Combined effects of carbon, nitrogen and phosphorus substrates on D-ribose production via transketolase deficient strain of Bacillus pumilus
2008
Srivastava, Rajesh K. | Wangikar, Pramod P.
BACKGROUND: D-ribose, a five carbon sugar, can be produced via mutant strains with impairment in the non-oxidative part of the pentose phosphate pathway (PPP). D-ribose is an important intermediate in the pharmaceutical industry. This work focuses on the effect of various substrates on D-ribose production with a transketolase deficient strain of Bacillus pumilus IFO13322.RESULT: D-ribose titer is found to increase with a concomitant decrease in the yield (on a g product g⁻¹ substrate basis) with increasing glucose concentration. Likewise, higher concentration of ammonium sulfate led to lower product yield while glucose and corn steep liquor concentrations were kept unaltered. Among the complex nitrogen substrates, cas amino acids showed better product yield than corn steep liquor. When tested for supplements of defined amino acids, media supplemented with tyrosine, phenylalanine, tryptophan and histidine gave better yields and higher biomass growth. This is possibly due to the fact that mutant strain is an aromatic amino acids auxotroph owing to impairment in aromatic amino acid biosynthesis. Further, higher phosphate concentrations in the media led to greater biomass formation and lower D-ribose yield.CONCLUSIONS: At higher glucose or ammonium sulfate concentrations, a greater proportion of the carbon was channeled toward byproducts such as acetate, and acetoin and biomass formation. Thus, the relative rates of PPP and in turn the D-ribose yield were dependent on not only the carbon substrate concentration but also the nitrogen and phosphorus substrates.
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