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Enzymes Involved in the Bioremediation of Pesticides
Published in Pankaj Bhatt, Industrial Applications of Microbial Enzymes, 2023
Sajjad Ahmad, Pankaj Bhatt, Hafiz Waqas Ahmad, Dongming Cui, Jiatai Guo, Guohua Zhong, Jie Liu
For the biodegradation of xenobiotics from the environment, laccase enzymes with and without mediators were investigated. For example, bacterial laccase enzymes without phenolic mediators to remove chlorpyriphos, dichlorophos, monocrotophos, and profenofos were investigated, and findings showed that they were effectively involved in the degradation process (Chauhan and Jha, 2018). Recently, Sarker et al. (2020) studied the remediation of hazardous fungicide metabolite 3,5-dichloroaniline (3,5-DCA) by laccase and MnO2 mediator with different amendments of phenolic mediators (catechol, syringaldehyde, syringic acid, caffeic acid, and gallic acid). This study explained that the catechol phenolic mediator with laccase significantly degrades the fungicide metabolites.
Genetic Regulation of Principal Microorganisms (Yeast, Zymomonas mobilis, and Clostridium thermocellum) Producing Bioethanol/Biofuel
Published in Ayerim Y. Hernández Almanza, Nagamani Balagurusamy, Héctor Ruiz Leza, Cristóbal N. Aguilar, Bioethanol, 2023
Dania Sandoval-Nuñez, Teresa Romero-Gutiérrez, Melchor Arellano-Plaza, Anne Gschaedler, Lorena Amaya-Delgado
Chemical inhibitors are commonly present during Z. mobilis fermentation because these products may be present in LCB residues or may be derived from the fermentation itself [80]. The study of the expression profile of Z. mobilis with diverse inhibitors helps to characterize the metabolic pathways involved in cell detoxification processes. Changes in the cell growth and ethanol yield of Z. mobilis ZM4 in the presence of inhibitors such as phenolic aldehydes, furfural, and ethanol have been evaluated. Phenolic aldehydes are formed in the pretreatment of LCB used as raw material for the production of biofuels and have been reported as toxic agents that can affect cell growth and fermentation [81]. Yi et al. evaluated the genomic response of Z. mobilis ZM4 in the presence of the inhibitors 4-hydroxybenzaldehyde, syringaldehyde, and vanillin, identifying overexpressed genes from the respiratory chain and transporter genes (Table 4.3) that help reduce inhibitors to their corresponding phenolic alcohols and maintain ethanol production [82].
Reuse of Treated Wastewater through Emerging Technologies
Published in Maulin P. Shah, Wastewater Treatment, 2022
Rifat Ara Masud, Farzana Yeasmin, M. Mehedi Hasan, Md. Kamruzzaman
An enzyme-redox mediator approach for remediation/degradation of different organic pollutants (wide spectrum of aromatic compounds) prevailing in the industrial effluent has attracted a great deal of attention recently. In the presence of certain redox mediators, several recalcitrant compounds can be degraded by specific enzymes. Redox mediators speed up the degradation reaction rate by transporting electrons from the bulk electron donors or from biological oxidation of primary electron donors to the electron-accepting organic compounds. With high redox potentials (>900 mV), easily diffusible, low-molecular-weight redox mediators attack the recalcitrant structural analogs and are able to be migrated into the aromatic structure of the specific compound. These redox mediators enhance the range of substrates for the enzymes and efficiency of degradation of the recalcitrant compounds by severalfold. Frequently used redox mediators include 1-hydroxybenzotriazole, violuric acid, veratryl alcohol, 2-methoxyphenothiazone, anthraquinone, 2,6- disulfonic acid, 3-hydroxyanthranilic acid, N-hydroxyacetanilide, phenol red, dichlorophenol red, syringaldehyde, acetosyringone, etc.
Comprehensive depolymerization of lignin from lignocellulosic biomass: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
Qinghua Ji, Xiaojie Yu, Li Chen, Abdullateef Taiye Mustapha, Clinton Emeka Okonkwo, Cunshan Zhou, Xianming Liu
The catalytic oxidation of lignin converts lignin into more complex platform chemicals or directly into fine target chemicals. In addition to vanillin and syringaldehyde, the oxidation products of lignin also include acetosyringone, ferulic acid, vanillic acid, syringic acid and p-hydroxybenzoic acid. Vanillin and dimethyl sulfoxide are two molecular chemicals produced in large quantities from industrial lignin. Vanillin (4-hydroxy-3-methoxybenzaldehyde) is the main flavor component of vanilla. It is mainly used as a flavoring agent or additive in the food industry, and as a vulcanization inhibitor or defoamer in agrochemical and pharmaceutical industries. Vanillin can be obtained by alkaline oxidation of lignin (lignin sulfonate), usually air, oxygen, nitrobenzene or metal oxides are used as oxidants.
Laccase-evoked removal of antibiotics: Reaction kinetics, conversion mechanisms, and ecotoxicity assessment
Published in Critical Reviews in Environmental Science and Technology, 2023
Kai Sun, Mei-Hua Chen, Xue-Min Qi, Dan Hong, Ling-Zhi Dai, Shun-Yao Li, Yi-Chen Lu, Han-Qing Yu
In particular, the laccase-evoked copolymerization pathway is another vital process for antibiotic removal in aquatic ecosystems (Bialk et al., 2005; Sun et al., 2017). The catalysis of laccase in the cross-coupling reaction is based on intermolecular C–C, C–O, and C–N bonds (Morsi et al., 2020; Shi et al., 2014). As displayed in Figure 6, laccase first caused the oxidation of protocatechuic acid (a model humic constituent) to generate a quinone, and then sulfapyridine (SPD) aniline nitrogen (a reactive site in SPD molecule) cross-coupled with the quinone at position 3 (Bialk et al., 2007). In addition, laccase also mediates the covalent cross-coupling of sulfonamide antibiotics (i.e. SDZ, sulfamethazine (SMZ), and SMX) and S-type compounds (i.e. syringic acid, syringaldehyde, and acetosyringone), to form various codimers through C–N bonds (Shi et al., 2014). Another study by Gulkowska et al. (2013) indicated that laccase oxidized unreactive hydroquinones in humic molecules to form reactive electron-loving quinones, which further cross-coupled with SMZ by C − N covalent bonds. Therefore, sulfonamide antibiotics can be chemically incorporated into supramolecular humic molecules by laccase, and the formation of copolymerization products would help to reduce the transferability and bioactivity of sulfonamide antibiotics (Sun et al., 2017). These results emphasized that laccase could evoke the transformation of antibiotics by two detectable mechanisms (i.e. oxidative decomposition and radical copolymerization), but the dominant reaction pathway needs to be further clarified.
Microbial conversion of lignin rich biomass hydrolysates to medium chain length polyhydroxyalkanoates (mcl-PHA) using Pseudomonas putida KT2440
Published in Preparative Biochemistry & Biotechnology, 2023
Suveera Bellary, Mallikarjun Patil, Aruna Mahesh, Arvind Lali
Major aromatics identified on GC-MS in both cotton stalk hydrolysate (CSH) and EFB hydrolysate (EFBH) included benzoic acid, vanillic acid, syringic acid, vanillin, syringaldehyde, trans para coumaric acid, and ferulic acid. As lignin is a complex biopolymer of guaiacyl (G), syringyl (S) and p-hydroxyphenyl (H) units in a randomly polymerized state, vanillic acid, syringic acid and trans para coumaric acid were chosen as respective representatives of the three units. For mixture compositions, vanillic acid was chosen because both CS and EFB are hardwoods and have high guaiacyl content.[25]Table 1 presents the composition of the two biomass feedstocks used in the work. Table 2 presents the composition of the corresponding nitric acid hydrolysates that were obtained in this work. The acid treatment resulted in more than 90% delignification is both cases. Total solubilized lignin could not be quantitatively determined and is therefore reported in terms of COD. However, the hydrolysate could be used to determine the lignin-derived compounds and these are listed in Table 3. The numbers corresponding to lignin content in biomass feedstocks in Table 1, and total lignin in hydrolysate reported in Table 3 do not exactly match but can be taken as being in fair agreement given the vast difference in the methods used.