in Europe, in two-step processing. Both steps are carried out by microorganisms, and
the second step (conversion of the insoluble dye to soluble one) is carried out anaerobically at a pH > 10. Although the process has been known for several centuries,
microbiologists drew attention to it only in the 1960s of the twentieth century, but the
first indigo-reducing alkaliphile, “Bacillus alkaliphiles,” was lost [84]. The second one,
Alkalibacterium psychrotolerans, was isolated only by 2004 [85]. The fermentation
broth at the different steps and ages in the production of indigo proved to be a fertile
material for the isolation of alkaliphiles, many of which represented new genera and
species. Hydrolysates of wheat bran and composted indigo leaves (sukumo) have been
proposed to use as ingredients in the fermentation fluid in the selective medium for
isolation of new indigo-reducing bacteria [86]. Readers can find detailed information
on indigo-reducing alkaliphiles in papers published by Yumoto’s group and coworkers
[84, 87, 88].
Besides indigo production, there are other technological processes which use
alkaline chemicals and accompanied by alkaline wastewater from factories and can
potentially be habitat for alkaliphiles. A good example is an isolation of the facultatively anaerobic Exiguobacterium aurantiacum from potato-processing alkaline
effluent which is formed in course of potato peeling by lye [89]. Other alkaliphilic
species of Exiguobacterium, E. alkaliphilum, had been isolated from alkaline wastewater drainage sludge of a soft drink beverage factory located near New Delhi, India
[90]. Species of genus Exiguobacterium were found to be ubiquitous, and at the time
of writing this chapter, 16 species from various natural habitats, including Antarctica,
are known and have been described. The olive oil extraction process also has an
alkaline step. The olive mill wastewater (alpeorujo) is treated by calcium hydroxide
(pH varies from 10.5 to 13.5) to absorb undesirable odor. The first species of the
genus Alkalibacterium, A. olivoapovliticus, was isolated from such a habitat
[91]. Currently, the genus comprises ten species. A later work on the molecular
identification of strains of microorganisms isolated from the alkaline alpeorujo
revealed the presence of Alphaproteobacteria, Gammaproteobacteria, Firmicutes,
and Actinobacteria representatives, some of which form novel phylogenetic lineages
[92]. Halomonas alkalicola has recently been isolated from a soapmaking tank
(pH 9.0–10.5) of a household product plant in China [93]. The organism is noteworthy due to its high upper pH, reaching 12.5.
2.6 Microbially Mediated Alkalinization
All the above examples are related to conditions where the alkalinity of the medium
was specified either naturally or artificially. However, there is also another way of
alkalinization, the microbiological or transient alkalinization in microniches. Some
experimental approaches were demonstrated by Horikoshi [1] where growing bacteria (Bacillus sp.) spontaneously increased the pH of unbuffered broth. Similar
observation has been done on aerobic spirillum Alkalispirillum mobile [94]. However, more detailed studies on this interesting direction are required, and the
64
V. V. Kevbrin
the second step (conversion of the insoluble dye to soluble one) is carried out anaerobically at a pH > 10. Although the process has been known for several centuries,
microbiologists drew attention to it only in the 1960s of the twentieth century, but the
first indigo-reducing alkaliphile, “Bacillus alkaliphiles,” was lost [84]. The second one,
Alkalibacterium psychrotolerans, was isolated only by 2004 [85]. The fermentation
broth at the different steps and ages in the production of indigo proved to be a fertile
material for the isolation of alkaliphiles, many of which represented new genera and
species. Hydrolysates of wheat bran and composted indigo leaves (sukumo) have been
proposed to use as ingredients in the fermentation fluid in the selective medium for
isolation of new indigo-reducing bacteria [86]. Readers can find detailed information
on indigo-reducing alkaliphiles in papers published by Yumoto’s group and coworkers
[84, 87, 88].
Besides indigo production, there are other technological processes which use
alkaline chemicals and accompanied by alkaline wastewater from factories and can
potentially be habitat for alkaliphiles. A good example is an isolation of the facultatively anaerobic Exiguobacterium aurantiacum from potato-processing alkaline
effluent which is formed in course of potato peeling by lye [89]. Other alkaliphilic
species of Exiguobacterium, E. alkaliphilum, had been isolated from alkaline wastewater drainage sludge of a soft drink beverage factory located near New Delhi, India
[90]. Species of genus Exiguobacterium were found to be ubiquitous, and at the time
of writing this chapter, 16 species from various natural habitats, including Antarctica,
are known and have been described. The olive oil extraction process also has an
alkaline step. The olive mill wastewater (alpeorujo) is treated by calcium hydroxide
(pH varies from 10.5 to 13.5) to absorb undesirable odor. The first species of the
genus Alkalibacterium, A. olivoapovliticus, was isolated from such a habitat
[91]. Currently, the genus comprises ten species. A later work on the molecular
identification of strains of microorganisms isolated from the alkaline alpeorujo
revealed the presence of Alphaproteobacteria, Gammaproteobacteria, Firmicutes,
and Actinobacteria representatives, some of which form novel phylogenetic lineages
[92]. Halomonas alkalicola has recently been isolated from a soapmaking tank
(pH 9.0–10.5) of a household product plant in China [93]. The organism is noteworthy due to its high upper pH, reaching 12.5.
2.6 Microbially Mediated Alkalinization
All the above examples are related to conditions where the alkalinity of the medium
was specified either naturally or artificially. However, there is also another way of
alkalinization, the microbiological or transient alkalinization in microniches. Some
experimental approaches were demonstrated by Horikoshi [1] where growing bacteria (Bacillus sp.) spontaneously increased the pH of unbuffered broth. Similar
observation has been done on aerobic spirillum Alkalispirillum mobile [94]. However, more detailed studies on this interesting direction are required, and the
64
V. V. Kevbrin