JACKSON, Miss. — Last May, Mobile-based BancTrust, the holding company that owns BankTrust, announced it had agreed to a merger with Jackson, Miss.-based Trustmark bank.

The deal, which was valued at $55.4 million and was expected to be completed by October. But, delays in the transition and delays in gaining approval from regulators put the deal off to February.

Last week, the two companies announced that all required regulatory approvals had been received for BancTrust to be merged into Trustmark and that “the transaction is expected to be effective as of the close of business on Friday, Feb. 15.”

Trustmark, based in Jackson, Miss., has more than 170 offices in Florida, Mississippi, Tennessee and Texas.

In a press release from Trustmark announcing the regulatory approval, BankTrust customers were urged to “continue to conduct their banking business as usual, using existing branches, checks and ATM or debit cards, until receiving notice from Trustmark that system changes have been completed, which is expected to occur by the end of the first quarter of 2013. At that point, BankTrust customers will have an expanded offering of products and services, as well as the added convenience provided by more than 170 Trustmark banking centers in Florida, Mississippi, Tennessee and Texas.”

“We are delighted to be joining forces with Trustmark and look forward to continuing to serve our customers as part of a strong, $12 billion regional banking organization,” BancTrust President and CEO W. Bibb Lamar Jr. said.

In information shared last year, during an analyst presentation after the merger was announced, Gerald R. Host, President and CEO of Trustmark, said the move is one that allows Trustmark to move into many Alabama markets, where BankTrust was the dominant bank, and into an overall market, where he sees growth on the horizon.

Information in the presentation showed BankTrust had a top-three position in five of the 10 markets mentioned, and held the top position in four of those markets.

The bank holds the top position in the Selma, Brewton, Monroeville and Greenville markets.

In Walton County, Fla., BankTrust had the No. 2 spot. In Mobile, BankTrust was the No. 5 bank with an 8.5 percent market share.

“We look forward to welcoming customers and associates of BancTrust to the Trustmark family,” Host said last week. “Expansion into attractive Alabama markets, including Mobile and Montgomery, as well as increasing scale in existing Florida Panhandle markets, represents a great opportunity for Trustmark.”

With assets of $2.0 billion, BancTrust provides an array of traditional financial services through 40 bank offices in the southern two-thirds of Alabama and nine bank offices in northwest Florida.