title: Effects of pH control with phthalate buffers on hot-water extraction of hemicelluloses from spruce wood.
abstract: Ground spruce wood was extracted with water at 170 °C at four different pH levels (3.8, 4.0, 4.2 and 4.4) achieved by using phthalate buffers. Static batch extractions were carried out in an accelerated solvent extractor (ASE-300). The extracted non-cellulosic carbohydrates, predominantly galactoglucomannans (GGMs), were characterised mainly by sugar unit analysis and molar mass determination. Compared to extraction with plain water, extractions with phthalate buffer solutions gave similar yields of non-cellulosic carbohydrates, but gave up to 70% less monosaccharides, and consequently higher molar masses of extracted GGMs. Moreover, at these pH levels, the hydrolysis of acetyl groups were decreased by 40% compared to extraction with plain water, thus maintaining the water solubility of GGMs. It is concluded that hot water extraction of hemicelluloses in high-molar-mass form (average Mw about 10 kDa) from wood in good yields (8% of wood) demands appropriate control of pH, to a level of about 4.
authors.affiliation: Laboratory of Wood and Paper Chemistry, Process Chemistry Centre, Åbo Akademi University, Porthansgatan 3, FI-20500 Turku/Åbo, Finland. tsong@abo.fi
authors.forename: Tao
authors.initials: T
authors.lastname: Song
authors.forename: Andrey
authors.initials: A
authors.lastname: Pranovich
authors.forename: Bjarne
authors.initials: B
authors.lastname: Holmbom
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D001709:Biotechnology / Q000379:methods*; D002021:Buffers; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008031:Lignin / Q000302:isolation & purification; D008351:Mannans / Q000737:chemistry; D008970:Molecular Weight; D009005:Monosaccharides; D010795:Phthalic Acids / Q000737:chemistry*; D028222:Picea / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D011134:Polysaccharides / Q000302:isolation & purification*; D012996:Solutions; D014867:Water / Q000737:chemistry*; D014934:Wood / Q000737:chemistry*
chemical_list: D002021:Buffers; D008351:Mannans; D009005:Monosaccharides; D010795:Phthalic Acids; D010936:Plant Extracts; D011134:Polysaccharides; D012996:Solutions; C443804:galactoglucomannan; D014867:Water; C032279:phthalic acid; C007916:hemicellulose; D008031:Lignin; D019342:Acetic Acid