7 research outputs found
Factors and levels in the response surface design.
<p>Factors and levels in the response surface design.</p
Effect of enzyme amount and substrate concentration.
<p>Response surface plots (A) and contour plots (B) of the DPPH radical scavenging activity of pumpkin seed hydrolysates affected by enzyme amount and substrate concentration.</p
Box-Behnken design matrix and the response values for the DPPH free radical scavenging ability (%) of pumpkin seed hydrolysates.
<p>Box-Behnken design matrix and the response values for the DPPH free radical scavenging ability (%) of pumpkin seed hydrolysates.</p
Significant test for each regression coefficient of the fitted regression model.
<p>*P<0.05, **P<0.01.</p
Effect of substrate concentration and hydrolysis time.
<p>Response surface plots (A) and contour plots (B) of the DPPH radical scavenging activity of pumpkin seed hydrolysates affected by substrate concentration and hydrolysis time.</p
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