Abstract:
Bacterial exopolysaccharides are versatile polymeric materials used in modern
industrial and agricultural biotechnology. The aim of this thesis was to isolate and
characterize exopolysaccharide producing Rhizobia and optimization conditions for
exopolysaccharide production. Potentially, 20 different nodulated faba bean were
collected, surface sterilized, crushed, serially diluted and inoculated onto yeast
extract mannitol agar. Then, seven highly mucoid Rhizobia isolates were selected and
grown yeast extract mannitol broth for EPS production. Provisionally, Rhizobia
isolates were characterized by biochemical tests. The EPS Produced were
precipitated by isopropanol, dried at 500C and concentration of EPS were measured
by phenol sulfuric acid methods and finally characterized by FTIR. The quantitative
data were analyzed by Minitab V 21.1.0, Origin Pro, 2023, Graph Pad prism V 8 and
Design Expert V 13. Four isolates of REPS16, REPS9, REPS5 and REPS11 showed
maximum yield of EPS when sucrose supplied as sole carbon sources 223mg/ 100ml,
215 mg/100ml, 201mg/100ml and 200 mg/100ml while, myo-inositol gave minimum
EPS yield 33mg/100ml-10mg/100ml whilst, nitrogen sources indicate220mg- 100mg
/100ml in yeast extract. The factors of sucrose, glucose, yeast extract, beef extracts
peptone, temperature and pH were found to have a profound impact on EPS
production (p<0.0001). As per 2-D and 3-D graph judging from these experimental
results, the preliminary optimization and optimized media for producing EPSs was
1.5 folds increase in sucrose, glucose and yeast extract, beef extract, peptone at 280C,
pH 7, 96hrs and 3.5mg/100ml NaCl. As per FTIR indicated that, all of the extracted
EPS from Rhizobia isolates were contained exopolysaccharide functional groups of –
CH-, C=O, C-O-C, -COOR, -OH, ester, aldehydes, ketone groups and some traces of
amines and sulphonates components of carbohydrates moieties. Overall, this study's
findings showed that it may be possible to isolate potential Rhizobia that produce
exopolysaccharide from the faba bean's root nodule, and enables industrial
exopolysaccharide production and maximizing yield as whole.
