International Biodeterioration & Biodegradation最新文献

Essential oil (EO) of Citrus limon fresh (LF) and lemon waste peel (LW) was extracted using the hydro distillation method. A total of 17 chemical constituents (97.02–97.26%) were identified using GC, GC-MS, and NMR techniques. Major monoterpene hydrocarbons including d-limonene (52.42–54.17%), α-terpineol (16.82–21.15%), β-pinene (6.74–9.15%) and γ-terpinene (2.16–3.59%) were further identified using ¹H and ¹³C NMR analysis. Furthermore, extracted EOs, their synergistic combinations and major constituent (d-limonene) were evaluated for fumigant toxicity, repellence, and ovipositional inhibitory (OI) potential using without food and with food conditions against pulse beetle, Callosobruchus chinensis and Callosobruchus maculatus. d-limonene was found to be most effective against C. chinensis and C. maculatus followed by LW oil in all the evaluated assays. EO of LW was found more effective against C. chinensis (LC₅₀ = 2899.11 μl L⁻¹) without food after 96 h than lemon fresh. Among synergistic combinations, LW and LF at 3:1 ratio without food reported more effective to C. chinensis (LC₅₀ = 277.85 μl L⁻¹) and C. maculatus (LC₅₀ = 322.38 μl L⁻¹) without food after 96 h. In repellent assay, EO of LW also displayed higher repellent to both species (RC₅₀ = 430.71 to 525.56 and μl L⁻¹). EO of LW showed higher OI (50.14 ± 3.09%) against C. chinensis at higher concentration after 24 h. EOs of LF and LW also inhibited glutathione -S-transferase and acetylcholine esterase activity in C. chinensis and C. maculatus.

Anoxygenic photosynthetic bacteria are common inhabitants of wastewater: we found that Rhodopseudomonas palustris and Afifella marina in eutrophic conditions only partially degraded the azo dye (50 mmol m⁻³), Methyl Red, but completely degraded it under specially defined conditions. The azo dye is potentially a source of both carbon and fixed nitrogen. Rhodopseudomonas palustris and Afifella marina can live heterotrophically, photoheterotrophically or photoautotrophically under anoxic conditions where they can fix N₂ if no organic nitrogen or NH₃ is available. If organic carbon sources are available or if NH₃ is present, the cells again only partially catabolised Methyl Red. In the absence of no alternative organic carbon sources and no NH₃, the cells almost completely spectroscopically decolourised Methyl Red in 4 days. In sewage ponds the ready availability of alternative organic carbon and NH₃ would result in only partial removal of Methyl Red. Rhodopseudomonas cells responded to the availability of Methyl Red in N-free media, by increasing both Optimum irradiance and maximum ETR (E_opt 276.3 μmol quanta m⁻² s⁻¹; ETR_max 391.4 μmol e⁻ g⁻¹ BChl a s⁻¹) compared to control cells incubated in PM media with no organic carbon source and no fixed N-source (E_opt 115.2 μmol quanta m⁻² s⁻¹; ETR_max = 153.0 μmol e⁻ g⁻¹ BChl a s⁻¹. If no alternative C or N sources are available, Rhodopseudomonas embedded in alginate biobeads will completely and repeatedly break down Methyl Red. The marine Afifella readily broke down Methyl Red but again breakdown was only complete if alternative carbon and no fixed nitrogen sources were available. The toxicity of the breakdown products produced by photosynthetic bacteria from azo-dyes needs to be followed up. Photosynthetic bacterial-alginate biobeads have long lifetimes (Rhodopseudomonas ≈ 2 months, Afifella > 6 months) making them of great biotechnological potential.

The anaerobic membrane biofilm reactor (An-MBfR) using dead-end hollow fiber membranes (HFMs) inevitably suffers the limited supply of gaseous electron donors to biofilms, as a result of the back-diffusion of inert gases. The microbial mechanisms, underlying the biofilm formation and decontamination performance of the An-MBfR disadvantaged by limited active gas supply, are still obscure in the literature. Herein, we investigated the evolution laws of biofilm ecology and function in a denitrifying H₂-based An-MBfR, from a multidimensional perspective. Results showed that despite the operating parameters of the reactor were set at the optimal values, the ununiform biofilms were developed on the HFMs, exhibiting a variation trend that with increasing distance from the near-gas end, the thickness and biomass of biofilms were decreased accompanied by their morphological change from the compacted to loosened. As hydrogenotrophic denitrifying bacteria (DNB) suffered limited H₂ supply to the biofilm, they could not produce abundant extracellular polymeric substances (EPS) and result in a high ratio of protein/polysaccharide (PN/PS) ratio in the EPS to facilitate the biofilm growth; their proliferation slowed down, especially in the outer layer of the biofilm at the far-gas end. The propagation of heterotrophic DNB was more active in the outer layer rather than inner layer of biofilms, ascribed to the abundant presence of PN and PS as well as increased NO₃⁻ availability. The variation trends in abundance of functional genes pertinent to the biofilm formation and NO₃⁻ reduction coincided well with the evolution laws of biofilm characteristics and DNB distribution. The findings provided mechanistic insights into the biofilm structure and microbial interaction in the denitrifying An-MBfR.

This study investigates the response of biofilm characteristics to variations in fluid depth and their influence on the corrosion behavior of carbon steel (C1020) under low-flow fluid conditions, utilizing Desulfovibrio vulgaris. The experiments were conducted in an anaerobic chamber at 30 °C, utilizing modified Baar's medium as the testing medium. The findings reveal that fluid depth significantly impacts biofilm-corrosion product composite formation, with deeper depths promoting thicker and more heterogeneous biofilm-corrosion product layer compared to shallower depths, where a thinner and more uniform biofilm-corrosion product layer is observed. Moreover, the characteristics of initially attached biofilms was verified as the primary factor affecting subsequent corrosion behavior during prolonged exposure. Corrosion analysis reveals that greater fluid depth leads to increased weight loss (91 ± 13.2 mg/cm²) and deeper pit depths (540 ± 69 μm), surpassing those observed in shallower test media (21 ± 2.3 mg/cm² and 105 ± 17 μm) after 28 days of exposure. The corrosion products within the biofilm were predominantly FeS and Fe₃(PO₄)₂·8H₂O. A direct relationship was observed between the thickness of this biofilm-corrosion product layer and the progression of pit depth, suggesting a strong correlation between carbon steel corrosion and biofilm development in limited fluid depths (e.g., 5–15 mm). Furthermore, a significant association between the deepest pits (average) and the number of sessile cells within the biofilm underscores the pivotal role of sessile cell numbers in carbon steel corrosion.

Nitrophenol pollutants, including para-nitrophenol (p-NP), are known for their harmful environmental impact due to their persistence, toxicity, and widespread distribution in water sources. While biodegradation generally offers a more effective removal of organic pollutants compared to chemical or physical methods, degrading persistent and toxic compounds like p-NP remains challenging. In this study, a microbial community derived from food processing wastewater was immobilized on coconut coir and adapted to p-NP before being employed for p-NP biodegradation. The spectroscopic analysis demonstrates the effective biodegradation performance of the adapted microbial community, achieving 99% degradation of 50 mg L⁻¹ p-NP in 38 min and 250 mg L⁻¹ p-NP in 4.65 h. The degradation ability of immobilized cells was determined across a broad range of stirring speeds, temperatures, pH levels, and p-NP solution volumes. Complete mineralization of p-NP was confirmed by chemical oxygen demand (COD) measurements of the treated solution and in-situ CO₂ generation. Notably, the p-NP degradation performance of the adapted immobilized microbial community remained stable for the first 40 days, with only a slight decrease observed after 47 days of cold preservation at 4 °C. An average p-NP degradation rate of 0.75 mg L⁻¹ min⁻¹ was maintained over 54 consecutive runs. Significant alterations in microbial diversity were identified through 16S metabarcoding analysis. The unadapted microbial community comprised a diverse range of genera, while the adapted community showed reduced diversity with an enrichment of specific genera known for p-NP degradation, such as unidentified members of the Micrococcaceae family, Paenarthrobacter spp., and Zoogloea spp.