Simultaneous and comparative assessment of parent and mutant strain of Rhizobium meliloti for nutrient limitation and enhanced polyhydroxyalkanoate (PHA) production using optimization studies |
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Authors: | Kshama Lakshman NK Rastogi TR Shamala |
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Institution: | a Department of Food Microbiology, Central Food Technological Research Institute, Mysore 570013, India b Department of Food Engineering, Central Food Technological Research Institute, Mysore 570013, India |
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Abstract: | Nutrient limitation conditions, optimization and comparison of polyhydroxyalkanoate (PHA) yields and biomass production by parent and mutant strains of Rhizobium meliloti were investigated. Complex interactions among concentrations of sucrose (5–55 g/l), urea (0.05–0.65 g/l) inoculum (10–250 ml/l) and K2HPO4 (0.5–2 g/l), were studied using central composite rotatable design (CCRD) experiments. Phosphate-limiting medium (0.33 g K2HPO4/l) in the presence of excess carbon (sucrose 42.5 g/l) results in more production of PHA (2.2 g/l) in the parent strain. In comparison, the mutant strain required moderate levels of sucrose (30 g/l), along with excess of phosphate (1 g/l) for high PHA content of cell biomass (80%) and PHA yield (3.3 g/l). Optimised PHA production (biomass 4.8 g/l and PHA 3.09 g/l) by the parent strain occurred at: sucrose 51.58 g/l, urea 0.65 g/l, K2HPO4 0.48 g/l and inoculum 10 ml/l. In the mutant strain, higher yields of biomass (9.05 g/l) and PHA (5.66 g/l) were obtained in Optimised medium containing: sucrose 55 g/l, urea 0.65 g/l, K2HPO4 1.0 g/l and inoculum 150.58 ml/l. |
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Keywords: | Central composite rotatable design Polyhydroxyalkanoate Rhizobium meliloti Response surface methodology Mutant Nutrient limitation |
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