Although Penicillium brevicompactum is a very important industrial strain for mycophenolic acid production, there are no reports on Ca2+/reactive oxygen species (ROS) synergistic regulation and calcium channels, Cch-pb. This study initially intensified the concentration of the intracellular Ca2+ in the high yielding mycophenolic acid producing strain NRRL864 to explore the physiological role of intracellular redox state in metabolic regulation by Penicillium brevicompactum. The addition of Ca2+ in the media caused an increase of intracellular Ca2+, which was accompanied by a strong increase, 1.5 times, in the higher intracellular ROS concentration. In addition, the more intensive ROS sparked the production of an unreported pigment and increase in mycophenolic acid production. Furthermore, the Ca2+ channel, the homologous gene of Cch1, Cch-pb, was investigated to verify the relationship between Ca2+ and the intracellular ROS. The Vitreoscilla hemoglobin was overexpressed, which was bacterial hemoglobin from Vitreoscilla, reducing the intracellular ROS concentration to verify the relationship between the redox state and the yield of mycophenolic acid. The strain pb-VGB expressed the Vitreoscilla hemoglobin exhibited a lower intracellular ROS concentration, 30% lower, and decreased the yield of mycophenolic acid as 10% lower at the same time. Subsequently, with the NRRL864 fermented under 1.7 and 28 mM Ca2+, the [NADH]/[NAD+] ratios were detected and the higher [NADH]/[NAD+] ratios (4 times higher with 28 mM) meant a more robust primary metabolism which provided more precursors to produce the pigment and the mycophenolic acid. Finally, the 10 times higher calcium addition in the media resulted in 25% enhanced mycophenolic acid production to 6.7 g/L and induced pigment synthesis in NRRL864.
Keywords: Penicillium brevicompactum; ROS; VHb; calcium; mycophenolic acid (MPA); pigment.