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Bioremediation for Sustainable Environmental Cleanup

the proteobacteria Shewanella pneumatophori SCRC-2738, Photobacterium profundum SS9 (both

of which are manufacturers of EPA) (Allen and Bartlett 2002, Metz et al. 2001) and Moritella

marina MP-1 (which is a generator of DHA), amongst others. Both the Sorangium cellulosum

species and the Aetherobacter sp. were found to contain two pfa gene clusters, which are responsible

for the production of linoleic acid (Garcia et al. 2011, Gemperlein et al. 2014). These organisms are

sluggish, tough to control, and challenging to manipulate genetically. As a result, P. putida is utilized

as a stable host for the expression of pfa gene clusters, which ultimately leads to the creation of high

quantities of LC-PUFA (Gemperlein et al. 2014, Gemperlein et al. 2016). In order to increase the

amount of polyunsaturated fatty acids that are produced by marine species, transposon mutagenesis

was utilized (Amiri-Jami et al. 2006).

8.4.7 n-Butanol

Currently, n-butanol is produced from petroleum compounds. It is used as a precursor in the

production of polymers and paints (Cuenca et al. 2016). Microorganisms can also produce butanol

from municipal solid waste and lignocellulose materials (Ezeji et al. 2007). Butanol can be produced

at concentrations of 5mg L^–1 in P. putida S12 by the heterologous expression of the Clostridium

acetobutylicum pathway (Nielsen et al. 2009). The gene glcB encodes an enzyme in the glyoxylate

shunt. The glcB mini-Tn5 mutant is mutated to prevent butanol assimilation.

8.4.8 Para-hydroxyl Benzoic Acid (PHBA)

It is a petroleum-derived chemical that is used in the chemical industry to produce liquid crystal

polymers, as well as paraben preservatives in food, pharmaceutical and cosmetic products (Ibeh

2011). High temperatures and pressures are difficult to achieve (Yoshida and Nagasawa 2007).

Research has been done on the production of PHBA in modified strains of Saccharomyces cerevisiae

and Escherichia coli (Barker and Frost 2001), Klebsiella pneumoniae (Müller et al. 1995). The

shikimate pathway produces aromatic amino acids (tryptophan, 2phenylalanine, tyrosine), quinones,

secondary metabolites and other compounds (Karpf and Trussardi 2009, Koma et al. 2012, Gosset

2009). By adding extra versions of the shikimate pathway genes aroA (5-enolpyruvylshikimate

3-phosphate synthase), aroL (shikimate kinase), aroB (3-dehydroquinate synthase) and aroF, strain

D2704 was able to obtain a titer of 12 g L^–1 and a C-mole yield of 13% (feedback-insensitive DAHP

synthase). As P. putida is resistant to PHBA, it is used in industrial production (Krömer et al. 2013,

Ebert et al. 2011, Poblete-Castro et al. 2012). It only uses the ED pathway to produce more NADPH

in order to prevent oxidative stress via the 3-dehydrogenase function (Ng et al. 2015, Chavarría

et al. 2013). Furthermore, random nitrosoguanidine mutagenesis was used to improve the results.

Pathways that degrade PHBA and those that compete with it have been removed. ubiC was not

the only gene that was overexpressed; a feedback-resistant DAHP synthase that was encoded by

aroGD146N was also overexpressed (Ebert et al. 2011).

8.4.9 Enzyme Production

Biofuels (bioethanol, biodiesel and bio hydrocarbon) are non-renewable fossil fuel alternatives

(Koçar and Civaş 2013). However, the cost and competition with conventional petroleum limit the

use of biofuels. Bio hydrocarbons produced by bacteria, fungi, algae and other microorganisms

are concerned with various fatty-acid-derived hydrocarbons and their microbial sources (Liu and

Li 2020). Cytochrome P450cam, for example, was isolated from P. putida (Ng et al. 2015). CamC

is the gene that encodes cytochrome P450cam. This protein is overexpressed in Escherichia coli

for large-scale production and structural studies (Gunsalus and Wagner 1978, Unger et al. 1986).

Dimerization is the primary issue with the wild type P450cam. As a result, DTT was used to dissolve

the disulphide bonds. To prevent dimerization, the cystine residue was later replaced with alanine

via site-directed mutagenesis (Nickerson and Wong 1997). Strain P. putida LUA15.1 isolated from