Acetone–Butanol–Ethanol Production from Eastern Canadian Yellow Birch and Screening of Isopropanol–Butanol–Ethanol-Producing Strains

Abstract

Yellow birch barks is one of the abundant species in Quebec with harvest surplus in several regions. Biofuels or biochemicals such as biobutanol can be produced using the surplus feedstock, however challenges such as the cost of pretreatment, production of unwanted by-products in the fermentation process, and the efficient recovery of solvents must be addressed to make it feasible. The objectives of this study are to establish the optimal conditions to produce biobutanol from Eastern Canadian yellow birch; to identify natural/local Clostridium sp. strains that are capable of producing Isopropanol-Butanol-Ethanol (IBE) from synthetic sugar mixtures, as candidates for metabolic engineering and to benchmark solvent producing ability with commercially available strains; and to elucidate the challenges of paradigm shift to IBE production. Alkali pretreatment of the biomass using chemical that are present in the Kraft process were performed, followed by enzymatic hydrolysis to obtain fermentable sugars and subsequent fermentation with Clostridium acetobutylicum DSM 792. The results showed that the produced Acetone-Butanol-Ethanol (ABE) solvent concentration were 6.6-8.2 g/L of acetone; 11.2-13.1 g/L of butanol; and 2.5-2.7 g/L of ethanol. The organic acids concentration was acetic acid, 1.1-1.8 g/L, and butyric acid, 0.1-0.2 g/L. Further fermentation experiments to benchmark IBE were performed using both Clostridium beijerinckii DSM 6423 and wild isolated strains, which revealed the gaps in terms of yields and the need to optimize the fermentation paradigm. Moreover, alternative process sequences for product recovery were identified, and the impact of prior liquid-liquid extraction elucidated.