7.7 Biotechnology in Plastic Bioremediation

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Pseudomonas putida (an oil-degrading bacterium), the first organism to be engi-

neered for novel catabolic efficiency, degrades different hydrocarbons. Pseudomonas

sp. are a metabolically diverse group of bacteria which are also active degrader of var-

ious types of the plastic polymer. An important aspect of genetic engineering is the

careful and detailed characterization of genes responsible for the production and

regulation of desired enzymes. To determine the flow of genes and genetic informa-

tion between microbial communities, ¹³C stable isotopic markers are utilized. The

13C-DNA gets stably incorporated as normal 12C-DNA and can be traced out. Once

characterized, one can genetically modify the desired microorganism for the degra-

dation of plastic waste. The technique, although it seems very simple, it comes with

various technical and ethical difficulties.

The bioremediation of plastic is mainly involved in finding and reporting of

microbial diversity and the biotransformation pathway. Deciphering metabolic

pathways and networks of host cells capable of attacking plastic is an essential step.

It will further support the engineering of whole cells and engineering enzymes

capable of plastic mineralization. The basic aim is to enhance the biocatalyst nature

of enzymes. A prominent example being the enhanced expression of cutinase from

Thermobifida cellulosilytica toward PET via site-directed mutagenesis in E. coli

BL21-Gold expression vector [37].

Various modern techniques which are now being used for genetic engineering as

follows:

1. 16S rRNA sequencing, microarray profiling, and the NextGen high-throughput

metagenome sequencing give insights about the phylogeny and expression sys-

tems.

2. The Cre/lox recombinase system can be used to manipulate gene expression lev-

els by inserting specific genes at the recognition site.

3. Zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases

(TALENs), which binds to the DNA site associated with the various catalytic

domain of enzymes, are also utilized to introduce new functions with reduced

error rates.

4. The most advanced and highly specific modern gene-editing tool is CRISPR-Cas

(clustered regularly interspaced short palindromic repeats). With this system, one

can insert programmed RNA to complementary DNA sequences and hence intro-

duce new genes at any location in the genome.

The complete understanding of genomics, proteomics, and metabolomics data

would provide an insight into the processes going on in any living system which

could be rewired to address the target. Here, computation biology comes into the

picture, which combines complex biological and engineering techniques to design

biological systems. It helps in digging out all the possible outcomes along with their

results and consequences via comparative algorithms that work at the back-end.

In silico studies, along with molecular modeling, have till now not been utilized in

the field of environmental remediation science. But the computational analysis will

prove to be the boon for research in this area and speed up the process to a greater

extent.