How to add environment variables in Bitnami virtual machine using Node.js?

I have successfully deployed a NodeJS app using Bitnami and now I would like to add database connection. Following secure practices I would like to add the credentials as environment variables, but I don't know where can I add them permanently.

Right now I run a script to add the environment variables, but I would like them to be available by default.

via Camilo Ortegón