Antioxidant and anti-inflammatory properties of sourdoughs containing selected Lactobacilli strains are retained in breads.

Sourdough fermentation influences several properties of leavened baked goods also because Lactic acid bacteria (LAB) and yeasts produce bioactive peptides with a positive effect on human health. In an early study, three Lactobacilli strains (L. farciminis H3 and A11 and L. sanfranciscensis I4) possessing different proteolytic activities were used to produce sourdoughs containing peptides equipped with anti-inflammatory and/or antioxidant properties. This work was aimed to assess whether these properties could be retained after cooking. The selected LABs were used to produce breads from which low molecular weight (LMW-) peptides were extracted. The results provide solid proofs of keeping both antioxidant and anti-inflammatory activities of peptides from cooked products. Sequences of LMW-peptides either from doughs and breads were determined by mass spectrometry: differences have been noticed in amino acidic composition and in sequences, however, all the strains produce peptides equipped with antioxidant and anti-inflammatory activities.

Effect of selected strains of lactobacilli on the antioxidant and anti-inflammatory properties of sourdough.

Sourdough fermentation of cereal foods is an excellent source of obtaining peptides due to the ability of lactic acid bacteria to activate cereal proteases and produce strain-specific peptidases. With the aim of identifying the lactic acid bacterial strains potentially most effective in producing bioactive peptides, 131 lactobacilli isolates from Italian sourdoughs, used in baking technology, have been screened for proteolytic and peptidase activity. Of these, 23 strains were selected and singly inoculated in liquid sourdoughs from which a Low Molecular Weight fraction containing peptides was obtained. Evaluation of the antioxidant and anti-inflammatory activities of the extracts was performed on cultured cells (RAW 264.7 murine macrophage, murine H-end endothelium cells and Human intestinal Caco-2 cells) by assaying Reactive Oxygen Species (ROS) content, NFkB/IkB expression level and Interleukin-1ß production. As a result, three lactobacilli strains showed a high antioxidant and anti-inflammatory ability enabling the development of model sourdoughs that will potentially increase the nutritional benefits of bread.

A single amino acid mutation affects elicitor and expansins-like activities of cerato-platanin, a non-catalytic fungal protein.

Cerato-platanin (CP) is a non-catalytic, cysteine-rich protein, the first member of the cerato-platanin family. It is a single-domain protein with a double Ψ/ß barrel domain resembling the D1 domain of plant and bacterial expansins. Similarly to expansins, CP shows a cell wall-loosening activity on cellulose and can be defined as an expanisin-like protein, in spite of the missing D2 domain, normally present in plant expansins. The weakening activity shown on cellulose may facilitate the CP-host interaction, corroborating the role of CP in eliciting plant defence response. Indeed, CP is an elicitor of primary defences acting as a Pathogen-Associated Molecular Patterns (PAMP). So far, structure-function relationship study has been mainly performed on the bacterial BsEXLX1 expansin, probably due to difficulties in expressing plant expansins in heterologous systems. Here, we report a subcloning and purification method of CP in the engineered E. coli SHuffle cells, which proved to be suitable to obtain the properly folded and biologically active protein. The method also enabled the production of the mutant D77A, rationally designed to be inactive. The wild-type and the mutated CP were characterized for cellulose weakening activity and for PAMP activity (i.e. induction of Reactive Oxygen Species synthesis and phytoalexins production). Our analysis reveals that the carboxyl group of D77 is crucial for expansin-like and PAMP activities, thus permitting to establish a correlation between the ability to weaken cellulose and the capacity to induce defence responses in plants. Our results enable the structural and functional characterization of a mono-domain eukaryotic expansin and identify the essential role of a specific aspartic residue in cellulose weakening.