Expression of the neutral protease gene from a thermophilic Bacillus sp. BT1 strain in Bacillus subtilis and its natural host: identification of a functional promoter

[The novel Adams-like microbial metalloendopeptidase]

Heterologous gene expression of extracellular minor metalloendopeptidase of Bacillus pumilus 3-19 in protease-deficient B. subtilis strain has been studied. The fraction of enzyme in total pool of B. pumilus 3-19 secreted proteases composes less than 8%. The enzyme was isolated from culture liquid of recombinant strain, its primary structure was determined, physicochemical properties were investigated. It was concluded that secreted metallo endopeptidase of B. pumilus 3-19 represents the first prokaryotic homolog of eukaryotic adamalysin/reprolysin protein family.

Production of the antimicrobial peptides Caseicin A and B by Bacillus isolates growing on sodium caseinate

AIMS

The aim of this study was to identify Bacillus isolates capable of degrading sodium caseinate and subsequently to generate bioactive peptides with antimicrobial activity.

METHODS AND RESULTS

Sodium caseinate (2.5% w/v) was inoculated separately with 16 Bacillus isolates and allowed to ferment overnight. Protein breakdown in the fermentates was analysed using gel permeation-HPLC (GP-HPLC) and screened for peptides (<3-kDa) with MALDI-TOF mass spectrometry. Caseicin A (IKHQGLPQE) and caseicin B (VLNENLLR), two previously characterized antimicrobial peptides, were identified in the fermentates of both Bacillus cereus and Bacillus thuringiensis isolates. The caseicin peptides were subsequently purified by RP-HPLC and antimicrobial assays indicated that the peptides maintained the previously identified inhibitory activity against the infant formula pathogen Cronobacter sakazakii.

CONCLUSIONS

We report a new method using Bacillus sp. to generate two previously characterized antimicrobial peptides from casein.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights the potential to exploit Bacillus sp. or the enzymes they produce for the generation of bioactive antimicrobial peptides from bovine casein.

Sequence analysis, cloning and over-expression of an endoxylanase from the alkaliphilic Bacillus halodurans

The BhMIR32 xyn11A gene, encoding an extracellular endoxylanase of potential interest in bio-bleaching applications, was amplified from Bacillus halodurans MIR32 genomic DNA. The protein encoded is an endo-1,4-beta-xylanase belonging to family 11 of glycosyl hydrolases. Its nucleotide sequence was analysed and the mature peptide was subcloned into pET22b(+) expression vector. The enzyme was over-expressed in a high density Escherichia coli culture as a soluble and active protein, and purified in a single step by immobilised metal ion affinity chromatography with a specific activity of 3073 IU mg-1.