Precise temperature regulation with soft IR heating

  • No need of electrical heating blankets, heating coils, jacketed vessels and thermal circulating baths
  • Microprocessor controlled infrared radiation heater conveniently placed beneath the fermentation vessel regulates the temperature
  • Extremely precise temperature control of ± 0.1°C is achieved
  • IR heater with high heat transfer and low heat capacity
  • Soft heating without hot spots at any medium volume, not even at lowest medium levels
  • Natural thermal convection occurs even without any mixing of the culture
  • Due to the low heat capacity of metals (corresponding to heat capacity of one ml of water!), the precise dosing of the supplied heat allows a very accurate control of the temperature in the medium
  • Inexpensive and safe (no electrocution risks) way of heating

Importance of precise temperature control

During fermentations and cell culturing, it is essential that the temperature in the fermentor/bioreactor is regulated precisely without exceeding the desired temperatures and without temperature oscillations.

As the working volume in a given vessel type can vary throughout the fermentation or cell culture (addition of acid, base, feed, harvest, sampling…), it is important that the heating system is able to adapt and control the temperature according to the changing volumes. This is achieved in the MINIFOR laboratory fermentor-bioreactor for all vessel types with working volumes from as low as 35 ml to up to 6 L with the unique infrared heating system at no additional cost.

Elimination of electrical heating blankets and the like

LAMBDA does not use electrical heating jackets, heating blankets, heating coils, silicone heating pads, double-walled or jacketed vessels in the bench-top fermentor and bioreactor for their well know disadvantages.

The double-walled or jacketed vessels have very high heat capacity and low heat transfer during sterilization, either with the jacket with or without water. The consequential longer sterilization time resulting in increased degradation of medium, longer cooling-down times and the need for cooling water supplies (condenser or chiller) with the corresponding necessity of additional tubing connections. The water cooling options increase the complexity around the culture vessel, the necessity of expensive circulating pumps, etc.

The main reason for using thermal circulating baths lies in the elimination of hot spots on the vessel walls. Whereas, the other electrical heating jackets, heating blankets, heating coils, silicone heating pads, heating fingers or rods can create hot spots directly in the medium. The common electrical heating methods are eliminated, because:

  • Their efficiency is limited by the quality of the contact between the heating surface and the vessel walls. The transmission of heat occurs only by diffusion, which is slow especially when the temperature gradient is small.
  • The medium has to be heated more than necessary to achieve significant heat transfer. When the desired temperature is attained, it must be cooled down to prevent temperature overshooting. It is obvious that the temperature control is difficult.
  • Slow cooling down, because the heating blanket acts as an isolation layer
  • Depending on the used working volume, the glass walls not in contact with the medium heat up very strongly and thus, overheating (and culture damage) occurs in these places (hot spots on the vessel walls)
  • The view into the vessel is restricted and it is not possible to illuminate cultures of algae from outside.
  • Heating clamps and heating mats prevent natural cooling of the vessel and a complementary cooling is then required. This increases both the cost and complexity of the system.
  • Even a small damage in electrical heating mats can lead to the risk of electric shock or electrocution.
  • Expensive, voluminous and unpractical handling

To eliminate all the above mentioned problems in using the electrical heating blocks and pads, LAMBDA invented an IR radiation heater which is placed under the bottom of the vessel.

Sun-like way of heating

The heating spiral is placed in a gilded parabolic reflector beneath the fermentation vessel. Heat rays are concentrated by the gilded parabolic reflector with 98% efficiency onto the bottom of the vessel, where about 50% is absorbed by the glass and about 50% is absorbed directly by medium. The heat of certain wavelength will be absorbed by glass; others pass through it and are absorbed directly by the water molecules in the medium, in a similar way as sun heats water. The result is an extremely soft heating without any hot spots, not even at lowest medium levels.

Only a short piece of metal wire is required to generate the infrared radiation! As metals have very low heat capacity, the IR heating can be rapidly switched ON or OFF.

It heats up and cools down extremely fast which lead to a much more precise temperature control in the vessel.

The novel heating system is also very convenient, because cables, tubing, connectors, the necessity of heating blankets or jacketed vessels and circulating water supplies are completely eliminated.

Even a very slight increase in temperature leads to natural thermal convection. Since the radiation is directed to the bottom of the vessel, the convection equalizes the temperature in the medium even without any agitation at all.

For example, the variation of the temperature set to 30°C gives deviations of only ± 0.1°C in the 1 liter vessel volume!