Sept 8 (Reuters) - Morgan Stanley Infrastructure Inc sweetened its takeover bid for waste management firm Augean on Wednesday with a 356.9 million pounds ($491.02 million) offer, topping a rival bid.

The infrastructure investor raised its offer to 340 pence per Augean share from the 280 pence bid it made in July, topping the 325 pence per share offer from Eleia Ltd, a group affiliated to London-based investment manager Ancala Partners LLP, last month.

($1 = 0.7268 pounds) (Reporting by Aby Jose Koilparambil in Bengaluru; Editing by Shailesh Kuber)