| Summary: | Carbamazepine is frequently detected in wastewater, impacts human health and the environment. This study evaluates the biodegradation of carbamazepine by Gram-positive bacteria Rhodococcus zopfii, specifically optimum biodegradation conditions and extracellular enzyme roles. The carbamazepine biodegradation optimization and bacteria growth for initial concentrations of carbamazepine, pH and temperatures were investigated. Extracellular enzyme assays were also examined. For the carbamazepine biodegradation, the optimum initial concentration, pH and temperature were at 10 mgL-1, pH 7 and 40 ℃, respectively with the carbamazepine biodegradation percentages ranging from 99.92 ± 0.04 % to 99.98 ± 0.14 %. The optimum parameter conditions for the bacteria growth were 5 mgL-1, pH 7 and 40 ℃ with a range from 9.61 ± 0.01 log CFUmL-1 to 10.35 ± 0.00 log CFUmL-1. The bacteria growth and the carbamazepine biodegradation occurred sequentially, with the bacteria growth preceding the carbamazepine biodegradation. The highest extracellular enzyme secreted by R. zopfii was aldehyde oxidase, followed by oxygen oxidoreductase, catechol 1,2 dioxygenase and catechol 2,3 dioxygenase. At the early of the biodegradation, oxygen oxidoreductase and aldehyde oxidase were secreted, then followed by catechol 1,2 dioxygenase and catechol 2,3 dioxygenase. A linear correlation between oxygen oxidoreductase with the biodegradation of carbamazepine was identified. Such phenomenon revealed R. zopfii metabolised carbon from the phenolic compound, thus reducing carbamazepine toxicity for defence and biodegradation mechanisms compared to growth. This study provides vital information for the biodegradation of carbamazepine using Gram-positive bacteria R. zopfii as a sustainable technology, mimics nature that is beneficial for wastewater treatment management and industry application. © 2024 The Authors
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