By Leticia Fucuchima and Roberto Samora

SAO PAULO, May 13 (Reuters) - Brazil's Amaggi has agreed to buy a 40% stake in FS, a leading corn ethanol producer in the country, the companies told Reuters on Wednesday, marking the agribusiness group's entry into the rapidly growing sector that is gaining ground against sugarcane-based biofuel.

The transaction, whose value was not disclosed, will support FS's growth plans. FS has three plants in Mato Grosso, with an annual production capacity of 2.5 billion liters of ethanol.

Corn ethanol accounted for 27% of total production in the Center-South region in the 2025/26 harvest, according to data from the Sugarcane and Bioenergy Industry Union (Unica).

The deal is expected to bring "significant synergies" in areas such as corn origination, optimization, logistics and exports, the companies said in a statement.

For Amaggi, the operation is part of a strategy to industrialize and vertically integrate its operations, said CEO Judiney Carvalho.

Amaggi, which operates in the production, trade, transportation and processing of grains, will become a shareholder in FS along with the U.S.-based Summit Agricultural Group. The partnership brings together "two companies with strong synergies in the way they operate," said Bruce Rastetter, shareholder and founder of the U.S. group.

The deal was submitted on Wednesday to Brazil's antitrust watchdog Cade, and its completion is subject to approval.