No abstract

Selenium is included in selenoprotein sequences, which participate in enzymatic processes necessary to preserve optimal health. Some lactic acid bacteria carry out the biotransformation of inorganic selenium in their metabolism. The complete biochemical mechanism of selenium biotransformation is still unknown; however, it is known that both the selenocysteine synthesis process and its subsequent incorporation into selenoproteins include serine as part of the action of seryl-RNAt synthetase. Therefore, the aim of this work was to determine the effect of serine during the biotransformation of selenium and the subsequence growth of Streptococcus thermophilus in a minimal medium. Two culture media were prepared, one enriched with the minimum inhibitory concentration of selenite (as Na 2 SeO 3 ) and the other as a mixture of the minimum inhibitory concentration of selenite and serine. The absorbed selenium concentration was measured by inductively coupled plasma, and the selenocysteine identification was performed by reverse-phase HPLC. In the second culture medium, decreases in both times, the adaptation and the logarithmic phase, were observed. According to the results, it was possible to establish that the presence of serine allowed the biotransformation of selenite into selenocysteine by Strep. thermophilus.

Multidrug-resistant Salmonella serotypes (M-RSs) were isolated from coriander, and an analysis done of the antibacterial activity of roselle calyx extracts against any of the identified strains. Onehundred coriander samples were collected from markets. Salmonella was isolated from the coriander samples by culture procedure. Susceptibilities to sixteen antibiotics were determined for the isolated Salmonella strains by standard test. The antibacterial effect of four roselle extracts (water, methanol, acetone and ethyl acetate), sodium hypochlorite, acetic acid and colloidal silver against M-RS isolates was evaluated on contaminated coriander. Thirty-one Salmonella strains were isolated from 23% of coriander samples. Identified Salmonella serotypes were typhimurium, typhi and montevideo. All isolated strains exhibited resistance to at least three antibiotics. Roselle extracts caused a greater reduction in concentration of M-RSs than the sodium hypochlorite, colloidal silver and acetic acid on contaminated coriander. Roselle calyx extracts may be a potentially useful addition to disinfection procedures of coriander. Practical applicationsThe colloidal silver solution (Microdyn) and sodium hypochlorite are widely used to disinfect fruit and vegetables in restaurants and home in Mexico. Even, the Health Secretariat of Mexico promotes their use as disinfectants of fruit and vegetables. Roselle (Hibiscus sabdariffa) calyces are reported to have an antimicrobial effect on pathogenic bacteria. There is no information about the reduction in the concentration of multidrug-resistant Salmonella serotypes (M-RSs) on coriander by typical disinfectant solutions, such as colloidal silver and sodium hypochlorite or roselle calyx extracts. M-RSs were isolated from coriander purchased in public markets in Mexico and challenged with roselle calyx extracts, sodium hypochlorite, colloidal silver and acetic acid. The roselle extracts caused a greater reduction in the concentration of M-RSs than sodium hypochlorite, acetic acid and colloidal silver on coriander. Roselle calyx extracts are a potentially useful addition to disinfection procedures of coriander in the field, processing plants, restaurants and homes.