Production of fructosyltransferase in mechanically stirred and air-lift bioreactors

Aureobasidium pullulans cells were cultivated in a 3 dm3 stirred bioreactor to optimize the production of fructosyltransferase (FTase). Batch experiments were focused on the influence of the initial sucrose concentration (150–350 g dm−3), sodium nitrate concentration (10–25 g dm−3), and stirring rate (180–540 min−1) on the process. It was found that the FTase specific activity per cell mass was positively influenced by the conditions that impeded the cell growth such as higher sucrose concentrations or lower oxygen transfer rates. Higher content of inorganic nitrogen substrate slightly increased the overall FTase production. The presence of fructose moiety-containing saccharides in the cultivation medium was observed to be indispensable for FTase production. An addition of a concentrated sucrose solution in the 40th cultivation hour therefore essentially resumed the FTase production. Finally, scale-up experiments were performed in 12 dm3 and 100 dm3 mechanically stirred bioreactors and in 20 dm3 and 60 dm3 air-lift bioreactors.