A company backed by Asia's richest woman, Nina Wang Kung Yu-sum, and Hong Kong property businessman Joseph Lau Luen-hung is among the bidders for the three Macau casino concessions. Ms Wang and Mr Lau are the major shareholders of Baia da Nossa Sehora Entertainment Company, one of the 21 companies revealed on Friday to have submitted tenders. The opening up of Macau's gambling market - which has gross revenue of about $15.5 billion a year - marks the end of Stanley Ho Hung-sun's 40-year monopoly on casinos. Each concession will last a maximum of 25 years. The Macau Government has increased the casino gross revenue tax rate from 31.8 per cent to 35 per cent. Successful companies must also pay up to five per cent of their gross revenue to the Government for social, infrastructure and educational projects. Las Vegas-style hotels and casinos and new management styles look likely to appear in the enclave if some of the world's gambling giants, including US outfits MGM Mirage and Sun Entertainment, and Aspinalls of Britain, win tenders. The founder of MGM Mirage, Stephen Wynn, is also a shareholder in another bid by Wynn Resorts (Macau). Mr Ho is tipped to win one of the concessions with his Sociedade de Jogos de Macau, a subsidiary of the Sociedade de Turismo e Diveroes de Macau (STDM), which holds the monopoly. Ms Wang, chairwoman of the Chinachem Group, said on Friday she was not confident of her chances. Her company is believed to have secured backing of about $400 million. Tender winners are expected to be announced by the end of the year, when Mr Ho's monopoly, which he has held since 1962, expires. New gaming laws passed in Macau in August do not state how many casinos each concessionaire will be allowed to run, with officials saying market forces would be the deciding factor. Mr Ho runs 11. The gross revenue from casino taxes was $5.3 billion last year, providing 62 per cent of the Macau Government's recurrent income.