The firmware number can be found in the main menu of the control panel that is placed on the front side of the Multi-Cultivator. Go to: Settings >> Device Info >> FW Version (for example: 1.0.3.9)

The software version including the active license type is stated in Service Information context menu in the main node of the Control Software Client (for example: License type: ADVANCED; Version: 0.7.14-1524)

Please, check that all cultivation vessels, silicone plugs and aeration glass tubing are at the same position. All aeration glass tubing should be in the same distance from the bottom of the cultivation vessel because the position of the aeration tubing end affects the size of the bubbles. Optimal position of the end is about 0.5 mm from the bottom of the vessel. Ensure that the end of the glass straw is sufficiently away from the bottom of the vessel not to hinder the bubbles coming out of the straw. Ensure that there are no kinks in the silicon tubing that may impede the flow of gas.

Based on our testing, the algae growth dynamics, growth rates and final optical density are comparable regardless if glass or stainless steel aeration straws are used. Also the CO₂ saturation time was similar irrespective of glass or stainless steel straws use. The tests were performed under standard cultivation conditions.

Moreover, a mass-flow meter or even set of mini flowmeters installed on the tubing between the manual taps and aeration glass straws could help to improve the control of the flow rates a little bit.

Please notice, the aeration system of the individual testing vessels is interconnected. That’s why the conditions that influence a pressure and flow rate into one testing vessel will simultaneously influence also other testing vessels. In general, the Multi-Cultivator is a low-cost device and therefore it doesn't include precise control of the gas flow rate into each tube.

Please, note that the backpressure valve is neither autoclavable nor sterilizable by ethanol.

In general, the OD 680 is linked to the chlorophyll absorption and can be used for an estimation of chlorophyll concentration whereas OD 720 determines light scattering on particles and can serve as a proxy for biomass growth.

The OD is defined as Log (Io/I) where Io is the irradiance that is transmitted through the cuvette filled with medium without algae or other organisms. This quantity must be measured as the reference and therefore the calibration with test tubes filled with distilled water or medium without algae must be done prior the experiment. I is the irradiance transmitted through the cuvette with algal or cyanobacterial suspension in which OD is measured. Log is the decadic logarithm of the Io/I ratio. Thus, optical density OD = 1 means that light at the respective wavelength is attenuated by algae or cyanobacteria 10 times relative to the reference. With OD = 2, the attenuation relative to the reference is 100 times.

In the Multi-Cultivator, there is a dual-chip LED 680/720 inbuild in the light panel and a light detector right opposite to the LED. The OD LED signal has to pass through several interfaces (water bath, test vessels, etc.) to reach the detector and so, it’s influenced not only by biomass concentration but also by rounded vessel shape, inserted aeration tubes, etc. The optical path of the test tubes is ca. 27 mm compared to the standard bench-top spectrophotometers in which the optical path is usually 10 mm. For all these reasons, the MC’s OD measurement is not fully comparable with the standard spectrophotometers however, it gives very good information about biomass growth.

The whole process of the OD measurement is automated in the Multi-Cultivator. The OD can be measured manually one time through the front control panel, or a protocol can be set where the OD measurements are performed in periodic intervals. Measured data can be later downloaded to a computer via the OD Viewer. Photobioreactor Control Software (optional) allows to set the OD measuring period, to display the OD data in graph in real time, to record and export them also during the running experiment. Moreover, a regression analysis online determining biomass growth rate can be applied on the OD data.

Non-linear measurements can go up to about 2.5 and 1 for OD 680 and 720, respectively. However the data distortion is considerable at this level.

A part of the variability is given also by an alignment of the OD measurement system in the individual slots (i.e. alignment of the measuring OD LED and OD detector) and by a tubular and not exactly identical shape of the experimental vessels. Also the biomass concentration influences the OD reading variability probably due to the scattered light absorption (the lower biomass concentration the higher relative OD reading variability).

The biomass OD reading variability was determined as the relative standard deviation of the OD 680 measurement. The relative standard deviation doesn’t usually exceed ± 10% and ± 5% for OD 680 readings around 0.1 and 0.5, respectively.

The detection and quantification limits were estimated from the mean of the blank and related standard deviation of the measurement. The detection limit was determined as triple of the standard deviation; the quantification limit as tenfold of the standard deviation.

Based on our testing, there was no significant evaporation under temperature of 27°C after one week of cultivation (ambient temperature around 22°C).

During high-temperature cultivation at 60°C, the evaporation from the test tubes was on average 5 mL (6.4%) after one week. The evaporation usually fluctuated between 1 – 10 mL (2 – 11%) in the individual test tubes. To avoid undesirable evaporation, it is crucial to seal up the vessels (stoppers, tubing and connections) properly.

Please remember, that the evaporation is highly dependent on the cultivation and ambient temperature. Also other conditions as for example: air sparging intensity (lower intensity = significantly lower evaporation), draught from the air-conditioner, tubing material, etc. may influence the result significantly.

Moreover, some specific problems may occur during low-temperature cultivation, as for example, water condensation, cooling water freezing, etc.

The Photobioreactor Control Software is a universal solution developed for a wide range of PSI cultivation devices comprising Multi-Cultivators, small- and large-scale Photobioreactors and their accessories. The Photobioreactor Control Software provides intuitive interface for real-time data visualization. The software further enables setting and control of the experimental conditions, data (experiments) recording and storing into the database, data export into MS Excel, remote access, advanced data analysis, etc. The software is available in two versions: Basic and Advanced. See our website for more details.

Notice: OD View runs under Windows operation system whereas Photobioreactor Control Software runs under Linux operation system.