Naima Aziz | University of Agriculture, Faisalabad, Pakistan (original) (raw)
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Papers by Naima Aziz
Background and aims The need for efficient use of phosphorus (P) in agriculture has been highligh... more Background and aims The need for efficient use of phosphorus (P) in agriculture has been highlighted recently by concerns about the finite amount of P fertilizer resources. However, in the Taihu Lake Region (TLR) of China, farmers' injudicious and excessive use of P fertilizer has led to a dramatic spike in P accumulation. Methods A five-year (ten consecutive crop seasons) pot experiment was conducted using four paddy soils with three P concentrations (2 P-rich, 1 P-moderate, and 1 Pdeficient soils) from the TLR under four P fertilization regimes: P fertilization only for the wheat season (PW), P fertilization only for rice season (PR), P fertilization for both rice and wheat seasons (PR+W), and no P fertilization during either season (Pzero; control). Results Over 5 years, compared to the PR+W treatment, the PW treatment did not decrease crop yield (P<0.05) because it could supply enough available P sources (124-210 mg kg -1 labile P and moderately labile P) for crop growth and similar microorganism community composition. Also, compared to the Pzero treatment, applied P fertilization significantly increased the concentration of labile P and moderately labile P. Additionally, applied P fertilization decreased acid phosphatase enzyme activity and increased the total relative abundance of microorganisms significantly in P-rich soil, although they decreased in P-deficient soil. Arbuscular mycorrhizal fungi (AMF) showed significant positive correlations with soil labile P (P<0.05), which indicated that AMF played important roles in the transformation of P in the soil P pool. Conclusions P fertilizer applied only for the wheat season may be a viable option for saving P fertilizer and sustaining crop yields in the current rice-wheat rotated system of China, and effective utilization of AMF which are related to P availability in the soil will be important in the future reasearch.
Exopolysaccharides (EPS) are high molecular weight polymers which are long chain composed of suga... more Exopolysaccharides (EPS) are high molecular weight polymers which are long chain composed of sugar residues and secreted by microorganisms into the surrounding environment. Bacterial EPS as a complex mixture of macro molecular poly electrolytes including polysaccharides, proteins and nucleic acids, each comprising variable molecular mass and structural properties. Bacillus subtilis (MTCC 121) was inoculated in EPS basal and malt medium which was maintained in 72hrs at 37°C, the dry weight of the fractionated products was found to be 1.58 ± 0.13 mg/100ml and 0.82 ± 0.10 mg/100ml in basal and malt medium, respectively. From the results, it was concluded that EPS extract was higher in EPS basal medium than malt medium. The physiochemical characterization of EPS was studied and the structure was confirmed by the FT-IR, GC-MS and HPLC analysis.
The ability to produce exopolysaccharides (EPS) is widespread among lactic acid bacteria (LAB), a... more The ability to produce exopolysaccharides (EPS) is
widespread among lactic acid bacteria (LAB), although
the physiological role of these molecules has not been
clearly established yet. Some EPS confer on LAB a
“ropy” character that can be detected in cultures that
form long strands when extended with an inoculation
loop. When EPS are produced in situ during milk fermentation
they can act as natural biothickeners, giving
the product a suitable consistency, improving viscosity,
and reducing syneresis. In addition, some of these EPS
may have beneficial effects on human health. The increasing
demand by consumers of novel dairy products
requires a better understanding of the effect of EPS on
existing products and, at the same time, the search for
new EPS-producing strains with desirable properties.
The use of genetically modified organisms capable of
producing high levels of EPS or newly designed biopolymers
is still very limited. Therefore, exploration of the
biodiversity of wild LAB strains from natural ecological
environments is currently the most suitable approach
to search for the desired EPS-phenotype. The screening
of ropy strains and the isolation and characterization
of EPS responsible for this characteristic have led to
the application over the past years of a wide variety
of techniques. This review summarizes the available
information on methods and procedures used for research
on this topic. The information provided deals
with methods for screening of EPS-producing LAB, detection
of the ropy phenotype, and the physicochemical
and structural characterization of these molecules, including
parameters related to their viscosifying properties.
To our knowledge, this is the first compilation
of methods available for the study of EPS produced
by LAB.
Background and aims The need for efficient use of phosphorus (P) in agriculture has been highligh... more Background and aims The need for efficient use of phosphorus (P) in agriculture has been highlighted recently by concerns about the finite amount of P fertilizer resources. However, in the Taihu Lake Region (TLR) of China, farmers' injudicious and excessive use of P fertilizer has led to a dramatic spike in P accumulation. Methods A five-year (ten consecutive crop seasons) pot experiment was conducted using four paddy soils with three P concentrations (2 P-rich, 1 P-moderate, and 1 Pdeficient soils) from the TLR under four P fertilization regimes: P fertilization only for the wheat season (PW), P fertilization only for rice season (PR), P fertilization for both rice and wheat seasons (PR+W), and no P fertilization during either season (Pzero; control). Results Over 5 years, compared to the PR+W treatment, the PW treatment did not decrease crop yield (P<0.05) because it could supply enough available P sources (124-210 mg kg -1 labile P and moderately labile P) for crop growth and similar microorganism community composition. Also, compared to the Pzero treatment, applied P fertilization significantly increased the concentration of labile P and moderately labile P. Additionally, applied P fertilization decreased acid phosphatase enzyme activity and increased the total relative abundance of microorganisms significantly in P-rich soil, although they decreased in P-deficient soil. Arbuscular mycorrhizal fungi (AMF) showed significant positive correlations with soil labile P (P<0.05), which indicated that AMF played important roles in the transformation of P in the soil P pool. Conclusions P fertilizer applied only for the wheat season may be a viable option for saving P fertilizer and sustaining crop yields in the current rice-wheat rotated system of China, and effective utilization of AMF which are related to P availability in the soil will be important in the future reasearch.
Exopolysaccharides (EPS) are high molecular weight polymers which are long chain composed of suga... more Exopolysaccharides (EPS) are high molecular weight polymers which are long chain composed of sugar residues and secreted by microorganisms into the surrounding environment. Bacterial EPS as a complex mixture of macro molecular poly electrolytes including polysaccharides, proteins and nucleic acids, each comprising variable molecular mass and structural properties. Bacillus subtilis (MTCC 121) was inoculated in EPS basal and malt medium which was maintained in 72hrs at 37°C, the dry weight of the fractionated products was found to be 1.58 ± 0.13 mg/100ml and 0.82 ± 0.10 mg/100ml in basal and malt medium, respectively. From the results, it was concluded that EPS extract was higher in EPS basal medium than malt medium. The physiochemical characterization of EPS was studied and the structure was confirmed by the FT-IR, GC-MS and HPLC analysis.
The ability to produce exopolysaccharides (EPS) is widespread among lactic acid bacteria (LAB), a... more The ability to produce exopolysaccharides (EPS) is
widespread among lactic acid bacteria (LAB), although
the physiological role of these molecules has not been
clearly established yet. Some EPS confer on LAB a
“ropy” character that can be detected in cultures that
form long strands when extended with an inoculation
loop. When EPS are produced in situ during milk fermentation
they can act as natural biothickeners, giving
the product a suitable consistency, improving viscosity,
and reducing syneresis. In addition, some of these EPS
may have beneficial effects on human health. The increasing
demand by consumers of novel dairy products
requires a better understanding of the effect of EPS on
existing products and, at the same time, the search for
new EPS-producing strains with desirable properties.
The use of genetically modified organisms capable of
producing high levels of EPS or newly designed biopolymers
is still very limited. Therefore, exploration of the
biodiversity of wild LAB strains from natural ecological
environments is currently the most suitable approach
to search for the desired EPS-phenotype. The screening
of ropy strains and the isolation and characterization
of EPS responsible for this characteristic have led to
the application over the past years of a wide variety
of techniques. This review summarizes the available
information on methods and procedures used for research
on this topic. The information provided deals
with methods for screening of EPS-producing LAB, detection
of the ropy phenotype, and the physicochemical
and structural characterization of these molecules, including
parameters related to their viscosifying properties.
To our knowledge, this is the first compilation
of methods available for the study of EPS produced
by LAB.