Rice bran treatment process for the production of 43.7 kg of hydrolysate solution containing 24.41 g/L of glucose and small amount of fructose from 5 kg of rice bran was developed and employed to produce polyhydroxyalkanoates in recombinant Escherichia coli and Ralstonia eutropha strains. Recombinant E. coli XL1-Blue expressing R. eutropha phaCAB genes and R. eutropha NCIMB11599 could produce poly(3-hydroxybutyrate) with the polymer contents of 90.1 wt% and 97.2 wt%, respectively, when they were cultured in chemically defined MR medium and chemically defined nitrogen free MR medium containing 10 mL/L of rice bran hydrolysate solution, respectively. Also, recombinant E. coli XL1-Blue and recombinant R. eutropha 437-540, both of which express the Pseudomonas sp. phaC1437 gene and the Clostridium propionicum pct540 gene could produce poly(3-hydroxybutyrate-co-lactate) from rice bran hydrolysate solution. These results suggest that rice bran may be a good renewable resource for the production of biomass-based polymers by recombinant microorganisms.
Keywords: Escherichia coli; Poly(3-hydroxybutyrate); Poly(3-hydroxybutyrate-co-lactate); Ralstonia eutropha; Rice bran pretreatment.
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