keep using a carbon source only for biosurfactant synthesis and not for multiplication, thus helping to reduce the production cost.4 Precursor addition for biosurfactant production. The quality and quantity of biosurfactant polymer influenced chemical and physical parameters, and the type of carbon and nitrogen source along with their ratios in the culture media [64].
4.8.4 Strain Improvement: Engineered for Higher Yield
In a study, Kosaric et al. [65] suggested four factors to reduce the cost of biosurfactants production. The first one was the type of microbes (selected, adapted, or engineered for higher yields). The second one was the nature of reaction condition (selected, adapted, or engineered for low capital and operating costs). The third one was the growth media composition and raw material nature and the fourth one was the process byproducts (minimum or managed as saleable products rather than as waste). In order to make commercially viable biosurfactants, it is important to improve and optimize the reaction condition using bioprocess engineering along with the use of hyperproducing microbial strain. To economize the production process and to obtain products with better commercial characteristics, the availability of hyperproducer strains and recombinants is important.
4.8.5 Enzymatic Synthesis of Biosurfactants
Enhanced enzyme productivity in microbes after genetic modification for enhanced biosurfactants production has been used by scientists to improve the productivity‐to‐cost ratio. The effectiveness and efficiency of enzymes have been maximized through the use of biotechnological techniques. The specificity of microbial enzymes, their catalytic properties, and mode of action can be altered and modified into more effective forms using these techniques.
4.9 Application of Biosurfactant for Heavy Metal Remediation
In the last few decades, many studies have been conducted and published by the scientific communities on biosurfactant production and remediation application. Due to the vast variation in chemical composition, their eco‐friendly behavior, and wide range of applications in various processes, biosurfactants are utilized extensively in many sectors, including hydrophobic organic compounds and heavy metal ions remediation, enhanced oil recovery, and cosmetics and pharmaceutical sectors, etc. In the present review article, authors pay attention to the biosurfactant application for remediation of heavy metals (Table 4.3).
Table 4.3 Heavy metal removal efficiency of different biosurfactants.
| Organism | Biosurfactant type | Contaminated environment | pH | Temperature (°C) | Metals | Efficiency | References |
|---|---|---|---|---|---|---|---|
| Commercial | Rhamnolipid | Soil | 6.5 | 25 | Cu | 37 | Dahrazma and Mulligan [16] |
| Ni | 33.2 | ||||||
| zn | 7.5 | ||||||
| Torulopsis bombicola | Sophorolipid | Soil | 5.4 | — | Cu | 25 | Mulligan et al. [17] |
| Zn | 60 | ||||||
| Bacillus subtilis | Surfactin | Cu | 15 | ||||
| Zn | 6 | ||||||
| Pseudomonas aeruginosa | Rhanmolipid | Cu | 65 | ||||
| Zn | 18 | ||||||
| Candida sphaerica | Anionic | Soil/water | — | — | Fe | 95 | Luna et al. [66] |
| Zn | 90 | ||||||
| Pb | 79 | ||||||
| Bacillus subtilis | Surfactin | Soil | — | — | Cd | 15 | Mulligan et al. [67] |
| Cu | 70 | ||||||
| Zn | 25 | ||||||
| Bacillus subtilis | Lipopeptide | Soil | 9 | 25 | Cd | 44.2 | Singh and Cameotra [68] |
| Co | 35.4 | ||||||
| Cu | 26.2 | ||||||
| Ni | 32.2 | ||||||
| Pb | 40.3 | ||||||
| Zn | 32.07 | ||||||
| Bacillus circulans | Crude surfactant | Soil | — | — | Cd | 97.66 | Das et al. [69] |
| Pb | 100 | ||||||
| Candida lipolytica UCP 0988 | Lipoprotein | Soil | — | — | Cd |
