초록
<P><B>Abstract</B></P><P>5‐Keto‐<SMALL>D</SMALL>‐fructose is a useful starting material for the synthesis of pyrrolidine iminosugars. It can be prepared by regioselective oxidation of <SMALL>L</SMALL>‐sorbose using pyranose 2‐oxidase (P2Ox) and O<SUB>2</SUB> as a cosubstrate. As the solubility of O<SUB>2</SUB> in aqueous solution is low and the affinity of P2Ox for O<SUB>2</SUB> is poor, we developed a new and efficient process for the production of 5‐keto‐<SMALL>D</SMALL>‐fructose based on engineered P2Ox from <I>Peniophora gigantea</I> and in situ generation of O<SUB>2</SUB> from H<SUB>2</SUB>O<SUB>2</SUB> with catalase. This kind of oxygen supply required efficient mixing of the bioreactor which was achieved by controlled feeding of H<SUB>2</SUB>O<SUB>2</SUB> close to the impeller tip where energy dissipation rate is highest. Thus bubbling, known to affect enzyme stability, was largely avoided, and the process could be run up to 145% oxygen super‐saturation which speeds‐up P2Ox activity. Under these conditions quantitative oxidation of 180 g L<SUP>−1</SUP> <SMALL>L</SMALL>‐sorbose to 5‐keto‐<SMALL>D</SMALL>‐fructose could be achieved within 4 h, resulting in a threefold higher overall productivity of the process compared to a process using gaseous oxygen supply. In addition, in situ generation of O<SUB>2</SUB> from H<SUB>2</SUB>O<SUB>2</SUB> lowered the oxygen demand of the process by a factor of 100 compared to gaseous oxygen supply. Biotechnol. Bioeng. 2012; 109: 2941–2945. © 2012 Wiley Periodicals, Inc.</P>