Enhancement of ε-poly-lysine production in ε-poly-lysine-tolerant Streptomyces sp. by genome shuffling.
Bioprocess Biosyst Eng
; 38(9): 1705-13, 2015 Sep.
Article
in En
| MEDLINE
| ID: mdl-25969386
ABSTRACT
ε-Poly-L-lysine (ε-PL) has been widely used as food additive. However, the self-inhibition of ε-PL on cell growth limits the accumulation of ε-PL in the wild-type strain. Here, we screened ε-PL-tolerant strain of Streptomyces sp. with higher ε-PL productivity by genome shuffling and studied the mechanism for the improvement. The initial mutant library was constructed by diethyl sulfate mutagenesis. After four rounds of protoplast fusion, a shuffled strain F4-22 with 3.11 g/L ε-PL productivity in shake flask, 1.81-fold in comparison with that of parent strain, was obtained. The higher aspartokinase activity was induced in F4-22 whereas no obvious changes have been found in ε-PL synthetic and degrading enzymes which indicated that the upstream reregulation of the precursor lysine synthesis rather than lysine polymerization or ε-PL degradation in shuffled strain accounted for the higher productivity. The activities of key enzymes in the central metabolic pathway were also enhanced in F4-22 which resulted in increased vigor of the strain and in delayed strain lysis during fermentation. These improved properties of shuffled strain led to the success of combining general two-stage fermentation into one-stage one in 5-L bioreactor with 32.7 % more ε-PL production than that of parent strain. The strategy used in this study provided a novel strain breeding approach of producers which suffered from ε-PL-like self-inhibition of the metabolites.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Polylysine
/
Streptomyces
/
Genome, Bacterial
/
Genetic Enhancement
/
DNA Shuffling
Language:
En
Journal:
Bioprocess Biosyst Eng
Journal subject:
BIOTECNOLOGIA
/
ENGENHARIA BIOMEDICA
Year:
2015
Document type:
Article
Affiliation country:
China