title: Fermentation of lignocellulosic sugars to acetic acid by Moorella thermoacetica.
abstract: A systematic study of bioconversion of lignocellulosic sugars to acetic acid by Moorella thermoacetica (strain ATCC 39073) was conducted. Four different water-soluble fractions (hydrolysates) obtained after steam pretreatment of lignocellulosic biomass were selected and fermented to acetic acid in batch fermentations. M. thermoacetica can effectively ferment xylose and glucose in hydrolysates from wheat straw, forest residues, switchgrass, and sugarcane straw to acetic acid. Xylose and glucose were completely utilized, with xylose being consumed first. M. thermoacetica consumed up to 62 % of arabinose, 49 % galactose and 66 % of mannose within 72 h of fermentation in the mixture of lignocellulosic sugars. The highest acetic acid yield was obtained from sugarcane straw hydrolysate, with 71 % of theoretical yield based on total sugars (17 g/L acetic acid from 24 g/L total sugars). The lowest acetic acid yield was observed in forest residues hydrolysate, with 39 % of theoretical yield based on total sugars (18 g/L acetic acid from 49 g/L total sugars). Process derived compounds from steam explosion pretreatment, including 5-hydroxymethylfurfural (0.4 g/L), furfural (0.1 g/L) and total phenolics (3 g/L), did not inhibit microbial growth and acetic acid production yield. This research identified two major factors that adversely affected acetic acid yield in all hydrolysates, especially in forest residues: (i) glucose to xylose ratio and (ii) incomplete consumption of arabinose, galactose and mannose. For efficient bioconversion of lignocellulosic sugars to acetic acid, it is imperative to have an appropriate balance of sugars in a hydrolysate. Hence, the choice of lignocellulosic biomass and steam pretreatment design are fundamental steps for the industrial application of this process.
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Box 352100, Seattle, WA, 98195-2100, USA.
authors.forename: Mandana
authors.initials: M
authors.lastname: Ehsanipour
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Box 352100, Seattle, WA, 98195-2100, USA.
authors.forename: Azra Vajzovic
authors.initials: AV
authors.lastname: Suko
authors.affiliation: School of Environmental and Forest Sciences, University of Washington, Box 352100, Seattle, WA, 98195-2100, USA. renatab@u.washington.edu.
authors.forename: Renata
authors.initials: R
authors.lastname: Bura
mesh_terms: D019342:Acetic Acid / Q000737:chemistry*; D001089:Arabinose / Q000737:chemistry; D018533:Biomass; D003470:Culture Media / Q000737:chemistry; D005285:Fermentation; D005662:Furaldehyde / Q000031:analogs & derivatives / Q000737:chemistry; D005690:Galactose / Q000737:chemistry; D005947:Glucose / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007218:Industrial Microbiology; D008031:Lignin / Q000737:chemistry*; D008358:Mannose / Q000737:chemistry; D058845:Moorella / Q000378:metabolism*; D000073893:Sugars / Q000737:chemistry*; D014994:Xylose / Q000737:chemistry
chemical_list: D003470:Culture Media; D000073893:Sugars; C036909:lignocellulose; C008046:5-hydroxymethylfurfural; D008031:Lignin; D014994:Xylose; D001089:Arabinose; D005662:Furaldehyde; D005947:Glucose; D008358:Mannose; D019342:Acetic Acid; D005690:Galactose
keywords: Acetic acid; Lignocellulosic sugars; Moorella thermoacetica; Steam explosion