Here's how you can use a keyboard command to toggle the Do Not Disturb feature on or off in Notification Center in OS X.
1. Hold down the Option/Alt key.
2. Click the Notification Center on the far right of the menu bar.
3. Notification Center will be set to Do Not Disturb.
4. Repeat to disable Do Not Disturb.
For more, see the original article at the link below.