Bio-based Laundry Detergents: Biotechnology Invasion into Our Day-to-Day Lives
Dr. Kaveesha J. Wijesinghe
Laundry detergents never fail to appear in the grocery lists of many households today. In around 1940’s synthetic detergents started arriving in marketplace offering more options for fabric care than the traditional bar soaps.
Laundry detergents are composed of several ingredients but the ability of laundry detergents to clean your dirty cloths lies with an ingredient called surfactants. Surfactants have unique chemical structure that allow it to interact with water as well as oil, two liquids that normally don’t mix (not miscible). The water loving structural part of these molecules are called the hydrophilic heads while the oil/lipid loving parts are called hydrophobic tails (‘hydro’ means water; ‘phobia’ means fear and ‘philia’ means affection!) (Figure 1).
The dirt stains that contain oil or grease cannot be removed by simply immersing the cloths in water as they do not dissolve in it and will remain attached to the cloths. Since surfactants have parts in their molecular structure that likes oil (the hydrophobic tails), surfactants can bind to dirt spots on the cloths using their hydrophobic parts, while the water loving hydrophilic heads will be interacting with water. If you immerse your dirty clothes in water that contain surfactants and provide mechanical agitation by scrubbing fabrics together or use a washing machine that produce swirling motions, surfactant molecules will be able to pull the dirt off from the cloths and extract them into water. Agitation cause surfactants and dirt molecules to assemble into microscopic spheres that can suspend in water. These microscopic spheres are called micelles and the hydrophilic heads of the surfactants molecules covers the outer surface of these spheres while trapping grease or oil from the stains among the oil-loving or hydrophobic tails of the surfactant molecules. Once dirt molecules are suspended in water, they can be drained off leaving you with clean cloths. (Figure 2 and 3).
The difference between bio-based laundry detergents and non-bio laundry detergents lies with the presence of one additional ingredient that is present in bio-based detergents: enzymes. Enzymes are biological catalysts that carry out nearly all chemical transformations that occur in living organisms. Enzymes are proteins themselves, encoded by genetic material of biological organisms. The role of enzymes in detergents is to breakdown chemical compounds in dirt stains which are difficult to remove with non-bio detergents. These chemical compounds can be proteins, lipids and carbohydrates. Generally, a mixture of enzymes is used in bio detergents; these include proteases that can specifically degrade protein molecules present in stains, amylases that breakdown carbohydrate-based stains, lipases that helps to degrade lipid-based stains and cellulase that can breakdown bonds among cotton fibers of the fabric to remove particulate type dirt attached to the cloths. Action of cellulases improves the softness and colour brightness of the fibric giving it a fresh appearance and this trait is often mentioned in commercial advertisements for detergents.
Including enzymes in laundry detergents have given many advantages to us. If we are using non-bio based laundry detergents, we often have to use higher temperatures to remove stains from the cloths. Also, multiple washing cycles may be needed to fully remove dirt on cloths which means the amount of detergents necessary for a single wash would be high and the water consumption will also be high. However, with enzymes, washing can be done at room temperature and at a faster rate, cutting down energy and water consumption as well as detergent usage. Further, with bio- laundry detergents, it is not necessary to use harsh washing conditions such as high alkalinity (high pH) or presence of strong oxidants. This not only makes the wash-water effluents more environmentally safe, but it also reduce damages to the fabric by strong chemicals. Thus, bio-based laundry detergents are economically cost-effective and has lesser negative impact on the environment.
From early 1930s, laundry detergent formulations started including enzymes and initially they were obtained from pancreatic extracts from slaughtered cattle or pigs. Proteases such as trypsin and chymotrypsin, carboxypeptidase, α-amylase and lipases were included in early detergents, however their stability and activity in the presence of surfactant molecules were very poor which limited their use. Further, obtaining pancreatic extracts in sufficient quantities for commercial production of enzyme containing laundry detergents was difficult. A company called NOVO was able to isolate a bacterial alkaline protease called alcalase that showed superior activity than trypsin, and it was highly stable in the presence of other ingredients used in laundry detergent formulas. Further, as this enzyme can be isolated from bacteria, which can be grown in large quantities within a small space, it became a highly cost-effective method to produce enzymes required for commercial-scale production of detergents. In 1963, alcalase was incorporated into commercial laundry detergents and it represented the first generation of industrial enzymes that were used in detergents.
Today, commercial scale production of industrially important enzymes, including enzymes used in laundry detergents are produced in genetically engineered microorganisms. Genetically engineered microorganisms carry DNA sequences that are foreign to them, and these DNA sequences encode proteins or enzymes that are useful for humans. In the case for enzymes useful for formulating laundry detergents, the genetically engineered microorganisms will encode proteases, lipases, amylases or cellulases that have desirable catalytic activities (fast activity at low temperatures) and/or stability such as being thermostable, showing resistant to detergents, oxidants and high pH levels (high alkaline-stability). These desirable catalytic activities and stability properties are achieved through protein engineering techniques that are available such as site directed mutagenesis technique where specific sites of the DNA sequence of the gene is altered to change the structure or the function of the protein.
Once microorganism encoding an enzyme with desired traits are developed, they will be grown in large fermenters with volumes ranging from 20–1,000 m3. These fermenters are supplied with nutrients derived from cheap and renewable raw material such as corn starch or sugar which makes the production very cost-effective. Most often, engineered microorganisms secrete the enzyme into fermentation medium which is then isolated to required degree of purity by an elaborate process. Isolated enzymes are then processed into liquid formulations to be used with liquid laundry detergents or if they are to be used with laundry powders then they will be processed as non-dusting granulated enzyme formulations. It is important that enzymes are formulated into a non-dusting formula as inhalation of enzymes in the form of dust or aerosol may result in an allergic response as they are foreign to the body.
The bio-based enzymes market for detergents is expected increase rapidly due to improved consumer awareness on detrimental effects of traditional all-chemical laundry detergents on the environment as well as increasing enactment of environmental regulations throughout the world. Therefore, research interests towards identifying microbial enzymes that has high catalytic activity and can function in challenging conditions such as low temperatures, oxidative or alkaline environments are likely to gain commercial interest.
Conclusion
When laundry detergents are composed entirely of chemicals, the washing process becomes less economically cost-effective and can cause significant harm to the environment. Washing process is made economical and greener by incorporating enzymes into laundry detergents that can degrade protein, oil and carbohydrate-based stains. When selecting enzymes that can be included in laundry detergents, we must pay attention to their stability in the presence of detergent molecules and oxidants, ability to with stand alkalinity and high temperature. These desired characteristics can be engineered in enzymes artificially through protein engineering. Commercial scale production of enzymes useful for laundry detergent formulations are achieved by using genetically engineered microorganisms which function as factories that produce the required enzymes.
References
- Bajpai D. Laundry detergents: a Bajpai, D. 2007 Laundry detergents: an overview. Journal of oleo science, 56(7), 327-340.
- Vojcic, L., Pitzler, C., Körfer, G., Jakob, F., Martinez, R., Maurer, K. H., & Schwaneberg, U. 2015 Advances in protease engineering for laundry detergents. New biotechnology, 32(6), 629-634.
- Hede, P. D., 2020 A beginner’s guide to enzymes in detergents. https://biosolutions.novozymes.com/en/dish/insights/article/beginners-guide-enzymes-detergents. (accessed 16 Feb 2022)
