Boston-based Berkshire Mortgage Finance has completed a $40 million acquisition of Irvine, Calif.-based Bankers Mutual, creating a loan servicing portfolio of $10 billion. Both firms specialize in federally insured Fannie Mae and Freddie Mac multifamily financing. In 1999, the combined originations of the two companies totaled more than $2.5 billion, with Berkshire closing $2 billion in loans. Less than 15% of Berkshire's originations were in California, and the company plans to increase its loan activity in that state through the acquisition. According to Berkshire Mortgage, the acquisition makes the combined entity the largest privately owned commercial mortgage banking firm in the United States.