which can react with carbonyl groups. Sulfur compounds are sensitive to oxidation
and to other reactions at high pH. Sugar rings can open, decompose, and react with
amino compounds. Nucleic acids are unstable and hydrolyze in alkali. Racemization
of many compounds occurs in alkali, especially in the presence of metal ions. The
very basic thing: the stability of nutrients in alkaline environment has been widely
neglected. The same stability problem exists for products that are secreted by
alkaliphile.
At least few people working in microbiology laboratory have inadvertently
autoclaved medium adjusted to the final pH of the growth medium (around
pH 10–11) and found that the alkaliphiles do not grow after inoculation. This
shows that fatal chemical reactions have occurred in the nutrient medium by the
combination of alkali and heat. This may be partly due to difficulty in transporting
chemically altered nutrients such as amino acids, sugars, and other nutrients (e.g.,
vitamins) from the medium to cells through specific cellular channel ports. Since
growth at high pH reduces contamination, it has been considered as an advantage
which avoids sterilization. However, it works only rarely. There are still enough
microbial species that can grow alkaline niche that challenges this biotechnological
advantage.
The adaptation of alkaliphilic microbes to live in alkaline conditions is extensively reviewed in this book and elsewhere. The secreted enzymes of alkaliphiles
have found a significant role in biotechnology, and there are a large number of
patented discoveries/inventions related to alkaliphilic proteins, genes coding them,
as well as to various methods using those enzymes. Small-molecule primary and
secondary metabolites are also of interests because the alkaline adaptation may have
demanded to develop special metabolic pathways and adaptations to operate in
alkaline condition including protection of the cells. A competition between
alkaliphilic microbial species exists which necessitates production of a set of antibiotics against competitors. Alkaliphiles may even produce substances which are
anti-bacteriophages and other viruses. Alkaliphiles are potential sources of new
metabolites which may not be found in microbes growing in acidic and neutral
environments. Certainly, this potential has not been fully explored yet. Some usual
metabolites are advantageously produced by alkaline fermentation. Environmental
technologies, e.g., bioremediation, can exploit the capability of alkaliphiles to
metabolize harmful substances in alkaline conditions.
The present discussion aims at compounds and processes related to metabolites
from alkaliphiles which are, or may become, of biotechnological interest. It is
attempted to answer what metabolites are unique to alkaliphiles. General aspects
of the central metabolism of alkaliphiles are examined first. Specific fields which
may have future applications in industrial scale are dealt with. The field of the
potential applications is wide; therefore, it is focused to those which are putatively
the most potential. It is recommended to see further details from other chapters of
this book and from cited reviews.
160
E. Khalikova et al.
and to other reactions at high pH. Sugar rings can open, decompose, and react with
amino compounds. Nucleic acids are unstable and hydrolyze in alkali. Racemization
of many compounds occurs in alkali, especially in the presence of metal ions. The
very basic thing: the stability of nutrients in alkaline environment has been widely
neglected. The same stability problem exists for products that are secreted by
alkaliphile.
At least few people working in microbiology laboratory have inadvertently
autoclaved medium adjusted to the final pH of the growth medium (around
pH 10–11) and found that the alkaliphiles do not grow after inoculation. This
shows that fatal chemical reactions have occurred in the nutrient medium by the
combination of alkali and heat. This may be partly due to difficulty in transporting
chemically altered nutrients such as amino acids, sugars, and other nutrients (e.g.,
vitamins) from the medium to cells through specific cellular channel ports. Since
growth at high pH reduces contamination, it has been considered as an advantage
which avoids sterilization. However, it works only rarely. There are still enough
microbial species that can grow alkaline niche that challenges this biotechnological
advantage.
The adaptation of alkaliphilic microbes to live in alkaline conditions is extensively reviewed in this book and elsewhere. The secreted enzymes of alkaliphiles
have found a significant role in biotechnology, and there are a large number of
patented discoveries/inventions related to alkaliphilic proteins, genes coding them,
as well as to various methods using those enzymes. Small-molecule primary and
secondary metabolites are also of interests because the alkaline adaptation may have
demanded to develop special metabolic pathways and adaptations to operate in
alkaline condition including protection of the cells. A competition between
alkaliphilic microbial species exists which necessitates production of a set of antibiotics against competitors. Alkaliphiles may even produce substances which are
anti-bacteriophages and other viruses. Alkaliphiles are potential sources of new
metabolites which may not be found in microbes growing in acidic and neutral
environments. Certainly, this potential has not been fully explored yet. Some usual
metabolites are advantageously produced by alkaline fermentation. Environmental
technologies, e.g., bioremediation, can exploit the capability of alkaliphiles to
metabolize harmful substances in alkaline conditions.
The present discussion aims at compounds and processes related to metabolites
from alkaliphiles which are, or may become, of biotechnological interest. It is
attempted to answer what metabolites are unique to alkaliphiles. General aspects
of the central metabolism of alkaliphiles are examined first. Specific fields which
may have future applications in industrial scale are dealt with. The field of the
potential applications is wide; therefore, it is focused to those which are putatively
the most potential. It is recommended to see further details from other chapters of
this book and from cited reviews.
160
E. Khalikova et al.