| Popis: |
The red microalga Porphyridium purpureum (Bory de Saint-Vincent, 1797) Drew et Ross, 1965 is of great interest to researchers as a source of various biologically valuable substances, the amount of which in microalgae cells is determined by the cultivation conditions. The phycobiliproteins content in P. purpureum cells depends directly on the nitrogen concentration in the culture medium and the level of cells illumination. Semi-continuous cultivation makes it easy to maintain these parameters at the specified level. A study of P. purpureum culture growth, accumulation and production of B-phycoerythrin (B-PE) pigment was carried out at low surface illumination, when the rates of pigment photodestruction processes were minimal. P. purpureum was grown by the semi-continuous (quasi-continuous) culture at a specific flow rate of 0.1 and 0.2 day-1 and at average surface illumination of 5 and 25 W/m2. The P. purpureum culture productivity increased by 1.6-1.7 times both with an increase in surface illumination from 5 to 25 W/m2, and with an increase in medium specific flow rate from 0.1 to 0.2 day-1. The maximum productivity values for the experimental conditions (0.21 g · l-1 · day-1) were noted under illumination of 25 W/m2 and 20% medium exchange rate, but they were 1.5-2 times lower than the pre-calculated ones. The content of protein and B-PE in P. purpureum cells decreased both with an increase in surface illumination (by 15-20%) and with an increase in the specific flow rate (1.5 times) for all variants. The change of the protein and B-PE content in P. purpureum culture had also unidirectional character and mainly corresponded to the variation in the P. purpureum culture density. The P. purpureum B-PE productivity increased by 1.5-1.9 times with an increase in surface illumination from 5 to 25 W/m2. The maximum B-PE productivity (13 mg · l-1 · day-1) was recorded for experimental variants with a surface illumination of 25 W/m2 (0.1 and 0.2 day-1). It was shown that an increase in specific illumination of P. purpureum cells from 7 to 26 W/g caused an increase in biomass productivity by 2.6 times, in B-PE productivity - by 1.8 times, and in protein productivity - by 1.7 times. Thus, light was the factor that determined the production characteristics of P. purpureum culture in the experiment, which is confirmed by the obtained experimental data. |
