How to dissolve PLA (polylactic acid)? I'm a maker and I've been interested in 3d printing for years.

I have found a technique for dissolve the PLA supports in a model printed in 3D in HIPS


I have printed the model in HIPS and the support in PLA
I have put the 3D model in a ultrasonic cleaner in the solution with water and sodium hydroxide 


(1 liter H2O + 200 grams NaOH)

The PLA has dissolved after 3 hours with temperature 65° and 1 hour of ultrasonic sound.

I attach a youtube link with a similar experiment

https://www.youtube.com/watch?v=uWYn5wJ72zY

Is it possibile use another substance / solution less dangerous and less toxic?

In theory, the PLA is biodegradable. Is it correct?

Ps:
I want use this combination of materials HIPS for model and PLA for Support.

Thank you in advance for the answers.
Ethyl acetate disolves PLA - which is typically the ingredient in non-acetone nail polish removers.

https://en.wikipedia.org/wiki/Ethyl_acetate

According to Wikipedia:


  "If the filament is soaked in a small amount of ethyl acetate, it will dissolve and can be used to clean 3D printing extruder heads or remove PLA supports. The boiling point of ethyl acetate is low enough to also smooth PLA in a vapor chamber, similar to ABS and acetone."