I need help with my Dad's gas issues...he's seen just about every MD and still has a lot of gas! Any one have any suggestions for this?

He has had bad gas (oral and rectal) for years. He has been on every medication they can think of and none seem to relieve it. In a 5 minute period he can belch up to 20 times! He has had ultrasounds and x-rays and they show free floating gas in his body. I thought that since science isn't working perhaps you have some answers (home remedies?). He is 86 and does not have dementia. He and I cared for my mom many years as she had Alz. We kept her home until the end and this site has been a Godsend to me. Blessings, Lindaz