*3.3.2.2 Degradation of pesticides by Actinobacteria*

Potential candidates for the degradation of resistant inorganic and organic contaminants are Actinobacteria. The most common pesticide-degrading Actinobacteria are *Arthrobacter*, *Streptomyces*, *Janibacter*, *Kokuria*, *Rhodococcus*, *Mycobacterium*, *Nocardia*, *Frankia*, *Pseudonocardia*, and *Mycobacterium* (**Table 6**). These bacteria are capable of growing and degrading a variety of pesticide chemical families, including carbamate (CB), organophosphorus (OP), organochlorine (OC), ureas, pyrethroids, and chloroacetanilide, among others [71]. Since members of the *Arthrobacter* genus exhibit diverse catabolic pathways for the detoxification of these substances, the majority of which are plasmid-encoded, the genus has been recognized as a degrader of several xenobiotics. Because of their dietary flexibility and resistance to environmental stress, this genus of microorganisms is found all over the world. *Arthrobacter* sp. AK-YN10 has been found to use plasmid-encoded information to degrade atrazine to cyanuric acid [105]. Endosulfan, which is based on organochlorines, is detoxified to endosulfan sulfate, which is then eliminated metabolically [102]. Atrazine is an effective nitrogen and carbon source for *Rhodococcus* sp. BCH2 [106].

*Streptomyces aureus* HP-S 01 was found to detoxify deltamethrin to 2-hydroxy-4-methoxy benzophenone and several other pyrethroids [104]. *Streptomyces* sp. M-7 has been discovered to have multi-pesticide resistance and can detoxify a variety of organochlorine pesticides such as aldrin, DDT, chlordecone (CLD), heptachlor, and dieldrin [107]. In soil microcosm assays, it may remove up to 78% gamma-HCH. *Streptomyces* sp. AC1-6 and ISP-4 can remove diazinon by up to 90%. Immobilized cells have various advantages over free suspended cells, including increased microbe retention in the reactor, improved cellular viability, and cell toxicity prevention, among other things [108]. Microbial and enzyme immobilization-mediated bioremediation procedures are more efficient, with a higher biodegradation rate [109]. Four distinct matrices were used to immobilize *Streptomyces* strains, either as pure cultures or as part of a consortium (polyvinyl alcohol, cloth sachets, silicone tubes, and agar). Immobilized microorganisms removed considerably more lindane than free cells. Additionally, the cells might be reused twice more before being discarded, lowering the overall cost of the biotechnology process [110].


#### **Table 6.**

*General characteristics of main genera of pesticide-degrading Actinobacteria.*

### *3.3.3 Bioremediation of petroleum refinery effluent*

Petroleum is a heterogenous mixture of hydrocarbons and resins which contains toluene, benzopyrene, benzene, and naphthalene. The majority of them are stable and poisonous and can cause cancer [111]. Bacteria and Actinobacteria (**Table 7**) are both excellent options for microbial oil recovery. Natural attenuation processes and biodegradation are being used to bioremediate petroleum-contaminated soil. For petroleum refinery effluent, bioaugmentation and compositing are effective remediation strategies [121]. However, because of the negative effects of the environment on microbial life, such as disintegration of cell membranes, denaturation of enzymes, poor solubility of oxygen, low solubility of hydrocarbons, and desiccation, employing Actinobacteria is limited [122]. *Pseudomonas* sp. and *Azotobacter vinelandii* are known to decompose petroleum. *Burkholderia cepacia* is capable of degrading hundreds of organic compounds. Microbial growth and activity are aided by the conversion of hydrocarbons into carbon dioxide and water, which releases energy [123]. Diesel was degraded by *Pseudomonas* sp., which removed long- and medium-chain alkanes [124]. In several treatment techniques devised by Wang et al., a microbial consortium consisting of *Actinomadura* sp., *Brevibacillus* sp., and an uncultured bacterial clone improved oil recovery for biopolymer manufacture [125].

By introducing bioemulsifiers and biosurfactants into the environment, the rate of bioremediation/biodegradation of organic contaminants improves [126]. It is dependent on the mechanism that is engaged in the interactions between microbial cells and insoluble hydrocarbons in surface-active compounds (SACs): (i) emulsification; (ii) micellarization; (iii) adhesion-deadhesion of microorganisms to and from hydrocarbons; and (iv) desorption of contaminants [126, 127]. The use of


#### **Table 7.**

*Actinobacteria capable of degrading petroleum hydrocarbon.*

*Application of Actinobacteria in Agriculture, Nanotechnology, and Bioremediation DOI: http://dx.doi.org/10.5772/intechopen.104385*

surfactants aids in the solubility of petroleum components because diesel oil biosurfactants increase oil mobility and bioavailability, hence improving biodegradation rates [128]. As a possible biosurfactant producer, *Nocardiopsis* B4 was discovered; this strain is important in the breakdown of poly-aromatic hydrocarbons (PAHs) in soils. A wide range of temperature, pH, and salt concentrations did not affect the biosurfactant activity, demonstrating its suitability for bioremediation [129].
