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SOUTH RANGE -- It's a common problem for microbrewers:  sour beer.  And it's caused by natural, airborne bacteria called Lactobacillus.

"You're always dealing with the outside forces, and the outside forces being the micro biology world of small, little guys that like to get in your way," says Dick Gray, co-owner of the Keweenaw Brewing Company.

Although the tiny micro-organism is harmless to consumers, it cost the KBC $15,000 to take care of.

The brewery can't afford to pasteurize its beer like bigger companies.  So, once the bacteria got into the beer, it built up and decreased the shelf life of the cans at vendors.  Like at White's Party Store in Marquette, where KBC lovers tasted the difference.

"They just said they bought a six pack last night and were drinking it and it wasn't the same beer they were used to, or when they opened the can it was much more carbonated than usual," says Chris Hutte of White's Party Store.

But as soon as word got back to the KBC, they sprung into action, recalling every can and dumping 700 barrels.

"This beer may be unaffected, but we couldn't guarantee that; we felt the right decision was to take the hit and get it removed and do it quickly, as fast as we could," says Gray.

The brewery shut down for six weeks while equipment was replaced and cleaned out.  They also invested in an $18,000 filtration system which will prevent the problem from ever happening again.

The new filtered beer has the same taste but a different look:  it's crystal clear.

Now with summer fast approaching, the company is trying to keep up with the high demand for their product.  They're just relieved to have the whole ordeal behind them.