Effect of aeration on organic acid production by Propionibacterium shermanii

Abstract

Propionibacteria have been reported as being oxygen sensitive bacteria. Nevertheless, in this work, we intend to show that Propionibacterium shermanii CDB 10014 is able to grow even at high volumetric oxygen transfer coefficients (K(L)a). Similar final cell concentrations were achieved in experiments at different K(L)a values, with increasing cell yield from 0.08 g/g cells in anaerobic conditions to 0.22 g/g at K(L)a 61 h-1. The organic acid production pattern changes depending on the K(L)a. At K(L)a higher than 36 h-1, propionic acid was not produced and acetic acid was the main product. At K(L)a higher than 20 h-1, lactic acid began to be produced. In further studies, no important differences in the growth yield were observed in the pH range 5.5-7.0, while the cell production was enhanced by temperatures in the range 30-35 °C.