In that case your best bet is to increase your memory limit.
ini_set('memory_limit','512M');
The problem with javascript data tables is that they load the entire data set into the DOM to allow things like pagination and sorting without hitting the server. That is ok for smaller data sets, but html and javascript isn't as efficient as a database for handling larger data sets.
Even once you get this working, you will probably see a delay when loading the page and working with the data table.