(649b) Effect of Distinctive Detoxification on Inhibitors Removal and Butanol Fermentation of Poplar Prehydrolysates

Authors: 
Zhang, Y., University of Cincinnati
Tu, M., University of Cincinnati
Xia, C., University of Cincinnati
The prehydrolysates from dilute acid biomass pretreatment contains fermentable sugars for biofuels, however, carbonyl degradation compounds present severe toxicity to the fermentation microbes. Furans (furfural and hydroxymethylfurfural), aliphatic acids (acetic acid, formic acid and levulinic acid) and phenolic compounds have been suggested to be the main inhibitors in biomass prehydrolysates. However, the most potent inhibitors have not been identified and the distinctive effect of various detoxification methods on a broad spectrum of inhibitory compounds has been less studied.

Effect of distinctive overliming and activated carbon (AC) detoxification on inhibitors removal and butanol fermentation of the poplar prehydrolysates was investigated. Gas chromatography-mass spectrometry (GC/MS) was used to analyze the degradation compounds, and 46 carbonyl compounds were identified as potential inhibitors including 2,5-furandicarboxyaldehyde and 2,5-hexanedione. It was observed that overliming and AC treatment alone could not make the prehydrolysates fermentable with Clostridium. The sequential overliming and AC resulted in remarkable fermentability and high butanol yield at 0.22 g g–1 sugar. Synergistic effect of overliming and AC detoxification on ABE fermentation was observed. We also examined the compositional changes in the prehydrolysates treated by overliming and AC. Overliming removed 75.6% of furan derivatives and 68.1% of aromatic monomers. In comparison, AC (5.0% w/v) removed 77.9% of furan derivatives and 98.6% of aromatic monomers. In addition, overliming removed much more 2,5-furandicarboxyaldehyde, 5-ethylfuran-2-carbaldehyde and 2,5-hexanedione than AC did. On the contrary, AC could remove considerably more phenolic acids than overliming. Our results showed cinnamic acid, dihydroxybenzoidc acid, coumaric acid, vanillic acid and ferulic acid could be removed by 100%, 100%, 100%, 85.74% and 10%, respectively after AC treatment. While they were reduced only by 74.69%, 13.99%, 1.13%, 32.61% and 60.94%, respectively after overliming. In the sequential detoxification, both dialdehydes/diketones and phenolic acids were extensively removed. This probably was the main reason why the sequential detoxification enabled a remarkable ABE fermentation for the prehydrolysates. Aliphatic acids (formic, acetic and levulinic acids) was not changed in the sequential detoxification.

This study revealed that the distinctive effect of overliming and AC treatment on the prehydrolysates detoxification. Overliming removed more dialdehydes and diketones than AC treatment, while AC removed more phenolic acids than overliming. Sequential overliming and AC treatment were required to make the prehydrolysates fermentable with Clostridium saccharobutylicum. The study also suggested different detoxification method was needed for ABE fermentation of the prehydrolysate as comparing ethanol fermentation.