Simultaneous Saccharification and Fermentation of Pretreated Eucalyptus grandis Under High Solids Loading

2017 ◽  
Vol 13 (3) ◽  
pp. 131-140 ◽  
Author(s):  
Shane McIntosh ◽  
Janice Palmer ◽  
Zhanying Zhang ◽  
William O.S. Doherty ◽  
Syed S. Yazdani ◽  
...  
Keyword(s):  
Simultaneous Saccharification And Fermentation ◽  
Eucalyptus Grandis ◽  
High Solids ◽  
Solids Loading ◽  
High Solids Loading ◽  
Simultaneous Saccharification

scholarly journals Overcoming factors limiting high-solids fermentation of lignocellulosic biomass to ethanol

2017 ◽  
Vol 114 (44) ◽  
pp. 11673-11678 ◽  
Author(s):  
Thanh Yen Nguyen ◽  
Charles M. Cai ◽  
Rajeev Kumar ◽  
Charles E. Wyman
Keyword(s):  
Ethanol Production ◽  
Product Inhibition ◽  
High Solids ◽  
Solids Loading ◽  
High Solids Loading ◽  
Separate Hydrolysis And Fermentation ◽  
Ethanol Yields ◽  
Solid Biomass ◽  
Tolerance To Ethanol ◽  
Simultaneous Saccharification

Simultaneous saccharification and fermentation (SSF) of solid biomass can reduce the complexity and improve the economics of lignocellulosic ethanol production by consolidating process steps and reducing end-product inhibition of enzymes compared with separate hydrolysis and fermentation (SHF). However, a long-standing limitation of SSF has been too low ethanol yields at the high-solids loading of biomass needed during fermentation to realize sufficiently high ethanol titers favorable for more economical ethanol recovery. Here, we illustrate how competing factors that limit ethanol yields during high-solids fermentations are overcome by integrating newly developed cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment with SSF. First, fed-batch glucose fermentations by Saccharomyces cerevisiae D5A revealed that this strain, which has been favored for SSF, can produce ethanol at titers of up to 86 g⋅L−1. Then, optimizing SSF of CELF-pretreated corn stover achieved unprecedented ethanol titers of 79.2, 81.3, and 85.6 g⋅L−1 in batch shake flask, corresponding to ethanol yields of 90.5%, 86.1%, and 80.8% at solids loadings of 20.0 wt %, 21.5 wt %, and 23.0 wt %, respectively. Ethanol yields remained at over 90% despite reducing enzyme loading to only 10 mg protein⋅g glucan−1 [∼6.5 filter paper units (FPU)], revealing that the enduring factors limiting further ethanol production were reduced cell viability and glucose uptake by D5A and not loss of enzyme activity or mixing issues, thereby demonstrating an SSF-based process that was limited by a strain’s metabolic capabilities and tolerance to ethanol.

Sign in / Sign up

Export Citation Format

Share Document