Bacterial Communities Associated with the Cycling of Non-Starch Polysaccharides and Phytate in Aquaponics Systems

Aquaponics are efficient systems that associate aquatic organisms’ production and plants by recirculating water and nutrients between aquaculture and hydroponic tanks. In this study, we characterised the bacterial communities in the freshwater aquaponics system that can mineralise polysaccharides and phytate by producing carbohydrate-degrading enzymes and phytases, by 16S rRNA gene sequencing and in vitro culture techniques. Around 20% of the operational taxonomic units (zOTUs) identified were previously reported to carry fibre-degrading enzyme putative genes, namely β-glucanase (1%), xylanase (5%), or cellulases (17%). Ten % of the zOTUs were previously reported to carry putative genes of phytases with different catalytic mechanisms, namely β-propeller (6%), histidine acid phytases (3%), and protein tyrosine phytase (<1%). Thirty-eight morphologically different bacteria were isolated from biofilms accumulated in fish and plant compartments, and identified to belong to the Bacilli class. Among these, 7 could produce xylanase, 8 produced β-glucanase, 14 produced cellulase, and 11 isolates could secrete amylases. In addition, Staphylococcus sp. and Rossellomorea sp. could produce consistent extracellular phytate-degrading activity. The PCR amplification of β-propeller genes both in environmental samples and in the isolates obtained showed that this is the most ecologically relevant phytase type in the aquaponics systems used. In summary, the aquaponics system is abundant with bacteria carrying enzymes responsible for plant-nutrient mineralisation.

Carbonic Anhydrase as CO2 capturing agent: its Classes and Catalytic Mechanisms

Carbonic anhydrase (CA; EC 4.2.4.1), metalloenzyme, can catalyze reversible hydration of CO2 (CO2 + H2O ↔ H+ + HCO3 -) with high efficiency (kcat ~106 s-1) and plays fundamental roles in many biological processes like photosynthesis, respiration, pH homeostasis and ion transport. Recently, CA has been considered as an important biocatalyst for CO2 sequestration technology because the accumulation of CO2 is the main cause for global climate change and it is critical to develop technologies that can reduce atmospheric CO2 level. This review deals with the classes and mechanisms of several CAs as CO2 capture agents

Inorganic Nanozymes: Prospects for Disease Treatments and Detection Applications

In recent years, with the development of nanomaterials, a slice of nanomaterials has been demonstrated to possess high catalytic activity similar to natural enzymes and counter the dilemmas including easy inactivation and low yield natural of enzymes, which are labeled as nanozymes. The catalytic activity of nanozymes could be easily regulated by size, structure, surface modification and other factors. In comparison with natural enzymes, nanozymes featured with a more stable structure, economical preparation and preservation, diversity of functions and adjustable catalytic activity, thus becoming the potentially ideal substitute for natural enzymes. Generally, the are mainly three types containing metal oxide nanozymes, noble metal nanozymes and carbon-based nanozymes, owing various applications in biomedical, energy and environmental fields. In this review, to summarize the recent representative applications of nanozymes, and potentially explore the scientific problems in this field at the same time, we are going to discuss the catalytic mechanisms of diverse nanozymes, with the emphasis on their applications in the fields of tumor therapy, anti-inflammatory and biosensing, hoping to help and guide the future development of nanozymes.

C-Glycoside metabolism in the gut and in nature: Identification, characterization, structural analyses and distribution of C-C bond-cleaving enzymes

C-Glycosides, in which a sugar moiety is linked via a carbon-carbon (C-C) bond to a non-sugar moiety (aglycone), are found in our food and medicine. The C-C bond is cleaved by intestinal microbes and the resulting aglycones exert various bioactivities. Although the enzymes responsible for the reactions have been identified, their catalytic mechanisms and the generality of the reactions in nature remain to be explored. Here, we present the identification and structural basis for the activation of xenobiotic C-glycosides by heterocomplex C-deglycosylation enzymes from intestinal and soil bacteria. They are found to be metal-dependent enzymes exhibiting broad substrate specificity toward C-glycosides. X-ray crystallographic and cryo-electron microscopic analyses, as well as structure-based mutagenesis, reveal the structural details of these enzymes and the detailed catalytic mechanisms of their remarkable C-C bond cleavage reactions. Furthermore, bioinformatic and biochemical analyses suggest that the C-deglycosylation enzymes are widely distributed in the gut, soil, and marine bacteria.

Crystal structures of glycogen-debranching enzyme mutants in complex with oligosaccharides

Debranching is a critical step in the mobilization of the important energy store glycogen. In eukaryotes, including fungi and animals, the highly conserved glycogen-debranching enzyme (GDE) debranches glycogen by a glucanotransferase (GT) reaction followed by a glucosidase (GC) reaction. Previous work indicated that these reactions are catalyzed by two active sites located more than 50 Å apart and provided insights into their catalytic mechanisms and substrate recognition. Here, five crystal structures of GDE in complex with oligosaccharides with 4–9 glucose residues are presented. The data suggest that the glycogen main chain plays a critical role in binding to the GT and GC active sites of GDE and that a minimum of five main-chain residues are required for optimal binding.

Abnormal Enhancement of Protein Disulfide Isomerase-like Activity of a Cyclic Diselenide Conjugated with a Basic Amino Acid by Inserting a Glycine Spacer

In a previous study, we reported that (S)-1,2-diselenane-4-amine (1) catalyzes oxidative protein folding through protein disulfide isomerase (PDI)-like catalytic mechanisms and that the direct conjugation of a basic amino acid (Xaa: His, Lys, or Arg) via an amide bond improves the catalytic activity of 1 by increasing its diselenide (Se–Se) reduction potential (E′°). In this study, to modulate the Se–Se redox properties and the association of the compounds with a protein substrate, new catalysts, in which a Gly spacer was inserted between 1 and Xaa, were synthesized. Exhaustive comparison of the PDI-like catalytic activities and E′° values among 1, 1-Xaa, and 1-Gly-Xaa showed that the insertion of a Gly spacer into 1-Xaa either did not change or slightly reduced the PDI-like activity and the E′° values. Importantly, however, only 1-Gly-Arg deviated from this generality and showed obviously increased E°′ value and PDI-like activity compared to the corresponding compound with no Gly spacer (1-Arg); on the contrary, its catalytic activity was the highest among the diselenide compounds employed in this study, while this abnormal enhancement of the catalytic activity of 1-Gly-Arg could not be fully explained by the thermodynamics of the Se–Se bond and its association ability with protein substrates.

Recent Development in Sludge Biochar-Based Catalysts for Advanced Oxidation Processes of Wastewater

Sewage sludge as waste of the wastewater treatment process contains toxic substances, and its conversion into sludge biochar-based catalysts is a promising strategy that merges the merits of waste reutilization and environmental cleanup. This study aims to systematically recapitulate the published articles on the development of sludge biochar-based catalysts in different advanced oxidation processes of wastewater, including sulfate-based system, Fenton-like systems, photocatalysis, and ozonation systems. Due to abundant functional groups, metal phases and unique structures, sludge biochar-based catalysts exhibit excellent catalytic behavior for decontamination in advanced oxidation systems. In particular, the combination of sludge and pollutant dopants manifests a synergistic effect. The catalytic mechanisms of as-prepared catalysts in these systems are also investigated. Furthermore, initial solution pH, catalyst dosage, reaction temperature, and coexisting anions have a vital role in advanced oxidation processes, and these parameters are systematically summarized. In summary, this study could provide relatively comprehensive and up-to-date messages for the application of sludge biochar-based catalysts in the advanced oxidation processes of wastewater treatment.