ORIGINAL RESEARCH PAPER NAD + -dependent xylitol dehydrogenase (xdhA) and L-arabitol-4-dehydrogenase (ladA) deletion mutants of Aspergillus oryzae for improved xylitol production A. Mahmud • K. Hattori • C. Hongwen • N. Kitamoto • T. Suzuki • K. Nakamura • K. Takamizawa Received: 4 December 2012 / Accepted: 8 January 2013 / Published online: 23 February 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract Xylitol dehydrogenase (XDHA) and L-arabitol dehydrogenase (LADA) are two key enzymes in xylan metabolism catalyzing the oxidation of xylitol to D-xylulose and arabitol to L-xylulose, respectively. In Aspergillus oryzae, XDHA and LADA are encoded by xdhA and ladA. We deleted xdhA and ladA and xdhA–ladA to generate mutants with decreased dehydrogenase activities and increased xylitol produc- tion. The mutants were constructed by homologous transformation into A. oryzae P4 (DpyrG) using pyrG as a selectable marker. The xylitol productivity of the mutants was measured using D-xylose as the sole carbohydrate source. xdhA, ladA, and the double- deletion mutant produced, respectively, 12.4 g xylitol/ l with a yield of 0.24 g/g D-xylose, 12.4 g/l with a yield of 0.33 g/g D-xylose, and 8.6 g/l at a yield of 0.26 g/g D-xylose. Keywords Aspergillus oryzae Á Deletion mutant L-Arabitol-4-dehydrogenase Á Xylitol Xylitol dehydrogenase Introduction Xylitol, a five carbon sugar alcohol, is abundantly present in fruits and vegetables. It inhibits the development of dental caries and acute otitis media (Makinen et al. 1995; Uhari et al. 1998) and is an ideal sweetener for diabetic patients because it is metabolized without insulin. Xylitol is commercially produced by chemical hydrogenation of Electronic supplementary material The online version of this article (doi:10.1007/s10529-013-1144-3) contains supplementary material, which is available to authorized users. A. Mahmud Á T. Suzuki (&) The United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan e-mail: suzuki@gifu-u.ac.jp A. Mahmud e-mail: tunisona@yahoo.com K. Hattori Á K. Nakamura Á K. Takamizawa Faculty of Applied Biological Science, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan e-mail: koji_h_polu@yahoo.co.jp K. Nakamura e-mail: knak2007@gifu-u.ac.jp K. Takamizawa e-mail: tak2003@gifu-u.ac.jp C. Hongwen Department of Bioengineering and Biotechnology, Huaqiao University, Xiamen 361021, Fujian, China e-mail: chenhw@hqu.edu.cn N. Kitamoto Food Research Center, Aichi Center for Industry and Science Technology, 2-1-1 Shinpukujicho, Nishi-ku, Nagoya 451-0083, Aichi, Japan e-mail: noriyuki_kitamoto@pref.aichi.lg.jp 123 Biotechnol Lett (2013) 35:769–777 DOI 10.1007/s10529-013-1144-3