Kraft Heinz offered to acquire Unilever for $143 billion, with Unilever among the larger employers in southwestern Connecticut with hundreds of engineers and marketing experts in Trumbull.

Unilever rejected the offer, according to multiple reports, with Kraft Heinz indicating its willingness to negotiate terms of any final transaction.

Shares of Unilever jumped 15 percent Friday to close at $48.85, while Kraft Heinz shares were up 11 percent to $96.65.

Kraft Heinz lists dual headquarters in Pittsburgh and Chicago; the company is controlled by Warren Buffett’s Berkshire Hathaway and 3G Capital, a New York City-based private equity investor whose CEO Alex Behring lives in Greenwich and chairs the board of Kraft Heinz.

Unilever operates a major research and development operation in Trumbull focused on personal care mainstays like Axe, Caress, Degree, Dove, Lever 2000, Pond’s, Q-Tips, Suave and Vaseline; with a digital simulation lab experimenting with packaging prior to actual production. In all, the company boasts some 400 brands, to include Ben & Jerry’s, Hellman’s and Lipton to name a few.

In its 2015 annual report, the town of Trumbull listed Unilever as the single largest private sector employer with 1,100 people at its Merritt Boulevard campus. A few years ago, the company vacated a 110,000-square-foot office and data center facility at 55 Merritt Blvd. with parking sufficient for more than 400 vehicles; the building remains available for purchase today at a listed price of $7.8 million.

Unilever arrived in Trumbull in 1986 via its acquisition that year of Chesebrough-Ponds, and a dozen years ago bolstered the site by relocating research teams there from Edgewater, N.J., and Rolling Meadows, Ill., with those sites tracing their respective product heritages to Lever Brothers and Helene Curtis.

All told, Unilever padded its existing 600-employee workforce in Trumbull at the time with an additional 1,000 jobs, including 100 employees from downtown Greenwich with the company selling off its former North American headquarters there at 33 Benedict Place.

In 2008, Unilever divested its North American laundry brands to include All, Snuggle and Wisk, with investors creating a new company based in Wilton called Sun Products. Germany-based Henkel acquired Sun last year, securing space in Stamford for a major new North American consumer products headquarters combining staff from Wilton and Arizona.

Following Kraft’s 2015 acquisition of Heinz, the combined company embarked on a massive integration restructuring that included the closure of seven U.S. plants at a cost of 2,600 jobs. In a conference call this week, Kraft Heinz executives gave no hint that a major deal was imminent, when asked about their appetite for deals amid the uncertain outlook for changes to U.S. tax law being contemplated by the Trump administration.

“We don’t need another acquisition to drive value,” said Paulo Basilio, chief financial officer of Kraft Heinz. “We have brands that can sell well (and) we have a lot of white space in front of us. ... We are going to evaluate any opportunity that makes sense for the company.”

Alex.Soule@scni.com; 203-354-1047; www.twitter.com/casoulman