Thread: Does BA sterilize filters?

Other than using an autoclave or pressure cooker, what is the best way to sterilize filters?

The reason I ask is that I’ve been doing tons and tons of research regarding filters (both bottle top and 47mm filtering flask types) and I’ve found that most, if not all, of the plastics that are utilized for the reservoir on top of the bottle top filters are not compatible with BA or BB or both.

So, I’ve decided to utilize my filtering flask/300ml funnel vacuum setup.

By the way, I’ve decided to use Whatman Regenerated Cellulose (RC) membranes. I tried the polypropylene-backed PTFE membranes; however, the BB melted the polypropylene backing from off the membrane (this is what led to me discovering that Bb and/or BA or not compatible with most bottle top reservoir plastics!

i did consider PVDF; however, half of the compatibility charts said PVDF was compatible with BB with other charts saying either BB is not compatible or there was no data available. Regenerated cellulose, according to all charts I seen, is comapatible with BB and BA.

So, again, how would you guys sterilize the filter discs/membranes?

From the CDC
"Alcohols are not recommended for sterilizing medical and surgical materials principally because they lack sporicidal action and they cannot penetrate protein-rich materials. Fatal postoperative wound infections with Clostridium have occurred when alcohols were used to sterilize surgical instruments contaminated with bacterial spores "
Alcohol is generally used as a disinfectant to wipe germs off a surface. Years ago if I remember right when they did use alcohol to sterilize they soaked things for 10 minutes. But that didn't always work. The BA alcohol in our solutions helps keep the germs at bay but mostly it is the filtering that does the job.

Originally Posted by balin

From the CDC
"Alcohols are not recommended for sterilizing medical and surgical materials principally because they lack sporicidal action and they cannot penetrate protein-rich materials. Fatal postoperative wound infections with Clostridium have occurred when alcohols were used to sterilize surgical instruments contaminated with bacterial spores "
Alcohol is generally used as a disinfectant to wipe germs off a surface. Years ago if I remember right when they did use alcohol to sterilize they soaked things for 10 minutes. But that didn't always work. The BA alcohol in our solutions helps keep the germs at bay but mostly it is the filtering that does the job.

well, looks like I’ll be buying an autoclave. Thanks again.

Apologies if I'm confused, but why aren't you just using disposal bottle top filters? They work perfectly well under normal filtering conditions. Just be careful with the heat of the liquid you are filtering. There's a fine line - warmer (hotter) liquid of course filters quickly. I usually brewed everything to around 200F for between 20-30 minutes, let cool til no longer steaming, but still quite warm, then filtered using disposable bottle-top filters.
Worked for years through hundreds if not thousands of filtering sessions.

Originally Posted by jackofspades

Apologies if I'm confused, but why aren't you just using disposal bottle top filters? They work perfectly well under normal filtering conditions. Just be careful with the heat of the liquid you are filtering. There's a fine line - warmer (hotter) liquid of course filters quickly. I usually brewed everything to around 200F for between 20-30 minutes, let cool til no longer steaming, but still quite warm, then filtered using disposable bottle-top filters.
Worked for years through hundreds if not thousands of filtering sessions.

Is there a particular brand of bottle top filter you would recommend?

To answer your question simply, Yes! BA will kill most everything that is of concern. Autoclaving won't even kill many of the bacterial spores mentioned because they are encapsulated in a "shell" which protects them from extreme environments, e.g. heat. In fact, mycologist will soak substrates overnight in warm water to sort of give these spores a false sense of security and many will "expose" themselves, making them susceptible to subsequent autoclaving.

Rather than buy an autoclave, try placing membranes into individual autoclave bags ( I have used simple vacuum seal/boiling bags) and vacuum sealing them. Put them in a pressure cooker for 30 minutes at 15psig.
This will "sterilize" your membranes. I have had success only with PVDF using this method as nylon tends to stick or melt into the bag.

All of the is quite pointless though if you aren't filtering and packaging under laminar flow. Baking your glass and autoclaving your filters is an exercise in futility if you them expose these depyrogentated items to open air.

In the "for-self" producing, home brew environment, I think simply placing/soaking filter membranes in BA prior to use ( I suggest nylon for cost and compatibility) and baking your glass filter rig just prior to use.
In our lab we bake all glassware in a lab oven for a minimum of one hour at 197 celsius. Much of it sits in the oven for hours and is cooled under laminar flow.
For the home brewer, try placing glassware in an oven bag and baking at 375F for 30 or more minutes. You can let cool in the oven and then open just prior to use. You can take it a step further by wiping the bags down with Iso alcohol before opening them.

I used to convert Finaplex pellets in the open kitchen air and never got sick. Makes me queasy thinking about those days but I also know most healthy people are unaffected by most of these pathogens.

Originally Posted by Enigma

To answer your question simply, Yes! BA will kill most everything that is of concern. Autoclaving won't even kill many of the bacterial spores mentioned because they are encapsulated in a "shell" which protects them from extreme environments, e.g. heat. In fact, mycologist will soak substrates overnight in warm water to sort of give these spores a false sense of security and many will "expose" themselves, making them susceptible to subsequent autoclaving.

Rather than buy an autoclave, try placing membranes into individual autoclave bags ( I have used simple vacuum seal/boiling bags) and vacuum sealing them. Put them in a pressure cooker for 30 minutes at 15psig.
This will "sterilize" your membranes. I have had success only with PVDF using this method as nylon tends to stick or melt into the bag.

All of the is quite pointless though if you aren't filtering and packaging under laminar flow. Baking your glass and autoclaving your filters is an exercise in futility if you them expose these depyrogentated items to open air.

In the "for-self" producing, home brew environment, I think simply placing/soaking filter membranes in BA prior to use ( I suggest nylon for cost and compatibility) and baking your glass filter rig just prior to use.
In our lab we bake all glassware in a lab oven for a minimum of one hour at 197 celsius. Much of it sits in the oven for hours and is cooled under laminar flow.
For the home brewer, try placing glassware in an oven bag and baking at 375F for 30 or more minutes. You can let cool in the oven and then open just prior to use. You can take it a step further by wiping the bags down with Iso alcohol before opening them.

I used to convert Finaplex pellets in the open kitchen air and never got sick. Makes me queasy thinking about those days but I also know most healthy people are unaffected by most of these pathogens.

Thank you for the very insightful post! I have studied and studied aseptic techniques. I will be using a bunsen burner while working in situations where asceptic techniques are important; I will purchase a flow hood in the very near future as well, along with an autoclave (I will also build a "clean room" in which the air is scrubbed 6 times per hour utilizing HEPA filtration.

The autoclave-bags-in-a-pressure-cooker is a great idea (I'll probably purchase Cardinal brand bags).

I also have studied and researched types of filter/membranes (over 15 hours of research--my degree is in research) and I have found that PVDF, UNLAMINATED PTFE (umlaminated meaning not backed by a polymer that does not resist the chemicals we use in AAS even though the PTFE portion will handle the solvents/esters), and Regenerated Cellulose. I purchased some 47mm 0.2 micron Whatman PTFE, polypropylene-backed membranes (can you say $500 mistake) and the Benzyl Benzoate melted the polypropylene from the filter/membrane (the filtered oil had a "clear crust" similar to that of a crust on top of lava after spewing from a volcano). After further research, PP is not compatible. So, I'll be using regenerated cellulose after extensive research (I may also give PVDF and unlaminated PTFE membranes a try).

Again, thank you for your helpful insights!

Im actually having trouble finding the right vacuum filter set up as well.

All the ones I keep finding advertised on Amazon or even on the autofil website mostly have pes filters dick don't work for gear filtration.

From the chart I saw about chemical compatibility the only filters that are compatible/ rated for both ba and BB is nylon or pvdf.

If u make any headway on this I'd love to know what worked for u and where u were able to find it.

Good luck

Sent from my SM-G965U using Tapatalk

Originally Posted by Oldskool

Im actually having trouble finding the right vacuum filter set up as well.

All the ones I keep finding advertised on Amazon or even on the autofil website mostly have pes filters dick don't work for gear filtration.

From the chart I saw about chemical compatibility the only filters that are compatible/ rated for both ba and BB is nylon or pvdf.

If u make any headway on this I'd love to know what worked for u and where u were able to find it.

Good luck

Sent from my SM-G965U using Tapatalk

I have yet to find a bottle-top filter that is totally compatible with the chemicals we use (the membranes/filters are fine in some instances, however, the plastic reservoir/funnel is the concern since these plastics are not compatible with BA and/or BB. It is my opinion, based on all of the research I’ve done, and even contacting bottle-top manufacturers, the bottle-top filters are not the way to go since these plastics will not withstand the solvents/esters. Ultimately, you’ll have small amounts of plastic in your gear.

Sure, some guys may say that since we only filter a small amount of gear through these filters that there will not be enough time for any chemical reactions/degradation of the funnel-reservoir to take place... well, I don’t want to take a chance of injecting plastic into my body, even though it may be a “small” amount of plastic.

That’s why I decided to use a 47mm 300ml glass funnel set-up (non-fritted) that uses a stainless steel mesh support screen. Oldskool I’ll get you a link to the one I use. The ones you see on amazon and eBay are not ideal, in my opinion, due to the type of funnel going into the filtering flask (most are “fritted”). Also, I remember RMEwrench stating that, if he remembered correctly, a nylon bottle-top melted on him during a filtering session. I also remember seeing a chemcial comparability chart where nylon wasn’t ideal so I eliminated it from my lineup of filters/membranes.

Originally Posted by JTH

Other than using an autoclave or pressure cooker, what is the best way to sterilize filters?

The reason I ask is that I’ve been doing tons and tons of research regarding filters (both bottle top and 47mm filtering flask types) and I’ve found that most, if not all, of the plastics that are utilized for the reservoir on top of the bottle top filters are not compatible with BA or BB or both.

So, I’ve decided to utilize my filtering flask/300ml funnel vacuum setup.

By the way, I’ve decided to use Whatman Regenerated Cellulose (RC) membranes. I tried the polypropylene-backed PTFE membranes; however, the BB melted the polypropylene backing from off the membrane (this is what led to me discovering that Bb and/or BA or not compatible with most bottle top reservoir plastics!

i did consider PVDF; however, half of the compatibility charts said PVDF was compatible with BB with other charts saying either BB is not compatible or there was no data available. Regenerated cellulose, according to all charts I seen, is comapatible with BB and BA.

So, again, how would you guys sterilize the filter discs/membranes?

BA and alcohols in general are used as disinfectants. So the filter won't get sterilized. TBH they are clean enough to be used for filtering. I've never heard of anyone having any problems. I know some people soak it in alcohol before they use it (and let it dry).

PVDF filters are compatible with BB and BA, never had any issues while using these filters. I've even used PES, those filters can usually handle a small amount of BB (if you filter it fast) without starting to break down.

My advice about those membranes is you can either sterilize them for real, I can send a small summary/Article that I've written about sterilizing equipment if you PM me. Or you just use it as is, that's what I've done.
If you decide to use the membrane discs as is, brew small batches that you'll use up in a short time.