Effect of irradiation intensity on cell growth and kalata B1 accumulation in Oldenlandia affinis cultures

Abstract

Light irradiation had remarkable effects on callus growth of Oldenlandia affinis with an optimum intensity of 35 μmol m⁻² s⁻¹. Biosynthesis of kalata B1, the main cyclic peptide in O. affinis, was induced and triggered with rising irradiation intensities. The highest concentration of kalata B1, 0.49 mg g⁻¹ DW characterised by the maximum productivity of 3.88 μg per litre and day was analysed at 120 μmol m⁻² s⁻¹, although callus growth was repressed. The light saturation point was established to be 35 μmol m⁻² s⁻¹, where kalata B1 productivity was in a similar order (3.41 μg per day) due to the higher growth index. O. affinis suspension cultures were shown to accumulate comparable specific kalata B1 concentrations in a delayed growth associated production pattern. These were dependent on irradiation intensity (0.16 mg g⁻¹ at 2 μmol m⁻² s⁻¹; 0.28 mg g⁻¹ at 35 μmol m⁻² s⁻¹). The batch cultivation process resulted in a maximum productivity of 27.30 μg per litre and day with culture doubling times of 1.16 d⁻¹. Submers operation represented a 8-fold product enhancement compared to callus cultivation.