ESSEN, Germany, June 7 (Reuters) - Billionaire Nicolas Berggruen, the son of a well-known art collector, appears to have won a key victory in the bidding for Karstadt, the German department store chain that collapsed a year ago.

A committee of Karstadt creditors chose Berggruen's bid over rival offers from German-Swedish financial investor Triton and the Highstreet consortium, owned by Goldman Sachs (GS.N), Deutsche Bank (DBKGn.DE) and Pirelli Real Estate.

Russian businessman Artur Pakhomov had also expressed interest, but insolvency administrator Klaus Hubert Goerg said on Monday 7 June he had not received a formal bid from Pakhomov.

Berggruen, who won with a clear majority, said he wanted to make Karstadt more attractive and more interesting.

No financial details were disclosed about the deal.

Berggruen has said he wants to save the Karstadt brand and the 25,000 jobs at stake and is asking for further concessions from property owners, like Highstreet, which owns about two-thirds of the Karstadt store space.

But Highstreet seems unwilling to make further concessions and said on Monday 7 June: "We will stick to the condition of our offer."

Administrator Goerg said a contract would be signed immediately with Berggruen, adding that he expects the deal to close by August. The deal still needs to be approved by the cartel office.

Karstadt department stores can be found in the center of virtually any large German city, and the chain's collapse in 2009 made the retailer one of the most high-profile victims of the recession in Europe's largest economy.

Parent company Arcandor AG (AROG.DE) imploded after management failed to extract a state bailout just after cash-strapped German carmaker Opel was rescued by the German government..

CULTURAL HERITAGE

Berggruen, dubbed the homeless billionaire for living in hotels, has a diverse investment strategy that ranges from injecting cash into Spanish media group Pisa, to the restoration of Berlin restaurant Cafe Moskau.

He is the son of Heinz Berggruen, a German-Jewish art dealer and later collector, who fled Nazi Germany in 1930s. He later returned to his birthplace of Berlin and gave 165 of his paintings to a cultural foundation for a fraction of the estimated value.

Berggruen Holding is a private investment firm and was founded in 1984 with a social and cultural investment focus. It now has net assets of more than $2 billion.

For the Karstadt bid, Berggruen Holding teamed up with U.S. celebrity fashion house BCBG Max Azria Group.

A German court is due to rule on Thursday 10 June whether the Karstadt insolvency plan is viable. A deal with a new investor is one of the key conditions for the plan. (Reporting by Matthias Inverardi, writing by Eva Kuehnen; Editing by Steve Orlofsky)