The Catalans have splashed out on the likes of Luis Suarez, Thomas Vermaelen, Jeremy Mathieu, Marc-Andre ter Stegen and Claudio Bravo during the close-season.
However, Bartomeu is certain that the new coach, recruited from Celta Vigo after Gerardo Martino resigned at the end of last term, will make the biggest impact at Camp Nou.
"Luis Enrique has been our most important signing of the season," the Blaugrana supremo said in a speech at Barcelona's 35th Supporters Club Congress.
"He was the first signing of this 'promised revolution' we were going to issue this summer.
"We already knew him as a player and also as the reserve-team manager. Luis Enrique provides us with passion, leadership and also hard-working sacrifices."
Bartomeu also reaffirmed his delight at the purchase of Suarez and revealed that the Uruguay international had wanted to move to Catalunya for some time.
"We made an effort because we want to have a competitive team," he added. "Luis Suarez is so excited to be here. He was wanted to play for Barca for many years."
Suarez is set to make his first appearance for Barca on Monday in the Joan Gamper trophy match against Leon, but he remains banned from competitive clashes until the end of October.