Interaction between silver fir (Abies alba) wood water extract and lactobacilli

Water extract from silver fir (Abies alba) wood represents a rich source of lignans and other phenols that are effective in different pathological conditions, such as diabetes, cardiovascular diseases and psoriasis. Its interaction with the gastrointestinal environment is crucial when the extract is orally administered. In this study we tested the in-vitro interaction between water extract of silver fir wood and ten different Lactobacillus species that are found in the gastrointestinal tract, vagina or are used in food industry. We tested both ways of interaction: 1) the bacterial influence on the chemical composition of the extract and 2) influence of the extract on the bacterial growth. We demonstrated that the extract is compatible with all of the bacteria and does not impair their growth. Furthermore the extract acted as a prebiotic for some bacteria including: L. paracasei, L. acidophilus, L. rhamnosus, L. gasseri, L. crispatus and L. bulgaricus, suggesting that the compounds in the extract can stimulate their growth. However, the ten lactobacilli did not show any chemical changes in lignan metabolism and the production of enterodiol and enterolactone, which are considered the final metabolic products of lignans and are produced by different gut bacteria. This study indicates that the silver fir wood extract is nutritious for some Lactobacillus bacteria and can be used as a prebiotic.

Lactic acid bacteria as oral delivery systems for biomolecules

Lactic acid bacteria (LAB) have become increasingly studied over the last two decades as potential delivery systems for various biological molecules to the gastrointestinal tract. This article presents an overview of characteristics of LAB as delivery systems and of the applications which have already been developed. The majority of LAB strains are able to survive the intestinal passage and some are also able to persist and colonize the intestine. Several strains were in fact described as members of the human commensal flora. They can interact with their host and are able to deliver large molecular weight biomolecules across the epithelium via M-cells or dendritic cells. The most widely applied LAB species has been Lactococcus lactis; however species from genus Lactobacillus are gaining popularity and the first examples from genus Bifidobacterium are starting to emerge. Bacteria are mostly applied live and enable continuous delivery of the biomolecules. However, killed bacteria (e.g. gram-positive enhancer matrix), with bound biomolecules or as adjuvants, are also being developed. The techniques for genetic modification of LAB are well known. This review focuses on the delivery of recombinant proteins and DNA, which can cause either local or systemic effects. We divide recombinant proteins into antigens and therapeutic proteins. Delivery of antigens for the purpose of vaccination represents the most abundant application with numerous successful demonstrations of the efficacy on the animal model. Therapeutic proteins have mostly been developed for the treatment of the inflammatory bowel disease, by the delivery of anti-inflammatory cytokines, or downregulation of proinflammatory cytokines. Delivery of allergens for the modulation of allergic disorders represents the second most popular application of therapeutic proteins. The delivery of DNA by LAB was demonstrated and offers exciting opportunities, especially as a vaccine. New discoveries may eventually lead to the transition of LAB as delivery systems in clinical practice.

Large increase in brazzein expression achieved by changing the plasmid /strain combination of the NICE system in Lactococcus lactis

AIMS

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

METHODS AND 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.

SIGNIFICANCE AND IMPACT OF THE STUDY

The choice of the plasmid/strain combination of the NICE system was shown to be of extreme importance in brazzein expression.

Optimization of fermentation conditions for the expression of sweet-tasting protein brazzein in Lactococcus lactis

AIMS

To improve the production of sweet-tasting protein brazzein in Lactococcus lactis using controlled fermentation conditions.

METHODS AND RESULTS

The nisin-controlled expression system was used for brazzein expression. The concentration of nisin for induction and the optical density (OD) at induction were therefore optimized, together with growth conditions (medium composition, pH, aerobic growth in the presence of hemin). Brazzein was assayed with ELISA on Ni-NTA plates and Western blot. Use of the M-17 medium, containing 2.5% glucose, anaerobic growth at pH 5.9 and induction with 40 ng ml(-1) nisin at OD 3.0 led to an approx. 17-fold increase in brazzein per cell production compared to non-optimized starting conditions. Aerobic growth in the presence of hemin did not increase the production.

CONCLUSIONS

Considerable increase in brazzein per cell production was obtained at optimized fermentation conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

Optimized growth conditions could be used in application of brazzein expression in L. lactis. The importance of pH and OD at induction contributes to the body of knowledge of optimal recombinant protein expression in L. lactis. The new assay for brazzein quantification was introduced.