Disassembly

The main goal is to avoid making a mess while disconnecting the turbidostat.

  1. Disconnect the tubing between the air pump and the humidifier by detaching it from the disc filter.

    This removes positive pressure from the system.

  2. Detach the Luer connection between the air line and the growth chamber cap.
  3. Stop the turbidostat controller by hitting q in the controller software.
  4. Detach the Luer connection between the waste line and the growth chamber cap. Drain any residual waste collected in the “S-trap” out of the line.

  5. Detach the Luer connection between the media pump line and the media reservoir. Cap the media pump line with a female Luer cap.

    Note that media generally will not drain from the media pump line while the tubing is still engaged by the peristaltic pump. If the media pump line is removed from the pump, however, then media will siphon out of the pump line when it is disconnected. To avoid this, detach and cap both ends of the media pump line before removing it from the peristaltic pump.

  6. Detach the Luer connection between the media pump line and the growth chamber cap. Cap this end of the media pump line with a female Luer cap as well.
  7. Remove the media pump line from the peristaltic pump.
    1. Flip the cover latch up until you can pull the cover off of the pump
    2. Remove the tubing restraints from the cover and pull the peristaltic pump tubing out of the restraints.
    3. Return the restraints to the cover. The tubing restraints are small and easily misplaced.
    4. Return the cover onto the pump.
  8. Lift the growth chamber carefully out of the plastic band of the detector.

  9. To compute more accurate absolute growth rate measurements, determine the exact culture volume in the growth chamber.

    The culture volume is needed to calculate the dilution rate, along with the fraction of time that the pump is switched on in order to maintain constant turbidity. The peristaltic pump delivers a very accurate and precise flow rate, allowing the volumetric rate of media addition to be determined. Converting this volumetric rate into a fractional dilution rate requires knowing the total volume of the culture. This volume is fairly consistent between different cultures and different systems, but it still provides the largest uncertainty in exact growth rate measurements.

Cleaning

The overall strategy is to clean all turbidostat parts with deionized water and then with 70% ethanol, and then allow it to dry.

  1. Fill a large beaker or other container with deionized water.
  2. Immerse the growth chamber cap and the media reservoir cap entirely in the deionized water.
  3. Connect a Luer syringe to each connector on the growth chamber cap and use the plunger to force water through it several times.
  4. Remove the growth chamber cap from the water.
  5. For each port, fill the syringe with 5 - 10 ml of 70% ethanol, attach it to the connector, and force the 70% ethanol through the tubing into a basin or sink. Pull the plunger back and force air through the tubing.
  6. Set aside the growth chamber cap to dry.
  7. Repeat this procedure for the media reservoir cap.

The long media pump line and waste line tubing can be cleaned by forcing water and 70% ethanol through with the media filtration pump.

  1. Connect the media pump line(s) and the waste line(s) in series and connect them to the media filtration line.

    It may be necessary to construct small adapters from 1cm ID 0.125in silicone tubing with barb to female Luer connectors on each end.

  2. Pump 100 ml of deionized water through the tubing, followed by enough air to purge all liquid from the tubing.
  3. Pump 50 ml of 70% ethanol through the tubing, followed by enough air to purge all liquid from the tubing.
  4. Disconnect the lines and set them aside to dry.