Union Bank of India is planning to come up with a follow-on public offer of 4.5 crore shares to raise Rs 500 crore."The bank has already received approvals from the NSE and BSE for the issue," Cherian Varghese, chairman and managing director of Union Bank of India, said."We are now awaiting Sebi's approval for the exact date of the issue," Varghese added.Post-issue, the government's stake would come down to 55.43% from the present 60.85%, Varghese said, adding the bank's capital adequacy ratio would go up above 12%.