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This study isolated a novel thermophilic heterotrophic nitrifying bacterium, Aeribacillus pallidus sp. GW-E, from aerobic composting. Under conditions of 55 °C, the utilization efficiency of NH₄⁺-N, NO₃⁻-N, and NO₂⁻-N were 87.42%, 21.44%, and 51.68%, respectively. Whole-genome analysis identified key nitrogen metabolism genes ( amt , npd , nirA , gdhA , glnA , and gltBD ) as well as heat stress-related genes ( GRPE , hslO , groES , groEL ). Response surface optimization revealed that under conditions of a C/N ratio of 15, a temperature of 54 °C, and a pH of 8, the NH₄⁺-N utilization efficiency reached 100%. Enzyme activity assays indicated that the activities of three enzymes in the ammonia assimilation pathway were GS 1.014 ± 0.030 U/mg, GDH 1.114 ± 0.090 U/mg, and GOGAT 11.611 ± 0.061 U/mg, which were significantly higher than those of other pathways ( P  < 0.05). Nitrogen balance analysis confirmed that approximately 40.04% of the nitrogen was assimilated. In conclusion, the bacterium primarily utilizes ammonia assimilation, with additional assimilated nitrate reduction and nitrification pathways for nitrogen transformation. This strain represents a valuable microbial resource and provides a theoretical basis for nitrogen retention in high-temperature composting systems.

Multidrug-resistant Gram-positive bacteria, including bacteria from the genus Staphylococcus, are currently a challenge for medicine. Therefore, the development of new antimicrobials is required. Promising candidates for new antistaphylococcal drugs are phage endolysins, including endolysins from thermophilic phages against other Gram-positive bacteria. In this study, the recombinant endolysin LysAP45 from the thermophilic Aeribacillus phage AP45 was obtained and characterized. The recombinant endolysin LysAP45 was produced in Escherichia coli M15 cells. It was shown that LysAP45 is able to hydrolyze staphylococcal peptidoglycans from five species and eleven strains. Thermostability tests showed that LysAP45 retained its hydrolytic activity after incubation at 80 °C for at least 30 min. The enzymatically active domain of the recombinant endolysin LysAP45 completely disrupted biofilms formed by multidrug-resistant S. aureus, S. haemolyticus, and S. epidermidis. The results suggested that LysAP45 is a novel thermostable antimicrobial agent capable of destroying biofilms formed by various species of multidrug-resistant Staphylococcus. An unusual putative cell-binding domain was found at the C-terminus of LysAP45. No domains with similar sequences were found among the described endolysins.

The production of the extracellular polysaccharide from the thermophilic bacterium Aeribacillus pallidus was carried out in the study. The polysaccharide was isolated and characterized by means of GC–MS, FT-IR, DSC, and XRD analyses. The rheological, foaming, and emulsifying properties of the polysaccharide were determined. Using a sucrose-rich medium, 27.1 mg dried EPS/100 mL was obtained with 94% carbohydrate and 1.5% protein. The monosaccharide profile of water-soluble EPS-IM17 was composed of rhamnose, arabinose, xylose, mannose, glucose, and galactose. The foaming capacity and stability of EPS-IM17 were 26.67% (± 4.71) and 40.01% (± 4.95), respectively, and the foaming stability was not affected by time. The emulsification index of EPS-IM17 was 64.54 (± 8.71) and decreased to 38.47 (± 10.44) after 24 h. EPS-IM17 had a crystalline structure. Solutions at different concentrations (10, 20, 40 mgmL -1 ) showed pseudoplastic behavior. In conclusion, this report could be a lead study for the use of Aeribacillus pallidus extracellular polysaccharide for different applications.

Lipases are hydrolytic enzymes owing much importance in industrial applications. These enzyme-based detergents are ecofriendly and produce a wastewater with low level of COD (chemical oxygen demand). In the present work, a novel halophilous, thermoalkaline, and detergent-tolerant lipase produced by a newly isolated Aeribacillus pallidus strain VP3 was studied. Considerable interest has been given to this lipase by the improvement of its catalytic activity through the optimization of the pH, the (C/N) ratio, and the inoculum size, using the response surface methodology based on the Box-Behnken design of experiments. A total of 16 experiments were conducted, and the optimized pH, (C/N) ratio, and inoculum size were 10, 1, and 0.3, respectively. The results of the analysis of variance (ANOVA) test indicated that the established model was significant ( p value < 0.05). The optimization of the production conditions leads to 2.83-fold of increase in the catalytic activity calculated as the ratio of the activity obtained after optimization (68 U) and the initial activity before optimization (24 U). All in all, the lipase of Aeribacillus pallidus could be considered as a potential candidate to be incorporated in detergent formulations since it shows a good stability towards detergents and wash performance.

An extracellular thermostable alkaline serine protease enzyme from Aeribacillus pallidus C10 (GenBank No: KC333049), was purified 4.85 and 17. 32-fold with a yield of 26.9 and 19.56%, respectively, through DE52 anion exchange and Probond affinity chromatography. The molecular mass of the enzyme was determined through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), with approximately 38.35 kDa. The enzyme exhibited optimum activity at pH 9 and at temperature 60 °C. It was determined that the enzyme had remained stable at the range of pH 7.0–10.0, and that it had preserved more than 80% of its activity at a broad temperature range (20–80 °C). The enzyme activity was found to retain more than 70% and 55% in the presence of organic solvents and commercial detergents, respectively. In addition, it was observed that the enzyme activity had increased in the presence of 5% SDS. KM and Vmax values were calculated as 0.197 mg/mL and 7.29 μmol.mL−1.min−1, respectively.

The valorization of protein-rich meat and bone meal (MBM) via composting is hampered by significant nitrogen loss. Genomic analysis of Aeribacillus pallidus (A. pallidus) strain 60 revealed a genetic repertoire encoding potent proteolysis and nitrogen assimilation. We hypothesized that this strain could function as a microbial catalyst to redirect nitrogen flux during MBM composting. In a laboratory-scale trial, inoculation with A. pallidus triggered a rapid thermal surge (reaching 70 °C) and proteolytic cascade, significantly accelerating maturation. Crucially, this process enhanced relative nitrogen retention, increasing final total Kjeldahl nitrogen (TKN) concentration by 10.87–13.33% and nitrate by 13.75–18.65% compared to controls. Physicochemical and microbial profiling revealed that these improvements were driven by an inoculant-induced environmental modification rather than sustained inoculant dominance. The created thermal niche facilitated a distinct two-stage succession: an initial enrichment of proteolytic genera (Thermoactinomyces, Ammoniibacillus) followed by the establishment of a putative nitrifying community dominated by Pseudoxanthomonas. This study illustrates how a pioneer inoculant can drive functional microbiome assembly through niche modulation, providing a targeted strategy for optimizing nitrogen recovery in protein-dense waste valorization.

Heat resistant thermophilic spore-forming bacteria, such as Aeribacillus (A.) pallidus, may contaminate the surfaces in food facilities resulting food spoilage of the products. The aim of this work was to determine the heat and disinfectant resistance of an A. pallidus strain that was isolated from a canning factory environment. Compared to other heat-resistant spore-forming bacteria, it did not prove to be very resistant to heat with a D10-values of A. pallidus from 12.2 min to 2.4 min (at 102 °C and at 110 °C), with a calculated z-value of 11.6 °C. Not only spores but vegetative cells showed resistance against all investigated disinfectants.

Background Pleurotus ostreatus is an edible mushroom popularly cultivated worldwide. Distilled grain waste (DGW) is a potential substrate for P. ostreatus cultivation. However, components in DGW restrict P. ostreatus mycelial growth. Therefore, a cost-effective approach to facilitate rapid P. ostreatus colonization on DGW substrate will benefit P. ostreatus cultivation and DGW recycling. Results Five dominant indigenous bacteria, Sphingobacterium sp. X1, Ureibacillus sp. X2, Pseudoxanthomonas sp. X3, Geobacillus sp. X4, and Aeribacillus sp. X5, were isolated from DGW and selected to develop a consortium-based microbial agent to compost DGW for P. ostreatus cultivation. Microbial agent inoculation led to faster carbohydrate metabolism, a higher temperature (73.2 vs. 71.2 °C), a longer thermophilic phase (5 vs. 3 days), and significant dynamic changes in microbial community composition and diversity in composts than those of the controls. Metagenomic analysis showed the enhanced microbial metabolisms, such as xenobiotic biodegradation and metabolism and terpenoid and polyketide metabolism, during the mesophilic phase after microbial agent inoculation, which may facilitate the fungal colonization on the substrate. In accordance with the bioinformatic analysis, a faster colonization of P. ostreatus was observed in the composts with microbial inoculation than in control after composting for 48 h, as indicated from substantially higher fungal ergosterol content, faster lignocellulose degradation, and higher lignocellulase activities in the former than in the latter. The final mushroom yield shared no significant difference between composts with microbial inoculation and control, with 0.67 ± 0.05 and 0.60 ± 0.04 kg fresh mushroom/kg DGW, respectively (p > 0.05). Conclusion The consortium-based microbial agent comprised indigenous microorganisms showing application potential in composting DGW for providing substrate for P. ostreatus cultivation and will provide an alternative to facilitate DGW recycling.

Thermophilic microorganisms represent an untapped reservoir of thermostable biocatalysts and stress-resilient biomolecules for industrial biotechnology. Aeribacillus pallidus, a Gram-positive moderate thermophile, has attracted attention for its enzymatic versatility and environmental adaptability, yet its genomic potential remains underexplored. Here, we present a comparative genomic analysis of 13 A. pallidus strains to uncover conserved and strain-specific traits relevant to biotechnology. Genomes ranged from 3.24 to 4.98 Mb, with GC content largely conserved (~39%) except for GS3372 (57.4%), indicating possible horizontal gene transfer. All strains encoded complete central metabolic pathways, while carbohydrate-active enzyme profiling revealed abundant glycoside hydrolases and glycosyltransferases, with GS3372 and MHI3390 enriched for lignocellulose-degrading enzymes. Secondary metabolite mining identified diverse biosynthetic gene clusters, including terpenes, sactipeptides, and bacteriocins, with PI8, W-12, and 8m3 exhibiting the greatest biosynthetic diversity. A core set of heat shock and universal stress proteins underscored robust thermotolerance. Phylogenomic and pan-genome analyses revealed high intraspecific diversity and an open pan-genome structure. Collectively, these findings position A. pallidus as a promising thermophilic chassis organism for sustainable applications, including biomass conversion, biofuel production, bioremediation, and the synthesis of heat-stable antimicrobial agents.

Hot springs are fascinating extreme environments for the isolation of polyextremophilic microorganisms with extraordinary characteristics. Since polyextremophilic bacterial growth are not as high as routine bacteria, the objective of this study was to investigate the effect of some environmental factors on biomass and metabolites productions in the newly isolated strain, from Larijan hot spring in Iran. The strain was identified as Aeribacillus pallidus Lhs-10 and deposited as CCUG 72355 and IBRC-M 11202 in Sweden and Iran, respectively. This thermoalkaliphilic strain can grow best at 50 °C, pH 8 and in the presence of 25 g/l NaCl. The physiological characterization of this strain show that [Ca/Mg] ratio affect its growth and biomass production with the best results obtained at the ratio of 2.5. Moreover, lactic and acetic acids production by this strain was affected by pH, aeration, and temperature, where a metabolic shift was detected from lactate to acetate production when the culture was aerated. Besides, its spores could tolerate heating at 80, 85, 90, 95 and 98 °C for 30 min without any reduction in the initial spore population, whereas D-value was defined 50 min at 98 °C. This newly lactic acid-producing strain of A. pallidus can be a promising strain that can be used in the harsh conditions in industrial processes.