Effect of stirring speed on the production of phenolic secondary metabolites and growth of Buddleja cordata cells cultured in mechanically agitated bioreactor

Shake-flask in vitro culture of Buddleja cordata cells produces large amounts of biomass and synthetizes verbascoside (VB), linarin and hydroxycinnamic acids, bioactive phenolic secondary metabolites (PSMs). In this work, we determined the effect of stirring speed on the growth of and production of PSMs [total phenolic, phenylethanoid glycoside and flavonoid contents (PeC, PeGC and FC, respectively)] by B. cordata cells cultured in two bioreactors. Two different stirring speeds (120 and 400 rpm) were tested in two stirred-tank bioreactors: a 2 L bioreactor equipped with a ring diffuser (B2RD) and a 3 L bioreactor with a sintered diffuser (B3SD). Growth kinetics of B. cordata cells were measured in the bioreactors and shake-flask systems. The stirring speed and type of bioreactor affected phases, parameters of growth and production of PSMs. The highest production of biomass (13.62 g L⁻¹) and PSMs [PeC of 64.63 mg gallic acid equivalents g⁻¹ (mg GAE g⁻¹); PeGC of 119.24 mg VB equivalents g⁻¹ (mg VBE g⁻¹); and FC of 5.02 mg quercetin equivalents g⁻¹ (mg QE g⁻¹)] occurred in B2RD at 400 rpm. These values were similar to the found in shake-flasks system. This work establishes the basis for bioprocess advances of B. cordata focused on the development of a sustainable strategy for the management of natural resources and as a source of bioactive PSMs on a large scale.