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| Articles
by
Samina Khalil |
Total Records (
1 ) for
Samina Khalil |
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Maliha Rashid
,
Samina Khalil
,
Najma Ayub
,
Sadia Alam
and
Farooq Latif
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After screening a large number of phosphate solubilizing microorganisms (PSM) isolated from rice
rhizosphere on the basis of solubilization index (SI) and pH drop ten best bacterial strains (10RB, 54RB, 57RB,
20RB, 21RB, 23RB, 22RB, 13RB, 20RB, 40RB) and three best fungal strains {(Aspergillus flavus(1RF),
Penicillium canescens(4RF), A. niger (8RF)}were further analyzed for their acid production ability using HPLC
technique. SI of 13 best isolates ranged from 2.16-6.23. SI and change of pH of these isolates showed abrupt
changes during seven days of incubation in Pikovskayas agar and broth medium respectively. This drop of pH
clearly indicated the production of organic acids. HPLC results confirmed that few PSM isolates produced
gluconic, fumaric, succinic, acetic and some unknown organic acids in smaller concentrations while oxalic and
citric acids in larger concentrations in their broth medium. Among bacterial strains 10RB produced largest
amount of organic acids (2.4747 g-l) while among fungal isolates Aspergillus flavus produced greatest amount
of acids (1.835 g-l) than the other two fungal strain. The concentration of glucose when analyzed during HPLC
was found less in all the cultural samples as compared to the control (13 g-l) that was without any PSM
culture. This shows that all the PSM strains utilized the carbon of glucose for the production of organic acids.
The abilities of these efficient strains for phosphorus (P) solubilization and immobilization were also
quantitatively investigated in Pikovskayas broth medium. The results showed that all the strains solubilized
(0.04-0.1%) and immobilized (0.1-0.4%) P but fungi immobilized more P than bacteria. Correlation among all the
parameters showed a positive(r = 0.2, P<0.1) correlation between the organic acid excretion and P solubilization
and a negative correlation was found between pH and P solubilization (r =-0.4, P<0.1) and immobilization
(r=-0.5, P<0.05). |
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