xylanase, and protease at different levels during degradation of plastic bags, while
polyhydroxyalkanoate (PHA) degrading microorganisms are known to produce
PHA depolymerases (Jendrossek et al. 1996; Jendrossek 2001).
After successful enzyme action the polymers are degraded to low weight
polymers, volatile compounds (Lwanga et al. 2018), water soluble products which
may be used as energy or carbon source (Jendrossek et al. 1996; Jendrossek 2001)
and these water soluble low weight polymers are further completely mineralized into
carbon dioxide and water (Tokiwa et al. 2009). Conversely, these polymer particles
enter the cell where they are exposed to cellular enzymes which provide further
connect with the pathways involved in its further degradation (Gewert et al. 2015).
The role of microorganisms in degradation of plastic in general and polymers in
particular is represented in Fig. 7.2.
Understanding the pathways connected with the plastic degradation and their
regulations needs to be completely evaluated in future. In this connection use of
nuclear magnetic resonance and other spectral analysis will provide more insights
into the intermediate compounds or polymers obtained during degradation process.
At present regular screening of the plastic or its associated polymer degrading
microorganisms is gaining momentum in present-day research.
Identifying a potential microbe having the ability to degrade plastics will help in
developing a natural bioremediation strategy to clean up the ecosystem in general
and agricultural soil in particular without much adverse effects on the ecological
processes (Bharadwaj et al. 2012). According to Mahdiyah and Mukti (2013),
bacteria, fungi, and actinomycetes belonging to 90 different genera were reported
to date and at present the list is increasing (Ru et al. 2020). These microbes are
generally isolated from the plastic or its polymer contaminated sites, soil dumping
areas and to have microbes for plastic degrading bacteria in agricultural fields, it
should be from rhizosphere soil (Kale et al. 2015). Presently they are observed from
different
families
including
pseudonocardiaceae,
thermonosporaceae,
micromonosporaceae, streptomycetaceae, and streptosporangiaceae. Table 7.3
POLYMERS
OLIGOMERS, DIMERS, MONOMERS
MICROBIAL BIOMASS,
CO 2 , H 2 O
MICROBIAL BIOMASS,
CH 4 , H 2 S, CO 2 , H 2 O
MICROORGANISMS
ExcreƟon of
extracellular
enzymes
Surface erosion
AssimilaƟon of
intermediates in
the cell
Intermediates
with more
solubility
AEROBIC
ANAEROBIC
Fig. 7.2 Role of microorganisms in polymer degradation
240
M. P. Raghavendra
polyhydroxyalkanoate (PHA) degrading microorganisms are known to produce
PHA depolymerases (Jendrossek et al. 1996; Jendrossek 2001).
After successful enzyme action the polymers are degraded to low weight
polymers, volatile compounds (Lwanga et al. 2018), water soluble products which
may be used as energy or carbon source (Jendrossek et al. 1996; Jendrossek 2001)
and these water soluble low weight polymers are further completely mineralized into
carbon dioxide and water (Tokiwa et al. 2009). Conversely, these polymer particles
enter the cell where they are exposed to cellular enzymes which provide further
connect with the pathways involved in its further degradation (Gewert et al. 2015).
The role of microorganisms in degradation of plastic in general and polymers in
particular is represented in Fig. 7.2.
Understanding the pathways connected with the plastic degradation and their
regulations needs to be completely evaluated in future. In this connection use of
nuclear magnetic resonance and other spectral analysis will provide more insights
into the intermediate compounds or polymers obtained during degradation process.
At present regular screening of the plastic or its associated polymer degrading
microorganisms is gaining momentum in present-day research.
Identifying a potential microbe having the ability to degrade plastics will help in
developing a natural bioremediation strategy to clean up the ecosystem in general
and agricultural soil in particular without much adverse effects on the ecological
processes (Bharadwaj et al. 2012). According to Mahdiyah and Mukti (2013),
bacteria, fungi, and actinomycetes belonging to 90 different genera were reported
to date and at present the list is increasing (Ru et al. 2020). These microbes are
generally isolated from the plastic or its polymer contaminated sites, soil dumping
areas and to have microbes for plastic degrading bacteria in agricultural fields, it
should be from rhizosphere soil (Kale et al. 2015). Presently they are observed from
different
families
including
pseudonocardiaceae,
thermonosporaceae,
micromonosporaceae, streptomycetaceae, and streptosporangiaceae. Table 7.3
POLYMERS
OLIGOMERS, DIMERS, MONOMERS
MICROBIAL BIOMASS,
CO 2 , H 2 O
MICROBIAL BIOMASS,
CH 4 , H 2 S, CO 2 , H 2 O
MICROORGANISMS
ExcreƟon of
extracellular
enzymes
Surface erosion
AssimilaƟon of
intermediates in
the cell
Intermediates
with more
solubility
AEROBIC
ANAEROBIC
Fig. 7.2 Role of microorganisms in polymer degradation
240
M. P. Raghavendra