Inhibition effects on fermentation of hardwood extracted hemicelluloses by acetic acid and sodium

• Published in: Bioresource technology Vol. 101; no. 6; pp. 1935 - 1940
• Main Authors: Walton, Sara, Heiningen, Adriaan van, Walsum, Peter van
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2010; [New York, NY]: Elsevier Ltd; Elsevier
• Subjects: Acetic acid; Acetic Acid - chemistry; Acetic acid inhibition; Biological and medical sciences; biomass; Bioreactors; Biotechnology; Biotechnology - methods; Carbohydrates - chemistry; Escherichia coli; Escherichia coli - metabolism; Escherichia coli K011; Ethanol; Ethanol - chemistry; Ethyl alcohol; Evaporation; Fermentation; Fundamental and applied biological sciences. Psychology; Hardwood; Hardwoods; Hemicellulose; Hydrogen-Ion Concentration; Hydrolysis; Inhibitors; kraft pulping; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; Organic Chemicals; Polysaccharides - chemistry; renewable resources; Sodium; Sodium - chemistry; Sodium Acetate; solvents; Time Factors; waste liquors; wood chips; Hemicellulose; Hardwood; Acetic acid inhibition; Fermentation; Escherichia coli K011; Sodium; Escherichia coli; Bacteria; Inhibition; Acetic acid; Enterobacteriaceae
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2009.10.043

Extraction of hemicellulose from hardwood chips prior to pulping is a possible method for producing ethanol and acetic acid in an integrated forest bio-refinery, adding value to wood components normally relegated to boiler fuel. Hemicellulose was extracted from hardwood chips using green liquor, a pulping liquor intermediate consisting of aqueous NaOH, Na 2CO 3, and Na 2S, at 160 °C, held for 110 min in a 20 L rocking digester. The extracted liquor contained 3.7% solids and had a pH of 5.6. The organic content of the extracts was mainly xylo-oligosaccharides and acetic acid. Because it was dilute, the hemicellulose extract was concentrated by evaporation in a thin film evaporator. Concentrates from the evaporator reached levels of up to 10% solids. Inhibitors such as acetic acid and sodium were also concentrated by this method, presenting a challenge for the fermentation organisms. Fermentation experiments were conducted with Escherichia coli K011. The un-concentrated extract supported approximately 70% conversion of the initial sugars in 14 h. An extract evaporated down to 6% solids was also fermentable while a 10% solids extract was not initially fermentable. Strain conditioning was later found to enable fermentation at this level of concentration. Alternative processing schemes or inhibitor removal prior to fermentation are necessary to produce ethanol economically.