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Kanna et al. AMB Express 2011, 1:15 http://www.amb-express.com/content/1/1/15

Page 7 of 8

Figure 4 Xylose yields from saccharification of xylooligosaccharides. The enzyme solution was prepared from culture medium with 4% solca flock. Closed symbol; Y-94, Open symbol; YKX1 Standard deviations are calculated from triplicate experiments.

study, cellulase activity increased gradually as the amount of ATP decreased (Fang et al. 2009,). Similarly in YKX1, xylosidase activity was highest at 7 days, which was when ATP concentrations decreased. The behavior of the enzymatic activity was similar to other cellulolytic enzyme in this previous report (Fang et al. 2009) because the promoter used was from cellulolytic enzyme expression. Furthermore, the amount of ATP in YKX1 was higher than that in Y-94 at 3 and 7 days (Figure 2). In contrast, the values of cellulase activity in CF-2612 and C-1 are negatively correlated ATP concen- trations (Fang et al. 2009). However, ATP levels in YKX1 were consistently high than those in Y-94.

shown). Therefore, YKX1 should be useful for enzyme production in practical applications that convert both cellulose and xylan into fementable monosaccharides.

Acknowledgements This work was supported by New Energy and Industrial Technology Development Organization (NEDO) of Japan. We would like to thank to Dr. Min-tian Gao for helpful discussion and Ms. Miyu Sumii and Ms. Reiko Yoshii for technical assistance.

Author details 1Biomass Technology Research Center, National Institute of Advanced Industrial Science and Technology, 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-0046 Japan 2Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan

Furthermore, the activities of other hemicellulolytic enzymes were similar in YKX1 and Y-94 (Table 2), indicating that the transformation was not affected by other hemicellulase. We generated a transformant of A. cellulolyticus that has higher b-xylosidase productivity than the parental strain without affecting cellulase or other hemicellulase productivity. We confirmed xylose yield improved by adding enzyme solution of YKX1, in saccharification experiments using rice straw (data not

Competing interests The authors declare that they have no competing interests.

Received: 9 May 2011 Accepted: 30 June 2011 Published: 30 June 2011

References Bailey MJ, Biely P, Poutanen K (1992) Interlaboratory testing of methods for assay

of xylanase activity. J Biotech 23:257270 Buaban B, Inoue H, Yano S, Tanapongpipat S, Ruanglek V, Champreda V,

Pichyangkura R, Rengpipat S, Eurwilaichitr L (2010) Bioethanol production

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