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20202
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Subject: Microbiology × End date: 2020 × Start date: 2020 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Interaction of Sesbania rhizobia with different species of Sesbania and kharif legumes
    (CCSHAU, Hisar, 2020-11) Jeniffer Christeena Masih; Gera, Rajesh
    Sesbania is an important wild legume as it can grow in wide range of soils like alkaline, waterlogged and acidic soils. It has high nitrogen fixation properties due to its association with rhizobia in both root and stem nodules. Rhizobia from wild legume like Sesbania may function as excellent plant growth promoting bacteria.Therefore, the present research was carried out to study the interaction of Sesbania rhizobia with different species of Sesbania and kharif legumes. A total of 25 Sesbania rhizobial isolates, which includes five isolates each from Sesbania aculeata, S. sesban, S. grandiflora, S. rostrata (root nodulating and stem nodulating), were included in the present investigation. Out of which 21 rhizobial isolates were obtained from departmental culture collection and 4 rhizobial isolates were isolated from soils collected from different locations of India using trap plant method. All the rhizobial isolates were able to produce IAA and ammonia, however, 92, 48 and 48 % rhizobia had the ability for phosphate solubilization, bacteriocin and siderophore production, whereas, 60% of rhizobia were able to utilize ACC. All the rhizobial isolates showed the presence of nifH and nodC genes. Five rhizobial isolates namely SSKr(ii), SGMg, SAUd(i), SRKr(iv)/r and SRTn/s from each Sesbania species were selected on the basis of different plant growth promoting traits, nodulation efficiency and amplification of nodC and nifH gene, to study their effect on different Sesbania species, mungbean and pigeonpea under sterilized conditions. The rhizobial isolates; SRKr(iv)/r (root nodulation) and SRTn/s (stem nodulation) were found to be most efficient isolates on the basis of nodule number and fresh nodule weight in cross nodulation within Sesbania species and other legumes. These isolates were also tagged with gfp gene to study their colonization on different parts of Sesbania rostrata. Recovery of GFP marked strains from root, root nodules, stem and stem nodules was 95 to100%. However, recovery of gfp marked strains from the surface of root and root nodules varied from 92 to100% while on the surface of stem and stem nodules, it ranged between 25 to 33%. Rhizobial isolate; SRKr(iv)/r showed good nodulation efficiency in all four Sesbania species and pigeonpea as compared to other rhizobial isolates under unsterilized conditions. Nodule occupancy of GFP marked strains; SRKr(iv)/rGFP+ and SRTn/sGFP+ under unsterilized condition was found to be 33-54 and 92% in case of root and stem nodules, respectively of Sesbania rostrata.
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    ThesisItemOpen Access
    Characterization and mass production of chitosan from fungi
    (CCSHAU, Hisar, 2020-06) Aathira S. Kumar; Malik, Kamla
    Chitosan is a linear cationic biopolymer consisting of β (1-4) bonds between 2-amino-2- deoxy-D glucopyranose and 2-acetamido-2- deoxy-D-glucopyranose. It is non-toxic, biocompatible, biodegradable, antimicrobial agent and has high charge density which paves way for its numerous applications especially in the field of agriculture, food and pharmaceuticals. Chitosan, besides chitin, occurs in fungal cell walls particularly of Ascomycetes, Basidiomycetes and Zygomycetes. The enzymatic deacetylation of chitin is the major mechanism for synthesis of chitosan in fungi. Hence, the biological alternatives (fungi) have been used for chitosan production through fermentation technologies. Chitosan has broad antimicrobial spectrum to which gram-negative, gram-positive bacteria and fungi are highly susceptible. In the present study, characterization and mass production of chitosan from fungi was standardized fermentation conditions and determined its antimicrobial properties against pathogenic microorganisms. A total of 18 morphologically different fungal isolates, 17 bacteria and 3 actinomycetes were isolated on chitin agar medium. Out of which, only 6 fungal isolates (FC1, FC3, FC7, FC8, FC9 and FC 16), 2 bacterial isolates (BC 1 & BC 12) and 1 actinomycete (AC 1) showed positive results by production of yellow colour on the chitin agar media supplemented with p-nitroacetanilide as indicator. FC 3 was the most efficient fungal isolate with highest yield of chitosan (0.096 g/100ml). Maximum chitosan production (0.265 g/100ml) was observed at temperature (35˚C) and pH 5 after 96 h of incubation. Glucose (0.309 g/100ml) and yeast extract (0.332 g/100ml) severed as the best carbon and nitrogen source for highest production of chitosan from FC3. When the growth media supplemented with agro-industrial waste @1% paddy straw +1% glucose (w/v) the yield of chitosan (0.315 g/100ml) was increased. The fungal isolates (FC3) showed maximum chitosan production in submerged fermentation (0.533 g/10g paddy straw) as compared to solid state fermentation (0.182 g/10g paddy straw). Therefore, mass production of chitosan from fungal isolate FC 3 was carried out by submerged fermentation in a bioreactor (BioFloR 120) and the yield of chitosan was found to be 5.37 g/l. Further, the chitosan extracted from isolate FC 3 was estimated for degree of deacetylation and it was observed 88.5%. On the basis of morphological and molecular characterisation, the fungal isolate FC 3 was identified as Aspergillus flavus. The antibacterial activities of chitosan at different concentrations were examined against Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus and Xanthomonas. The maximum inhibition zone (8. 0 mm) was observed at 1000 ppm against Escherichia coli. Whereas, the highest percentage of inhibition was observed at 3000 ppm for Rhizoctonia solani (90.73 %) and Fusarium oxysporum (76.27%).