title: Optimization of Brewery's spent grain dilute-acid hydrolysis for the production of pentose-rich culture media.
abstract: Dilute-acid hydrolysis of brewery's spent grain to obtain a pentose-rich fermentable hydrolysate was investigated. The influence of operational conditions on polysaccharide hydrolysis was assessed by the combined severity parameter (CS) in the range of 1.39-3.06. When the CS increased, the pentose sugars concentration increased to a maximum at a CS of 1.94, whereas the maximum glucose concentration was obtained for a CS of 2.65. The concentrations of furfural, hydroxymethylfurfural (HMF), as well as formic and levulinic acids and total phenolic compounds increased with severity. Optimum hydrolysis conditions were found at a CS of 1.94 with >95% of feedstock pentose sugars recovered in the monomeric form, together with a low content of furfural, HMF, acetic and formic acids, and total phenolic compounds. This hydrolysate containing glucose, xylose, and arabinose (ratio 10:67:32) was further supplemented with inorganic salts and vitamins and readily fermented by the yeast Debaryomyces hansenii CCMI 941 without any previous detoxification stage. The yeast was able to consume all sugars, furfural, HMF, and acetic acid with high biomass yield, 0.68 C-mol/C-mol, and productivity, 0.92 g/(L.h). Detoxification with activated charcoal resulted in a similar biomass yield and a slight increase in the volumetric productivity (11%).
authors.affiliation: INETI, Departamento de Biotecnologia, Estrada do Paço do Lumiar 22, 1649-038 Lisboa, Portugal.
authors.forename: Florbela
authors.initials: F
authors.lastname: Carvalheiro
authors.forename: Luís C
authors.initials: LC
authors.lastname: Duarte
authors.forename: Raquel
authors.initials: R
authors.lastname: Medeiros
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Gírio
mesh_terms: D000434:Alcoholic Beverages; D000596:Amino Acids / Q000737:chemistry; D001203:Ascomycota / Q000378:metabolism; D001709:Biotechnology / Q000379:methods*; D002241:Carbohydrates; D002455:Cell Division; D002852:Chromatography, Ion Exchange; D003470:Culture Media / Q000737:chemistry*; D002523:Edible Grain / Q000737:chemistry*; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007220:Industrial Waste; D007475:Ion Exchange Resins; D007700:Kinetics; D015233:Models, Statistical; D010429:Pentoses / Q000737:chemistry*; D019800:Phenol / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014993:Xylitol / Q000737:chemistry
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D003470:Culture Media; D007220:Industrial Waste; D007475:Ion Exchange Resins; D010429:Pentoses; D011134:Polysaccharides; C017721:casamino acids; D019800:Phenol; C007916:hemicellulose; D014993:Xylitol