Determination amount and percentage of biologically atmospheric nitrogen fixing by local blue green algae isolates

J.I. Al- Shahrii, Yousef

	Determination amount and percentage of biologically atmospheric nitrogen fixing by local blue green algae isolates
Tikrit Journal of Pure Science
Article 1, Volume 19, Issue 6, 2014, Pages 26-39
Author
Yousef J.I. Al- Shahrii
Abstract
Abstract In present work, specific method was utilized for determining biologically atmospheric nitrogen fixing which includes three steps: digestion, distillation and titration. Nitrogen fixing was determined in seven species of local blue green algae isolates (in Mosul city), these species (Nostoc muscorum, Anabaena helicoidea, Arthrospira platensis, Lyngbya taylorii, Oscillatoria limnetica, Oscillatoria tenuies and Chroococcus limneticus). The best incubation period which achieved a high amount of nitrogen fixing is fifteen day and it was reached to (20.80, 19.01, 15.12, 12.48, 16.40, 16.60 and 8.01 mg/L) for understudy isolates, respectively. Also the highest percentage of nitrogen fixing was achieved for understudy isolates which synomounosly increased with increasing amount of nitrogen fixing, (1.48, 1.12, 1.22, 0.99, 1.28, 1.31 and 0.89%). Also, the results revealed that the frequency of heterocysts of filamentous algae (Nostoc and Anabeana) was increased with increasing incubation period and for fifteen day. Generally, the highest rate of daily growth and weights of biomass was achieved after fifteen day. Increasing of final pH was also observed as compared with initial pH for all understudy isolates and under affect all incubation period. This study revealed that the amount of nitrogen fixing for tested isolates affected directly with exogenous nitrogen source supply into the medium, so the amount of nitrogen fixing was increased because the utilized method determined the total amount of nitrogen in sample and also the addition of nitrogen source into the medium stimulated the growth and elevated the biomass, protein content and percentage of nitrogen. Furthermore, the final pH increased significantly from initial pH under this condition. The results showed, a remarkable declined in heterocysts frequency when nitrogen source was added to the medium. The effect of illumination regime on nitrogen fixation was also studied, the data revealed, that the tested isolates showed variation in their response under this condition. Nostoc, Anabeana and Arthrospira showed maximum ability of nitrogen fixing when illuminated under (18 hour light :6 hour dark) while the remaining algae revealed maximum nitrogen fixing values when illuminated under continuous photoperiod, also the percentage of nitrogen fixing, the rate of daily growth rate, biomass weights and protein content showed same manner.
Keywords
nitrogen fixation; Nostoc; Anabaena; Arthrospira; Heterocyst

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