thermophiles (Dalmaso et al. 2015). Sulfur and hydrogen serve as the source of
electron for lithotrophs. As most of the hyperthermophiles are strictly anaerobic,
organotrophic, and lithotrophic, they are able to survive in solfataric fields of
terrestrial ecosystem as well as deep reservoir of oils. Hyperthermophiles are also
adapted to survive in these places as they are neutrophilic and slightly acidophilic.
One of the archaea that has been isolated from geothermally heated sea floors is
Pyrodictium. The optimal temperature for growth of this microorganism is 105
C,
whereas the minimum and maximum temperature range is 82
C and 110
C,
respectively (DeCastro et al. 2016).
Biotopes are biotic and abiotic factors that regulate the growth of all living
organisms. Shallow submarine hydrothermal systems and abyssal hot vent systems
are also the places, where thermophiles exists. These systems are collectively known
as black smokers, and the range of temperature prevailing in these systems is about
270–380
C. The black smokers are mineral rich hot waters that make cloud of
precipitated material on mixing with seawater. The pH of the smoldering coal refuse
piles (another biotype) is acidic and has reservoirs of geothermally heated soil.
Thermophiles are isolated from these habitats too (Manoharan et al. 2015).
3.6
Thermophilic Enzymes: Potential Platform in Bioethanol
Production
At many stages, biofuel production involves elevated temperature and acidic pH.
Extremophillic microorganisms have the potential to grow in extreme conditions
with the active physiological state. It is because of these potentials that
extremophiles have replaced mesophiles that were used in conventional methods.
For instance, Thermoanaerobacterium saccharolyticum has potential to consume
xylose (pentose sugars from hemicellulose fraction of plant cell wall). Engineered
form of T. Saccharolyticum has shown great assurance in bringing forth huge
quantities of ethanol and reducing other side reactions or products (Coker 2016).
The enzymes of thermophiles are of great interest. Owing to the thermal stability
of the enzymes, hyperthermophiles are receiving special attention as the implications
of this discovery are many. In the coming years, there is a feasibility to design
enzymes, which are capable to perform at higher temperatures. These enzymes play
important role in the manufacture of methane, leaching of metals and its recovery,
and for usage in systems, where enzymes get immobilized. With the aid of latest
thermostable enzymes discovered, chemical syntheses are now possible directly in
which the compounds can be selectively and stereochemically modified. This makes
modern biological sciences a thrilling and elaborated area, where microbiologists
and biotechnologists can contribute significantly (Arora and Bell 2012). There are a
variety of hydrolases that are produced by thermophiles. Prominent among them are
lipases that degrade lipids, peptidase that degrades peptide bonds of proteins,
amylase that degrades starch, and cellulose, as previously discussed, degrades
cellulose. These enzymes, due to their immense utility, are researched extensively.
Enzymes generated from thermophiles have potential to perform in adverse
74
L. Bhatia et al.
electron for lithotrophs. As most of the hyperthermophiles are strictly anaerobic,
organotrophic, and lithotrophic, they are able to survive in solfataric fields of
terrestrial ecosystem as well as deep reservoir of oils. Hyperthermophiles are also
adapted to survive in these places as they are neutrophilic and slightly acidophilic.
One of the archaea that has been isolated from geothermally heated sea floors is
Pyrodictium. The optimal temperature for growth of this microorganism is 105
C,
whereas the minimum and maximum temperature range is 82
C and 110
C,
respectively (DeCastro et al. 2016).
Biotopes are biotic and abiotic factors that regulate the growth of all living
organisms. Shallow submarine hydrothermal systems and abyssal hot vent systems
are also the places, where thermophiles exists. These systems are collectively known
as black smokers, and the range of temperature prevailing in these systems is about
270–380
C. The black smokers are mineral rich hot waters that make cloud of
precipitated material on mixing with seawater. The pH of the smoldering coal refuse
piles (another biotype) is acidic and has reservoirs of geothermally heated soil.
Thermophiles are isolated from these habitats too (Manoharan et al. 2015).
3.6
Thermophilic Enzymes: Potential Platform in Bioethanol
Production
At many stages, biofuel production involves elevated temperature and acidic pH.
Extremophillic microorganisms have the potential to grow in extreme conditions
with the active physiological state. It is because of these potentials that
extremophiles have replaced mesophiles that were used in conventional methods.
For instance, Thermoanaerobacterium saccharolyticum has potential to consume
xylose (pentose sugars from hemicellulose fraction of plant cell wall). Engineered
form of T. Saccharolyticum has shown great assurance in bringing forth huge
quantities of ethanol and reducing other side reactions or products (Coker 2016).
The enzymes of thermophiles are of great interest. Owing to the thermal stability
of the enzymes, hyperthermophiles are receiving special attention as the implications
of this discovery are many. In the coming years, there is a feasibility to design
enzymes, which are capable to perform at higher temperatures. These enzymes play
important role in the manufacture of methane, leaching of metals and its recovery,
and for usage in systems, where enzymes get immobilized. With the aid of latest
thermostable enzymes discovered, chemical syntheses are now possible directly in
which the compounds can be selectively and stereochemically modified. This makes
modern biological sciences a thrilling and elaborated area, where microbiologists
and biotechnologists can contribute significantly (Arora and Bell 2012). There are a
variety of hydrolases that are produced by thermophiles. Prominent among them are
lipases that degrade lipids, peptidase that degrades peptide bonds of proteins,
amylase that degrades starch, and cellulose, as previously discussed, degrades
cellulose. These enzymes, due to their immense utility, are researched extensively.
Enzymes generated from thermophiles have potential to perform in adverse
74
L. Bhatia et al.