BALTIMORE, Dec. 18ÛÓThe presidents of MarylandÛªs private colleges warned yesterday that inflation is threatening their academic quality and the future of their institutions and appealed for increased state aid.</br></br>At a press conference here organized by the Maryland Independent College and University Association, the school presidents said they were asking the state legislature for a modest increase in aid this year, which already is budgeted at $4.3 million, and said they probably would seek a major increase in 1977.</br></br>Sister Kathleen Feeley, the president of the College of Notre Dame in Baltimore, who heads the association, . said that five of the stateÛªs 13 major private colleges ran a deficit during the last academic year, ranging from $2,000 up to $459,000.</br></br>Although none is on the verge of bankruptcy, she said two already are in serious financial difficulty.</br></br>She said that overall the private colleges are still slightly in the black but that by 1980 they expect an annual deficit of $8.2 million.