Aims: Investigation of concerted effects of cations, i.e. Mg 2+ and Mn 2+ , in combination with their anions, i.e. sulphate, chloride and acetate (Ac), on the physiology of Bacillus licheniformis carrying pHV1431::subC to improve the fermentation medium for serine alkaline protease (SAP) production, whereupon, determination of the acid that can be used in pH control.
Methods and Results:The cell concentrations increased with the increase in MnSO 4 and Mn(Ac) 2 concentrations, and the highest values were obtained at C o MnSO 4 ¼ 0AE20 mmol l )1 and C o MnðCH 3 COOÞ 2 ¼ 4AE0 mmol l )1 , as 2AE3 and 2AE2 g l )1 , respectively. However, C o MnCl 2 did not influence biomass concentration. SAP production was inhibited with MnCl 2 after C o MnCl 2 ¼ 0AE60 mmol l )1 , but with MnSO 4 SAP production was inhibited drastically. Whereas, at high concentrations of Mn(Ac) 2 SAP production increased and the highest activity was obtained as A SAP ¼ 1285 U ml )1 at t ¼ 65 h. With the Mg compounds, cell concentrations increased with the increase in the concentrations of MgSO 4 , MgCl 2 and Mg(Ac) 2 ; and the anions did not show any influence on the cell growth. Similar to the results of Mn compounds, the glucose consumption rate increased with the increase in MgSO 4 and MgCl 2 concentrations; contrariwise, decreased with the increase in Mg(Ac) 2 concentrations, due to the use of acetate as the second carbon source.MgCl 2 ¼ 1AE60 mmol l )1 and C o MgðAcÞ 2 ¼ 0AE40 mmol l )1 were the optimum concentrations separately, and the highest SAP activity was obtained with Mg(Ac) 2 as A SAP ¼ 1338 U ml )1 at t ¼ 47 h. Consequently, ion acetate and its acid HAc appear, respectively, as the superior anion for the essential cations and the control agent for pH control in the bioreactor. Finally, optimum initial concentrations and the concerted effects of Mg(Ac) 2 and Mn(Ac) 2 were investigated, and the optimum concentrations were found respectively as 0AE40 and 0AE80 mmol l )1 , while the maximum activity was obtained as A SAP ¼ 1010 U ml )1 at a shortened cultivation time of t ¼ 39 h. Conclusions: Mn(Ac) 2 and Mg(Ac) 2 together enhanced the cell formation and SAP synthesis rates, moreover, SAP synthesis started at an earlier cultivation time. Significance and Impact of the Study: Each inorganic compound with its cation and anion has dual effect on the metabolism. Mg 2+ and Mn 2+ at their specific concentrations influence the regulation of the pathways that might cause better coupling of supply and demand for the amino acids on the basis of the amino acid composition of the enzyme molecule.