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DUBAI, Nov 28 (Reuters) - Saudi Arabia's top sovereign wealth fund, the Public Investment Fund (PIF), plans to buy a major stake in Adeptio, the Gulf-based investment firm which controls Kuwait Food Co (Americana) , the PIF said on Monday.

The PIF would buy 50 percent of Adeptio from United Arab Emirates-based billionaire Mohamed Alabbar, who would keep the rest of Adeptio. It did not give financial details of the deal.

Last month, a subsidiary of Adeptio completed the acquisition of a 67 percent stake in Americana from the Kharafis, a wealthy Kuwaiti merchant family, for about $2.35 billion. Adeptio now plans a mandatory tender offer for remaining shares in Americana held by public shareholders.

Americana, with operations across 13 countries and over 60,000 employees, owns the Middle East franchises for fast food chains KFC and Pizza Hut and also produces branded consumer foods.

The PIF said its Adeptio deal was part of efforts to boost investment in non-oil sectors and diversify its portfolio geographically and across asset classes, while securing long-term financial returns for Saudi Arabia.

Under economic reforms announced early this year, the Saudi government said it aims eventually to expand the PIF, founded in 1971 to finance development projects in the country, from $160 billion to about $2 trillion and increase investments abroad.

The Adeptio transaction is the first big food sector deal announced by the PIF this year. Previously it focused on the technology sector; it bought a $3.5 billion stake in U.S. transport firm Uber in June, and last month said it might invest up to $45 billion over five years in a technology investment fund that it would create with Japan's SoftBank Group .

(Reporting by Andrew Torchia. Editing by Jane Merriman) ((andrew.torchia@thomsonreuters.com; +9715 6681 7277; Reuters Messaging: andrew.torchia.thomsonreuters.com@reuters.net))