Application of Whey Permeate Fermented with Kefir Grains for the Shelf-Life Improvement of Food and Feed

Fungal contamination by Aspergillus parasiticus and A. flavus causes negative effects on the production of food cereals. Kefir is an ancient fermented beverage obtained by the fermentation of different substrates with kefir grains. An important waste produced by the dairy cheese industry is the whey permeate, which nowadays is a strong ambient contaminant. The aim of this work was the standardization of the whey permeate fermenting conditions with kefir grains, the assessment of the antifungal activity of the cell-free-supernatants (CFS) from these fermentations and to compare it with that obtained with CFS of milk fermented with kefir grains. Finally, we studied if the addition of kefir fermented whey permeate to food (bread) and feed (poultry) could produce shelf life improvement. The optimal condition to obtain CFS with fungicidal effect was a fermentation with 10% w/v of kefir grains, at 30°C, for 24 hours until a pH 3.7. We found that CFS from whey permeate caused fungal inhibition, whereas CFS of kefir grains grown in milk showed lower antifungal activity. Additionally, the addition of kefir-fermented whey permeates in food (bread) and feed (poultry) improved their resistance to fungal contamination. This is the first report about the application of kefir-fermented whey permeate to improve the shelf life, suggesting its potential use as a biopreservative.

Oxidative stress in Microcystis aeruginosa as a consequence of global climate change

Cyanobacteria are phototrophic organisms with great ecological and economical importance.Species of the genus Microcystis are known for their potential ability to synthesize toxins,notably microcystins.There is a growing interest in the evaluation of oxidative stress in relation to the impact of global climate change on natural ecosystems in different trophic levels.Several studies have focused on the analysis of organismal responses to mitigate the damage by controlling the generation of reactive oxygen species.Variations in environ-mental factors caused by climate change generate a situation of oxidative damage in Microcystis aeruginosa as a direct or indirect consequence.In this study we evaluate the effects of ultraviolet radiation and temperature on physiological and biochemical responses of a native M.aeruginosa(strain CAAT 2005-3).The results from the exposure to ultraviolet radiation doses and temperature changes suggest a high ability of M.aeruginosa to detect a potential stress situation as a consequence of reactive species production and to rapidly initiate antioxidant defenses.Increased catalase activity is an antioxidant protection mechanism in M.aeruginosa for short and long term exposure to different changes in environmental conditions.However,we found a ultraviolet-B radiation threshold dose above which oxidative stress exceeds the antioxidant protection and damage occurs.In addition our results are in agreement with recent findings suggesting that microcystins may act as protein-modulating metabolites and protection against reactive oxygen species.It is concluded that cyanobacteria have adaptative mechanisms that could lead to the replacement of species highly susceptible to oxidative stress by others with a higher system of antioxidant protection.

Microcystis aeruginos strain[D-Leu^(1)]Mcyst-LR producer,from Buenos Aires province,Argentina

Objective:To show the toxicological and phylogenetic characterization of a native Microcystis ceruginosa(M.aeruginosa)strain(named CAAT 2005-3)isolated from a water body of Buenos Aires province,Argentine.Methods:A M.aeruginosa strain was isolated from the drainage canal of the sewage treatment in the town of Pila,Buenos Aires province,Argentina and acclimated to laboratory conditions.The amplification of cpcBA-IGS Phcocyanin(PC,intergenic spacer and flanking regions)was carried out in order to build a phylogenetic tree.An exactive/orbitrap mass spectrometer equipped with an electrospray ionization source(Thermo Fisher Scientific,Bremen,Germany)was used for the LC/ESI-HRMS microcystins analysis.The number of cell/mL and[D-Leu^(1)]Mcyst-LR production obtained as a function of time was modelled using the Gompertz equation.Results:The phylogenetic analysis showed that the sequence clustered with others M.aeruginosa sequences obtained from NCBI.The first Argentinian strain of M.aeruginosa(CAAT 2005-3)growing under culture conditions maintains the typical colonial architecture of M.aeruginosa with profuse mucilage.M.aeruginosa CAAT 2005-3 expresses a toxin variant,that was identified by LC-HRMs/Orbitrapas as[D-Leu^(1)]microcystin-LR([M+H]+=1037.8 m/z).Conclusions:[D-Leu^(1)]microcystin-LR has been also detected in M.aeruginosa samples from Canada,Brazil and Argentina.This work provides the basis for technological development and production of analytical standards of toxins present in our region.