Cool DIY Shaker Incubator Cooler

by Syed Atif Ali, Labtimes 01/2013

Schematic diagram of the DIY low-temperature shaker incubator.

Syed Atif Ali, molecular biologist and senior lecturer at the University Sains Malaysia encountered a problem that many life scientists all around the world may be familiar with: lots of ideas but to little money to realise them. To make the best of it, Syed came up with a cleverly-constructed, low-temperature shaker incubator.

Recombinant protein/antibody expression work in a lab often requires reliable temperature control below the ambient temperature of the lab. Being a junior faculty with limited means and common equipment available, it has been a daunting task to equip the lab with all the desired equipment.

In order to express the recombinant proteins in soluble form, the bacterial cultures need to be expanded at temperatures between 16 and 18 °C, which traditionally requires a low-temperature shaker incubator comprising cooling and heating capacity. Such incubators generally have a price tag anywhere from $ 6,000 (4,500 €) to over $12,000, (9,000 €), which was clearly out of our budget range.

Air conditioned cells

After some thought, I came up with the idea of constructing or more correctly, assembling a low-temperature shaker incubator by myself. The overall idea was to place a bench-top orbital shaker next to a portable air conditioner in an enclosure with access doors.

Portable air conditioners have been on the market for some time. They are self-contained units, which draw in the warm ambient air, pass it across freon-coolant filled coils, thereby reducing its temperature and blowing the cooled air out of the unit. The by-product in this process is warm air and some condensation water. These units need to be placed next to an outdoor venting access (6 to 7 feet, 1.8 to 2.2 m) and have available drainage for water (though less critical as the units can be emptied ­manually). These air conditioners can lower the surrounding temperature to as low as 16 °C as well as maintain a controlled temperature within 1 to 2 °C. Portable air conditioners come in different sizes and cooling capacities (measured in British thermal units [BTUs] per hour).

A cheap unit with a cooling capacity of 10,000 BTU was purchased. A 10,000 BTU capacity air conditioner can efficiently cool an area of 400 to 450 square feet (372 to 420 m2), which was amply sufficient for our purpose.

The doors on both sides allow for easy access to the shaker and removal of the air conditioner unit if needed.

Initially, a plexiglass enclosure was planned but for the desired dimensions, such an option was relatively expensive. I therefore settled on a less costly custom-made enclosure constructed of aluminium and glass. The enclosure was 3 feet long, 2 feet wide and 3 feet high (1 foot = 0,3 m). The backside of the enclosure was, however, plexiglass to easily cut two holes, one of 5 inch diameter (for the vent duct pipe, 1 inch = 2.54 cm) and another of one inch diameter (for the water drainage pipe). The enclosure has two glass doors on either side to access the orbital shaker. In addition, a power outlet was added to the inside of the enclosure to plug in the air conditioner and the shaker.

After introducing the air conditioner in the enclosure, almost 2 x 1.5 feet area is left to place one medium size or two small size orbital shakers. The reason for enclosing the entire air conditioner unit was because the temperature sensor is located on the backside of the unit. Had the temperature sensor been located on the front, it may have been possible to enclose only part of the unit and gain additional space. However, given the height of the enclosure, there would be space for a shelf and space for another shaker.

Stable temperature range

We have been using this DIY low-temperature shaker incubator for almost a month now. The temperature is very stable and well within ±2 °C. We are now able to produce soluble proteins by growing our bacteria at low temperatures. We can also make competent bacterial cells with very high efficiency by growing them at 18 °C.

In conclusion, we spent (~$350; ­260 ­€) on the air conditioner, (~$170; 128 €) on the enclosure, and (~$1,000; 750 €) on the orbital shaker. Altogether, it cost us less than $1,600 (1,200 €) to get a functional low-temperature shaker incubator.

Last Changed: 07.02.2013

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