Co-production of Gluconic Acid and Fructo-oligosaccharides by Aureobasidium pullulans from Sugarcane Molasses: Effect of Oxygen Transfer Rate in Stirred Tank and Airlift Bioreactors

Aureobasidium pullulans NCYC 4012 was used to produce gluconic acid (GA) and fructo-oligosacchar ides (FOS) from sugarcane molasses (ScM). For the first time, three types of bioreactors operating at different conditions of oxygenation-a stirred tank reactor (STR) operating under atmospheric pressure varying stirring rate, a pressurized STR under increased air pressure up to 4 bar of air, and an airlift reactor under atmospheric pressure varying aeration rate-were employed for GA and FOS biosynthesis by A. pullulans. The highest oxygenation conditions favored GA production in the three bioreac-tors, whereas the synthesis of FOS was not favored by high oxygen availability. GA yields close to 1 g.g(-1) (grams of GA produced per grams of glucose consumed) were achieved in bioreactors under atmospheric pressure, and the highest titer of GA of 75 g.L-1 was obtained in the airlift bioreactor. In this last, the highest concentration of total FOS of 65 g.L-1 and yield of FOS of 0.58 g.g(-1) were obtained.