Relation between Antibacterial Activity against Food Transmitted Pathogens and Total Phenolic Compounds in Grape Pomace Extracts from Cabernet Sauvignon and Syrah Varieties

Grape pomace is the main by-product of wine production that concentrates bioactive metabolites of polyphenolic nature with antibacterial activity. Since grape pomace composition varied depending on grape variety, climate, vineyard location, and winemaking technology, it is important to study the composition and antibacterial activity of each variety separately. In this study, antibacterial activity against different food pathogens was evaluated and its relation with polyphenols content was determined. Grape pomace from Cabernet Sauvignon and Syrah varieties was extracted with methanol/HCl 1% (v/v), followed by sequential extractions with hexane, chloroform and ethyl acetate. Ethyl acetate fraction had the highest antibacterial activity determined through the microdilution method, reaching over 90% of inhibition at 500 μg·ml-1 with the exception of Salmonella Typhi (70% of inhibition). Staphylococcus aureus and Escherichia coli were the most susceptible strains, exceeding 50% of inhibition at 62.5 μg·ml-1. Ethyl acetate fraction contains the highest phenolic concentration in both Cabernet Sauvignon (132.2 mg of GAE g-1) and Syrah (102.6 mg of GAE g-1) pomace, as determined by the Folin-Ciocalteau method. Antibacterial activity present in grape pomace extracts is in direct relation to the polar phenolic content, in particular that from Cabernet Sauvignon.

Thiol-Mediated Reduction of <i>Staphylococcus aureus</i>Tellurite Resistance

The goal of this work was to enhance tellurite toxicity against Gram positive bacteria, especially Staphyloccocus aureus. Using a combination of assays (growth inhibition zones, growth curves, and minimal inhibitory concentrations), tellurite toxicity against this bacterium was tested in the presence of various SH- and OH-containing compounds. Results showed that the noxiousness of tellurite was strongly enhanced in the presence of 2-mercaptoethanol or dithiothreitol. The potentiating effect was observed in S. aureus ATCC 6538 (the model organism of this study) and in other Gram positive bacteria such as Bacillus subtillis ATCC 6051 and the methicillin-resistant S. aureus strain 622-4. No enhancing effect was observed in Gram negative bacteria such as Escherichia coli BW25113, Salmonella Typhimurium LT2 and Klebsiella pneumoniae ATCC 11388. These results open new perspectives for studying the treatment of multidrug-resistant Gram positive bacteria, which are responsible for numerous nosocomial infections.

Efficiency of RAPD in assessing genetic variation in commercially viable local varieties of blueberry (<i>Vaccinium</i>)

The growth in both production and plantation surface area of blueberries in Chile has been positive, with an estimated surface area of 13,057 hectares (16.9% planting surface) and production in the order of 56,000 tons (16.3% mundial production). Of all the different species of blueberry there are several varieties that have advantages with regard to certain conditions;for example, one variety adapts better to the climate of a particular area, while others are better for early or late harvests, they can also be resistant to fungus, bacteria, etc. Companies are very interested in this issue because prior knowledge of such data can bring financial benefits. Blueberries have a significant degree of morphological variation, which enables recognition of different clones with different environmental adaptation characteristics, but it also allows us to discriminate between different levels of fruit quality, which is of commercial interest. However, these morphological characteristics are late in their expression, making it impossible to recognize the clones in the early stage of their development. A more efficient tool to be able to recognize different clones is the use of molecular markers. Of the techniques based the RAPD (randomly amplified polymorphic DNA). They have the advantage that the method has no need for prior knowledge of the DNA sequence. It is of great interest to the private sector to have prior access to information on the types of clone they possess, in order to then be able to differentiate the varieties, but for this it is necessary to obtain a quick and economical technique. In this study, through the use of RAPD-PCR, it is possible to differentiate between different varieties of Vaccinium grown in Chile in order to then optimize blueberry production in terms of time and resources.

Electrochemical reduction of Cr(Ⅵ)in the presence of sodium alginate and its application in water purification

Chromium(Cr)is used in many manufacturing processes,and its release into natural waters is a major environmental problem today.Low concentrations of Cr(Ⅵ)are toxic to human health and living organisms due to the carcinogenic and mutagenic nature of this mineral.This work examined the conversion of Cr(Ⅵ)to Cr(Ⅲ)via electrochemical reduction using gold electrode in an acidic sodium alginate(SA)solution and subsequent removal of the produced Cr(Ⅲ)-SA by the polymer-enhanced ultrafiltration(PEUF)technique.A solution of SA in nitric acid was used both as an electrolytic medium during the voltammetric measurements and bulk electrolysis and as an extracting agent during the PEUF technique.The electroanalysis of Cr(Ⅵ)was performed by linear sweep voltammetry in the presence of acidic SA solution to study its voltammetric behavior as a function of the Cr(Ⅵ)concentration,pH,presence of Cr(Ⅲ),SA concentration and scan rate.In addition,the quantitative reduction of Cr(Ⅵ)to Cr(Ⅲ)was studied through the bulk electrolysis technique.The results showed efficient reduction with well-defined peaks at approximately 0.3 V vs.Ag/AgCl,using a gold working electrode.As the pH increased,the reduction signal strongly decreased until its disappearance.The optimum SA concentration was 10 mmol/L,and it was observed that the presence of Cr(Ⅲ)did not interfere in the Cr(Ⅵ)electroanalysis.Through the quantitative reduction by bulk electrolysis in the presence of acidic SA solution,it was possible to reduce all Cr(Ⅵ)to Cr(Ⅲ)followed by its removal via PEUF.