Skimming Theory

[Mogrash]

I understand the concepts and physics behind skimming. Proteins and lipids collect at the water/air interface.

This is all fine and dandy for hydrophobic proteins that float, but what about hydrophillic proteins? I would tend to think they will not be collecting at the surface and would not be efficiently removed by skimmers. Is there something I'm missing?

 

[billsreef]

Some carbon will take care of what the skimmer doesn't

 

[barbra]

A skimmer removes that which is not water-soluble, it can't do much for things that bind with water and won't ride the surface.

 

[Mogrash]

Barbara, I know that. I'm asking how are we removing all the waste that can't be exported by skimmers. Hydrophobic waste is likely a small amout of the total waste produced as most proteins are hydrophillic.

Billsreef, how is carbon going to remove all the hydrophillic proteins that a skimmer can't remove? If that was the case the carbon should look like a cesspool. Seems more likely that these are just uptaken by algae and bacteria. If so, wouldn't that make other exports of waste besides a skimmer critical, if not more important than a skimmer? Just pondering...

 

[billsreef]

Indeed my answer was a bit too simplistic. Yes, carbon will remove some but probably not all. It will still be a significant amount and if you don't change your carbon often enough it will end up like a cesspool Water changes will remove some and also many of the biological process going on in the tank will utilize a great deal of it.

 

[Ninong]

Re: Skimming Theory

<a href=showthread.php?s=&postid=9425727#post9425727 target=_blank>Originally posted</a> by Mogrash
This is all fine and dandy for hydrophobic proteins that float, but what about hydrophillic proteins? I would tend to think they will not be collecting at the surface and would not be efficiently removed by skimmers. Is there something I'm missing?

I think what you may be missing is the fact that the proteins and other dissolved organics that can be skimmed out of the water column are bipolar molecules (hydrophillic and hydrophobic).

Shane Graber discusses this concept in detail here.

 

[Mogrash]

Ninong: No, I'm a not missing that. However, the majority of proteins in their natural conformation are not bipolar as a molecule (although all proteins contain some hydrophobic and some hydrophillic amino acids). Yes, membrane bound proteins will have a hydrophobic portion that is embedded in the lipid bilayer but those proteins would naturally be ideal candidates for the protein skimmer. The most abundant proteins are all hydrophillic, at least in their non-denatured state. Afterall, most proteins are interacting in an aqueous environment. I don't know Shane's background so I'm unsure if he has scientific data backing this up or making some assumptions from a limited background...

 

[Mogrash]

<a href=showthread.php?s=&postid=9541308#post9541308 target=_blank>Originally posted</a> by billsreef
Indeed my answer was a bit too simplistic. Yes, carbon will remove some but probably not all. It will still be a significant amount and if you don't change your carbon often enough it will end up like a cesspool Water changes will remove some and also many of the biological process going on in the tank will utilize a great deal of it.

In that case, why skim at all since potentially the majority of proteins will not be skimmed out, while lipids and other organic molecules will? Would water changes and carbon be more economical vs skimmer electricity? Or large refugiums/scrubbers?

I mean, I have noticed that if I let detritus sit in my sump for a bit my skimmer eventually starts pulling out gobs and gobs of skimmate. If I siphon out the detritus it severly cuts down the amount of gunk the skimmer is pulling out. That alone makes me wonder just how efficient these things are.

 

[Ninong]

<a href=showthread.php?s=&postid=9542155#post9542155 target=_blank>Originally posted</a> by Mogrash
I don't know Shane's background so I'm unsure if he has scientific data backing this up or making some assumptions from a limited background...

If you mean his day job, he's a chemist. He's also on the editorial staff of an online reefkeeping magazine on another reefkeeping bulletin board.

P.S. -- In his Reef Central profile, he gives his occupation as "industrial chemist."

 

[Mogrash]

Hrm. Industrial chemist. Ninong, do you know if anyone has done some actual science behind skimmers?

 

[Ninong]

<a href=showthread.php?s=&postid=9542468#post9542468 target=_blank>Originally posted</a> by Mogrash
Hrm. Industrial chemist. Ninong, do you know if anyone has done some actual science behind skimmers?

What do you mean by "actual science?" Do you mean a quantitative and qualitative analysis of the skimmate or a scientific review of the mechanics involved?

There are several hobby level articles that have been written on protein skimmers over the past decade or so. They are discussed in Delbeek & Sprung (1994, 2005) and in Fossa & Nielsen as well as several articles in the various online reefkeeping magazines.

http://www.reefkeeping.com/authors/rhf.php] Dr. Randy Holmes-Farley[/url] (V.P. Research, Genzyme, and moderator emeritus of Reef Central's Chemistry forum) has written an article on skimming.

Dr. Frank Marini (a biochemist/microbiologist), has written an article on skimming.

Several people have performed analyses of skimmate. Dr. Ron Shimek has done some work in this area and Eric Borneman, a Ph.D. candidate at the University of Houston, discusses this topic in this thread on another board.

 

[Mogrash]

I read some papers on protein separation with foam. Quite complicated stuff.
If someone is interested this is what I got out of it:
1)the water-air interface can denature some proteins
2)extent of denaturing is very variable even between hydrophillic proteins
3)low pH apparently helps the interaction
4)charge of the protein also changes separation ability

all of this is due to the sequence of amino acids and the secondary and tertiary structure of the protein.

 

[Mogrash]

<a href=showthread.php?s=&postid=9542791#post9542791 target=_blank>Originally posted</a> by Ninong
What do you mean by "actual science?" Do you mean a quantitative and qualitative analysis of the skimmate or a scientific review of the mechanics involved?

Yes to the first, maybe to the second if they provide references. Thanks for the links!

 

[Ninong]

<a href=showthread.php?s=&postid=9542822#post9542822 target=_blank>Originally posted</a> by Mogrash
Yes to the first, maybe to the second if they provide references. Thanks for the links!

I edited my post to add a couple more links.

I'm not sure if I can find links to the skimmate analyses but I'll look around a bit and see what I can find.

 

[Ninong]

OK, here you go: Skimmate analysis by Dr. Ron Shimek

 

[Mogrash]

Hrrm, Randy's article is good on how skimming works (which I understood) but a bit unclear on how much total protein/lipids is actually removed. At face value I would tend to say most proteins are not removed based on his 'hydrophobic' comment.

If you look at Eric's thread. While interesting it hasn't gone beyond the 'quick and dirty' science yet. What strikes me is the size of the particulate matter. While it could be massive protein/lipid aggregates the micron size of the stuff is way way above single cell size.

Shimek's analysis was great for chemicals, a bit weak for organic info. Especially, given how some of the key aspects are missing. It also doesn't discuss what is left in the water vs what is skimmed out-which is really the question I have.

I admit I read these articles quickly (at work!). Will try to go over this some more. Wish I had an extra skimmer-I could quite easily measure protein concentrations in water skimmed vs not skimmed.

 

[billsreef]

<a href=showthread.php?s=&postid=9543150#post9543150 target=_blank>Originally posted</a> by Mogrash
Wish I had an extra skimmer-I could quite easily measure protein concentrations in water skimmed vs not skimmed.

If you got the means to make those measurements, perhaps just simply measuring your tank water where it enters the skimmer and again where it exits, might provide some interesting data. I've got a hunch this could get quite interesting

 

[Mogrash]

Well, it wouldn't be a very controlled experiment. Need to think if it would work properly.

Assuming the saltwater itself will not interfere with the reaction it would be quite easy to do. I measure protein concentrations all the time before I do a Western Blot. I guess I need to decide how I should treat the sludge/skimmate. Do I need to lyse the samples? Sonicate them, etc... Should I prefilter it much like Eric is doing?

Speaking of protein, time to go cook some steaks! be back in a bit

 

[Mogrash]

Hrrmm...
Well measuring my tank water and skimmate wouldn't tell us what type of proteins are being removed, but it might be interesting nonetheless. At least we would know total export of proteins. Time to go clean my skimmer as I don't remember when I last cleaned it.

And why haven't you done this yet billsreef? You are a marine biologist...

 

[billsreef]

<a href=showthread.php?s=&postid=9544990#post9544990 target=_blank>Originally posted</a> by Mogrash
And why haven't you done this yet billsreef? You are a marine biologist...

Need to be a bit more of a chemist for that stuff

Besides, if I started buying up the stuff needed for that type of testing, I'd need to find a good excuse to explain it all to my boss