Shear conditions in clavulanic acid production by Streptomyces clavuligerus in stirred tank and airlift bioreactors

Abstract

In biochemical processes involving filamentous microorganisms, the high shear rate may damage suspended cells leading to viability loss and cell disruption. In this work, the influence of the shear conditions in clavulanic acid (CA) production by Streptomyces clavuligerus was evaluated in a 4-dm(3) conventional stirred tank (STB) and in 6-dm(3) concentric-tube airlift (ALB) bioreactors. Batch cultivations were performed in a STB at 600 and 800 rpm and 0.5 vvm (cultivations B1 and B2) and in ALB at 3.0 and 4.1 vvm (cultivations A1 and A2) to define two initial oxygen transfer conditions in both bioreactors. The average shear rate ([Formula: see text]) of the cultivations was estimated using correlations of recent literature based on experimental data of rheological properties of the broth (consistency index, K, and flow index, n) and operating conditions, impeller speed (N) for STB and superficial gas velocity in the riser (UGR) for ALB. In the same oxygen transfer condition, the [Formula: see text] values for ALB were higher than those obtained in STB. The maximum [Formula: see text] presented a strong correlation with a maximum consistency index (K (max)) of the broth. Close values of maximum CA production were obtained in cultivations A1 and A2 (454 and 442 mg L(-1)) with similar maximum [Formula: see text] values of 4,247 and 4,225 s(-1). In cultivations B1 and B2, the maximum CA production of 269 and 402 mg L(-1) were reached with a maximum [Formula: see text] of 904 and 1,786 s(-1). The results show that high values of average shear rate increase the CA production regardless of the oxygen transfer condition and bioreactor model.

Characterization of the Metabolic Response of Streptomyces clavuligerus to Shear Stress in Stirred Tanks and Single-Use 2D Rocking Motion Bioreactors for Clavulanic Acid Production

“…The shear stress values (τ max ) in the STR reactor presented in Table 1 were consistent with results from previous studies on cultivation of filamentous organisms in stirred tank bioreactors [3,31]. Shear stress higher than 6 Pa, as observed in STR reactors, triggers stress responses in sensitive strains like CHO cells.…”

“…CA is produced by the gram-positive filamentous bacterium Streptomyces clavuligerus in submerged cultures under phosphate limitation. Shear conditions in CA production has been previously explored in airlifts [3] and stirred tank reactors [4]; however, the physiological response of S. clavuligerus to shear forces and its relationship with CA secretion is not completely understood. Many efforts have been carried out to increase the yield of CA since not only nutritional, but also environmental and degradation factors compromise the product yield in submerged cultivations of S. clavuligerus [5,6].…”

Effect of aeration and agitation on extractive fermentation of clavulanic acid by using aqueous two‐phase system

“…There seems to be an inverse correlation between CA concentration (Figure C) and residual glycerol concentration (Figure B), which would confirm that product formation is directly associated to substrate consumption. Comparable results were reported for conventional system in stirred tank bioreactor by Cerri and Badino and Viana et al, who obtained around 300 and 490 mg L −1 of CA at 0.5 vvm/600 rpm and 2.0 vvm/800 rpm, respectively. This comparison demonstrates the feasibility of using extractive fermentation to produce/extract CA solely in a single step.…”

Morphogenesis of Streptomyces in Submerged Cultures

“…However, the morphology of Streptomyces fradiae showed an inverse correlation, with low or medium shear stress favoring pelleted growth, while high shear stress caused mycelia of S. fradiae to fragment. Because faster mixing also increases mass transfer, it typically increases growth rate and biomass accumulation (Heydarian et al, 1999) and can therefore also have a major impact on the production of secondary metabolites (Cerri & Badino, 2012;Heydarian et al, 1999;Rosa, Baptista Neto, Hokka, & Badino, 2005). Because faster mixing also increases mass transfer, it typically increases growth rate and biomass accumulation (Heydarian et al, 1999) and can therefore also have a major impact on the production of secondary metabolites (Cerri & Badino, 2012;Heydarian et al, 1999;Rosa, Baptista Neto, Hokka, & Badino, 2005).…”