# Propagation of Inoculum for _Haematococcus pluvialis_
## 3 Results  
This paper presents the system for the propagation of inoculum designed to conduct research and produce microalgae biomass. The system is composed of six 90 dm\({}^{3}\) photobioreactors, which together create an experimentation system with a combined volume of over 0.5 m\({}^{3}\). Initially, the preparation of inoculum on such scale was executed using traditional, commercial solutions used earlier over the course of experiments conducted on a laboratory scale (Figure 3). The propagation of microalgae was conducted using laboratory bottles of 5 dm\({}^{3}\) volume. A magnetic stirrer was used to agitate the contents of the vessels. The vessels were illuminated using typical fluorescent lamps. Carbon dioxide was dosed manually by opening the valve (by hand) and leaving it open for a set period. No measuring sensors were installed in the bottles. This solution had many disadvantages. Bottles were placed on a laboratory countertop to provide laboratory personnel access to all elements of the system. As a result, the entire system took up a large area of the laboratory. The use of mechanical agitation and manual dosing of carbon dioxide was  
Figure 3: Inoculum propagation station designed using typical laboratory equipment. reflected in the low productivity of such cultivations. Additionally, there was an infection problem. The content of the two five-liter bottles was used to inoculate a single photobioreactor of 90 dm\({}^{3}\) volume. Due to the intensification of the experiments, it became necessary to build a prototype of a station for propagating the inoculum intended for six main 90 dm\({}^{3}\) airlift photobioreactors. The photobioreactors were used to conduct experiments using _Haematococcus pluvialis_ microalgae. The experiments lasted for approximately 4 weeks (Figure 4). The system used scaling-up of cultivation by a factor of 10 per step with eight days allocated for each stage [13]. As a result, it was possible to prepare a suitable amount of inoculum to start experiments in all six main photobioreactors (volume of 90 dm\({}^{3}\)) within 24 days. One photobioreactor from the inoculation station was intended to be used to inoculate one 90 dm\({}^{3}\) photobioreactor. Using eight photobioreactors, in the propagation station, in comparison to using six main photobioreactors, allowed for the experiments to proceed smoothly and to gain a safety buffer in case of an accident, e.g., contamination of cultivation, a necessity to repeat the experiments or anomalies in the propagation process. Eight air-lift photobioreactors constituted the primary part of the inoculum propagation station. The weight of one full photobioreactor with top and bottom domes (used for closing the photobioreactor) and the remaining equipment amounted to about 25 kg. The photobioreactors were installed in specially designed storage units fitted with wheels to facilitate the work of laboratory staff operating the station. Each storage unit was big enough for 2 photobioreactors (Figure 5). The control board was in the form of a docking station. Storage units with photobioreactors were rolled next to the control board, where they were attached to the temperature and pH sensor cables, power cable for the LED lighting, and pneumatic cables used for dosing gases. Such a solution allowed saving laboratory space. A top dome was fitted with a connector, which made it easier to use the photobioreactor. The connector was used for filling the photobioreactor. The bottom dome was fitted with a connector that allowed for gas to be introduced. The connector has also allowed pumping inoculum to the inoculated photobioreactor. Control board and storage units with photobioreactors were made based on the modular system of MB aluminum profiles (ITEM, Solingen, Germany). Figure 4: System for preparing inoculum for photobioreactors of 90 dm\({}^{3}\) volume. The limitation of the developed system for propagation of inoculum is the lack of a separate temperature regulation system for each of the eight photobioreactors.