Oxytetracycline production by Streptomyces rimosus: gas and temperature patterns in a solid-state column reactor

During oxytetracycline production by Streptomyces rimosus TM-55 on sweet potato residue in a solid-state column reactor, the moisture content increased by between 2 and 5% (w/w) during incubation, from an initial content of 70 to 73%, and pH initially increased from 6.0 to 7.3, followed by a gradual decrease to 6.2. Appropriate aeration enhanced oxytetracycline production, while mixing only once daily decreased it. The temperatures in the centre and upper layers of each reactor were higher than elsewhere in static non-aerated cultures. The maximum CO2 concentration ranged from 2.9 to 3.2% (v/v) and the minimum O2 concentration was 11.0 to 17.2% (v/v) in static cultures. Under optimal conditions, each gram of dry substrate produced the equivalent potency of 12 mg oxytetracycline.