Profiles of xylose reductase, xylitol dehydrogenase and xylitol production under different oxygen transfer volumetric coefficient values

Author(s)

Branco, Ricardo F. ^[1] ; dos Santos, Julio C. ^[1] ; Sarrouh, Boutros F. ^[1] ; Rivaldi, Juan D. ^[1] ; Pessoa, Jr., Adalberto ^[1] ; da Silva, Silvio S. ^[1]

Affiliation

^[1] Univ Sao Paulo, Engn Sch Lorena, Dept Biotechnol, BR-12602810 Sao Paulo - Brazil

• Document type: Journal article
• Source: JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY; v. 84, n. 3, p. 326-330, 2009.
• Field of knowledge: Biological Sciences - Microbiology
• Web of Science Citations: 17

Abstract

Xylitol is a sugar alcohol (polyalcohol) with many interesting properties for pharmaceutical and food products. It is currently produced by a chemical process, which has some disadvantages such as high energy requirement. Therefore microbiological production of xylitol has been studied as an alternative, but its viability is dependent on optimisation of the fermentation variables. Among these, aeration is fundamental, because xylitol is produced only under adequate oxygen availability. In most experiments with xylitol-producing yeasts, low oxygen transfer volumetric coefficient (KLa) values are used to maintain microaerobic conditions. However, in the present study the use of relatively high KLa values resulted in high xylitol production. The effect of aeration was also evaluated via the profiles of xylose reductase (XR) and xylitol dehydrogenase (XD) activities during the experiments. The highest XR specific activity (1.45 ± 0.21 U mgprotein-1) was achieved during the experiment with the lowest KLa value (12 h-1), while the highest XD specific activity (0.19 ± 0.03 U mgprotein-1) was observed with a KLa value of 25 h-1. Xylitol production was enhanced when KLa was increased from 12 to 50 h-1, which resulted in the best condition observed, corresponding to a xylitol volumetric productivity of 1.50 ± 0.08 gxylitol L-1 h-1 and an efficiency of 71 ± 6.0%. The results showed that the enzyme activities during xylitol bioproduction depend greatly on the initial KLa value (oxygen availability). This finding supplies important information for further studies in molecular biology and genetic engineering aimed at improving xylitol bioproduction. (AU)

• FAPESP's process: 08/57926-4 - Research and development aiming at the integrated exploitation of sugarcane bagasse for the biotechnological production of lignocellulosic ethanol
• Grantee: Silvio Silvério da Silva
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants