Effect of Thermodynamic Parameters Variation on Cell Growth of Azotobacter Specie for Bio-fertilizer Applications

Abstract

The effect of changes in thermodynamic parameters on cell growth of Azotobacter specie was investigated. Isolation and confirmation of Azotobacter species was also carried out. This was done by identification of their external morphology, coupled with biochemical confirmatory tests. Central Composite Design of the Response Surface Methodology was employed in the design to investigate the influence of covariates variables (Temperature and Stir rate) on the criterion variable (cell growth). Stuart Orbital Shaker incubator was used in experimental culturing of Azotobacter microbe in line with the designed outlay that required 13 runs. In each case, temperature was altered from 290C to 370C and stir rate altered from 138rpm to 222rpm sequentially within 48hours while the cell growth determined through the viable cell count technique. Impacts of other thermodynamic parameters like pressure, enthalpy and entropy, on cell growth were equally detected. Azotobacter was revealed to have quadratic increase in growth rate from 2E+07Cfu/ml to 4E+07Cfu/ml in response to linear temperature increase from 290C to 370C, linear growth increment from 2E+07Cfu/ml to 3E+07Cfu/ml in response to linear stir rate increase from 138rpm to 222rpm and exponential growth increment from 2E+07Cfu/ml to 6E+07Cfu/ml in response to the combined factors. An improved design of culturing equipment that incorporate and make provision for the direct control of the enumerated thermodynamic parameters was then recommended.