Ethanol production from eucalyptus wood hemicellulose hydrolysate by Pichia stipitis

Abstract

Ethanol production was evaluated from eucalyptus wood hemicellulose acid hydrolysate using Pichia stipitis NRRL Y-7124. An initial lag phase characterized by flocculation and viability loss of the yeast inoculated was observed. Subsequently, cell regrowth occurred with sequential consumption of sugars and production of ethanol. Polyol formation was detected. Acetic acid present in the hydrolysate was an important inhibitor of the fermentation, reducing the rate and the yield. Its toxic effect was due essentially to its undissociated form. The fermentation was more effective at an oxygen transfer rate between 1.2 and 2.4 mmol/L h and an initial pH of 6.5. The hydrolysate used in the experiences had the following composition (expressed in grams per liter): xylose 30, arabinose 2.8, glucose 1.5, galactose 3.7, mannose 1.0, cellobiose 0.5, acetic acid 10, glucuronic acid 1.5, and galacturonic acid 1.0. The best values obtained were maximum ethanol concentration 12.6 g/L, fermentation time 75 h, fermentable sugar consumption 99% ethanol yield 0.35 g/g sugars consumed, and volumetric ethanol productivity 4 g/L day. (

Obtenção biotecnológica de xilitol a partir de cavacos de eucalipto

“…Segundo Fengel e Wegener, (1989) a xilose pode ser degradada a furfural durante o processo de concentração, fato que, no presente trabalho, não ocorreu, pois foi observado que o aumento da concentração dos açúcares glicose, xilose e arabinose foi diretamente proporcional ao fator de concentração do hidrolisado (3 vezes). O ácido acético, considerado como forte inibidor da fermentação de xilose-xilitol (Ferrari et al, 1992;Felipe et al, 1996) teve sua concentração elevada de forma não proporcional (1,2 vezes) ao fator de concentração do hidrolisado, provavelmente devido à volatilização parcial na etapa de concentração.…”

Ethanol Production Efficiency of an Anaerobic Hemicellulolytic Thermophilic Bacterium, Strain NTOU1, Isolated from a Marine Shallow Hydrothermal Vent in Taiwan

“…The ethanol yield from hemicellulose acid hydrolysate by Pichia stipitis NRRL Y-7124 was 0.41 g g −1 , equivalent to 80.4% theoretical conversion efficiency (10), that by E. coli KO11 was 0.51 g g −1 (2), and that by Pachysolen tannophilus (6), Pichia stipitis NRRL Y-7124 (10), Saccharomyces cerevisiae (30), and Pichia stipitis (1) was less than 0.05 g g −1 (w/w). The maximum ethanol yield (0.509 g g −1 ), equivalent to 98.8% theoretical conversion efficiency, was similar to that of E. coli KO11.…”

“…After celluloses, hemicelluloses are the next most abundant polysaccharides in lignocellulosic biomasses (30). Although considerable research has focused on converting biomass cellulose to ethanol (38,39), less has been done on bioconverting hemicellulose components (6,10).…”

Economics, Environmental Impacts, and Supply Chain Analysis of Cellulosic Biomass for Biofuels in the Southern US: Pine, Eucalyptus, Unmanaged Hardwoods, Forest Residues, Switchgrass, and Sweet Sorghum

“…The rotation length between eucalyptus harvesting can be 3 to 4 years with a MAI of 10 to 18 green tonnes per acre per year (12.3 to 22.4 dry tonne ha -1 year -1 ) (Gonzalez et al 2009(Gonzalez et al , 2011a. In addition to ethanol production, eucalyptus has been investigated for pellet production for bioenergy purposes (Ferrari et al 1992;Gonzalez et al 2011a, b).…”