Photobioreactors
Precise Phototrophic Cultivation of Algae and Cyanobacteria
FAQs
FAQs
Multi-Cultivators

  • What is the difference between OD View and Photobioreactor Control Software?
  • OD View was a simple utility developed for Multi-Cultivator MC 1000. It was intended for simple OD and temperature data download from the device.

    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.

  • How to find the serial number, firmware number or software version of the Multi-Cultivator?
  • The serial number is marked on the label on the rear side of the Multi-Cultivator (for example: SN-MC-1000-337). Please note, the serial numbers of the Multi-Cultivator and its power supply must fit.

    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)

  • What is the best position of the aeration glass straw in the test tubes?
  • The best position of the aeration glass straw is on either side of the tube (to avoid the shading of the OD sensor that is aligned with the center of cultivation tube).

    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.

  • Is it possible to replace the fragile glass aeration straws with any suitable substitution?
  • Yes, the fragile glass aeration straws may be replaced with stainless steel aeration tubes that are easier and safer in manipulation.

    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.

  • What is the recommended flow rate of aeration?
  • Usually, we use aeration flow rates around 1 L/min for the Multi-Cultivator and 1.3 L/min for the Multi-Cultivator coupled with the Turbidostat module and connected filter on the turbidostat’s air pump input.

  • How to adjust exactly same air flow rate into each testing tube?
  • Please, see following video for a hint how to adjust the aeration.

    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.

  • Is the main aeration dispenser tube (black tube with 8 small valves) autoclavable?
  • The aeration tube with valves can be autoclaved at 75 C only. The aeration dispenser can also be sterilized with 70% ethanol. The humidifier (1L glass bottle with the cap) and silicone tubes can be autoclaved at 121°C.

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

  • How are performed the optical density measurements?
  • The method is based on light absorption / scattering of certain wavelengths (680 and 720 nm) by chlorophyll and cells.

    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.

  • What is the maximum optical density that can be measured? Is the OD measurement linear?
  • Based on our testing, the OD 680 was usually found to be linear in the range 0.1 – 0.9 (up to 1.0). The OD 720 was usually linear in the range 0.05 – 0.4 (up to 0.5). The linearity of individual devices may differ slightly. Please note, that the optical path of the test tubes is ca. 27 mm.

    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.

  • Why the identical algal biomass concentration shows slightly different OD in various cultivation slots?
  • The variability of the OD reading in different cultivation slots is given especially by an improper or insufficient mixing before the distribution of the algal inoculum into individual cultivation vessels.

    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.

  • What are the detection and quantification limits of the OD measurements?
  • The OD detection and quantification limit for Multi-Cultivator is 0.01 and 0.04, 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.

  • Is there any increased evaporation from the test tubes during the experiment? Is the water level in the test tubes topped up automatically, allowing minimal user supervision?
  • The humidified sparging air along with the condensation system grant minimal medium evaporation. That’s why there is no automatic water level detection in the test tubes and no medium is added during a batch-designed experiment automatically.

    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.

  • Is there any temperature gradient among the testing tubes?
  • The testing tubes are immersed in a thermostatic water bath in order to control and keep the required cultivation temperature. The temperature homogeneity of the water bath and thus also of the testing tubes is ensured by proper water mixing with the installed water pump.

  • Is it possible to keep the cultivation temperature below the 15°C?
  • Yes, this might possible under special circumstances. With a specific firmware modification the cultivation temperature can be set down to 5°C. However, the device itself is not designed (insulated) for such a type of cultivation and also the cooling system doesn’t provide sufficient cooling capacity. Therefore, it is necessary to keep also the ambient temperature at low level (around 10°C) to ensure a low-tempered cultivation.

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

  • Is there any significant difference between algal growth dynamics under cool white and warm white LED lights?
  • We didn’t identify any significant difference in growth dynamics of Chlorella vulgaris and Cyanothece sp. cultivated under cool white and warm white LED illumination during the linear growth phase. Also vital absorbance spectra of biomass were qualitatively comparable. Common cultivation conditions without any particular stress were used during the test.

  • Is there any light interference among the individual cultivation slots?
  • The illumination of the adjacent slots interferes a little bit. Approximately 2% of the illumination may penetrate into the adjacent slot.

Photobioreactors
  • How to find the serial number, firmware number or software version of the Photobioreactor?
  • The serial number is marked on the label on the rear side of the Photobioreactor (for example: SN-FMT-WR-337). Please note, the serial numbers of the Photobioreactor and its power supply must fit.

    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 >> BR FW Version (for example: 3.0.4.2) and Settings >> Device Info >> TR FW Version (for example: 3.0.0.8)

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

  • Which Photobioreactor panel (blue/red or white/red) works better for cyanobacteria growth?
  • Cyanobacteria use phycobilins as additional photosynthetic pigments with absorption maximum in red region, therefore cyanobacteria are more sensitive to the red light and usually a combination of white/red light panel is recommended for the cyanobacterial cultivation.

  • Is it possible to measure pH, dO2 and dCO2 simultaneously?
  • Yes, this is possible. There are three ports in the lid that are intended for pH/temp, dO2 and dCO2 sensors. It is necessary to purchase each sensor module separately. The sensors values are recorded automatically by the Photobioreactor Control Software.

  • Is it possible to calibrate pH, O2 and CO2 sensors by help of the Photobioreactor Control Software?
  • Yes, this is possible through a context menu of each sensor. Simple pH, dO2 and dCO2 calibrations and also temperature dependent dO2 calibration are available.

  • What is the recommended flow rate of the aeration?
  • The aeration flow rate depends on the size of the cultivation vessel and also on the experimental and cultivation organisms’ demands. Usually, we use aeration flow rates around 200-300 mL/min for 400 mL PBR, around 500-800 mL for 1000 mL PBR and around .

    The mentioned levels are only illustrated and may differ significantly based on the different experimental requirements.

  • Is it possible to connect more Photobioreactors to one Gas Mixing System?
  • In general, this is possible. However, this configuration is not that accurate as the connection of one PBR with one GMS 150 unit which is highly recommended.

    The connection can be arranged through a simple branching of the output GMS tubing. We recommend to purchase additional air PWM pumps (optional) and valves with mini flow-meters (not in our offer) to adjust the gas flow rates into the individual PBR.

  • Is the OD measurement linear?
  • Based on our testing, the OD 680 was usually found to be linear in the range 0.1 –1.0. The OD 720 was usually linear in the range 0.05 – 0.5. The linearity of individual devices may differ slightly. Please note, that the optical path of the cultivation vessel is ca. 24 mm. Non-linear measurements can go up to about 3.5 and 1 for OD 680 and 720, respectively. However, the data distortion is considerable at this level.

  • Is there any excessive evaporation from the Photobioreactor during the cultivation? Have you addressed this issue somehow?
  • We are routinely using the gas humidifier (bottle with distilled H2O) on tubing line in each Photobioreactor. Therefore, we don’t experience any considerable evaporation under common cultivation conditions in the air-conditioned laboratory.

  • What is the pressure rating of the Photobioreactor vessel?
  • Maximum inner pressure inside the 400 mL and 1 L vessels should be always below 2 bars (alternatively below 1.5 bar for 3 L vessel) during cultivation. In general, we strongly do not recommend to over-pressure the cultivation vessels.

    All cultivation cuvettes are autoclavable under 121°C at 101 kPa above the atmospheric pressure. VERY IMPORTANT: at least one sensor port must be open (covered with the aluminum foil).

  • Is there a chance to see how the Photobioreactor Control Software works?
  • Yes, there are video tutorials in the product Gallery on the PSI web site.
Large-Scale PBRs

Software

  • What is the difference between OD View and Photobioreactor Control Software?
  • OD View was a simple utility developed for Multi-Cultivator MC 1000. It was intended for simple OD and temperature data download from the device.

    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.