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4 Biosurfactants for Heavy Metal Remediation and Bioeconomics
Shalini Srivastava1, Monoj Kumar Mondal2, and Shashi Bhushan Agrawal1
1 Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India
2 Department of Chemical Engineering and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh, India
CHAPTER MENU
2 4.2 Concept of Surfactant and Biosurfactant for Heavy Metal Remediation
3 4.3 Mechanisms of Biosurfactant–Metal Interactions
4 4.4 Substrates Used for Biosurfactant Production 4.4.1 Biosurfactants of Bacterial Origin 4.4.2 Biosurfactanats of Fungal Origin
5 4.5 Classification of Biosurfactants
6 4.6 Types of Biosurfactants 4.6.1 Glycolipids 4.6.2 Rhamnolipids 4.6.3 Sophorolipids 4.6.4 Trehalolipids 4.6.5 Surfactin 4.6.6 Lipopeptides and Lipoproteins 4.6.7 Fatty Acids, Phospholipids, and Neutral Lipids 4.6.8 Polymeric Biosurfactant 4.6.9 Particulate Biosurfactants
7 4.7 Factors Influencing Biosurfactants Production 4.7.1 Environmental Factors 4.7.2 Carbon and Nitrogen Sources for Biosurfactant Production
8 4.8 Strategies for Commercial Biosurfactant Production 4.8.1 Raw Material: Low Cost from Renewable Resources 4.8.2 Production Process: Engineered for Low Capital and Operating Costs 4.8.3 Improved Bioprocess Engineering 4.8.4 Strain Improvement: Engineered for Higher Yield 4.8.5 Enzymatic Synthesis of Biosurfactants
9 4.9 Application of Biosurfactant for Heavy Metal Remediation
10 4.10 Bioeconomics of Metal Remediation Using Biosurfactants
12 References
4.1 Introduction
In the present era, irresponsible and irrational actions of innumerable industrial units such as steel manufacturing, glass manufacturing, electroplating, leather tanning, ceramics, wood preservations, and chemical processing, along with applications of huge amounts of chemical fertilizers, release too much toxic metal ions in the surrounding atmosphere and becomes a major problem for environmental pollution [1–5]. In the current scenario, a major environmental problem is the pollution of heavy metals due to their non‐degradable and bioaccumulative nature in the environment. The toxicity and bioaccumulation tendency of heavy metals in living organisms is a serious health hazard. Environmental contamination due to heavy metals has greatly increased the recommended limit by various concerned agencies [6–10]. With the chemical or biological processes, one cannot break heavy metals into non‐toxic form but can only transform them into less toxic forms [11]. Even at very low concentrations, heavy metals are toxic and also have the potential to contaminate the food chain, where they accumulate and impose damage to living organisms. The metal ion toxicity depends on the exposure quantity to the organism, the absorbed dose and its type, the route, and the duration of exposure [12]. Liver and kidney damage, certain learning disabilities, and in extreme cases even birth defects are some common ailments that have a direct connection with metal toxicity [13]. Therefore, it has become an extremely important responsibility of scientists to find an eco‐friendly approach for metal ion remediation from the environment and consequently to preserve the health of the living [14].
In this effort, numerous attempts have been made, fixing specifically on toxic metal remediation from a ruined environment [15]. Treatment of contaminated soils with water, inorganic and organic acids, chemical and metal chelating agents such as EDTA are some of the most common techniques used for metal ion remediation from soils [16]. Techniques like thermal treatment, stabilization, excavation, and hazardous waste sites transportation of contaminated soil for landfill have several fundamental drawbacks since they cannot totally remediate metals, but only restrain them in the polluted soil and also cover huge land spaces [17]. A good metal complexing agent is required that possesses the properties of solubility, environmental stability, and a good complexation potential for the efficient removal of heavy metal ions from contaminated environments [18]. Biosurfactant application in both aqueous solutions and soils for metal ion removal have gained much attention in several studies [19, 20]. Biosurfactants that are surface‐active metabolite possess metal complexing properties, reported to be effective in remediation of heavy metal contaminated sites [13]. There are several reasons to assign biosurfactants as capable substitute agents for remediation purposes [4, 21]. These reasons are their better environmental compatibility and biodegradability, less toxic nature, and most importantly utilization of inexpensive agro‐based raw materials and organic wastes for their production [22]. The biosurfactants have a specific property to retain their activity even at extreme condition of high or low temperature, pH, and salt concentration.