The effects of the oxygen transfer coefficient and substrate concentration on the xylose fermentation by Debaryomyces hansenii |
| |
Authors: | J Carlos Roseiro M Amália Peito Francisco M Gírio M T Amaral-Collaço |
| |
Institution: | (1) LNETI-Departamento de Tecnologia das Indústrias Alimentares, Unidade de Biotecnologia, R. Vale Formoso, 1, P-1900 Lisboa, Portugal |
| |
Abstract: | Relevant production of xylitol by Debaryomyces hansenii requires semiaerobic conditions since in aerobic conditions the accumulated reduced adenine dinucleotide coenzyme is fully reoxidized leading to the conversion of xylitol into xylulose. For oxygen transfer coefficient values from 0.24 to 1.88 min-1, in shake flasks experiments, biomass formation increased proportionally to the aeration rate as shown in the oxygen transfer coefficient and xylose concentration isoresponse contours. The metabolic products under study, xylitol and ethanol were mainly growth associated. However, for oxygen transfer coefficient above 0.5 min-1 higher initial xylose concentration stimulated the rate of production of xylitol. This fact was less evident for ethanol production. The direct relationship between increased biomass and products formation rate, indicated that the experimental domain in respect to the aeration rate was below the threshold level before the decreasing in metabolic production rates reported in literature for xylose-fermenting yeasts. The fact that ethanol was produced, albeit in low levels, throughout the experimental design indicated that the semiaerobic conditions were always attained. Debaryomyces hansenii showed to be an important xylitol producer exhibiting a xylitol/ethanol ratio above four and a carbon conversion of 54% for xylitol.Abbreviations KLa
oxygen transfer coefficient
- DO(T)
dissolved oxygen (tension)
- OUR
oxygen uptake rate
- NAD(H)
oxidised (reduced) nicotinamide adenine dinucleotide
- NADP(H)
oxidised (reduced) nicotinamide adenine dinucleotide phosphate
- CRC
catabolic reduction charge
- C
oxygen concentration in the culture medium
- C*
oxygen concentration at saturation conditions
- Yi
response from experiment i
-
parameters of the polynomial model
- x
experimental factor level (coded units)
- R2
coefficient of multiple determination
- t
time |
| |
Keywords: | d-Xylose fermentation" target="_blank">d-Xylose fermentation Debaryomyces hansenii Xylose-fermenting yeasts Oxygen transfer coefficient Xylitol Ethanol Doehlert experimental design |
本文献已被 SpringerLink 等数据库收录! |
|