Large increase in brazzein expression achieved by changing the plasmid /strain combination of the NICE system in Lactococcus lactis.
OBJECTIVE
To evaluate brazzein production in Lactococcus lactis using the nisin-controlled expression (NICE) system. The approach is through analysis of different plasmid/strain combinations.


RESULTS
Two plasmid/strain combinations of the NICE system were used in brazzein expression: L. lactis NZ9000 harbouring plasmid pNZ8148, and L. lactis IL1403 harbouring plasmid pMSP3545. The former combination proved superior, with a >800-fold increase in His-tagged brazzein expression (to 1.65 mg l(-1) of fermentation broth), comparable to expression levels in Escherichia coli. Improved expression resulted in a minor increase in secretion to the medium with the use of the Usp45 signal peptide. The yield of wild-type brazzein corresponded to that of His-tagged brazzein. Wild-type brazzein was partially soluble and low-intensity sweetness was detected.


CONCLUSIONS
The plasmid/strain combination of the NICE system has a significant impact on the expression of brazzein where a >800-fold increase was achieved. The greatly increased expression of brazzein resulted in minor improvement in secretion and low-intensity sweetness.


CONCLUSIONS
The choice of the plasmid/strain combination of the NICE system was shown to be of extreme importance in brazzein expression.
Department of Biotechnology, JoZef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia. ales.berlec@ijs.si
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Berlec
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Strukelj
D015870:Gene Expression; D005818:Genetic Engineering / Q000379:methods*; D013294:Lactococcus lactis / Q000235:genetics* / Q000378:metabolism; D009561:Nisin / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids / Q000235:genetics*
D010940:Plant Proteins; C090521:brazzein protein, Pentadiplandra brazzeana; D009561:Nisin