Abstract:
Mixed cultures from sludges of dairy industry including, Acetogens, a bacterial group using propionic acid or lactic acid as a selective substrate; and, Methanogens, using methanol or H₂:CO₂ (80:20) as selective substrate were isolated. After six week-incubation of mixed cultures of Acetogens and Methanogens at a ratio of 1:1 at 37̊C high quantity of methane production of 2.0 x 10⁵ nmole was obtained. This optimal production was from Acetogens isolated by using propionic acid and Methanogens by using methanol or H₂:CO₂ (80:20) as selective substrate cultivated in a medium containing 5 mM lactic acid with sand as a carrier matrix with subsequent addition of H₂:CO₂ (80:20) in the second week of cultivation and at the same time. It was observed that final pH of both conditions are consecutively 6.65 and 6.74 which are optimal for Methanogens growth.