Lithuanian side Neptunas produced a plucky performance, but a 20-point haul from forward Bertans helped the hosts grind out an ultimately convincing victory.
Ably assisted by Thomas Heurtel (13 points and 10 assists) and Fernando San Emeterio (12 points, including the first basket of the new season), Bertans were able to control the match.
And all three players were singled out for praise by coach Marco Crespi.
The Italian said: "Heurtel has played a very good game, looking for team's best, trying to make the team play together.
"And I think that Davis Bertans and Fernando San Emeterio did a good job defensively, especially on the weak side when we tried to put pressure on the ball. We controlled the game more than we did in previous days."
Neptunas twice took the lead in the opening quarter to suggest that an upset may be in the offing, but they were quickly extinguished as Bertans scored a trio of three-pointers in the first half to gradually edge Laboral Kutxa into a match-winning position.
Simas Galdikas' ensured Neptunas made a game of it until the final quarter, when the class of Heurtel proved to be the difference.