Targeted gene deletions for polysaccharide slime formers
View Patent ↗The present invention provides improved polysaccharides (e.g., gellan and diutan) produced by mutant gene N, M or I Sphingomonas strains containing at least one genetic modification that favors slime-forming polysaccharide production. Methods of making the mutant Sphingomonas strains and the culture broth containing such mutant Sphingomonas strains are also provided.
1. A Sphingomonas mutant strain comprising a deletion mutation in gene gellan N (gelN), wherein said Sphingomonas mutant strain has been genetically engineered to eliminate expression of gene gelN, wherein said mutant strain produces a slime form polysaccharide that has improved rheology as compared to polysaccharide naturally produced by the wild-type Sphingomonas strain ATCC 31461.
2. The Sphingomonas mutant strain of claim 1 , wherein said deletion mutation is due to a double crossover homologous recombination deletion in gene gelN.
3. The Sphingomonas mutant strain of claim 1 , wherein said Sphingomonas mutant strain produces gellan that has lower broth viscosity as compared to gellan naturally produced by the wild-type Sphingomonas strain ATCC 31461.
4. The Sphingomonas mutant strain of claim 1 , further comprising a mutation in a second gene.
5. The Sphingomonas mutant strain of claim 4 , wherein second gene mutation is in gene gellan M (gelM).
6. The Sphingomonas mutant strain of claim 5 , wherein said Sphingomonas mutant strain produces gellan that has lower broth viscosity as compared to gellan naturally produced by the wild-type Sphingomonas strain ATCC 31461.
7. The Sphingomonas mutant strain of claim 4 , wherein said second gene mutation is in gene gellan I (gelI).
8. The Sphingomonas mutant strain of claim 7 , wherein said Sphingomonas mutant strain produces gellan that has lower broth viscosity as compared to gellan naturally produced by the wild-type Sphingomonas strain ATCC 31461.