Buying a new incubator shaker may seem like a simple job. You could select the same model again, the cheapest version, or the shaker with the fastest delivery time. Nothing to worry about as it’s a simple standard product, so anything will do the job. However, this approach leaves out a vital factor – what quality of results can you expect at the other end of your bioprocess?
The key factors to consider when purchasing any incubator shaker are summarized below:
- The capacity needed
- The type of culture vessel
- Free-standing or stackable systems
- Type of organism to be cultivated
- The final location
All these factors should combine to result in a detailed user requirement specification (URS), defining what is needed and allowing meaningful comparisons when choosing between suppliers. Helping you to reach this point is the aim.
How much capacity do you need?
This covers several separate but related points. As a starting point you should define:
- Your total requirement as litres of culture, total biomass, or the number of separate experiments for screening and statistical analysis.
- How will the cultures be grown: volume per well or tube or flask?
This should determine capacity in terms of numbers of culture vessels. This is also defined by the filling volume for each vessel. A shake flask is typically filled at around 20% of its total volume but much better oxygenation can be achieved if a filling volume of 10-15% is used. This can double the number of shake flasks required, but increased biomass yield may reduce the number of flasks needed.
- Will the containers all be of a single type?
For example, a tray of 2 Litre shake flasks, or mixtures e.g. 10 x 250 mL flasks, 2 Falcon-tube racks, plus some 500 mL flasks. This sort of flexibility will need universal trays and may reduce overall capacity slightly while increasing usage.
Which types of culture vessel do you use?
The role of the incubator shaker now includes more than just traditional Erlenmeyer flasks. Shake flasks have several common variants, including the wide, baffled Fernbach flasks, single use flasks as well as special flasks for high-density culture. Racks for test tubes are also commonly used alongside shake flasks. When selecting a dedicated rack make sure that the rack can be angled to improve mixing and encourage better growth. Finally, modern screening and design of experiment (DoE) studies can be performed in various sorts of microwell plates. When this is the main application for a shaker, a dedicated unit with a short 3 mm shaking throw, humidification and special trays can both increase the number of experiments per run and improve the quality of the results.
Typical culture vessels for incubator shakers:
- Shake flasks
- Test tubes
- Microwell plates
The total number and type of culture vessel, including weight, height, and distribution on the shaker tray are required to determine the number of shaker units required, either stacked or as single systems.
Do you need a single system or a stackable solution?
Lower capacity units can be stacked in more locations or mounted under a laboratory bench. Other factors such as total weight, working height and the ability to split up and move individual units can also influence this decision.
Which type of organism will be cultured?
This is the critical point for the actual users (who may or may not be the specifiers). The type of organism to be cultured can have major significance for the specifications of the incubator shaker. For bacteria and yeast, a standard incubator shaker with a 25 mm throw and basic temperature control will do the job. Insect and mammalian cell cultures are at the opposite end of the requirement spectrum. They are more fragile in terms of response to shear stress, affected by more environmental conditions and more prone to contamination.
The key parameters to look out for include:
- Shaking throw
- Shaking speed
- Temperature range
Each of these parameters has its own acceptance criteria. Have a look at our blog post: 5 Key Factors for Reliable Screening Results in Incubator Shakers to learn more about drive capabilities, temperature uniformity and the different types of humidification systems available on the market.
What is the final location of the incubator shaker?
This is also a multi-faceted decision. More than any other consideration, it’s concerned with the practicalities and will often be constrained by what is possible for a given situation. Key questions to answer include:
Will the incubator shaker be located on the ground floor or on upper stories of a building?
Stackable systems can weigh half a metric ton or more, and special consideration needs to be given to floor loading. Splitting the weight into smaller units may prove more cost effective and flexible. Reliable total dimensions, weights and visual inspection of possible locations are the key ingredients for success.
Will the final location be suitable?
This covers aspects such as adequate ventilation all around a system. Space may be needed for gas cylinders or external steam generators for humidification. Allow space for gas cylinders or external steam generators for humidification. Also, consider the space required (horizontal or vertical) for the opening of incubation chamber doors.
Is the location able to be kept clean and disinfected easily?
A common source of contamination within the incubation chamber will be the local environment. Air moves through the shaker, which may have a high load of bacterial or fungal spores. Leaving room for good air circulation and a design created for easy cleaning the incubation chamber can help reduce this risk.
What about usability aspects?
The incubator shaker supplied must be usable without major alteration of good laboratory practices. Usability aspects include ergonomic aspects, safety considerations and ease of handling. These points can provide a useful distinction between suppliers if all the basic specifications can be met. Examples include:
- Easy access to the shake flasks. The opportunity to pull a tray out to exchange flasks without having to totally remove it fully can be a great advantage.
- For a stacked system, the top deck should be accessible to operators without the need for steps or a kick stool.
Ease of handling
- Easy cleaning. If the incubation chamber can be quickly cleaned and spills wiped up quickly, this is more likely to be done by operators.
- Special options to improve culture outcomes by minimizing the need to open the incubation chamber. This can include biomass estimation to eliminate sampling, automated addition of feed/inductant and analysis of exit gas from flasks.
- Automatic tray locking, so shaking cannot begin unless the shaker tray is locked into place.
- Auto-restart when the incubator chamber door is closed. This stops the operator forgetting to re-start shaking. A soft start/stop system will ensure smooth progress to the operating speed.
The need for a quality solution to your incubator shaker needs cannot be stressed too highly. It forms the base on which all additional production, scale-up and experimental research is based. The influences which poor control, construction and design can have on culture conditions argue for proven equipment.
Producing a full user requirement specification (URS) for purchase of incubator shakers allows meaningful comparisons between suppliers and prompts a review of both current and future needs. Apart from the equipment needs, other factors such as delivery time, warranty, support, and quality assessments can be added. Special options and qualification for regulatory approval can be added for advanced applications.
The main elements of an incubator shaker URS will include:
- Capacity – in terms of numbers, sizes, and overall quantities.
- Choice of culture vessels– usually shake flasks or micro-well plates.
- Single or multi-deck solution requirements.
- Parameter specifications according to the organism to be cultured. This may be the longest and most detailed part of the URS.
- Location aspects, such as total weight, size and required environmental conditions.
- Usability aspects. Some of these may be integral to the design of the incubator shaker or additional options.