Phosphogypsum was bioconverted by pure strain of Desulfotomaculum ruminis bacteria and a mixed culture of bacteria isolated from the phosphogypsum dumping area. The process was carried out in a medium containing phosphogypsum, a modified Starkey medium and inoculums 4 or 10% by vol. The dairy and brewing industry wastewaters and sodium lactate were used as carbon sources. The bioconversion phosphogypsum was 91%, 89% and 69%, respectively. The bioconversion considerably increased when pH of the process medium was strictly controlled..