Comparison of two posthydrolysis processes of Brewery's spent grain autohydrolysis liquor to produce a pentose-containing culture medium.
A readily fermentable pentose-containing hydrolysate was obtained from Brewery's spent grain by a two-step process consisting of an auto-hydrolysis (converting the hemicelluloses into oligosaccharides) followed by an enzymatic or sulfuric acid-catalyzed posthydrolysis (converting the oligosaccharides into monosaccharides). Enzymatic hydrolyses were performed with several commercial enzymes with xylanolytic and cellulolytic activities. Acid-catalyzed hydrolyses were carried out at 121 degrees C under various sulfuric acid concentrations and reaction times, and the effects of treatments were interpreted by means of a corrected combined severity factor (CS*), which varied in the range of 0.80-2.01. Under the tested conditions, chemical hydrolysis allowed higher pentose yields than enzymatic hydrolysis. Optimized conditions (defined by CS* = 1.10) allowed both complete monosaccharide recovery and low content of inhibitors. Liquors subjected to posthydrolysis under optimal conditions were easily fermented by Debaryomyces hansenii CCMI 941 in semiaerobic shake-flask experiments, leading to xylitol and arabitol as major fermentation products. The bioconversion process was improved by hydrolysate concentration and supplementation of fermentation media with casamino acids.
Duarte
Luís C
LC
INETI, Departamento de Biotecnologia, Estrada do Paço do Lumiar 22, 1649-038 Lisboa, Portugal.
Carvalheiro
Florbela
F
Lopes
Sónia
S
Marques
Susana
S
Parajó
Juan Carlos
JC
Gírio
Francisco M
FM
D000434:Alcoholic Beverages; D000596:Amino Acids / Q000737:chemistry; D001709:Biotechnology / Q000379:methods*; D003470:Culture Media / Q000737:chemistry*; D002523:Edible Grain / Q000737:chemistry*; D005285:Fermentation; D006868:Hydrolysis; D007220:Industrial Waste; D007700:Kinetics; D010429:Pentoses / Q000737:chemistry*; D019800:Phenol / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014993:Xylitol / Q000737:chemistry
D000596:Amino Acids; D003470:Culture Media; D007220:Industrial Waste; D010429:Pentoses; C017721:casamino acids; D019800:Phenol; D014993:Xylitol