The company’s AdventureCapital operation reached its initial target of £1m in just under 72 hours when it was launched last month.
The brewery sold 4.79% of its share capital to its 2012 investors at the end of the campaign after reaching its initial target.
Beer that ‘stands out’
I&G founder and master brewer Dougal Gunn Sharp said: “Raising £2.5m is an amazing achievement. It is testament to the belief the public has in our potential to change the future of beer in the UK and abroad.
“We have worked tremendously hard over the past 13 years to brew great-tasting, award-winning beer and this campaign has given us the opportunity to do even more.
“I am looking forward to meet many investors at our next annual meeting.”
He added: “I believe this is clear proof that the public desires beer that stands out from the masses, that is flavoursome and brewed with passion.
“We are looking forward to working closely with our AdventureCapital community to keep innovating, experimenting and brewing brilliant beer.”
The campaign aims to double I&G’s turnover from £12.5m to £25m over the next three years.
Additional funds from investors will allow the company to expand its food concept, the Beer Kitchen, in England next year after opening its third site in St Andrews, Fife, in October.
Plans to install a barrel-ageing hall and a new filtration technology are also in place to develop the beer’s brewing process and new flavours.