Biomass pretreatment inherently generates a number of compounds which can inhibit enzymatic and microbial processes required for biofuel production. AFEX has a unique set of decomposition products1, including a number of nitrogen-containing compounds produced through the interaction of ammonia and various cell wall components (e.g., amides). Some decomposition products formed/released from cell walls during AFEX are potentially inhibitory to enzymes/microbes1, while other products can enhance enzymatic hydrolysis and fermentation yields1,2. To determine which compounds are inhibitory or stimulatory to enzymatic hydrolysis and fermentation they must be isolated from AFEX treated biomass and structurally elucidated using suitable analytical techniques. In this study, AFEX treated corn stover decomposition products were extracted using hot water and fractionated based on differences in molecular weight and hydrophobicity. The extract was fractionated via ultracentrifugation, ultrafiltration (3-10 kDa MWC filters), and C18 solid phase extraction. Fractions were collected after each step and used to carry out enzymatic hydrolysis (crude cellulase mixtures) and fermentation (Saccharomyces cerevisiae 424A, LNH-ST) studies. Detailed LC-MS/MS based mass spectrometric analysis was also carried out for some fractions. Our results indicate that there is a complex relationship between the products formed/released from grass cell walls during AFEX pretreatment and their downstream impact on hydrolytic enzymes and ethanologens.
1. Chundawat et al. 2010, Biores Technol 101:8429-8438
2. Lau et al. 2010, Biores Technol 101(20):7849-7855