Q: Can I separate ingredients that I use from those that somebody else uses in the database?

The short answer is: "yes".

There's multiple possiblities to do this in a nice way. Here's some best practices:

The best is to create a seperate user for every user in the database, and then when you go into the database's ingredient list, you can click on ‘search and filter’ in the gray toolbar. There you can filter on the user that imported the ingredients
 
If that’s impossible (and you’re already using the same account), you could also choose to use seperate categories and filter on those.