TQPL Supplies for aseptic technologies.

PTFE venting - FAQ and information resource


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Frequently asked questions and information resource as applied to Adhesive Microfiltration Discs (AMD) and Flasking Patches (FP) as supplied by TQPL.

Q. Why should I vent my cultures? Increased air exchanges lead to increased plant growth in many in-vitro systems. Eliminate or reduce vitrification, glassiness, hyperhydricity. Remove or vent ethylene, phenolic and other deleterious gasses. An improved in-vitro environment leads to vigorous growth and better establishment of plants out of culture. Achieve good aeration without dehydration

Q. Why should I use PTFE? Microfibril enmeshment is superior to many other methods for contamination free venting as particle are filtered out and trapped between the many fibrils of the PTFE.

Q. What is PTFE? It is the chemical abbreviation for polytetrafluroethylene a highly versatile polymer and in this instance manufactured specifically for aseptic venting.

Q. What is the pore size if the PTFE used in Adhesive Microfiltration Discs and Flasking Patches? The pore size and PTFE structure is sufficiently small enough to stop the passage of mites, dust, fungi, yeast, bacteria and other microbiological contamination agents.

Q. Can I compare the pore size with other filter systems? The unique PTFE structure of the Adhesive Microfiltration Discs (AMD) ensures filtration efficiency is not simply a factor of pore size. For this reason pore size is not critical and for commercial reasons is not revealed to customers.

Q. Why is hydrophobicity important in the AMD and FP? The level of hydrophobicity is critical in achieving venting between the internal flask environment of high relative humidity (95-100%) and the external air. AMD and FP allow high air exchange and low levels of moisture passage helping control dehydration of cultures and media.

Hydrophobicity has been controlled at manufacture to strict specifications and indeed provides a level of humidity / airflow control other venting systems do not provide.

Q. Will moisture ingress contaminate cultures? Generally AMD and FP venting does not allow inward passage of moisture from environmental dampness, humidity or water splashes. Although not recommended it is possible to store AMD and FP vented cultures for short periods of time in humid growing areas such as greenhouses without contamination loss, such cultures should be watched carefully as standard laboratory procedure,

Q. Can I use PTFE venting to eliminate contamination due to mites? Mite infestation of cultures can be stopped by the use of our PTFE venting systems. Mites cannot pass through the PTFE while the adhesive ring provides a strong mite barrier. Where mites are a problem the AMD should be selected in preference to the FP as it has an especially strong and wide layer of 'miteproof' adhesive. All non-venting points of entry for mites should be eliminated.

Q. Can I obtain technical information about the use of AMD and FP? We supply technical information with orders and can be contacted with specific questions about our products. We will always try and help based on our many years of experience in PTFE venting. Our products can be used for a range of venting uses with plant and cell culture systems. They can also be used for non in-vitro situations.

Q. What is your experience in PTFE venting? We first started using multilayered PTFE venting systems in early 1995, and we believe we were the first in the UK to introduce such technology to the commercial world of orchid raising. We continue to use both AMD and FP to vent cultures and achieve optimum growth rates in the plants we produce.

Q. Why have we never heard about Adhesive Microfiltration Discs, Flasking Patches and PTFE venting before? This is relative new technology and it is only recently we have launched a web site regarding these products. We have been selling PTFE venting systems since 1998 though before then we kept such good ideas to ourselves and our commercial customers! Flasking patches were only introduced in late 2000 after extensive trials as an inexpensive alternative to Adhesive Microfiltration Discs.

Q. Can I obtain Adhesive Microfiltration Discs (AMD) or Flasking Patches (FP) locally? We supply worldwide. We are the only source of AMD's and FP's developed specifically for plant micropropagation and flasking needs with the correct venting characteristics for long term aseptic cultures. Purchasing direct from ourselves allows savings on price and offers technical advice from within the in-vitro industry. We do not have agents or intermediaries but supply direct from TQPL.

Q. Are all PTFE venting systems the same? No, this is very apparent as soon as you examine, compare or use our AMD or FP. The AMD's are uniquely laminated with polypropylene mesh while the FP are made from toughened PTFE to withstand the rigors of commercial laboratory use. We consider many other products to be inferior to our own which were manufactured according to our in-vitro requirements.

Q. I have seen some PTFE vents curl up at the edges which makes them look fragile and unsuitable, and wonder if yours do this? This does not occur with our product during normal usage. Our AMD's are strengthened with welded polypropylene mesh and respond well in flex tests, while the FP's are made from toughened PTFE to provide rigidity.

Q. How can I ensure the correct air exchange rate? This is affected by many factors including the structures of the PTFE filter, the venting hole size, along with the volume of the culture vessel. The growing room conditions, the air flow over the discs and the phototranspiration. The growth rates of the plants and plant type can all have an influence. In addition the use of static or shaken cultures can determine the required air flow demands for optimal growth. Correct balance of all these factors should be aimed for or problems may occur. We can advise.

Q. Why do I need to optimize air exchange for in-vitro cultures? Good air exchange allows any depletion in carbon dioxide levels to be eliminated which is important in photomixotrophic cultures (air-vented cultures with a sugar carbon source in the media). The in-vitro environment is improved with the diffusion of carbon dioxide and deleterious phenolic and ethylene gasses. Many plants in-vitro are intolerant to these gasses. Good air exchange improves the in-vitro environment allowing cultures to grow at maximum or optimal growth. Culture time and plant growth needs to be optimized in many systems for rapid turn around and competative economic considerations.

Q. Will good venting help with establishment of plants out of culture in the nursery? Our experience has been that survival of plantlets is improved when well vented and good air exchange is achieved during culture. This may well be due to the 'hardening' effect of evapotranspiration as plants grow photomixotrophically. Note - Ratcliffe Orchids Ltd., can achieve 100% survival of Paphiopedilum plants with no losses from flasks of seedlings vented with AMD or FP.

Q. How many times can I use Adhesive Microfiltration Discs? These AMD's are primarily used in-vitro for single usage. This is to ensure aseptic integrity and safety of valuable cultures. Quality control over the air exchange rate for the life of the cultures or plants can be easily achieved by single usage. This also overcomes problems with filter contamination load over time which leads to reducing air flow rates. See below. The 'disposable' price of these filters is often small compared to the value of plants. We recommend single usage but on occasions where less valuable stock is being grown repeated autoclaving can be tried as the customers own risk and evaluated accordingly.

Q. What is filter contamination load? This is the entrapped debris, particles and microorganisms removed during the process of filtration from air or gasses passing through the filters. This increases over time and use and is a factor of the external filtration environment. An increased contamination load affects filtration efficiency, air flow and increases potential contamination risk.

Q. How many times can I use Flasking Patches? Flasking Patches are an inexpensive alternative to Adhesive Microfiltration Discs, and are more limited in their uses. Single usage is recommended. For flexible containers or in a more robust environment it is suggested that the standard AMD should be used,

Q. How can I ensure the best air filtration for my cultures? Single usage of AMD or FP ensures optimal filtration efficiencies and quality control of filtration rate.

Q. How can I stop contamination from the air supply? If you ensure your containers do not leak air or contamination and adopt AMD or FP venting, with correct autoclaving procedures, subsequent venting contamination can be eliminated by the correct use of these PTFE venting systems.

Q. Why do I need to achieve quality controlled venting? Uniform air exchange allows uniform batch growth of cultures and improves the quality control of plants. This is especially important where either rapidly growing cultures are being grown by either liquid or solid culture batch techniques. Long-term in-vitro cultures also need to optimize growth conditions to allow uniform growth. Any limiting factor will become exaggerated over time.

Q. I normally use cotton wool to vent my cultures, should I change? The principle disadvantages with using cotton wool, is possible contamination risk. Liquids can leak in both directions carrying contamination or inviting it in - even with non-absorbent cotton wool . Uneven air flow occurs between different bungs and flasks - according to how firmly the cotton wool has been plugged. Good practice requires the use of hazardous chemicals and a required 'cotton wool depth' of at least 1 inch to eliminate contaminating agents. It is often necessary to further cover the cotton wool with foils or polythene films.

Shipping in-vitro can cause problems with rapid air inflow using conventional cotton wool.

Q. I have seen disks stuck to flasks that look like discoloured medical bandaged are these PTFE? Some orchid flaskers use medical bandages to vent their flasks. These suffer from discolouration, and often need to be applied both internally and externally. They are not PTFE vents, and suffer from clogging and swelling fibers over time - leading to a drop off in efficiency of air flow and filtration. Our PTFE vents are glistening white!

Q. Will I have to drill a hole in my containers before applying an AMD or FP? You will have to drill a hole, and the diameter is critical, we can advise with orders if requested. For a clean hole in plastic we advise the use of an electric drill with metal cutting drill bit. Information sheets provided give details of the procedure.

Q. Can AMD be used with rubber bungs or Kimax rubber closure lids? Yes, we can advise, and by this means risks of moisture ingress can be eliminated and quality controlled hydrophobic venting adopted.

Q. What other uses can PTFE venting discs be put to? Our discs can be used for a variety of different uses other than in-vitro venting. There are many industries where sub-micron particle retention is required to eliminate particles from air or gas passage They can also be used to provide a route to equalize pressures. Their hydrophobic nature means they have uses with moisture sensitive equipment. The unique use of an adhesive makes these discs very versatile.

If you wish to discuss this please contact us and we are only too willing to advise if we can.

Q. Can Adhesive Microfiltration Discs be used for carbon dioxide enrichment studies? The growth of plants by photoautotrophic micropropagation and a high carbon dioxide concentration is a developing field. These provide an alternative to fragile gas-permeable films and at present are being evaluated by the leading scientists in the field at Chiba University, Japan. We await their results.

Q. Are there alternative methods than an autoclave for sterilizing the AMD or FP? Both of these discs can be sterilized using gamma radiation, a suitable ultraviolet source or ethylene oxide gas sterilant.

Q. Can I ship my cultures by air carrier without contamination? Yes, both of our types of PTFE discs provide a safe way to vent cultures for air travel, where pressure changes make it vitally important that a reliable system is used. This is especially important where using a non-rigid container or flask. Without venting such containers will distort and blow the lids off. For flexible containers we recommend the AMD to ensure the best integrity and arrival of cultures intact and aseptic integrity ensured.

Our Plant Culture Containers weigh only 19gms so provide an excellent option for international shipping and with AMD fitted have proved completely safe for transporting plants in-vitro around the world. We have no contamination losses from such transport systems. There is no need for any additional taping or sealing as the lids are snap secure.

Q. Can germplasm be stored at reduce temperature with reduced venting? Experience has shown that the AMD's can be adapted to such techniques without problems sometimes associated with dehydration of media or drying out of plant material.

Q. Can long term cultures such as orchids be safely vented for many months? Yes. PTFE venting with AMD's is an ideal approach and has many advantages compared to conventional venting. Our experience with this crop is that aseptic integrity is safe and venting for periods of 18 months can readily be achieved.

Q How many times can I autoclave PTFE discs such as the AMD or FP? We suggest single usage for optimal venting and quality control. However the AMD and FP consist of material that can be repeatedly autoclaved. PTFE, polypropylene, and the adhesive are all repeatedly autoclavable. We would not advise removing the discs between autoclaving as this will damage the integrity of the PTFE and adhesive. We would advise proceed with caution if such an approach is adopted. Some of our customers report repeated use with success.

Flasking Patches or Adhesive Microfiltration Discs? The choice between single layered PTFE and multilayered PTFE and polypropylene.

The venting system of choice for most instances should be the multilayered PTFE. For this gives the advantages of the unique air filtering action of microporous PTFE with the added strength of polypropylene mesh. AMD's are the product used by most of our customers and what we use for commercial flasking.

However single layer PTFE has been used for aseptic venting for many years in the orchid world with success, especially where no alternatives have been available.

TQPL / Brookside / Southern Lane / New Milton / Hampshire / BH257JE / United Kingdom Tel/Fax/Ans: 01425 616 608 / Int. +44 1425 616 608 / e-mail to: tq@tissuequickplantlabs.com