alkaline effluents from different industries and avoids the use of mineral acids. This
has been demonstrated by the alkaliphilic strain of Exiguobacterium which reduces
the pH of an industrial waste from 12 to 7.5 [293] and an alkaliphilic strain of
Enterococcus faecium which reduced a chlor-alkali industrial effluent pH from 12 to
7 within 3 h [294].
Alkaliphiles are also useful in managing poultry wastes, which are rich in keratin.
Due to their tough to degrade nature, keratin wastes are often disposed by chemical
and mechanical hydrolysis or by incineration to avoid their accumulation. But these
approaches are not benign to the environment. On the other hand, the use of
microbes or enzymes that degrade these wastes is desirable because of its efficiency
in solubilizing keratin at milder conditions and its ability of valorizing the keratin
waste to value-added products without any negative impact on the environment.
Keratinolytic alkaliphiles can be used effectively in managing poultry wastes and an
impressive range of publications that demonstrate this potential are available as
reviewed by [295].
5 Concluding Remarks
Alkaliphiles have come a long way in the history of biotechnology, a journey
depicted with several success stories. Indeed, today, alkaliphiles are well-established
commercial sources of alkaline active enzymes used such as in detergent, paper and
pulp, and leather and textile industries. With further studies, this application range of
alkaline active enzymes can dramatically expand and play a crucial role in the
enzyme market. To tap the great biocatalytic potential, it is imperative to expand
the exploration to the nontraditional enzymes and look for new applications. However, as it stands now, most of the studies on enzymes of alkaliphiles focus on few
hydrolases which are related to the existing established market. Moreover, the story
of alkaliphiles goes well beyond alkaline active enzymes. Several other studies have
shown the promising potential of alkaliphiles in the production of novel as well as
known biochemicals of great biotechnological importance. On the other hand, the
industrial application of all these interesting substances is still lagging behind. This
may be partly due to the unavailability of the products in the market which
discourage industrialists to try and apply it. There could be several reasons why
these products are not available in the market. One of the bottlenecks that limit the
production of the valuable substances may be the cultivation of alkaliphiles is not
well-established unlike the cultivation of the common microbes such as yeast,
Aspergillus, and Escherichia coli. Even most of the alkaline active enzymes available in the market are produced heterologously in non-alkaliphilic expression hosts.
Thus, in order to efficiently utilize the full potentials of alkaliphiles, it is necessary to
develop the cultivation system and develop few selected alkaliphiles as hosts for
heterologous expression, metagenome library construction, metabolic engineering,
and other related uses. It is delighting to see that some laboratories are moving in this
direction and interesting results from expression of proteins as well as engineering of
36
G. Mamo and B. Mattiasson
has been demonstrated by the alkaliphilic strain of Exiguobacterium which reduces
the pH of an industrial waste from 12 to 7.5 [293] and an alkaliphilic strain of
Enterococcus faecium which reduced a chlor-alkali industrial effluent pH from 12 to
7 within 3 h [294].
Alkaliphiles are also useful in managing poultry wastes, which are rich in keratin.
Due to their tough to degrade nature, keratin wastes are often disposed by chemical
and mechanical hydrolysis or by incineration to avoid their accumulation. But these
approaches are not benign to the environment. On the other hand, the use of
microbes or enzymes that degrade these wastes is desirable because of its efficiency
in solubilizing keratin at milder conditions and its ability of valorizing the keratin
waste to value-added products without any negative impact on the environment.
Keratinolytic alkaliphiles can be used effectively in managing poultry wastes and an
impressive range of publications that demonstrate this potential are available as
reviewed by [295].
5 Concluding Remarks
Alkaliphiles have come a long way in the history of biotechnology, a journey
depicted with several success stories. Indeed, today, alkaliphiles are well-established
commercial sources of alkaline active enzymes used such as in detergent, paper and
pulp, and leather and textile industries. With further studies, this application range of
alkaline active enzymes can dramatically expand and play a crucial role in the
enzyme market. To tap the great biocatalytic potential, it is imperative to expand
the exploration to the nontraditional enzymes and look for new applications. However, as it stands now, most of the studies on enzymes of alkaliphiles focus on few
hydrolases which are related to the existing established market. Moreover, the story
of alkaliphiles goes well beyond alkaline active enzymes. Several other studies have
shown the promising potential of alkaliphiles in the production of novel as well as
known biochemicals of great biotechnological importance. On the other hand, the
industrial application of all these interesting substances is still lagging behind. This
may be partly due to the unavailability of the products in the market which
discourage industrialists to try and apply it. There could be several reasons why
these products are not available in the market. One of the bottlenecks that limit the
production of the valuable substances may be the cultivation of alkaliphiles is not
well-established unlike the cultivation of the common microbes such as yeast,
Aspergillus, and Escherichia coli. Even most of the alkaline active enzymes available in the market are produced heterologously in non-alkaliphilic expression hosts.
Thus, in order to efficiently utilize the full potentials of alkaliphiles, it is necessary to
develop the cultivation system and develop few selected alkaliphiles as hosts for
heterologous expression, metagenome library construction, metabolic engineering,
and other related uses. It is delighting to see that some laboratories are moving in this
direction and interesting results from expression of proteins as well as engineering of
36
G. Mamo and B. Mattiasson