Comparisons of high titer ethanol production and lignosulfonate properties by SPORL pretreatment of lodgepole pine at two temperatures

Abstract

Mountain pine beetle killed lodgepole pine wood chips were pretreated by SPORL (Sulfite Pretreatment to Overcome the Recalcitrance of Lignocelluloses) at 180 °C for 25 min and 165 °C for 75 min using the same chemical loadings, which represent the same pretreatment severity. The pretreated whole slurries were used to produce lignosulfonate and ethanol through simultaneous enzymatic saccharification and combined fermentation (SSCombF) up to solid loadings of 18% without detoxification. Low temperature pretreatment reduced furan formation, which facilitated ethanol production as measured by ethanol productivity and sugar consumption. The improved carbohydrate yields at 165 °C also produced high ethanol yields (liter per tonne wood) at all SSCombF solids loadings. An ethanol yield and titer of 306 L per tonne wood, or approximately 72% theoretical, and 47.1 g L⁻¹, respectively, were achieved without detoxification at 165 °C. Lignosulfonates (LS) produced from the two SPORL runs are highly sulfonated but have lower molecular weight than a commercial high purity softwood LS. Both infrared and NMR spectra of LS from SPORL treated wood chips were compared with those of the commercial LS. The LSs from SPORL treated wood chips were found to have better dispersion properties than the commercial LS.