PLA biodegradation cocktail for 3D printing?

[Patrik D'haeseleer]

So I was soaking the print nozzle of our 3D printer in acetone to get it unclogged. Problem is, we've printed both ABS and PLA plastic with it, and I know PLA doesn't dissolve in acetone. In fact, there's very little in terms of relatively safe solvents that will dissolve PLA. Which is rather ironic, since PLA is supposed to be biodegradable and stuff.

So here's a very interesting suggestion I stumbled upon while googling for a solution, by "Kevin R" on the Ultimaker forum:

https://groups.google.com/d/msg/ultimaker/8s1bq_9LsRM/VXz40PTjJq8J
"I've actually been looking into using PLA and PCL for a product I'm going to launch in the new year, so I've been learning about the biochemistry for their decomposition because... well... I'm a nerd. The problem with PLA is that really isn't as biodegradable as one might think, but it can be none the less (which is a far cry that what ABS can claim). To make a truly safe and environmentally friendly method of removing PLA supports, you would want to use a combination of a hydrolase (either/or a lipase and protease... protease seems to be best) and a polymerase to break down the polymer. These are the enzymes that fungi and bacteria use to catalyze the decomposition of the PLA into to its base units. At best PLA isn't overly biodegradable, so using the fungi alone would take a while. You could isolate and separate the hydrolase and polymerase, disperse them in water at relatively concentrated levels and use them as a bath (in theory they should last forever if you don't denature them). The best fungi for this (and seemingly the only fungi that can completely breakdown PLA) seems to be Tritirachium album but aside from a couple of us, who around here could get their hands on that? Here's a fun fact though: the second best fungi for PLA decomposition is Penicillin roqueforti which is your friendly neighborhood bread mold! This is the same fuzzy stuff that grows on your bread if you leave it too long and is what makes blue cheese blue. If there is a biologist in our midst with some free time, they might be able to get a culture to pump out the polymerase and protease into a solution that we could dip our parts into (heated up to the right activation temperature of course). If you feed the culture gelatin you might be able to spur the secretion of the polymerase."

That sounds entirely feasible, and an enzyme cocktail to dissolve PLA plastic might even be commercializeable, given the exponential growth in 3D printing these days. Would make for a wonderful synergy between two of the hottest nerd topics of the century - DIY 3D printing and DIYbio!

Patrik

[David Reeves]

Hi Patrik,

I had that very same idea independently a few weeks ago, agree it would be fantastic, and have been working on researching alternatives, as I'm also interested in 3D printing and trained in molecular biology. I have tried some initial experiments with commercially available enzymes (e.g. proteinase K from the above-mentioned Tritirachium) and some biological detergent mixtures (see the interesting comment in the linked thread about dishwasher tablets!), but haven't seen significant degradation of 3 mm filament yet over several days. The problem with these enzymes is that while they do degrade plastic, it is usually measured over the course of weeks or months - the specific activity is usually really low. My guess is some serious mutagenesis work will be necessary to get the rate up to where it would be useful. Then there is the type of enzyme - the hydrolases and lipases have broad specificity, but have problems with solid plastic due to adsorption issues (most experiments are done with thin PLA film). Some of the more PLA-specific proteases have potential for higher rates of reaction but tend to require tailoring to a specific formulation of plastic. Recombinant production of a synthetic gene for the enzyme might yield plenty of product, but they commonly end up in the periplasmic space or in inclusion bodies in E. coli, which is annoying. Also, several mg of protein would be needed per litre of bathing solution, so we're talking fermenter-size enzyme production to get enough, so cell-free translation systems are out. Are there any diybio solutions yet for producing several mg of synthetic protein?

I haven't given up quite yet though; Stratasys already sells their 'WaveWash' system for their FDM printers which looks suspiciously like an enzyme-based solution, so I think it's possible, but the question is whether it is possible using the bulk plastic most of us currently print with at home.

Best,

Dave

Patrik

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[Nathan McCorkle]

On Thu, Aug 8, 2013 at 5:59 AM, David Reeves <drre...@gmail.com> wrote:
> Hi Patrik,
>
> I had that very same idea independently a few weeks ago, agree it would be
> fantastic, and have been working on researching alternatives, as I'm also
> interested in 3D printing and trained in molecular biology. I have tried
> some initial experiments with commercially available enzymes (e.g.
> proteinase K from the above-mentioned Tritirachium) and some biological
> detergent mixtures (see the interesting comment in the linked thread about
> dishwasher tablets!), but haven't seen significant degradation of 3 mm
> filament yet over several days. The problem with these enzymes is that while
> they do degrade plastic, it is usually measured over the course of weeks or
> months - the specific activity is usually really low. My guess is some
> serious mutagenesis work will be necessary to get the rate up to where it
> would be useful.

But then, for a lot of people, plastic's resistance to degradation is
what makes it high-value. Lignocellulolytic organisms haven't evolved
to devour a tree in a day because if they did that A) they wouldn't be
able to eat the tree all by themselves so quickly, encouraging other
organisms to thrive and B) they would liquify all the biomass so
quickly they extinguish their food supply quite quickly... unless they
had super-refined control of the enzyme synthesis or fast enzyme
response time otherwise.

In that respect, finding a better solvent or non-self-propagating
method seems more attainable than massive mutatgenesis or Genetic
Modification.

[Dakota Hamill]

I remember talking to an old chemist who worked with PLA and said they used to use NaOH to dissolve it.

http://connection.ebscohost.com/c/articles/64481403/degradation-poly-l-lactic-acid-bio-composites-by-alkaline-medium-under-various-temperatures

Quick google search shows that might be possible but I didn't read much into it.  If it is cheap enough to not have to worry about dealing with huge vats of heated NaOH or a slow degradation with an enzyme mix, seems better to just buy it.   

[Mac Davis]

I've talked to a friends who did some 3D printing, and he also said he used NaOH in water to dissolve PLA. 

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[Simon Quellen Field]

Let's hope the nozzle isn't zinc or aluminum.

:-)

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[Cathal Garvey (Phone)]

Was thinking that..is there a pH band between aluminium catalysis and PLA dissolution/degradation? And would a soft-base work rather than a mineral base?

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[Patrik D'haeseleer]

By the way, methylene chloride (aka dichhloromethane) seemed to work just fine to clear out the PLA. Can be found in Weld-on #4, the solvent of choice for welding laser-cut acrylic, so you may already have some in house. Pretty nasty stuff though - definitely not be used without good ventilation.

But then the point of this thread was *not* to find a good chemical solution to dissolve PLA, but to discuss enzymatic/DIYbio approaches...

[jarlemag]

Interesting idea. I've created a Mendeley group with a number of possibly relevant articles. Feel free to contribute: http://www.mendeley.com/groups/3571741/pla-biodegradation/

-JP

[Xabier Vázquez Campos]

PLA is usually considered degradable rather than biodegradable as the biodegradation only happens under very specific conditions. Indeed it can be degraded enzymatically and proteinase K seems to be one of the best options though it needs optimisation of the conditions. Also, the degree of crystallinity affects a lot to the potential enzymatic degradation, being very diminished when this parameter is higher than about 25%.
It also depends on the solvent used. I found some articles using enzymes in organic solvents being the best toluene at 50° C.

Regarding biodegradation s. str., it only happens (at least at good rates) under anaerobic conditions as those found in industrial composting taking up to 90 days, however, it doesn't occur in home-made composters. Degradation produces high ammounts of methane.

[jarlemag]

Thanks for the information! Seems like it might be tricky or not feasible to achieve biodegradation at a reasonable timeframe. Would you mind sharing some of your references?

Best regards,
JP

[Xabier Vázquez Campos]

Here you have. I just found the last one, and it may give you some more reliable info about biodegradation, which seems some more feasible than I said before

[jarlemag]

Thanks!

-JP