Polyaspartic acid (PASP) is a molecule with potential across a variety of industries. Polyaspartic acid's benefits are many and, as we've outlined in previous posts, can be leveraged in so many great ways, from protecting oil and gas equipment from the harmful impacts of scale deposition to increasing plant nutrient uptake and, hence, agricultural efficiency (just to name a couple).
Even if you aren't familiar with polyaspartic acid, L-aspartic acid, the parent monomer for polyaspartic acid, is familiar with you (hint: it's one of the amino acids produced naturally in the human body). With that in mind, we'll walk you through some important things to know about this amino acid and its polymeric form.
In this article, we'll review:
L-aspartic acid background
While we will talk about polyaspartic acid (polyaspartates) and its role in various industries, let's first start by talking about it from the perspective of the human body.
L-aspartic acid is what we call a nonessential amino acid. What does that mean? It is an amino acid that is produced by the body, even if we don't get it from a food source. Aspartic acid is one of 11 nonessential amino acids the body can synthesize, which also include:
- alanine
- arginine
- asparagine
- cysteine
- glutamic acid
- glutamine
- glycine
- proline
- serine
- tyrosine
These are some of the protein building blocks — in addition to nine essential amino acids — that help lead to many of the human body's most important functions, including building muscle, repairing tissue, and generating hormones and brain chemicals.
L-Aspartic Acid and polyaspartic acid
As we mentioned elsewhere -- see our article on sustainable water treatment biopolymers -- biopolymers can be leveraged in a wide variety of industries and applications.
L-aspartic acid has a molecular formula of C4H7NO4, and could be chemically converted into polyaspartic acid.
Polyaspartic acid, commonly abbreviated as PASP, is a biodegradable, versatile polypeptide that carries useful capabilities stemming from its chemical properties. The biopolymer can, for industrial purposes, come in the form of polyaspartate salts (Na, K, or ammonium).
PASP's amide backbone is structurally analogous to the peptide bonds in proteins, which makes it susceptible to enzymatic cleavage by environmental bacteria. Specifically, Sphingomonas and Pedobacter species isolated from freshwater produce specialized poly(aspartic acid) hydrolases (PahZ enzymes) that hydrolyze the polymer down to free aspartic acid — the same amino acid the body produces (Tabata et al.).
Meanwhile, its carboxylic acid pendant groups (pendant groups are attached to a backbone chain of a molecule) grant it acidic properties and a negative charge when ionized (Adelnia et al.).
As research continues in a variety of fields, use cases for polyaspartates and other biopolymers continue to increase, particularly in light of sustainability initiatives. In addition to the aforementioned use cases, polyaspartates can be even be used as a stabilizing agent in wines, as one study showed (Bosso et al).
Polyaspartic Acid Benefits
Below are just a few benefits of polyaspartic acid:
- Biodegradability means the chemistry won't persist in the environment for an extended period of time. Per OECD 301 testing, to be deemed readily biodegradable, it must achieve at least 60% biodegradation within 30 days, which PASP and its salts meet.
- Favorable biocompatibility in many cases— PASP and its derivatives have been studied extensively for their uses in biomedical applications (Adenlia et al., 2021).
- Multifunctionality (i.e., potentially eliminate the need to hold multiple chemistries in inventory)
- Chelation of ions (e.g., calcium, magnesium) that can lead to scale deposition
- Effective in a wide range of industries and use cases
What can polyaspartic acid be an alternative to?
As a sustainable option for a wide variety of industries, polyaspartic acid naturally — no pun intended — is an alternative to other things that don't have the same sustainability bona fides.
So, what are these options? Below we'll review a few chemical treatment options for which polyaspartic acid can be a replacement and/or alternative to:
HEDP
Polyaspartic acid products can be a sustainable replacement for hydroxyethylidene diphosphonic acid, or HEDP (also known as etidronic acid). HEDP has a molecular formula of C2H8O7P2.
HEDP is traditionally used in a wide variety of capacities, including as a scale and corrosion inhibitor in cooling towers and in oilfield equipment.
Per an OECD SIDS analysis, HEDP and its salts are "not readily biodegradable in laboratory studies carried out under standard conditions."
"Although these data suggest the potential for persistence, there is, however, evidence of partial degradation by abiotic processes in natural waters, and biodegradation following acclimation, or under conditions of low inorganic phosphate," the SIDS report continues. "In the presence of commonly found metal ions possessing redox properties, such as iron and copper, metal-catalysed photodegradation can be rapid, which promotes further biodegradation."
Polyacrylamides
Polyacrylamides, often abbreviated as PAM, are typically used in the agricultural sector as soil conditioners and as a flocculant in water treatment capacities.
With respect to health-related concerns, one study of polyacrylamide degradation noted: "Although PAM is relatively nontoxic to humans, animals, fish, or plants,6,33,65,147 the acrylamide monomer can be adsorbed via dermal exposure and inhalation, and it is a known neurotoxin and a potential carcinogen148: it is immediately dangerous at concentrations of 0.06 mg/L and is lethal (LD50) at 150–200 mg/kg body weight.149,150,151 A 13-week exposure to acrylamide in drinking water at a concentration above 1 mg/kg/day leads to peripheral nerve alterations as observed under electron microscopy" (Xiong et al).3
In a regulatory view, acrylamide has been designated in Group 2A (i.e., probably carcinogenic to humans) since 1994 by the International Agency for Research on Cancer (IARC). The toxicological profile for acrylamide from the Agency for Toxic Substances and Disease Registry (ATSDR) notes that "OSHA has required employers of workers who are occupationally exposed to acrylamide to institute engineering controls and work practices to reduce and maintain employee exposure at or below permissible exposure limits (PELs)."
PBTC
PBTC, or phosphonobutane tricarboxylic acid, is often used as a corrosion and scale inhibitor in the cooling tower industry. PBTC has a molecular formula of C7H11O9P.
Another phosphonate, like HEDP, PBTC is commonly used in the cooling tower industry as a corrosion inhibitor. According to the OECD Existing Chemicals Database, PBTC is "classified as 'non biodegradable" but is photolytically degraded in water. A review of phosphonates (Nowack, 2003) notes that "No biodegradation of phosphonates during water treatment is observed ..."
Summary
L-aspartic acid is a building block for a powerful biopolymer with seemingly endless possibilities. Furthermore, the biodegradability of L-aspartic acid-based polymers, polyaspartates, makes them a more sustainable option than some of the traditional treatment chemicals (including those noted above).
Polyaspartates, like other classes of biopolymers, will have a key role to play in the ongoing sustainability movement.
Interested in learning more about Dober's biopolymer offerings? We'd be happy to chat about our products and how they can help you achieve a more sustainable — yet still effective and efficient — operation.
