Understanding the detail of how the bioleaching works is well...

Understanding the detail of how the bioleaching works is well above my pay grade, however I know that science discovered a nylon eating bacteria before Susumu Ohno hypothesized that the nylon-degrading enzyme NylB arose de novo via a frameshift mutation within a hypothetical precursor protein.
Google it!

Do you get my drift? We can sometimes use biological systems and get results without full understanding of the underlying biochemistry.

A single celled organism consists of millions of molecular “nanomachines”. Most of these are protein-based, many are catalysts called enzymes. My understanding is that one or more enzymes produced in the cellular metabolism acts as a catalyst which somehow frees the gold. Whether that reaction happens within the cell as part of its metabolism, or perhaps the catalyst is excreted into the mix, I don’t pretend to know.

Anyhow as long as it works I’m happy.