Olympus Corp said on Monday it had agreed to sell its microscope unit to private equity firm Bain Capital for 427.6 billion yen ($3.1 billion), in what would be the Japanese company's biggest divestment yet.

The sale of the unit, which also makes industrial endoscopes and x-ray analysers, comes as Olympus speeds the overhaul of its business portfolio, so as to focus solely on medical technology.

The unit is to be transferred to Bain on Jan. 4 next year, subject to antitrust regulatory approvals in Japan and abroad.

In a statement, Olympus said the transfer to Bain would be in its best interest to allow the business to grow with more agile and flexible decision-making based on market needs.

Bain won over global private equity firms such as Carlyle Group and KKR & Co, people with direct knowledge have said.

Private equity has been targeting Japan, the world's third-largest economy, where conglomerates have been hiving off non-core assets.

Bain owns flash memory chip maker Kioxia Holdings Corp and is proceeding to a second bidding round for Toshiba Corp.

In its overhaul, Olympus has invited activist investor ValueAct Capital on to its board, bought several overseas medical equipment firms and sold its digital camera business that had been a longtime money-loser.

Its shares have nearly tripled since it started to re-organise itself early in 2019.

Olympus, which began more than a century ago as a domestic maker of microscopes, spun off the unit in April for a potential sale even though it was profitable.

With assets of 165 billion yen by the end of June, the unit has forecast operating profit of 26.5 billion yen for the current financial year.

($1=138.7400 yen)