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12 Microbes and Agri-Food Waste as Novel Sources of Biosorbents

12.4

Use of Genetically Engineered Microorganisms

and Agri-Food Waste

Alteration of the genetic material of the microorganism to increase the potential of

efficient strain for the removal of metal ions is carried out through genetic engi-

neering technology. It has been proved proficient against the wide range of contam-

inants present in the environment. Their use, along with agri-food wastes, can also

be thought to a prolific option. Hpn (UniProt P0A0V6) from Helicobacter pylori has

been recognized as heavy metal adsorption protein, which has strong binding affin-

ity for Nickel (Ni) [18]. Genetically engineered Escherichia coli strains (pMt-Thio)

were proved to have increased metal biosorption ability of microbes’ biosorbents for

lead (Pb) and cadmium (Cd) ions. It was found that pMt-Thio resulted in noteworthy

improvement in biosorption ability, particularly for Pb biosorption, hence could be

recognized as a promising technique for decontaminating material from Cd and Pb

ions [14]. Deinococcus radiodurans bacteria have the potential to ingest and exploit

toluene and ionic mercury (Hg) from radioactive waste [19].

GolS, a transcriptional regulator, which belongs to MerR group, from Salmonella

regulates the functioning of two transcriptional factors that are capable of accu-

mulation of gold (Au⁺), and this GolS protein has the promising capacity to bind

Au⁺ while discriminating copper (Cu⁺) [20]. Expressing recombinant Oreochromis

mossambicus fish metallothionein (MT) in E. coli was utilized as a better biosorbent

for Hg exclusion, where cytoplasmically expressed tMT exhibited high Hg adsorp-

tion [21]. The recombinant Gram-positive merP gene (GB) and Gram-negative

merP gene (GP) biosorbents resulted in a significant increase in both adsorption

capacity and rate for the zinc (Zn²⁺) and Cr³⁺ metals. It was proved that recom-

bining metal-binding proteins on genetically engineered E. coli could be efficient

practice for producing well-developed heavy metal biosorbents [22]. The genetically

engineered bacterium Bacillus cereus BW-03 (pPW-05) has greater potential for the

biosorption of inorganic Hg [23].

Agri-food wastes are high-volume, eco-friendly, low-cost, easily applicable,

processed, and easy to recover materials that have strong affinity and selectivity

for heavy metals as biosorbents [8]. These moieties generally constitute greater

amounts of cellulose, hemicellulose, lignin, and proteins and also beneficial as

renewable natural resources and ideal for sustainable waste management [9]. Ligno-

cellulosic biomasses are a promising resource and can be employed as biosorbents

for water decontamination and can act as feedstocks to generate activated carbons

[9]. Agri-food wastes, broccoli stalks, cauliflower cores, and coconut shell wastes

are utilized as biosorbents for heavy metals [6]. Durio zibethinus rind, which is also

recognized as an agri-food waste, significantly acts as a biosorbent for the removal

of heavy metals such as Pb, Cd, Cu, Zn, and Ni [11]. Agro-wastes, for instance,

charcoal, wheat and rice straw, rice husk, and sludge are better biosorbents by

enhancing microbial biomass [9] and also offer nutrients and more exterior surface

area for their proper growth [14].

Coffee husks are practised as biosorbents for the elimination of methylene blue

dye. Therefore, this agri-food waste can be utilized as a cost-effective and easily