Environmental Engineering Reference
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S. cerevisiae
(Howson and Davis
1983
; Greiner
et al.
2001
),
Saccharomyces castellii
(Segueilha
et al.
1993
) and
Arxula adeninivorans
(Sano et al.
1999
). Nakamura et al. (
2000
), identified among
numerous yeast species that
Pichia spartinae
and
Pichia rhodanensis
exhibited the highest levels
of extracellular phytase with optimal tempera-
tures at 75-80 ﾰC and 70-75 ﾰC and optimum pH
at 3.6-5.5 and 4.5-5.0, respectively. The pres-
ence of intracellular phytase was also verified
in
S. cerevisiae
. In a recent work, Olstorpe et al.
(
2009
) developed a reliable, fast and easy-to-use
screening method that clarifies the ability of dif-
ferent yeast strains to utilise phytic acid as the
sole phosphorous source. After measuring the
specific phytase they established that
A. adenini-
vorans
displayed the highest intra- and extracel-
lular specific activities and that the extracellu-
lar phytase activity detected in
Pichia anomala
was strain-specific. The authors also concluded
that there were large differences in both extra-
and intracellular phytase activities amongst the
screened species. Recently yeasts present in the
gut of aquatic species have also been studied for
phytase activity. Hirimuthugoda et al. (
2007
),
isolated and identified two phytase-producing
strains,
Yarrowia lipolitica
and
Candida tropica-
lis
in the intestine of sea cucumber. These strains
produced high amounts of extracellular and cell-
bound phytase. Li et al. (
2008
) isolated a marine
yeast strain
Kodamea ohmeri
BG3 in the gut of a
marine fish that produced phytase and showed its
highest activity at pH 5.0 and temperature 65 ﾰC.
Yeasts have been reported to be a rich genetic
resource for heat-resistant phytase; however,
the possibility of applying these phytases in the
industry has not been extensively investigated
(Kaur and Satyanarayana
2009
).
cillus amylovorus
,
Escherichia coli
,
B. subtilis
,
Bacillus amyloliquefaciens
and
Klebsiella sp
.,
have been applied for phytase synthesis (Pandey
et al.
2001
). Gram-negative bacteria are known
to produce phytase intracellularly, while Gram-
positive bacteria and fungi produce it extracellu-
larly (Greiner et al.
1993
). An enzyme which lib-
erated phosphate from phytic acid was shown to
be present in culture filtrates of
B. subtilis
. This
enzyme differed from other previously known
phytases in its metal requirement and in its speci-
ficity for phytate. It required Ca
2+
specifically
for its activity (Powar and Jagannathan
1982
).
Greiner et al. (
1993
), purified two periplasmatic
phytases, named P1 and P2 from
E. coli
. The P2
enzyme was characterised as a 6-phytase based
on its hydrolysis of phytate. Sreeramulu et al.
(
1996
), identified that
L. amylovorus
could have
the potential to improve the nutritional qualities
of cereal and pulse-based food fermentations.
After the screen of a range of strains of lactic ac-
id-producing bacteria, for the synthesis of extra-
cellular phytase, they verified that
L. amylovorus
B4552 under submerged cultivation conditions
was the highest producer. The strain
Bacillus sp
.
DS11A was isolated by Kim et al. (
1998
), as a
producer of a thermostable phytase (DS11 phy-
tase), which could improve the value of some
grains, rice flour in particular. In their work,
Sajidan et al. (
2004
) showed that a
Klebsiella
sp.
strain ASR1 hydrolysed phytate. A recombi-
nant version of this enzyme was identified as a
3-phytase and was different from other general
phosphatases and phytases. These researchers
proposed the
phyK
gene product as an interesting
candidate for industrial and agricultural applica-
tions. In general, the phytases from bacteria have
a pH optimum between neutral and alkaline (Vats
and Banerjee
2004
) and have temperature optima
from 40 up to 70 ﾰC (Kim et al.
1998
; Cho et al.
2003
). According to Igbasan et al. (
2000
) within
bacterial phytases, an enzyme with high thermal
stability (
Bacillus
phytase) or high proteolytic
stability (
E. coli
phytase
)
does exist. The future
of bacterial phytases will depend on them being
developed for their favourable properties as feed
additives.
3.
Bacterial phytases
Phytases have been detected in several types of
bacteria, such as
bacilli
,
enterobacteria
, anaero-
bic ruminal bacteria and
Pseudomonas
(Jorquera
et al.
2008
; Kumar et al.
2013
). Although it was
only after 1980s that several bacterial strains
(wild or genetically modified) such as
Lactoba-
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