OIO Holdings, a provider of engineering and blockchain-related services, said it bought Moonstake for an undisclosed amount in an all-stock transaction.

Moonstake is the second-largest staking business in Asia, Singapore Exchange-listed OIO said in an emailed release Monday, with assets staked passing $900 million as of end-May.Through its 100% ownership of Moonstake, OIO will receive a commission of up to 0.5% of staking assets."The commission-based model provides us with good visibility of earnings," said Rudy Lim, CEO of OIO’s blockchain business subsidiary.  The firm emphasized that the trend toward proof-of-stake reduces environmental concerns over proof-of-work validation, otherwise known as mining, on blockchains such as Bitcoin's.Ethereum plans to move to proof-of-stake validation later this year.