Efficient secretion of (R)-3-hydroxybutyric acid from Halomonas sp. KM-1 cultured with saccharified Japanese cedar under microaerobic conditions

In the presence of d-glucose, consumption of pentoses such as d-xylose is somewhat repressed by most bacteria. However, in Halomonas sp. KM-1, simultaneous utilization of a pure hexose and pentose for growth and PHB production has been observed. Moreover, this strain has been shown to preferentially utilize d-xylose from a mixture of hexose and pentose. In addition, the KM-1 strain produced (R)-3-hydroxybutyric acid ((R)-3-HB) by using saccharified Japanese cedar (Cryptomeria japonica) wood. The concentration of intracellular PHB after aerobic cultivation for 24 h was 8.4 g/L, and after shifting to microaerobic conditions and further cultivation for 18 h, the concentration of (R)-3-HB in the medium reached 8.0 g/L. These results show that the KM-1 strain can efficiently utilize saccharified Japanese cedar and secreted (R)-3-HB under microaerobic conditions.