Microbiology International

Are You Autoclaving Liquids Properly?

2012-01-26T14:26:00.002-05:00

Using an autoclave may seem like a simple task. Usually pushing a button and letting the autoclave run its cycle is all the user needs to do, but does that really mean that your liquids are reaching the correct sterilization temperature? Are you sure your items are reaching 121^oC for 15 minutes? Are you sure because the gauge on the autoclave reads 121^oC? Does that temperature represent the ambient temperature in the chamber or the temperature inside your liquids? Some of these questions may raise doubt about the autoclave on your bench right now and what is really happening inside the unit.
Today we explore some basic principles of using an autoclave with liquids and how your choice of machine, could save you lots of money in energy savings.

Autoclaving Liquids Properly

When autoclaving liquids in the laboratory it is important to achieve correct sterilization temperature for the correct period of time. In the case of sterilizing liquid waste the primary goal is to neutralize all living organisms so the waste can be disposed of safely. With liquid wastes it is therefore important to be sure the liquids reach 121^oC for a specified period of time; usually 15 - 20 minutes. Generally, over sterilizing (i.e. remaining at 121^oC for longer than 15 - 20 minutes) is not a problem as the waste will just be disposed of. When sterilizing other liquids such as growth media - over sterilizing can present a problem as going above 121^oC or remaining at 121^oC for longer than 15 - 20 minutes could have deleterious effects on the performance of the media.

Accurate control of the autoclave process is of paramount importance in order to reproducibly achieve desirable results. The vast majority of autoclaves being used in labs today are unable to accurately and reproducibly perform liquid sterilization cycles. This is mainly due to the fact that most autoclaves utilize a single temperature probe that determines the absolute temperature within the sterilization chamber; but does not directly measure the temperature of the liquids being sterilized. Autoclave operators therefore often either over sterilize, or under sterilize liquids and usually "guess" at how long an autoclave cycle should be to correctly sterilize their liquids. Often times the volume of liquid being sterilized is ignored when considering the duration of the cycle - this is a critical misstep as higher liquid volumes require more energy and hence longer heat up times to reach 121^oC.

The only way to safely and accurately perform a liquid sterilization cycle is to directly measure the temperature of the liquid throughout the entire heating, sterilizing and cooling phase of the cycle. The latest generation of high quality laboratory autoclaves utilize a flexible PT100 temperature probe that can be directly placed in the liquid being sterilized or in a reference vessel with water (containing the same volume as the liquid being sterilized). The flexible temperature probe provides feedback directly to the microprocessor controlling the sterilization cycle meaning that the sterilization phase will not begin until the liquid reaches 121^oC and the sterilization time will only begin to countdown once the specified sterilization temperature has been attained. Only laboratory autoclaves with the design features described ensure liquids reach the correct temperature for the correct period of time. Additionally, during the cooling phase accurate temperature measurement ensures boil over will not occur as the pressure release can be controlled based on the liquid temperature. This level of control and monitoring prevents the operator from opening a properly equipped autoclave containing super heated liquids as the microprocessor will prevent door opening until the liquids reach a safe handling temperature (usually 80^oC).

Laboratories performing liquid sterilization should confirm they are using autoclaves that provide the level of control and sophistication to directly monitor and control liquid temperature, and sterilization vessel pressure. Relying on a one size fits all sterilization time and "slow exhaust" setting for liquids will not provide accurate, reproducible liquid sterilization results.

Why choose round or cylindrical autoclave chamber vs. rectangular?

The pressure inside an autoclave chamber naturally attempts to make the chamber round. Therefore a cylindrical chamber can have thinner walls and weighs less than a rectangular chamber. Since cylindrical chambers have less metal; heat up and cool down occurs more efficiently with less energy consumption and faster cycle times. Cylindrical chambers provide better steam circulation on front loading models. Due to the circular profile of the working chamber and the ‘square’ profile of most autoclave loads there will normally be space around the sides of the load for steam circulation. If the steam cannot get to the load or the air cannot escape sterilizing will not be effective. Extra care and skill must be employed when loading a rectangular chamber to ensure that steam circulation is not restricted by overfilling the autoclave chamber. Again, if steam cannot get to the load or air cannot escape then sterilizing will not be effective.

Cylindrical autoclaves offer more efficient steam circulation and air removal, combined with lower operating costs due to increased efficiency in heat up and cool down times. Long term savings can be realized with lower operating costs, more reliable sterilizing and faster cycle times. See below how a Systec Autoclave from Microbiology International can be an energy efficient autoclave which could save you thousands per year in electricity.

	Other Autoclaves	Systec Autoclave
Autoclave Steam Generator (Kw)	30	18
Estimated hours per day autoclave will run	4	4
Estimated days per week autoclave will run	3	3
Estimated weeks per year autoclave will run	48	48
Utility costs (Dollars / kWh)	$0.13	$0.13
Estimated Annual Energy Cost	$2,246.40	$1,347.84
Estimated annual savings: $898.56

Whitley A35 Anaerobic Chamber - Look Ma no Sleeves

2010-07-28T10:33:00.009-04:00

With 30 years of experience in designing workstations for a variety of applications and having listened to our users, the Whitley A35 Anaerobic Workstation is born. This latest incarnation fulfils the diverse needs of both our research and clinical customers.

The A35 is the first anaerobic workstation to be offered with our new gloveless/sleeveless system. Sample manipulation within a secure anaerobic environment is now as easy as working aerobically on the laboratory bench. The working and storage areas of the chamber are temperature controlled with an impressively low gradient throughout. This allows the full internal volume to be used as an CO₂ incubator if desired.

One other advantage of the sleeveless system is that it uses 8x less gas when entering the workstation compared with a conventional porthole system. The airlock is flushed with nitrogen as an additional cost-saving.
Here is a video on the A35 Anaerobic workstation.

WASP Spiral Plater - Spiral Plating Eliminate Serial Dilutions

2009-05-01T16:05:00.006-04:00

The WASP2 spiral plater boasts a host of innovative features ensuring it is still the most widely used spiral plater. It eliminates the need for serial dilutions, offers a reduction in cost per test and standardizes counting methods.
Fully microprocessor controlled and allowing depositions onto 10cm and 15cm plates in logarithmic volumes of 50ul,100ul and 200ul and a linear deposition of up to 400ul. The stylus arm dispenses liquid sample either uniformly across the plate or as a continuously decreasing volume, equivalent to a thousand-fold dilution. The unique stylus geometry and volume allows deposition on plates of varying agar height and up to eight consecutive depositions from one sample draw without the need to wash or collect more sample.

One feature unique to WASP 2 is its ability to load sample, inoculate a plate and then clean the stylus with only one keystroke. WASP 2 has an automatic cleaning cycle, with provision for both sterile water and a self-leveling bleach reservoir system. The automatic wash cycle uses a large, 500ml disinfectant reservoir, as well as autoclaveable 100ml containers for sterile water. This eliminates contamination problems associated with using a large, replenishable reservoir. Automation of the cleaning cycle gives the operator time to remove the inoculated plate and prepare for the next sample, thus streamlining operation.

Systec Autoclaves D Series

2009-04-21T11:14:00.010-04:00

Features:

Innovative automatic safety door lock. Easy and safe. When the lid is closed, the lid is automatically locked by a circumferential ring system. A special lip seal made of heat resistant silicone provides reliable sealing. As steam pressure builds the seal becomes tighter.The lid also opens easily – either at the push of a button or automatically at the end of a sterilization cycle. The door-locking system is temperature dependent and adheres to national and international safety standards. The door remains locked as long as there is excess pressure in the chamber. The lid, like other parts of the pressure vessel and housing, is made of stainless steel. The modern design faceplate, which also contains the control panel, display and part of the control technology, is made of heat resistant and insulated plastic. There is no risk of the operator coming into contact with hot components.

Controls – new generation.Microprocessor and softwareThe Systec V-Series autoclaves have “comprehensive intelligence”: Pressure is controlled via an electronic pressure transducer. Additionally, there is a flexible temperature sensor in the sterilization chamber or in a reference vessel (for liquids) and another sensor at the coldest part of the chamber, the condensate outlet. The microprocessor, specially developed for our laboratory autoclave, controls all relevant functions such as steam pressure, temperature and sterilization time as well as optional rapid cooling, pre / post-vacuum and drying.
Menu-presented instructions in easy to read text form.Membrane keyboard with acoustic confirmation signal. Ergonomically located in a logical and easy tooperate position.

Design – pure innovation! Steam generation! A steam generator is incorporated in the housing providing substantial benefits:

– No heating elements and no reservoir for dirty water in the chamber

– With stand-by pre-heating option, only 10 min. heating time to 121° C with an empty chamber

– Improved removal of air from the empty chamber via pulsed heating (rapid attainment of optimal steam atmosphere, even without a vacuum)

– Accuracy better than ± 0.3 C with empty chamber

– Quicker cooling as neither hot water in the chamber nor the separate steam generator need be cooled

– After cooling, steam is immediately available for the next sterilization run.

Full Product Details!!

Systec MediaPrep

2009-04-21T10:55:00.009-04:00

Prepare and sterilize microbiological media
in less than 90 minutes

The compact class. For up to 30 litres

Easy and safe to handle.

Locking of the door and loading hatch is
dependent on temperature and pressure.
Inadvertent opening is not possible!
The inner vessel holder is exchangeable
and easy to remove and clean.
Every MediaPrep is so equipped and
controlled that it can be used as a normal
autoclave.

Heating and cooling systems are highly effective. Powerfull heating elements enable particularly
rapid heating to be carried out. Rapid cooling is by water circulation and support presssure directly at the external walls of the media vessel using sterilized demineralized water. The water is brought to cooling temperature using a plate heat exchanger with a water connection. The
total process time including heating, sterilizing and cooling to 50° C lasts from 60 – 120 minutes, depending on the size of the vessel, the quantity of media and the temperature of cooling water. The support pressure avoids an overboiling respectively foaming of the media. In
Mediaprep 10, 20 and 30 a compressor is built-in.

Microprocessor Controlled:
Sterilization cycle is fully programmable by the user. User defined parameters include sterilization temperature, time and pouring temperature. PT100 probe directly measures temperature of media throughout cycle. Detailed batch information (time / temperature / pressure) is available directly from the optional ticket printer or via connection to external PC using ADMC software

The powerful heating elements are adapted to the size of the vessel and hence facilitate
rapid heating. Rapid cooling is the same as in the smaller vessels with water circulation and support pressure directly at the external walls by means of sterilized and demineralized water brought to cooling temperature using a plate heat exchanger with a water connection. The
support pressure avoids an overboiling respectively foaming of the media. If no external compressed air is available, Mediaprep 45, 65, 70 and 120 can optional be equipped with a separate compressor