La. Stat. tit. 33 § 4334
When the bonds are secured by a mortgage, the act shall be executed by the mayor or acting mayor of the municipality in the name and under the seal of the municipality. When the act has been executed and recorded the property thus mortgaged shall remain mortgaged for the security of the bonds in principal and interest, until they have been fully paid and discharged. The act whereby the income and revenues of such public utility are pledged (when the income and revenues are pledged to secure the bonds) shall be executed by the mayor or acting mayor of the municipality in the name and under the seal of the municipality. The act shall be recorded in the office of the recorder of mortgages for the parish in which the municipality is situated. It may be stipulated in the act of mortgage or pledge, as the case may be, that the whole or any part of the property or revenue thus mortgaged or pledged may be released from the mortgage or pledge when bonds secured thereby are paid in part.
La. R.S. § 33:4334