Gluconic acid production in packed bed bioreactor

In this study, gluconic acid production with Aspergillus niger was investigated by using molasses and pulp from the by-products formed during sugar production from beet instead of glucose, which is an important cost element as a raw material source in the Raimbault columns. The main purpose of this study is to determine the bioreactor operating conditions in the Raimbault columns and to observe the effects of these variables on gluconic acid production. Column diameter was chosen 3 cm to reduce radial temperature gradients in the Raimbault column and it was designed with a height of 20 cm production. In the study, the effect of operating parameters such as fermentation medium temperature, particle size of pulp, filling amount in column and aeration rate, on gluconic acid production in the Raimbault column bioreactor was examined via Central Composite Design and the results were analyzed statistically. Gluconic acid amounts in samples taken at certain times were determined using high performance liquid chromatography. As result variables, gluconic acid concentration and gluconic acid efficiency were analyzed separately. With the experimental results in which the gluconic acid concentration was selected as the response variable, it was seen that the appropriate mathematical expression that was statistically suggested was a model as quadratic form. The appropriate model proposed for the efficiency result variable, which also has the effect of time as the result variable, was obtained in the form of linear mathematical equations. An increase in gluconic acid production was observed with the increase in the filling amount and the decrease in the particle size. The filling amount in the column content is an important reactor operating parameter. It was observed that gluconic acid concentration and productivity increased linearly with the increase in filling amount. It has been observed that the bath temperature in which the Raimbault column system is kept is an important parameter in gluconic acid production, and the optimum ambient temperature is around the center point (29 ⁰C). The highest gluconic acid concentration (40 g /L) was obtained at the center point of the air feed rate and filling amount (0.5 L / hr, 10 g), lower particle size (0.6 mm) and ambient temperature.