Simpson Thacher & Bartlett and Sullivan & Cromwell have secured advisory roles on French dairy firm Danone’s acquisition of a 25 percent stake, worth $550 million, in Chinese baby milk powder maker Yashili International Holdings.

The stake acquisition strengthens Danone’s links to Yashili’s largest shareholder and China’s biggest dairy firm, China Mengniu Dairy Co, whose stake will be diluted as a result of the deal. Danone owns a stake of around 10 percent in Mengniu, according to a February statement.

Simpson Thacher advised Danone on the transaction, led by partner Douglas Markel in Beijing with assistance from counsel Venus Lo in Hong Kong.

Sullivan & Cromwell represented Yashili on the deal, headed by Hong Kong partner Kay Ian Ng and Beijing partner Gwen Wong.

“We are today strengthening the winning team formed by Danone and Mengniu by acquiring an equity stake in Yashili - combining Mengniu’s wide-reaching network in China with Danone’s international expertise in infant milk products,” Danone’s CEO, Emmanuel Faber, said in a statement.

Yashili specialises in infant milk formula products, making it one of the better known brands in a market that Euromonitor estimates will double in size against last year to hit $31 billion by 2017.

Danone holds around 6 percent of China’s milk powder market, according to Euromonitor, down from 10.2 percent in 2009. It lags rivals Nestle SA, Mead Johnson and local firms Beingmate Baby & Child Food Co and Biostime International Holdings.