* Bain-led consortium bought Toshiba Memory last year for $18 bln. : TOKYO (Reuters) - U.S. private equity firm Bain Capital has picked Nomura and Mitsubishi UFJ Morgan Stanley to manage an initial public offering of Japan’s Toshiba Memory, a deal that could happen as early as September, people familiar with the matter said. The listing of the world’s second-largest maker of NAND flash memory chips, which a Bain-led consortium bought for $18 billion last year, could be Japan’s biggest IPO this year.