The Impact of Storage Parameters on Downstream Bioprocessing of Biomass

Transcription

1 The Impact of Storage Parameters on Downstream Bioprocessing of Biomass Arun Athmanathan Nathan S. Mosier Laboratory of Renewable Resource Engineering Dept. of Agricultural and Biological Engineering

2 Acknowledgments Project funded by Midwest Center for Bioenergy Grasses Research [USDA-NIFA Award ] Collaborative work alongside Isaac Emery I would like to thank: Dr. Nick Carpita and Dr. Cliff Weil for the sorghum biomass Addison Rempe, Adam Dillard, Barron Hewetson, Shuai Wang and Sarah DeFlora for all their help Linda Liu for her help with the HPLC Everyone at LORRE for their support

3 Biomass Storage: Moisture Storage losses caused by microbial activity, which requires moisture and aeration Transportation cost per ton DM increase with moisture content What impact(s) does dry storage have on bioprocessing of cellulosic biomass?

4 Accessibility and Bioprocessing Cellulase accessibility key to effective bio-based conversion of lignocellulose Key Parameter: Available Pore Surface Area Diameter of fungal cellulase approximately 51Å Grethlein et al (1985): Digestibility α [Pores of 51Å diameter] Lin and Ladisch et al (1985): Pretreatment increases [Pores of diameter 51Å diameter] Jeoh et al (2007): Drying after pretreatment reduces enzyme accessibility of corn stover Grethlein et al. Biotech. & Bioeng. Vol. XXVI Pg (1985) Lin & Ladisch et al. Biotech. & Bioeng. Vol. XXVII Pg (1985) Jeoh et al. Biotech. & Bioeng. Vol. 98 (1) Pg (2007)

5 Accessibility and Bioprocessing Reproduced from Lin and Ladisch et al 1985

6 Accessibility and Bioprocessing Questions: Can drying before the pretreatment step i.e. dry storage affect accessibility of herbaceous biomass to hydrolytic enzymes? Can liquid hot water pretreatment reverse negative impacts brought about by drying?

7 Experimental Design: Feedstock Sweet sorghum bagasse Sorghum grown at Purdue University Farms & harvested Nov Stalks crushed and juice extracted Bagasse shredded using a yard waste chipper Warm water wash to remove soluble sugars Stored frozen at -20 C until use

8 Feedstock Composition analysis Component Percentage (Dry) Mean RD Glucan Xylan Arabinan Acid Insol. Lignin Acid Sol. Lignin

9 (Dry) Feedstock Particle Size Distribution

10 Experimental Design: Hydrolysis 3 drying scenarios (Final MC<10%): Room temperature (Similar to field drying) Oven drying at 45 C Lyophilization at -50 C Cellulase hydrolysis (NREL LAP 009): Triplicate Enzyme loading: 4 FPU + 10 CBU g -1 glucan = 4.10 mg protein g -1 glucan (1.41 mg g -1 dry-biomass) 1% w/w Solids Loading

11 Hydrolysis: Dried Sorghum

12 Hydrolysis: Dried Sorghum High Loading: 40 FPU CBU g -1 glucan 14.1 mg protein g -1 dry biomass

13 Results: Dried Sorghum Hydrolysis Never dried sorghum is most digestible at low enzyme loading Reduction in digestibility at low loading independent of drying means Distinction removed at higher enzyme loadings

14 Hydrolysis: Pretreated Sorghum Liquid hot water pretreatment: 200 C for 10 min Severity factor = 3.94 Solids washed to remove pretreatment-generated inhibitors (Kim, Ximenes et al.) Washed solids hydrolyzed (LAP 009): Enzyme loading: 4.1 mg protein g -1 glucan (1.41 mg g -1 dry biomass) 1% w/w Solids Loading Ximenes, Kim et al. Enzyme & Microb. Tech. Vol. 46 Pg (2010)

15 Hydrolysis: Washed Pretreated Sorghum

16 Hydrolysis: Pretreated Sorghum Hydrolysis repeated at high enzyme loading: 40 FPU CBU g-glucan mg protein g-glucan mg protein dry-g biomass -1

17 Hydrolysis: Pretreated Sorghum (High Loading)

18 Conclusions: Dry bagasse shows marginally lower digestibility at low enzyme loading hydrolysis Method of drying has no effect Effect of drying not observed: At higher enzyme loading After pretreatment

19 Storage Project: Dry Matter Loss Sorghum bagasse baled dry and wet: Indoor storage Exposed to air Sampled for dry matter and composition Result: Initial Moisture Content Dry Matter Loss (%) (Mean ± SD) 8 Weeks 24 Weeks Dry (11% MC) 0.1 ± ± 1.6 Wet (27.3% MC) 23.0 ± ± 2.7

20 Wet Sorghum DM Loss 80% Free sugars loss 55% Xylan loss 17% Glucan loss 10% Lignin loss

21 Conclusions: Drying prior to pretreatment does not have a strong negative effect on digestibility Primary storage loss: Carbohydrates Carbohydrate loss biased toward more easily obtained sugars Free sugars > hemicellulose > cellulose > lignin Future work Effect of carbohydrate loss during storage on digestibility Effect of storage on other biomass (switchgrass)

22 Questions?