15
structural similarity, resulting in the depolymerization of two carbons in each cycle
(Eyheraguibel et al. 2017).
Microbial bioremediation efficiency can be enhanced by making a suitable and
competent consortium instead of using a single culture. The synergic metabolism
between each microbial strain can increase the degradation rate of the complex
substrate, and also they would contribute to the intermediary catabolic steps for
other contributing strain (Varjani et al. 2015). However, this interdependence is difficult to measure experimentally, and understanding between biogeochemistry and
metabolic processes of synthetic polymer utilization is still a void advance in the
bioremediation area (Kujawinski 2011). The integration of technical and theoretical
advances might help to clear our understanding of the microbial response and plastic mineralization mechanism (Dvořák et al. 2017).
1.5 Mechanism of Plastic Biodegradation
Recently, it had been proved that microbes have the potential to degrade complex
structures like plastics and utilize them for growth and development. The principle
of biodegradation is similar to that of other carbon-based substrates for microorganisms. Certainly, plastics act as carbon sources where microbes break their branched
carbon chain into smaller and low molecular weight monomers or oligomer derivatives, which facilitate the intake of the released compounds in the cell to enter their
carbon metabolism (Koutny et al. 2006). Wilkes and Aristilde (2017) suggested the
surface brittlement and a decrease in hydrophobicity as a result of bond breakage
due to photo-oxidation as well as CO 2 from polyethylene, when exposed to UV
radiation; however, the addition of stabilizers protects the polymers from these abiotic disruptions.
The photochemical reaction involves the Norrish cleavage type (I and II) reaction, in which free radical and peroxide formation takes place, followed by chain
cleavage and carbonyl and ester group formation (Wilkes and Aristilde 2017).
Higher ambient temperatures have increased the rate of degradation because the
activation energies for oxidative degradation are low for common plastics (Andrady
2015). The same phenomenon is also accountable for variable rates of weathering
of differently colored plastics (Bucki et al. 2018). The microbial interaction over
plastics and degradation entails a cluster of process due to its water insolubility and
high molecular size. The process starts with the surface attachment to extracellular
secretion for the chain depolymerization and fragments into smaller size, facilitating entry of the molecule inside the cell where most of the biochemical processes
occur, and carbon dioxide and water are produced as end products (Pathak and
Navneet 2017). In some cases, the extracellular enzyme acts only on the plastic
surface where the internal structure remains intact, which also limits the degradation process (Kale et al. 2015).
Microorganisms flourish in various environmental conditions where many
microbes render according to their surroundings as an outcome of adaptation.
1 Microbial Degradation of Plastics and Its Biotechnological Advancement
structural similarity, resulting in the depolymerization of two carbons in each cycle
(Eyheraguibel et al. 2017).
Microbial bioremediation efficiency can be enhanced by making a suitable and
competent consortium instead of using a single culture. The synergic metabolism
between each microbial strain can increase the degradation rate of the complex
substrate, and also they would contribute to the intermediary catabolic steps for
other contributing strain (Varjani et al. 2015). However, this interdependence is difficult to measure experimentally, and understanding between biogeochemistry and
metabolic processes of synthetic polymer utilization is still a void advance in the
bioremediation area (Kujawinski 2011). The integration of technical and theoretical
advances might help to clear our understanding of the microbial response and plastic mineralization mechanism (Dvořák et al. 2017).
1.5 Mechanism of Plastic Biodegradation
Recently, it had been proved that microbes have the potential to degrade complex
structures like plastics and utilize them for growth and development. The principle
of biodegradation is similar to that of other carbon-based substrates for microorganisms. Certainly, plastics act as carbon sources where microbes break their branched
carbon chain into smaller and low molecular weight monomers or oligomer derivatives, which facilitate the intake of the released compounds in the cell to enter their
carbon metabolism (Koutny et al. 2006). Wilkes and Aristilde (2017) suggested the
surface brittlement and a decrease in hydrophobicity as a result of bond breakage
due to photo-oxidation as well as CO 2 from polyethylene, when exposed to UV
radiation; however, the addition of stabilizers protects the polymers from these abiotic disruptions.
The photochemical reaction involves the Norrish cleavage type (I and II) reaction, in which free radical and peroxide formation takes place, followed by chain
cleavage and carbonyl and ester group formation (Wilkes and Aristilde 2017).
Higher ambient temperatures have increased the rate of degradation because the
activation energies for oxidative degradation are low for common plastics (Andrady
2015). The same phenomenon is also accountable for variable rates of weathering
of differently colored plastics (Bucki et al. 2018). The microbial interaction over
plastics and degradation entails a cluster of process due to its water insolubility and
high molecular size. The process starts with the surface attachment to extracellular
secretion for the chain depolymerization and fragments into smaller size, facilitating entry of the molecule inside the cell where most of the biochemical processes
occur, and carbon dioxide and water are produced as end products (Pathak and
Navneet 2017). In some cases, the extracellular enzyme acts only on the plastic
surface where the internal structure remains intact, which also limits the degradation process (Kale et al. 2015).
Microorganisms flourish in various environmental conditions where many
microbes render according to their surroundings as an outcome of adaptation.
1 Microbial Degradation of Plastics and Its Biotechnological Advancement