Degradation of estrogens by laccase from Myceliophthora thermophila in fed-batch and enzymatic membrane reactors

• Published in: Journal of hazardous materials Vol. 213-214; pp. 175 - 183
• Main Authors: Lloret, L., Eibes, G., Feijoo, G., Moreira, M.T., Lema, J.M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30-04-2012
• Subjects: air; Biodegradation, Environmental; Bioreactors; effluents; Enzymatic membrane reactor; estradiol; Estradiol - chemistry; Estrogenic activity; estrogenic properties; Estrogens; Estrogens, Non-Steroidal - chemistry; estrone; Estrone - chemistry; Fed-batch; Hydrogen-Ion Concentration; Laccase; Laccase - chemistry; Laccase - metabolism; Membranes, Artificial; Myceliophthora thermophila; oxygen; Sordariales - enzymology; synthetic estrogens; ultrafiltration; wastewater treatment; Water Pollutants, Chemical - chemistry; Fed-batch; Enzymatic membrane reactor; Estrogens; Estrogenic activity; Laccase
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2012.01.082

► Estrogen removal was optimized in fed-batch bioreactors by evaluating the effect of the main process parameters. ► An enzyme membrane bioreactor (EMR) was proposed for the continuous degradation of estrogens. ► Estrone was degraded up to 95% and estradiol was not detected in the effluent of the EMR under steady state conditions. ► The residual estrogenic activity of the effluent was largely reduced up to 97%.
Several studies reported that natural and synthetic estrogens are the major contributors to the estrogenic activity associated with the effluents of wastewater treatment plants. The ability of the enzyme laccase to degrade these compounds in batch experiments has been demonstrated in previous studies. Nevertheless, information is scarce regarding in vitro degradation of estrogens in continuous enzymatic bioreactors. The present work constitutes an important step forward for the implementation of an enzymatic reactor for the continuous removal of estrone (E1) and estradiol (E2) by free laccase from Myceliophthora thermophila. In a first step, the effect of the main process parameters (pH, enzyme level, gas composition (air or oxygen) and estrogen feeding rate) were evaluated in fed-batch bioreactors. E1 and E2 were oxidized by 94.1 and 95.5%, respectively, under the best conditions evaluated. Thereafter, an enzymatic membrane reactor (EMR) was developed to perform the continuous degradation of the estrogens. The configuration consisted of a stirred tank reactor coupled with an ultrafiltration membrane, which allowed the recovery of enzyme while both estrogens and degradation products could pass through it. The highest removal rates at steady state conditions were up to 95% for E1 and nearly complete degradation for E2. Furthermore, the residual estrogenic activity of the effluent was largely reduced up to 97%.