## 1 Introduction  
Nonylphenols (NPs) are toxic xenobiotic compounds classified as endocrine-disrupting chemicals (EDCs) capable of interfering with the hormonal system of various organisms and are, therefore, considered emerging contaminants. NPs are biodegradation products derived from nonylphenol polyethoxylates (NPEOs), nonionic surfactants widely used by industries involved in the manufacture of pesticides, detergents, emulsifiers, cosmetic products, and textiles, among others [1]. Effluents and sewage sludge from wastewater treatment plants (WWTPs) are the primary sources of NPs in the environment [2] since both industrial discharges and municipal waste streams containing NPEOs arrive at WWTPs, where they are biodegraded to NPs, contaminants that are more persistent and estrogenic [3]. NPs are highly lipophilic and persistent metabolites and are more resistant to biodegradation than NPEOs [4], remaining in wastewater effluents and predominantly adsorbed onto sewage sludge due to their strong hydrophobicity (log Kow range: 5.4-5.92, [5]). Consequently, NPs are found in environmental matrices such as wastewater [6], surface water and sediments [7], soils (due to water irrigation with NP-contaminated sources or due to the use of sewage sludge as an organic amendment) [8], and even in the air [9]. This widespread environmental presence leads to animal and human exposure, primarily through the consumption of contaminated food [10]. In humans, NPs persist in gastrointestinal tissues for extended periods, causing damage to the central nervous system (cognitive functions, memory deficiencies, and depressed behavior) [11] and gut damage (colonic barrier and gut microbiota) [12]. These findings have raised growing concern over NPs, which are now recognized as urgent environmental contaminants requiring action [13]. In this sense, the use of NPEOs and NPs is regulated, and their use has been limited or banned in many applications in the European Union [14; 15; 16] or the United States [17; 18], among others. Physical and chemical methods have been tested to remove NPs mainly from water [6], but bioremediation methods based on bioaugmentation are preferred to be applied in WWTPs due to their low cost, high selectivity, and minor secondary pollution, being considered environmentally friendly treatments [1]. Biological processes in secondary treatments in WWTPs (involving aerating the primary effluent to encourage the growth of microorganisms in the activated sludge) and sludge treatment (involving the dewatering of sludge on drying beds and aerobic digestion through composting) present opportunities for the deployment of bioremediation to remove NPs from WWTPs [19; 20]. NP biodegradation focused on the use of pure bacterial strains, mainly _Sphingomonas_[21; 22; 23; 24; 25; 26], _Stenotrophomonas_, and _Pseudomonas_[27; 28; 29; 30; 31], as well as _Rhizobium_ and _Sphingobium_[32]. The genus _Bacillus_ was also used for NP degradation, as observed by [PERSON] et al. who saw [33; 34] that the _Bacillus sphareictus_ CT7 strain isolated from sludge samples manifested the best NP degrading ability in sludge, and three strains identified as Bacillus sp. expressed the best biodegradation of NPs adsorbed on mangrove sediment. An NP-degrading enzyme from _Bacillus cereus_ could be purified and characterized [35]. Also, [PERSON] et al. [20] observed that _Bacillus_ was the dominant bacterial species in NP biodegradation during aerobic composting of sewage sludge. In this way, we have previously reported that the _Bacillus safensis_ strain isolated in our lab was able to degrade 4-n-NP (as a representative of 4-NPs), both in an aqueous solution and when adsorbed on sewage sludge [36]. NPs are anthropogenic contaminants formed by a complex mixture of isomers (about 211) with differently branched and linear carbon chains, but about 90% are 4-NP isomers.