What distinctions do scientists make between chemicals and substrates?

[davidmich]

HI

I’m interested in the biodegradability of detergents and soaps in river, lakes and other aquatic environments. When science journals discuss the non-biodegradability of substrates in detergents and soaps what are they referring to? What are some examples of such substrates (phosphate being one I believe).How do they differ from the other chemical compounds?
I look forward to your feedback.

[Riemann]

A substrate is a chemical that’s simply being identified according to its role in a reaction. It’s the “target” chemical for an enzyme or other catalyst, a reactant (input chemical) that’s used up in an enzymatic reaction.

As for your specific example - it’s difficult when you paraphrase using the very word that you are seeking to understand. Can you give a direct quote or link to an article?

[Riemann]

@Riemann

As for your specific example - it’s difficult when you paraphrase using the very word that you are seeking to understand. Can you give a direct quote or link to an article?

And it does now occur to me that there’s a possibility that you might be encountering use of the word in one of its several other completely different senses…

Substrate

[davidmich]

@Riemann

And it does now occur to me that there’s a possibility that you might be encountering use of the word in one of its several other completely different senses…

Substrate - Wikipedia

Thanks Riemann.I believe it’s this definition"

“Substrate (biochemistry), a molecule that is acted upon by an enzyme”
Which molecular compounds are there in soaps or detergents that are non-degradable or virtually so?

[Riemann]

@davidmich

…Which molecular compounds are there in soaps or detergents that are non-degradable or virtually so?

Soap and detergent molecules have a hydrophilic part and a hydrophobic part. That’s what allows them help break up and dissolve hydrophobic oily contaminants. And it’s the hydrophobic hydrocarbon part of the molecule that matters in biodegradation. We have long known that bacteria found naturally in the environment can quite easily digest straight-chain hydrocarbons (including all soaps) but not the branched-chain hydrocarbons found in some synthetic detergents.

That’s the basic story, but perhaps there’s more to it now with additives, I don’t know.

[davidmich]

@Riemann

Soap and detergent molecules have a hydrophilic part and a hydrophobic part. That’s what allows them help break up and dissolve hydrophobic oily contaminants. And it’s the hydrophobic hydrocarbon part of the molecule that matters in biodegradation. We have long known that bacteria found naturally in the environment can quite easily digest straight-chain hydrocarbons (including all soaps) but not the branched-chain hydrocarbons found in some synthetic detergents.

That’s the basic story, but perhaps there’s more to it now with additives, I don’t know.

Thanks Riemann. That’s a very helpful start.

[Nava]

There are two different definitions being mixed.

The substrate OF the soap is the substances the soap will dissolve, the oils and other substances that stains are made of.

The substrate IN the soap is often used to refer to the inactive parts of the soap, what in other situations is called a “filler” or “excipient”.

Phosphates aren’t substrates, they are active ingredients (they react with some of the substances in stains helping them dissolve; so, they’re doing the soap’s job). But the reactive part is the phosphate group, and it can be attached to bigger or smaller parts: an inorganic phosphate is biodegradable but will cause biota problems (it’s a fertilizer, leading to overgrowth) and may be too agressive on the clothing; an organic phosphate with a long and branched carbon chain will not be biodegradable (it won’t act as a fertilizer, but it will stay around forever); an intermediate size (small, unbranched organic chain) will be biodegradable but not as good a fertilizer as the inorganic version.

[davidmich]

@Nava

There are two different definitions being mixed.

The substrate OF the soap is the substances the soap will dissolve, the oils and other substances that stains are made of.

The substrate IN the soap is often used to refer to the inactive parts of the soap, what in other situations is called a “filler” or “excipient”.

Phosphates aren’t substrates, they are active ingredients (they react with some of the substances in stains helping them dissolve; so, they’re doing the soap’s job). But the reactive part is the phosphate group, and it can be attached to bigger or smaller parts: an inorganic phosphate is biodegradable but will cause biota problems (it’s a fertilizer, leading to overgrowth) and may be too agressive on the clothing; an organic phosphate with a long and branched carbon chain will not be biodegradable (it won’t act as a fertilizer, but it will stay around forever); an intermediate size (small, unbranched organic chain) will be biodegradable but not as good a fertilizer as the inorganic version.

Thanks for clearing that up Nava. But the substrates in soaps could also be the mica, dyes, and zeolites. Correct? Are these generally non-biodegradable or are bacteria able to break them down?

[Nava]

Yes, those would be substrates in the “inert component”/“filler” meaning. Mica and zeolites are two types of minerals (mica is a complex silicate and one of the three components of granite, zeolites are mainly-aluminum silicates): they won’t biodegrade but they are also not worrisome in that they won’t affect life when they come from a soap any more than when they’re part of a chunk of rock. Dyes may or may not be biodegradable, may or may not be biologically inert.