**4. Results and discussion (Removal tactics for heavy metal contamination)**

### **4.1 Nano-technological innovations**

Developing urbanization, environmental pollution leads to heavy metal contamination in water. Contaminated water is hazardous to human-beings as well as to other living organisms. Nano-technological innovations like nano-polymer composites, metal-oxides nanomaterials, non-carbon nanomaterials, such as layered double hydroxides etc. have potential application in the removal of heavy metals from contaminated water [78]. Mudzielwana et al. reported that toxic metal ions from wastewater can be removed by metal oxide nano-particles [79]. **Figure 4** shows different nano-technological innovations associated to bio-remediation of heavy metal.

Titanium oxide (TiO2) and zinc oxide (ZnO) nano-particles (NPs) are some reported semi-conductors having potential effect against heavy-metal water contamination removal [79]. It is reported earlier that, toxic heavy metal can be decontaminated from waste water with Cu, Ag and Fe-induced NPs [98, 99]. Nanobioremediation is also a low-cost method for pollution reduction in water and soil. The various application of nanotechnology for de-contamination of heavy metal are given below:

It is reported that NPs reduce the heavy metal stress in plants, heavy metals present in soil is absorbed by NPs which minimizes the bio-availability and mobility of metals [100]. For example, Sebastian et al. reported that application of Fe3O4 NPs reduce the mobility of heavy metal Cd [101]. Konate et al. and Yao et al. again reported that the antioxidant enzyme-activated NPs for e.g. CeO2 NPs, Mn3O4 NPs, Fe3O4 NPs have ability reduce ROS (Radical Oxygen Species). Therefore, helps in the reduction of crop production loss due to the stress [100, 102].

### *Monitoring Strategies for Heavy Metals in Foods and Beverages: Limitations for Human… DOI: http://dx.doi.org/10.5772/intechopen.110542*

HMs like Hg, Cd, Pb, As etc. are accumulated in crop from polluted soil and transmitted to human after consumption [98]. Nano-biosensors can detect the heavymetal phyto-toxicity [98]. Nano-biosensors with great specification for detection of heavy metals, can be applied to various areas like nutrient monitoring, agriculture fertilizers, pesticides etc.; boosts the crop yield [98].

'Biosorption' is a biologically derived method used for elimination of organic as well as inorganic matter [103, 104]. Nano-technological application with biosorption is known as "Nano-biosorbents"; recent technique for heavy metal removal. Carboxyl group (dCOOH) and hydroxyl (dOH) groups present in biosorbents facilitate absorption of heavy metal [105]. For instance, rice husk based graphene quantum dots is an effective nano- biosorbent used for La (III) and Pb (III) removal [106].

Bio-surfactants possess both lyophilic and hydrophilic activities are molecules on living spaces or secreted by microbes [98]. Microbe-induced bio-surfactants are used for remediation of heavy metals like Zn, Cu, and Ni [98]. *Bacillus subtilis* based surfactant i.e., lipopeptide bio-surfactant play a crucial role in bio-remediation of heavy metals from soil. Nanoparticle capped bio-surfactants are called nano-bio-surfactants are also useful in the bioremediation of heavy metals. For e.g. (synthesized from *Pseudomonas aeruginosa*) [105–107] with *Rhamnolipid* capped Zn NPs removal of heavy metals can be achieved [108].

### **4.2 Soil state-of-art remediation of heavy metal**

Heavy metal contamination in plant-based foods and beverages actually originated from contaminated soil. Some remediation technique of HMs from soil are: application of strong-chelating ligand [109], high-surface-area-absorbent [110, 111], phytoremediation [112] etc.

In bio-remediation by chelating-ligands the heavy metals present in functional groups of soil surface are liberated. But the consumption of high number of chelating ligands, nutrient loss from soil are some main draw-backs associated with the technique [109]. The mobility and bio-availability of heavy metals can be reduced by the of high-surface-area absorbent. This method requires long-term monitoring to capture immobilized HMs [113].

Phytoremediation of HMs is a high-energy efficient recent treatment. It requires long times for treatment with a probability of creating secondary pollution by accumulations metals in biomass [110].

### **4.3 Plant phenolic compounds for heavy metal removal**

Phenolic compounds are one of the major secondary metabolite present in plant have high tendency to chelate metals, play a crucial role in growth and development of plants [112]. Hydroxyl group (dOH) and carboxyl group (dCOOH) groups are present in phenolic compounds. Some examples of polyphenol compounds found in plants are: catechin, caffic acid, gallic acid, ferulic acid, syringic acid, sinapic acid, epicatechin, epi-gallocatechin etc. The hydroxyl and carboxyl groups present in phenolic compounds can bind with heavy metals. High nucleophilic character of atomic rings of phenolic compounds may be the reason for metal-polyphenol capping [114]. Because of heavy metal exposure; the production of phenolic compounds in plant increases [112], if the exposure happens to useful metals like Cu, Fe and Zn necessary for plant growth. On other hand Cd, Pb, As are toxic for plant's life and growth.

### **Figure 5.**

*Possible chelation by hydroxyl (*d*OH) group and carboxyl (*d*COOH) groups of plant phenolic compounds with heavy metal [115, 117].*

Radical oxygen species (ROS) formation occurs in plant, when plants are exposed to heavy metal contamination; simultaneously responsible for physiological changes in plants [115].

Plants with lower anti-oxidant activity or with lower amount polyphenols than the amount of ROS, suffers more damage [116]. Therefore, plant phenolic compounds plays protective role depending on heavy metal stress conditions as well as on environmental conditions.

The chelation of polyphenol molecule with heavy- metal is shown **Figure 5** [115].

### **4.4 Role of chemical chelating ligands in heavy metal toxicity removal**

Chelation therapy based on co-ordination chemistry is a most promising medical treatment for toxic heavy metal removal. Chelating ligands bind with toxic metals to form metal-complexes. The metal-complex so formed are being extracted by body further [118]. For instance, 2,3-dimercaprol has been used to remove Pb and As poisoning, meso-2,3-dimercaptosuccinic acid is used for extraction of metal etc. [118]. *Monitoring Strategies for Heavy Metals in Foods and Beverages: Limitations for Human… DOI: http://dx.doi.org/10.5772/intechopen.110542*

The chelating ligands under use for metal removal should be of low toxicity, higher solubility in water with good penetration ability through cell membrane [119]. Some example of clinical application of ligands in chelation are: EDTA (Ethylene Diamine Tetra Acetic acid), Trientive, D-pecicillamine, Deferiorone etc. [119]. It is reported that, arsenic based metal poisoning can be removed by chelating ligand BAL (British anti-Lewisite) and but fewer limit of toxicity was detected in 1960s due to presence of thiol group and further it was modified to DMSA (2,3- Dimercaptosuccinic acid) [119].

Thus, chelation therapy imposes the removal of heavy metal toxicity from human health in the form of metal-ligand complexes. Hence, patients are free from metal toxicity and at the same time free from heart attack, stroke, swelling and other health related issues associated with heavy metal toxicity [119].

### **4.5 Microbial culture bio-absorbents for bioremediation of heavy metal**

Bio-absorption is an efficient profitable method used for water pollution removal [120]. Micro-organisms induced bio-absorbents are used effectivity for HM removal now-a-days. But the efficacy of microbial bio-absorbent is dependent on the ambient environment, absorbing material and heavy metal to be removed etc. [120]. Bacteria, yeast, fungi, algae etc., may be used as bio-absorbents on the basis of ion-exchange ability, physical absorption, complex formation capacity, precipitation, process conditions (acidity of medium. Bio-sorbent concentration), sorption center density, immobilization techniques etc., to remove toxic metals like Hg, Pb, As, Cd in addition to precious metals Au, Ag, Pt [121, 122].

Modak et al. [123] and Vijayaraghavan et al. [124] reported that dead microbial biomass shows lots of benefits over living cells like low cost, high sorption–desorption rate, absence of nutrients etc [121, 122]. The microbial cell wall with different functional groups having varying geometry like carbonyl, hydroxide, amino, sulfate etc., plays main role for removal of heavy metals from aqueous solutions [125].

Gram-positive bacteria, gram-negative bacteria, cyanobacteria, yeast can be used as bio-sorbents and these micro-biosorbents are small in size with low density and low elasticity. For example, the immobilization of Cd (III) ions by *Bacillus subtillis*, removal of Cu (II) b *Arthobacter* Sp*.,* absorption of Pb (II) and Cu (II) by *Bacillus drentensis* MG21831T biomass was reported earlier [126].

### **5. Conclusions**

The present chapter explains about some sources of heavy metal contaminations in foods and beverages, various parameters for heavy metal toxicity measures, analytical tools for heavy metal detection and new approaches of heavy metal remediation's from food stuffs. We observed from earlier reports that, environmental pollutions (soil and water pollution) is the main reason of heavy metal contamination in plantbased foods, which transmitted to cooked foods and other processed foods and further to humans. Again, storage of beverages in metal- based utensil or processing, brewing procedure, use of contaminated water are some other potential reasons of heavy metal contamination. The permissible limits of ingestion of heavy metals associated with food stuffs should be evaluated by different methods suggested by WHO, USEPA, SON, FAO/WHO etc. The analytical methods focused in the chapter are ICP-OES, ICP-MS, AAS etc. The various bio-remediation techniques like application of nanotechnological innovations, microbial bio-absorbents, bio-surfactants are also

summarizes in the chapter. We hope, the chapter will help the researchers to get some information of heavy metal remediation, sources of heavy metal contamination in foods and beverages etc.
