ABSTRACTA commercial oxygen reducing membrane fraction obtained from Escherichia coli (OxyraseTM) has been shown in our laboratory to stimulate growth of many facultative anaerobic organisms, including starter cultures. The purpose of this study was to isolate “Food Grade” membrane fractions from Acetobacter xylinum and Gluconobacter oxydans and to compare their activities with the membrane fractions from E. coli prepared in our laboratory and Oxyrase. Cells were grown in afermentor, harvested by centrifugation, and disrupted by a French press (ca. 15,000 psi). The suspension was fractionated and filtered before use. The maximum activity of membrane fractions of Gluconobacter and Acetobacter were from cultures grown to 24 and 44 h, respectively. Formate, lactate, succinate, and α‐glycerophosphate were tested as H‐donors for enzyme activity. When lactate and α‐glycerophosphate were used as substrates, Acetobacter membrane fractions were able to deplete 100% oxygen in 5 min. It required 8 and 30 min, respectively, when succinate and formate were used. Gluconobacter membrane fractions were effective with lactate and α‐glycerophosphate. With succinate and formate, they took about 60 min or longer to reduce O2completely. E. coli membrane fractions made in our laboratory depleted O2more effectively (1 min) than Oxyrase (3–5 min) when formate was u