title: Oxygen uptake rate in production of xylitol by Candida guilliermondii with different aeration rates and initial xylose concentrations.
abstract: The global oxygen uptake rate (OUR) and specific oxygen uptake rates (SOUR) were determined for different values of the volumetric oxygen mass transfer coefficient (15, 43, and 108 h(-1)), and for varying initial xylose concentrations (50, 100, 150, and 200 g/L) in shaking flasks. The initial cell concentration was 4.0 g/L, and there was only significant growth in the fermentation with the highest oxygen availability. In this condition, OUR increased proportionally to cell growth, reaching maximum values from 2.1 to 2.5 g of O2/(L x h) in the stationary phase when the initial substrate concentration was raised from 50 to 200 g/L, respectively. SOUR showed different behavior, growing to a maximum value coinciding with the beginning of the exponential growth phase, after which point it decreased. The maximum SOUR values varied from 265 to 370 mg of O2/(g of cell x h), indicating the interdependence of this parameter and the substrate concentration. Although the volumetric productivity dropped slightly from 1.55 to 1.18 g of xylitol/(L x h), the strain producing capacity (Y(P/X)) rose from 9 to 20.6 g/g when the initial substrate concentration was increased from 50 to 200 g/L. As for the xylitol yield over xylose consumed (Y(P/S)), there was no significant variation, resulting in a mean value of 0.76 g/g. The results are of interest in establishing a strategy for controlling the dynamic oxygen supply to maximize volumetric productivity.
authors.affiliation: Departamento de Engenharia Bioquímica, Escola de Química/CT, Universidade Federal do Rio de Janeiro, Ilha do Fundão, RJ, Brazil.
authors.forename: Maria Antonieta P
authors.initials: MA
authors.lastname: Gimenes
authors.forename: Luiz Cláudio S
authors.initials: LC
authors.lastname: Carlos
authors.forename: Luís F F
authors.initials: LF
authors.lastname: Faria
authors.forename: Nei
authors.initials: N
authors.lastname: Pereira
mesh_terms: D000332:Aerobiosis; D002175:Candida / Q000254:growth & development / Q000378:metabolism*; D005285:Fermentation; D007700:Kinetics; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D013997:Time Factors; D014993:Xylitol / Q000096:biosynthesis*; D014994:Xylose / Q000378:metabolism*
chemical_list: D014994:Xylose; D010100:Oxygen; D014993:Xylitol