MSc

The study entitled “Development of encapsulated formulation of Azospirillum lipoferum and its evaluation” was conducted during 2017-2020, in the Department of Agricultural Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram, with the objective to develop calcium alginate based encapsulated formulation of Azospirillum lipoferum and to evaluate its shelf life, slow release and biodegradation.
The culture of Azospirillum lipoferum was procured from the Department of Agricultural Microbiology, College of Agriculture, Vellayani. An experiment was carried out to standardize the protocol for preparation of calcium alginate based encapsulated formulation of Azospirillum lipoferum in completely randomized design with different filler materials such as standard starch, white flour, corn starch and talc at three different concentrations viz., 5, 10 and 15 % and control treatment with 2 % sodium alginate alone replicated thrice. One month after the bead preparation, highest viable count of A.lipoferum was recorded in encapsulated formulation amended with 15% standard starch. A significant decline in the total viable population was observed in treatment amended with 15 % talc after a month compared to encapsulated formulation amended with 15 % standard starch. Based on the viable count, encapsulated formulation of A.lipoferum amended with 15 % standard starch was adjudged as the best filler material.
Along with the standardization of filler material, size, weight and economics of encapsulation were also monitored. The size and weight of beads of 2.53 mm and 19.44 g respectively was found to be higher for corn flour 15 % amended beads whereas the lowest was recorded in control. Regarding economics of encapsulation, treatment with starch 15% showed the highest cost of ₹.79.05/100 mL and the lowest of ₹.20.25/100 mL was observed in control.
The fabricated device performed efficiently and a total of 39.5 g of encapsulated beads was formed per hour from 293 mL of matrix. The average size of beads was 1.57 mm and average weight per bead was found to be 0.0082 mg. When
the device was operated with 1L of encapsulation matrix, a total of 166.3 g of beads was obtained.
The encapsulated formulation of A. lipoferum amended with 15% standard starch was selected for shelf life studies at room temperature and refrigerated conditions (4 0C) for a period of ten months. At monthly intervals, significantly higher viable count was recorded in encapsulated beads stored at refrigerated condition throughout the shelf life study. The moisture content of beads was also monitored during shelf life study. Beads kept under refrigerated condition showed moisture content in the range of 14.48 % to 10.29 % while at room temperature the same was in the range of 13.67 % to 7.57 %.
The rate of release of immobilized bacteria from encapsulated beads was evaluated. A higher colony count of A. lipoferum was observed after gentle shaking of beads in 75 mL of sterile saline solution at 32±2 0C for 24 hours. A gradual release was also observed for the first three weeks.
Biodegradation of encapsulated beads with and without A. lipoferum in both sterile and non-sterile soil at weekly intervals for five weeks was evaluated using Biodegradation scale developed by Bashan (1996). As the biodegradation data was non-parametric, Kruskal-Wallis rank sum test and Dunn’s multiple comparison test were done to compare the treatments. A. lipoferum inoculated beads in non-sterile soil showed the highest scale of biodegradation throughout the biodegradation study (mean value 1.75) and beads without bacteria in sterile soil showed the lowest scale (mean value 0.97).
In the present investigation, calcium alginate based encapsulated formulation of A. lipoferum amended with 15 % standard starch as filler material in 2 % sodium alginate exhibited the highest viable count. A device was fabricated which was efficient in the production of beads. In terms of long term storage and moisture retention, beads stored under refrigeration (4 ͦ C) was found to be better. The rate of release of A. lipoferum from the encapsulated formulation was more during the first 24-48 hours and gradual release was observed during the first three weeks.
Biodegradation studies of encapsulated beads of A.lipoferum revealed that beads inoculated with A.lipoferum in non-sterile soil showed highest biodegradation throughout the period of investigation.