Polyaspartic acid is a miracle 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: 
Summary
- The chemical structure of L-aspartic acid
- Uses of L-aspartic acid in industry
- Uses of polyaspartates in industry
- What types of chemistries polyaspartates can replace (i.e., serve as an alternative to)
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, 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 polyaspartic acid sodium salt (Na, K, or ammonium).
PASP has an amide-backbone, which affords it degradability. 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).1
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).2
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
- Biocompatibility, meaning not harmful to living tissue
- 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, and in agriculture, to name a few use cases.
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
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.
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.
References
1. Adelnia Hossein, Blakey Idriss, Little Peter J., Ta Hang T. Hydrogels Based on Poly(aspartic acid): Synthesis and Applications. Frontiers in Chemistry, Vol. 7, 2019. https://www.frontiersin.org/articles/10.3389/fchem.2019.00755. DOI=10.3389/fchem.2019.00755. ISSN 2296-2646.
2. Bosso, A., Motta, S., Panero, L., Petrozziello, M., Asproudi, A., Lopez, R., & Guaita, M. (2020). Use of polyaspartates for the tartaric stabilisation of white and red wines and side effects on wine characteristics. OENO One, 54(1), 15–26. https://doi.org/10.20870/oeno-one.2020.54.1.2527
3. Xiong, B., Loss, R.D., Shields, D. et al. Polyacrylamide degradation and its implications in environmental systems. npj Clean Water 1, 17 (2018). https://doi.org/10.1038/s41545-018-0016-8
