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Biotechnol Lett. 2017 Feb;39(2):289-295. doi: 10.1007/s10529-016-2245-6. Epub 2016 Nov 3.

Development of Bacillus subtilis mutants to produce tryptophan in pigs.

Author information

1
Chr. Hansen A/S, Bøge Allé 10-12, 2970, Hørsholm, Denmark. dkkbj@chr-hansen.com.
2
Chr. Hansen A/S, Bøge Allé 10-12, 2970, Hørsholm, Denmark.
3
Department of Animal Science, Aarhus University, Foulum, 8830, Tjele, Denmark.

Abstract

OBJECTIVES:

To generate tryptophan-overproducing Bacillus subtilis strains for in situ use in pigs, to reduce the feed cost for farmers and nitrogen pollution.

RESULTS:

A novel concept has been investigated-to generate B. subtilis strains able to produce tryptophan (Trp) in situ in pigs. Mutagenesis by UV was combined with selection on Trp and purine analogues in an iterative process. Two mutants from different wild types were obtained, mutant 1 (M1) produced 1 mg Trp/l and mutant 2 (M2) 14 mg Trp/l. Genome sequence analysis revealed that M1 had three single nuclear polymorphisms (SNPs) and M2 had two SNPs compared to the wild type strains. In both mutants SNPs were found in genes regulating tryptophan synthesis. Reverse transcription PCR confirmed up-regulation of the tryptophan synthesis genes in both mutants, the expression was up to 3 times higher in M2 than in M1.

CONCLUSIONS:

Tryptophan-excreting B. subtilis strains were obtained with UV-mutagenesis and analogue selection and can be used in animal feed applications.

KEYWORDS:

Bacillus subtilis; Tryptophan; UV-mutagenesis; mtrB; trpS

PMID:
27812824
PMCID:
PMC5247549
DOI:
10.1007/s10529-016-2245-6
[Indexed for MEDLINE]
Free PMC Article

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