Nalanda Capital, the Singapore-based private equity (PE) investment firm, has acquired 5.25% in NYSE-listed WNS (Holdings), the second largest business process outsourcing firm in India, for an undisclosed amount.The PE firm, founded by ex-Warburg Pincus honcho Pulak Prasad, has acquired 22.10 lakh American Depository Shares of WNS, according to an SEC filing of WNS.Nalanda Capital, a $400 million equity fund, has a mandate to invest only in publicly listed firms. It had earlier picked up 14.9% stake in Jaipur-based Vaibhav Gems.