If so many capships and a Titan is not enough to repell the culture there have to be several culture centers at close by planets.

You need to attack a few more planets and destroy their culture centers. Keep in mind that with Global Unity you need to actually wipe out any Advent Loyalists planets to entirely remove their culture spread.

Once their culture centers are destroyed, colonize the planet, build one tradeport and the maximum possible ammount of culture centers. This should allow you to finally advance.

As weird as it sounds, sometimes I find it more effective to put caps one planet away from the culture I'm clearing. Caps work best when there is culture coming towards the planet is at, not at a planet already surrounded by it.

Alternatively, if you have maxed out cap and a titan just blow up the nearest enemy culture centers.

The advice I was going to say has already been said. If you aren't able to repel culture at one planet, odds are there's at least one planet with multiple media centers in orbit. I found the AI had built like seven media hubs in one gravity well at one point on one of my maps; it made clearing them out incredibly frustrating, since I had to send out a few scouts to find the source of the culture.

And as was also said, one the Advent, especially the Loyalists, get their culture research finished, their culture is incredibly difficult to combat.

ai loves building lots of culture towers.  I agree ^, get caps between culture generating world and the one you want to colonize.  Also, use anti-module fleet with anti-fighter fleet to rip through culture towers.

Just build cultural buildings close to the enemy to push your own culture out there.

Nice tip Darksxx.

I'm going to disagree Stress, Ive taken over many planets with this tactic.  it has always allowed me to colonize a planet with Aux in place.  And I'm referring to a planet that has already been bombarded.  it when you get that notice enemy culture is to high to allow you access to colonizing the planet. this is where aux comes in and lets you take it.

I dont usually have to use this tactic, but I will double check it to be sure.

Okay, yea I have done this with the TEC too.  So yes, the Advent do have an advantage with culture speading. 

I was just referring to the question that was asked on how to beat it,  so yes it takes a little longer to take a planet if you have to wait out the culture spread.  so the fastest way Ive found was to Aux a starbase and move on to the next.

Quoting what others said in some threads, the cap is hardcoded at 1. However you can spawn more via abilities.

Or you can add the research, and appropriate entity's, and edits in the player faction file. On top the existing factions Titan that will unlock another factions Titan so that you have a choice of which titan you can build. How you would do that is a little above my pay grade.

Back on topic..

Only advent starbases can be equipped with culture spread.... and you should do it only when absolutly necessary as it is quite a waste of  a starbase.