Upflow anaerobic sludge bed reactors fed on glucose were used to investigate the effects of Ce3+ on soluble microbial products (SMP) production, which is the majority of the residual chemical oxygen demand present in the effluent. It was found that Ce3+ concentration of 0.05 mg/L had no significant effect on the amount of SMP production, whereas that of 1 mg/L led to the increase in SMP production. The molecular-weight distribution and carbohydrate analysis indicated that an increase in SMP production may be partly attributed to the release of extracellular polymeric substances (EPS) into the bulk solution resulted from cerium toxicity, and the nucleic acids analysis suggested that increased cell lysis also contributed to SMP accumulation in the presence of Ce3+. The increase in SMP production in the presence of Ce3+ is possibly a consequence of the release of EPS and increased cell lysis due to cerium toxicity.

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