Although biological surfactants have been used thousands of years before the invention of chemical surfactants, nowadays the chemical analogs are more widespread because are thought to be cheaper. Chemical surfactant usage has been growing quickly in the last several decades. In 1970, the worldwide production of surfactants was 10 million tons, reaching 40 million tons in 2000 and 5 billion tons in 2018.
About 60% of surfactants are used as detergents and compounds for personal care products. Additionally, surfactants are used in almost every other human activity and product. Some other applications include pharmaceutical and supplements, oil and gas, agriculture, personal care and cosmetics, coatings and paintings, textile, food, construction and more.
However, there are many concerns regarding the usage of chemical surfactants that led scientists, manufacturers and policymakers to the need for natural surfactants, such as biosurfactants, which can be produced in equally large amounts and at a low price.
These concerns include:
Environmental Impact
- After use, residual surfactants are discharged into sewage systems or into surface waters. As a result, some of them are dispersed into soil, water or sediment. When present in high concentrations in water, surfactants may damage plants and animals.
- Small concentrations, although not causing death, were demonstrated to have a toxic effect on fish. Cyprinus carpio, after exposure to surfactant at concentration 0.01 mg/L, moved 5 times slower and consumed 2.8 times more oxygen (Barbiery et al., 1998).
- Apart from acute toxicity, some surfactants, due to their chemical structure, have the ability to bind to biomolecules such as proteins, peptides, and DNA (Bhattacharya and Mandal, 1997).
- The production of surfactants contributes to global warming because the waste products contain significant amounts of NOx, CO2, SO2, hydrocarbons, waterborne wastes and solid wastes (Pittinger et al., 1993).
- A concentration of the surfactants higher than 0.1 mg/L causes foam formation, preventing the dissolving of oxygen in water; leading to organisms’ death (Yuan et al., 2014).
Human Toxicity:
- When a contaminated aquatic animal is eaten by a human, enzyme production in the human is disrupted, weakening human’s immune system (Yuan et al., 2014).
- Perfluorinated surfactants are found in drinking water and the concentrations do not differ significantly from the concentration of these surfactants in the surface water (Exner and Farber, 2006).
- Although the concentrations observed in drinking water were not acutely toxic, the perfluorinated surfactants, as well as sodium dodecylbenzene sulfonate (SDBS), have an ability to accumulate in human tissues such as liver and blood, causing accumulative carcinogenic and reproductive interference effects (Exner and Farber, 2006).
- Long-term use of detergents and cleaning products containing surfactants may cause skin irritation and increase the risk of atopic dermatitis, psoriasis and eczema in individuals with sensitive skin (Cowley and Farr, 1992; Draelos et al., 2013; Yuan et al., 2010).
- Some cationic surfactants, which are second most used surfactants, damage human lymphocytes and lyse human cells in concentrations even below the CMC (Antoni and Szabo, 1982; Partearroyo et al.,1990).
Statistical analyses of surfactant concentrations in the environment reveal that they are found in concentrations higher than their predicted, no-effect concentrations. As was concluded in the analytical report on the global market of chemical surfactants, the market’s growth is predicted to slow due to several factors affecting the massive application: volatility in raw material prices, regulations on environmental issues, pollution control laws, the toxic nature of surfactants and an increased demand for “green” products.
As disagreements regarding the safety of other commonly-used surfactants continue, it is expected that additional surfactants will be revealed to be highly toxic and, consequently, banned.
It was suggested that all these trends lead to the increased demand for bio-based surfactants, which are going to replace chemical surfactants.
Because biosurfactants are naturally-ocurring, they are safe, favorable to the environment and allow the use of claims including “green” and “organic” for products, making them a valuable substitute for chemical surfactants. Biosurfactants were shown to be more effective than chemical surfactants and due to lower CMC are more economically beneficial.