3571

3374

كارشناسي ارشد

خاكشناسي

اصفهان: دانشگاه صنعتي اصفهان،دانشكده كشاورزي

1385

سيزده، 103، [II] ص.: جدول، نمودار

ص. ع. به فارسي و انگليسي

فرشيد نوربخش

محمود تبريزچي

23/4/86

حسين گفتارمنش، نفيسه نيلي

مهندسي كشاورزي

ID3374

به فارسي و انگليسي: قابل رويت در نسخه ديجيتال

AbstractNowadays plant residues and organic solid wastes are considered to improve soil fertility insustainable agriculture Decomposition of residues in forest floors is a necessary process intransformation of soil organic matter to humus Determination of nitrogen mineralization inorganic residues has been practiced by many workers Enzymes are central to nitrogenmineralization and turnover L asparaginase hydrolyses l asparagine to l aspartic acid andammonia and hence plays a key role in mineralization of organic nitrogen Soilmicroorganisms and plants are two main sources of soil L asparaginase Few studies havebeen conducted to evaluate enzyme activities in solid wastes and plant residues This studyaims to determine the kinetic and thermodynamic parameters of l asparaginase in differentplant residues and then to optimize the assaying method of l asparaginase activity for solidwastes and plant residues Wheat and barely residues cow manure and swage sludge oakand Leilaki litters were sampled The organic materials were air dried at room temperature passed through a 1mm sieve and kept in refrigerator The effects of pH sample weight substrate concentration incubation time and temperature were studied Lineartransformations of Michaelis Menten were used to calculate kinetic parameters Arrheniusand Eyring equations were used for determining the activation energy and enthalpy ofactivation respectively Results showed that l asparaginase activity were limited at pHvalues lower than 8 and higher than 10 The maximum activity of L asparaginase in theorganic materials was achieved at 30 to 50 mM for the different materials An increasingtrend was observed in l asparaginase activity as incubation temperature increased from 10to 40 C Our results implied that l asparaginase was denatured above 50 C The optimumassay conditions of l asparaginase activity were pH 10 0 2 g sample weight 50mm L asparagine concentration 2 hours of incubation at 37 C The maximum velocity of l asparaginase activity was ranged from 43 48 to 178 57 g NH4 N g 1 h 1 The Km values variedfrom 14 82 to 44 92mm Wheat residues showed the greatest Km value while othermaterials were not significantly different The activation energy ranged from 25 50 to 44 7and the enthalpy of activation ranged from 23 03 to 44 23 kJ mol 1 The activity of L asparaginase was determined at 7 temperature intervals between 10 to 70 C and the averageQ10 values were calculated The average values were ranged from 1 4 to 1 84 Overall themethod used in determination of l asparaginase activity in soil samples can be used inorganic residues with minor modifications Although the responses of the materials ofdifferent origin to incubation conditions were dissimilar similar responses were observedin each category including plant residues organic wastes and forest litters

فرشيد نوربخش

محمود تبريزچي

حسين گفتارمنش، نفيسه نيلي