Present study was designed to evaluate the relative efficacy of 1-amino cyclopropane-1-carboxylic acid (ACC), 2-Keto-4-methyl thiobutyric acid (KMBA) and Î±-keto glutaric acid (KGA) for the microbial production of ethylene (C2H4) in two Pakistani soils. Effects of various amendments (Glucose, NH4NO3 antibiotics, etc.) and incubation conditions (pH, incubation temperature, incubation time, aeration, etc.) on the substrate-dependent C2H4 production in soil was determined. Moreover, effect of trace elements, viz, Ag (I), Fe(II), Fe(III), Ni(II), Zn(II), A1(III) Co(II), antibiotics (streptomycin, cycloheximide, penicillin G, chloroampthenicol) and electron complexes like, EDTA, sodium benzoate, hydroquinone, mannitol and uric acid on substrate-dependent C2H4 soil was also recorded. Kinetics and thermodynamics of the substrate dependent C2H4 biosynthesis in soil were calculated.
Results revealed that ACC and KMBA enhanced C2H4 production in both organic matter rich (S1) and organic matter poor(S2) soils while KGA was unable to induce C2H4 synthesis in any of the two soils. Addition of glucose or NH4NO3 strongly inhibited substrate-dependent C2H4 biosynthesis. All the trace elements added except Fe(III) stimulated ACC or KMBA-dependent C2H4 Production while all the antibiotics caused inhibition. Except 1mM of mannitol and hydroquinone, all other concentrations of various electron complexes strongly inhibited C2H4 synthesis.
Taking into consideration various incubation conditions, 35oC incubation temperature, pH 7.6 incubation time 120 hours and shaking was found to be optimum for substrate-dependent C2H4 production in soil. Comparison of the two soils revealed that more C2H4 was produced in S1as compared to S2 under all sets of conditions. Kinetics of the data revealed that the reaction is first order in S1 did not follow any order in S2. Thermodynamic calculations indicated that ACC-and KMBA-dependent C2H4 producing reaction was catalyzed by ethylene forming enzyme(EFE).