Acid‐catalyzed steam pretreatment of lodgepole pine and subsequent enzymatic hydrolysis and fermentation to ethanol

Abstract

Utilization of ethanol produced from biomass has the potential to offset the use of gasoline and reduce CO₂ emissions. This could reduce the effects of global warming, one of which is the current outbreak of epidemic proportions of the mountain pine beetle (MPB) in British Columbia (BC), Canada. The result of this is increasing volumes of dead lodgepole pine with increasingly limited commercial uses. Bioconversion of lodgepole pine to ethanol using SO₂‐catalyzed steam explosion was investigated. The optimum pretreatment condition for this feedstock was determined to be 200°C, 5 min, and 4% SO₂ (w/w). Simultaneous saccharification and fermentation (SSF) of this material provided an overall ethanol yield of 77% of the theoretical yield from raw material based on starting glucan, mannan, and galactan, which corresponds to 244 g ethanol/kg raw material within 30 h. Three conditions representing low (L), medium (M), and high (H) severity were also applied to healthy lodgepole pine. Although the M severity conditions of 200°C, 5 min, and 4% SO₂ were sufficiently robust to pretreat healthy wood, the substrate produced from beetle‐killed (BK) wood provided consistently higher ethanol yields after SSF than the other substrates tested. BK lodgepole pine appears to be an excellent candidate for efficient and productive bioconversion to ethanol. Biotechnol. Bioeng. 2007;98: 737–746.