Comparison of Efficiency and Cost of Methods for Conditioning of Slurries of Steam-Pretreated Softwood

Inhibitors formed during pretreatment impair lignocellulose bioconversion by making enzymatic saccharification and microbial fermentation less efficient, but conditioning of slurries hydrolysates can improve fermentability sometimes also digestibility. Conditioning pretreated softwood using four industrial reducing agents (sodium sulfite, sodium dithionite, borohydride, hydrogen) was compared with standard methods, such as overliming treatment activated charcoal. A dosage approx. 1 mM sulfur oxyanion (sulfite or dithionite) per percent water-insoluble solids (WIS) in the slurry found to result good fermentability. Treatment 10–20% WIS 15 under mild reaction conditions (23°C, pH 5.5) resulted sulfonation solid phase improvements 18–24% for dithionite 13–16% sulfite. Among different methods studied, sulfite superior respect cost-efficient improvement Treatments liquid 58–76% reduction content formaldehyde. The comparison indicates that biomass oxyanions warrants further attention.