News comment on Kohlberg Kravis Roberts'  "indicative proposal" to acquire Perpetual has focused on the private equity group's interest in the growth potential of the Australian fund manager now compulsory superannuation contributions are about to rise from nine to 12 per cent of salary.If the deal goes ahead KKR may want to sell Perpetual's corporate trust division. The unit's operations cover securitisation trustee services and outsourced mortgage processing.Perpetual processed 199,000 mortgages in the 2009/10 financial year and had $210 billion of securitised assets under administration.The corporate trust division contributed 24 per cent of Perpetual's pre-tax earnings for the 2009/10 year. The group reported a net profit of $90.5 million.Perpetual is the biggest player in the market for securitisation trustee services, and a significant force in mortgage processing. The corporate trust division would make a viable standalone business. Its weakness is its falling margins. As the securitisation side of the business has stalled over the past couple of years, growth has come from mortgage processing. The division's EBITDA margin fell from 45 to 37 per cent.