2 research outputs found
Analysis of Gluten in a Wheat-Gluten-Incurred Sorghum Beer Brewed in the Presence of Proline Endopeptidase by LC/MS/MS
Most
gluten-reduced beers are produced using an enzyme called proline
endopeptidase (PEP), which proteolyzes the gluten by cleaving at proline
residues. However, the gluten content of beers brewed in the presence
of PEP cannot be verified since current analytical methods are not
able to accurately quantitate gluten in fermented foods. In this work,
mass spectrometry was used to qualitatively characterize the gluten
in a wheat-gluten-incurred sorghum model beer brewed with and without
the addition of PEP. Hydrolyzed gluten peptides and chymotryptic gluten
peptides produced from intact gluten proteins were detected in beer
brewed in the presence of up to 6 times the manufacturer’s
recommended dosage of PEP. The observation of chymotryptic gluten
peptides indicates that some gluten proteins remained, at least partially,
intact after fermentation and enzymatic treatment. Less intact gluten
was observed in beer brewed in the presence of PEP, but more hydrolyzed
gluten peptides were consequently observed in PEP-containing beer.
Gluten peptides that contained immunogenic sequences known to be associated
with celiac disease were detected in PEP-containing beer
Bactericidal Effects of Silver Nanoparticles on Lactobacilli and the Underlying Mechanism
While
the antibacterial properties of silver nanoparticles (AgNPs)
have been demonstrated across a spectrum of bacterial pathogens, the
effects of AgNPs on the beneficial bacteria are less clear. To address
this issue, we compared the antibacterial activity of AgNPs against
two beneficial lactobacilli (<i>Lactobacillus delbrueckii subsp.
bulgaricus</i> and <i>Lactobacillus casei</i>) and
two common opportunistic pathogens (<i>Escherichia coli</i> and <i>Staphylococcus aureus</i>). Our results demonstrate
that those lactobacilli are highly susceptible to AgNPs, while the
opportunistic pathogens are not. Acidic environment caused by the
lactobacilli is associated with the bactericidal effects of AgNPs.
Our mechanistic study suggests that the acidic growth environment
of lactobacilli promotes AgNP dissolution and hydroxyl radical (•OH)
overproduction. Furthermore, increases in silver ions (Ag<sup>+</sup>) and •OH deplete the glutathione pool inside the cell, which
is associated with the increase in cellular reactive oxygen species
(ROS). High levels of ROS may further induce DNA damage and lead to
cell death. When <i>E. coli</i> and <i>S. aureus</i> are placed in a similar acidic environment, they also become more
susceptible to AgNPs. This study provides a mechanistic description
of a pH-Ag<sup>+</sup>-•OH bactericidal pathway and will contribute
to the responsible development of products containing AgNPs