Abstract
We studied the preservation of Azotobacter chroococcum C26 using three dry polymers: carrageenin, sodium alginate, and HPMC, using a method of accelerated degradation. Bacterial viability, as response variable, was measured at three temperatures in four different times, which was followed by calculation of bacterial degradation rates. Results showed that temperature, time of storage, and protective agent influenced both viability and degradation rates (P;lt;0.05). We observed, using the Arrhenius thermodynamic model, that the use of polymers increased the activation energy of bacterial degradation compared to control. We obtained thermodynamic models for each polymer, based on the Arrhenius equation, which predicted the required time for thermal degradation of the cells at different temperatures. Analysis of the models showed that carrageenin was the best polymer to preserve A. chroococcum C26 since ~ 900 days are required at 4 ºC to reduce its viability in two log units. We conclude, therefore, that long-term preservation of A. chroococcum C26 using dry polymers is suitable under adequate preservation and storage conditions.
Highlights
Plant growth-promoting bacteria –PGPB– are microorganisms that can grow in, on, or around plant tissues and stimulate plant growth by numerous mechanisms (Vessey 2003)
The present findings showed that preservation of A. chroococcum C26 using polymers is a suitable alternative to maintain its viability throughout the time
A general analysis evidenced that higher temperatures and longer times of storage have a significant role on bacterial viability
Summary
Plant growth-promoting bacteria –PGPB– are microorganisms that can grow in, on, or around plant tissues and stimulate plant growth by numerous mechanisms (Vessey 2003). Azotobacter, a cystforming bacteria, is able to fix nitrogen under aerobic conditions. In some members of this bacterial genus, it has been shown that nitrogen fixation can be performed using up to three different nitrogenase enzymes that use different metal cofactors (Becking et al 2006, Garrity et al 2005). Because many members of Azotobacter exhibit plant-growth promoting features, this genus is included within the PGPB group (Kizilkaya 2008, Krumnow et al 2009, Rojas-Tapias et al 2012). Universitas Scientiarum, Journal of the Faculty of Sciences, Pontificia Universidad Javeriana, is licensed under the Creative Commons 2.5 of Colombia: Attribution - Noncommercial - No Derivative Works.
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