Comparison of two posthydrolysis processes of brewery's spent grain autohydrolysis liquor to produce a pentose-containing culture medium

• Published in: Applied biochemistry and biotechnology 2004, Vol.113 (1-3), p.1041-1058
• Main Authors: Duate, L.C, Carvalheiro, F, Lopes, S, Marques, S, Parajo, J.C, Girio, F.M
• Format: Article
• Language: English
• Subjects: Alcoholic Beverages; Amino Acids - chemistry; arabinitol; Biochemistry; Bioconversion; Biotechnology - methods; Breweries; Cell culture; Culture Media - chemistry; Debaryomyces hansenii; Edible Grain - chemistry; enzymatic hydrolysis; Enzymes; Fermentation; Grain; Hemicellulose; Hydrolysates; Hydrolysis; Industrial Waste; Kinetics; Liquor; Monosaccharides; Oligosaccharides; Pentose; Pentoses - chemistry; Phenol - chemistry; spent grains; Studies; Sulfuric acid; Temperature; Time Factors; Xylitol; Xylitol - chemistry; Yeast
• ISSN: 0273-2289; 1559-0291; 0273-2289
• DOI: 10.1385/ABAB:115:1-3:1041

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.