Phytase-producing bacteria (PPB) is being investigated as plant growth promoting rhizobacteria (PGPR) to improve the phosphorus (P) nutrition and growth of plants grown in soil with high phytate content. Phytate is dominant organic P forms in many soils and must be hydrolyzed to be available for plants. Indian mustard (Brassica juncea) is a plant with economic importance in agriculture and phytoremediation, therefore biotechnological tools to improve growth and environmental stress tolerance are needed. In this study, we isolated and characterized PPB from Himalayan soils and evaluated their effect on growth and P uptake by B. juncea under greenhouse conditions. Sixty five PPB were isolated and based on phytate hydrolysis, three efficient PPB were chosen and identified as Acromobacter sp. PB-01, Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13. Selected PPB showed ability to grow at wide range of pH, temperature and salt concentrations as well as to harbour diverse PGPR activities, such as: solubilization of insoluble Ca-phosphate (193-642 μg ml(-1)), production of phytohormone indole acetic acid (5-39 μg ml(-1)) and siderophore. Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13 showed 50 and 70 % inhibition of phytopathogen Rhizoctonia solani, respectively. Greenhouse potting assay also showed that the bacterization of B. juncea seeds with Tetrathiobacter sp. PB-03 and Bacillus sp. PB-13 significantly increased the biomass and P content in 30 days old seedlings. This study reveals the potential of PPB as PGPR to improve the growth of B. juncea.

Heavy metals are the intrinsic component of the environment with both essential and nonessential types. Their excessive levels pose a threat to plant growth and yield. Also, some heavy metals are toxic to plants even at very low concentrations. The present investigation (a pot experiment) was conducted to determine the affects of varying chromium(VI) levels (0.0, 0.5, 1.0, 2.0, and 4.0 mg chromium(VI) kg−1 soil in the form of potassium dichromate) on the key enzymes of nitrogen metabolism in clusterbean. Chromium treatment adversely affect nitrogenase, nitrate reductase, nitrite reductase, glutamine synthetase, and glutamate dehydrogenase in various plant organs at different growth stages as specific enzyme activity of these enzymes decreased with an increase in chromium(VI) levels from 0 to 2.0 mg chromium(VI) kg−1 soil and 4.0 mg chromium(VI) kg−1 soil was found to be lethal to clusterbean plants. In general, the enzyme activity increased with advancement of growth to reach maximum at flowering stage and thereafter decreased at grain filling stage.

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Phytic acid is the major storage form of organic phosphorus in nature- and plant-based animal feed. It forms insoluble complexes with nutritionally important metals and proteins that are unavailable for monogastric or agastric animals. Phytases initiate the stepwise hydrolysis of phytic acid and release inorganic orthophosphate. In the present investigation, the phytase gene from a phytase producing Bacillus licheniformis strain PB-13 was successfully expressed in Escherichia coli BL21. Recombinant phytase 'rPhyPB13' was found to be catalytically active, with an activity of 0.97 U/mL and specific activity of 0.77 U/mg. The rPhyPB13 was purified to 14.10-fold using affinity chromatography. Similar to other β-propeller phytases, purified rPhyPB13 exhibited maximal activity at pH 6.0-6.5 and 60 °C in the presence of 1 mM Ca(2+) and was highly active over a wider pH range (pH 4.0-8.0) and high temperature (80 °C). It has shown maximum activity towards Na-phytate as substrate. The observed K m , V max and k cat of purified rPhyPB13 were 1.064 mM, 1.32 μmol/min/mg and 27.46 s(-1), respectively. PhyPB13 was resistant to trypsin inactivation, activated in presence of Ca(2+) and inhibited in presence of EDTA. Crude rPhyPB13 has good digestion efficiency for commercial feed and soybean meal. These results indicate that PhyPB13 is a β-propeller phytase that has application potential in aquaculture feed.

Abstract. Kaur R, Saxena A, Sangwan P, Yadav AN, Kumar V, Dhaliwal HC. 2017. Production and characterization of a neutral phytase of Penicillium oxalicum EUFR-3 isolated from Himalayan region. Nusantara Bioscience 9: 68-76. Micronutrient bioavailability from cereals is poor to monogastric animals due to presence of phytate as a chelating agent in seeds and an exogenous application of phytases is required to overcome antinutritional effect of phytate. In the present investigation, 40 fungal isolates including Aspergillus, Penicillium, Trichoderma, Toliposporium, Cladosporium, Talaromyces etc. from different habitats were screened positive for phytase activity on specific media. On the basis of phytase production potential in solid state fermentation conditions, plant epiphytic fungi Penicillium oxalicum strain EUFR-3 has been observed with maximum phytase activity of 12.8 U/g. The biochemical properties i.e. activity and stability under optimum pH and temperature, and effect of modulators on phytase activity from this isolate were studied for its prospective application in human food. The P. oxalicum EUFR-3 phytase (PhyP-EUFR3) had maximum activity at pH 7.0 and temperature 40 °C. It was stable in pH range of 3-8 with more than 60 % activity throughout investigation. The thermostability of PhyP-EUFR3 was about 30 % residual activities after 10 min at 80 °C. Further purification, characterization and study of catalytic mechanism will be useful in better utilization of this phytase in human food for increased bioavailability of important metal ions.