  We present the first detection of the ground-state OH emission line at 1612
MHz toward the prototypical carbon-rich planetary nebula (PN) NGC 7027,
utilizing the newly installed ultra-wideband (UWB) receiver of the
Five-hundred-meter Aperture Spherical radio Telescope (FAST). This emission is
likely to originate from the interface of the neutral shell and the ionized
region. The other three ground-state OH lines at 1665, 1667, and 1721 MHz are
observed in absorption and have velocities well matched with that of HCO$^+$
absorption. We infer that the OH absorption is from the outer shell of NGC
7027, although the possibility that they are associated with a foreground cloud
cannot be completely ruled out. All the OH lines exhibit a single blue-shifted
component with respect to the central star. The formation of OH in carbon-rich
environments might be via photodissociation-induced chemical processes. Our
observations offer significant constraints for chemical simulations, and they
underscore the potent capability of the UWB receiver of FAST to search for
nascent PNe.
