With PMPro, every payment made through the Braintree gateway will use your default merchant account. Some sites using Braintree have multiple merchant account IDs to allow them to accept payment in different local currencies.
This code recipe shows you how to set a specific merchant account ID to create a Braintree transaction for payments in this membership site.
This code is only needed if you have multiple merchant account IDs and want to use a non-default account for this site. If no merchant account ID is specified, PMPro and Braintree will use your default merchant account.