The 26-year-old lightweight Chechen finished Christodoulou (12-5) – who took the fight on less than a month's notice – within 38 seconds of the second round.
Christodoulou attempted to go for a takedown, which Taisumov countered by throwing the 27-year-old Greek fighter to the ground. From there, Taisumov threw a barrage of punches that would eventually knock Christodoulou out before the referee stepped in.
During a post-fight interview, Taisumov, who trains at Tiger Muay Thai and MMA Training Camp with UFC veteran Roger Huerta, would later apologise several times for hitting Christodoulou after he was knocked out.
"I didn't see that he was out and that is why I am apologizing for that. That was not nice. If I didn't see that he was out, maybe the referee also didn't see that he was out."
This was Taisumov's fourth fight in the UFC – the premier promotion in the sport – and second win in a row following a first round TKo win over Marcin Bandel on October 4.
Later this month, fellow Phuket fighter Tarek Suleiman (3-0) will take on undefeated fighter Christopher Silve in Desert Force 15 in Abu Dhabi on February 9.