DETROIT, MI - Jolly Pumpkin's signature sour beers should be available on tap in Detroit's Midtown neighborhood by April, bringing another craft beer destination to the city.

Tony Grant, a principal of Northern United Brewing Company, said the Jolly Pumpkin team is working to fill the completely empty 5,000-square-foot 441 West Canfield space in order to hit their early 2015 target opening.

"We're full go," Grant said. "We're in the build-out right now...we're in there cranking things out."

Grant said Jolly Pumpkin is aiming to complete construction by March, leaving enough time open in April. The restaurant, focussing on sour beers and pizza, will be on the same block as Shinola, Willys Detroit, RUNdetroit and Fellow Barber.

Each Jolly Pumpkin location is unique. In Dexter, where the beer is brewed, oak-aged and bottled, there's a tasting room. In Ann Arbor, Jolly Pumpkin is a cafe and brewery. In Traverse City, they're know as a restaurant, brewery and distillery.

Jolly Pumpkin Detroit will be a pizzeria and brewery, Grant said, and the empty shell of a building will harness the business's character while remaining unique to Detroit.

"(The empty building) was more work, but we got to be more creative," Grant said. "The space will be consistent in terms of who we are."

Jolly Pumpkin started in 2003 as the first "all-sour" brewer in the United States. Brewing operations are based in Dexter, but some beers are crafted in Traverse City as well, Grant said.

Old barrels fill the Jolly Pumpkin manufacturing facility in Dexter, Mich., on Oct. 25, 2013.

All of the beers made at Jolly Pumpkin are oak-aged and bottle-conditioned, which is part of the sour brewing process. Essentially, naturally-occurring microbiological cultures produce unique flavors in the beers as they age for three months to over a year. The Jolly Pumpkin sours often carry light, tart and complex flavor profiles.

There isn't a brewer in Detroit currently making a sour, mainly because the cultures needed to obtain the right flavor have a knack for "contaminating" other non-sour beers.

That said, sour brewing is much more popular now than it was in 2003.

"Sour beers are really taking off," Grant said, "but it's been a long time."

Grant said Jolly Pumpkin has had its eyes on Detroit for some time.

"We've always wanted to be in Detroit," he said. "We have to opportunity on this space, and we ran with it."

The Midtown location will allow Jolly Pumpkin to tap into the craft beer culture in the city, which is important, because craft brewers have to support each other.

"Craft brewing is an industry of diversity," Grant said. Adding sours to the Detroit mix will be fun.

According to a release put out last fall, Jolly Pumpkin will source its food menu from local suppliers such as Avalon Bakery, McClures Pickles and Calder Dairy. Grant did say that the Detroit location will focus on the pizzas, which has been a long-time goal for the Northern United Brewing Co.

Northern United Brewing Co. encompasses the Grizzly Peak and North Peak Beer Co. craft beer brands and the Civilized Spirits and Bonafide Wine brands.

Ian Thibodeau is the entertainment and business reporter for MLive Media Group in Detroit. He can be reached at ithibode@mlive.com, or follow him on Twitter.