra of BC synthesized from commercial glucose (black straight line) and chestnut shell hydrolysates (red... 106
Figure 5.1. Graphical summary on the development of an upstream process for improving bacterial cellulose production by Gluconacetobacter xylinus ATCC 53524. 110
Figure 5.2. Graphical summary on the development of alkali pretreatment processes for improving glucose conversion from chestnut shells. 111
Figure 5.3. Graphical summary on the microbial production of bacterial cellulose using chestnut shell hydrolysates by Gluconacetobacter sp. LYP25. 112