Evaluation of N2-fixation efficiency of azotobacter in Alginate-encapsulated and free cell systems

ABSTRACT

The nitrogenase activity of alginate encapsulated and non- encapsulated cells of six Azotobacter strains was compared in liquid medium. The nitrogenase activity [expressed as n moles C2H4/hr/ml] of the non-encapsulated cells of the best strain [strain No. 6] was 85 n moles C2H4/hr/ml. However, alginate encapsulated cells tremendously increased the nitrogenase activity to 5050 n moles C2H4/hr/ml. In pots experiment, the results showed that inoculant cells introduced to wheat plants in alginate are protected from adverse soil effects over 60 days. Cell number in the rhizosphere soil of plants inoculated with encapsulated cells reached 210 x 106/g, whereas the number at the same time in plants inoculated with free cells was 79 x 106/g. Sufficient cells were able to reach and colonize wheat roots 20 days following introduction of beads. Plants inoculated with encapsulated cells had significantly higher dry weight and higher nitrogen content as compared to those inoculated with free cells