Sharp's Brewery in Cornwall has been bought by multi-national drinks firm Molson Coors in a £20m deal.
Molson Coors said it would retain Sharp's brewery at Rock, which produces 75,000 barrels a year.
Sharp's employs about 80 people at its Rock brewery and makes Doom Bar, one of the most popular cask beers in the UK.
Molson Coors, which has distributed Doom Bar around the UK for several years, said the deal was a "tremendous opportunity" for growing Sharp's.
Real ale group Camra called the buyout the "acquisitive actions of a global brewer... for short-term profit".
And it questioned the firm's commitment to the smaller firm and its other beers such as Cornish Coaster and Sharp's Own.
Molson Coors said it was "100% committed to real ale and cask beer at Rock" and the brewery there could be expanded as a result of the deal.
Mark Hunter, chief executive of Molson Coors in the UK, said it was a "great marriage of two businesses with similar values".
He added: "We respect and want to preserve the unique culture of Sharp's Brewery and the special appeal of their brands to beer drinkers."
Stuart Howe, head brewer at Sharp's, said: "We are delighted to be joining the Molson Coors team, all of whom are passionate about Sharp's Brewery and committed to the Doom Bar brand."
The buy-out comes after several years of growth for the Cornish brewery.
In the year to 31 October 2010, Sharp's reported a turnover of £16.1m, up from £11.4m the year before; while profits came in at £1.63m, up from £428,000 in 2009.
Doom Bar is named after a notorious sandbank at the mouth of the Camel Estuary near the brewery in Rock.
Sharp's other cask brands include the Rick Stein-inspired Chalky's Bark and Chalky's Bite.