Two strains of bacteria from oilfield slickwater and their performance in partially hydrolyzed polyacrylamide biodegradation

Partially hydrolyzed polyacrylamide (HPAM) is widely used in oil recovery, but the HPAM residues also induce environmental pollution. In this study, two strains of bacteria, SCE2 and NMYGYB4, have been isolated from oilfield slickwater and identified as Tistrella bauzanensis (SCE2) and Brucella sp. (NMYGYB4). The optimal biodegradation conditions of Tistrella bauzanensis SCE2 were inoculation time 36 h, shaking speed 175 rpm, inoculum amount 3% (v/v), pH 3.0, and incubation temperature 37 °C with urea and glucose as the nitrogen and carbon sources. And the optimal biodegradation conditions of Brucella sp. NMYGYB4 were 12 h, 185 rpm, 2% (v/v), pH 7.0 and 37 °C with yeast powder and sucrose as the nitrogen carbon sources. HPAM removal rate of Tistrella bauzanensis SCE2 and Brucella sp. NMYGYB4 reached 75.3% and 63.59% at optimal conditions. The degraded samples were analyzed with GPC, FTIR, 1H NMR and HPLC. The results showed that HPAM was broken into small fragments, and amide group has been converted into carboxyl group, and no toxic acrylamide monomer was produced. The specific activities of extracellular amidases of Tistrella bauzanensis SCE2 and Brucella sp. NMYGYB4 were 5.31 U/mg and 4.79 U/mg, respectively. This work will provide novel bacteria strains for HPAM-containing wastewater treatment.