Oxygen transfer during citric acid biosynthesis in 7 and 15 000 liters stirred tank reactors
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In laboratory scale, submerged citric acid fermentation enabled to obtain similar to the industrial bioreactor volumetric oxygen transfer rate (kLa) amounted to 240 h-1. Nevertheless, such level of kLa seems not to be necessary for the process. Bioreactors used for the production of citric acid using Aspergillus niger W78B strain, assuring kLa at the 120 h-1 level in a overproduction phase, allowed achieving the oxygen uptake rate by cells in the range 12-15 mmol dm-3 h-1 and a product on substrate yield factor (YP/S) higher then 0.8 g g-1. Thus, the resignation from the widespread in literature strategy of pO2 maximization as an essential prerequisite for high citric acid yield, allowed obtaining the significant 20% improvement in the yield of product formation in the case of molasses media and 7% on synthetic one. Therefore, it can be stated that excessive media aeration during submerged citric acid biosynthesis is not suitable for yield and/or cost of product formation.
Publication order reference
W. Podgorski, Katedra Biotechnologii Zywnosci, Instytut Chemii i Technologii Zywnosci, Akademia Ekonomiczna, ul. Komandorska 118/120, 53-345 Wroclaw, Poland