Promoting nitrogen conversion in aerobic biotransformation of swine slurry with the co-application of manganese sulfate and biochar

This study aimed to explore the co-application of MnSO4 (Mn) and biochar (BC) in nitrogen conversion during the composting process. A 70-day aerobic composting was conducted using swine slurry, supplemented with different levels of Mn (0, 0.25%, and 0.5%) and 5% BC. The results demonstrated that the treatment with 0.5MnBC had the highest levels of NH4+-N (3.07 g kg-1), TKN (29.90 g kg-1), and NO3--N (1.94 g kg-1) among all treatments. Additionally, the 0.5MnBC treatment demonstrated higher urease, protease, nitrate reductase, and nitrite reductase activities than the other treatments, with the peak values of 18.12, 6.96, 3.57, and 15.14 mg g-1 d-1, respectively. The addition of Mn2+ increased the total organic nitrogen content by 29.59%-47.82%, the acid hydrolyzed ammonia nitrogen (AN) content by 13.84%-57.86% and the amino acid nitrogen (AAN) content by 55.38%-77.83%. The richness of Chloroflexi and Ascomycota was also enhanced by the simultaneous application of BC and Mn. Structural equation modeling analysis showed that Mn2+ can promote the conversion of Hydrolyzed Unknown Nitrogen (HUN) into AAN, and there is a positive association between urease and NH4+-N according to redundancy analysis. Firmicutes, Basidiomycota, and Mortierellomycota showed significant positive correlations with ASN, AN, and NH4+-N, indicating their crucial roles in nitrogen conversion. This study sheds light on promoting nitrogen conversion in swine slurry composting through the co-application of biochar and manganese sulfate.

Impact of elevated phosphogypsum on soil fertility and its aerobic biotransformation through indigenous microorganisms (IMO's) based technology

Phosphogypsum (PG) is a waste by-product of phosphate fertilizer industry, produced in huge amount during the manufacture of phosphoric acid by economic wet process. Assessment of PG toxicity on soil has been poorly emphasized, therefore an efficient methods needs to be adopted to assess its toxic effect on soil fertility. We also need an effective eco-technological strategies for better waste PG management in order to improve the environmental health. The present study aimed to investigate the impact of PG toxicity on fertile soil and utilization of indigenous microorganisms for aerobic detoxification of PG contaminated soil to evaluate the scope for biostimulation based in situ bioremediation. In this study it is evident that application of PG to fertile soil in certain concentration results highly acidic, sulfate rich, aerobic environment, thus severely weakens the metabolic activity of the indigenous microorganisms. This investigation via microcosm based study further evaluated the intrinsic biotransformation ability of these microorganisms and found that was enhanced significantly (>95% reduction in sulfate concentration in 180 days) with carbon, nitrogen and phosphate amendments. Community level physiological profiling analyses indicated distinct shift in metabolic abilities following carbon amendments. Our study for the first time may help to formulate a strategy in aerobic biotransformation of PG contaminated soil environment, yet appreciable rate by supplying adequate nutrients.

Rates and product identification for trenbolone acetate metabolite biotransformation under aerobic conditions

Trenbolone acetate metabolites are endocrine-active contaminants discharged into the aquatic environment in runoff from agricultural fields, rangelands, and concentrated animal feeding operations. To investigate the environmental fate of these compounds and their biotransformation mechanisms, the authors used inocula from a variety of different water sources and dosed biologically active microcosms with approximately 1400 ng/L of trenbolone acetate metabolites, including 17β-trenbolone, trendione, and 17α-trenbolone. To investigate aerobic biotransformation rates and interconversions between known trenbolone acetate metabolites, gas chromatography-tandem mass spectrometry was used to measure concentrations and assess product distributions as a function of time. High-resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to characterize novel transformation products and potential transformation pathways. Kinetic analysis yields observed half-lives of approximately 0.9 d, 1.3 d, and 2.2 d for 17β-trenbolone, trendione, and 17α-trenbolone, respectively, at 20 °C, although colder conditions increased half-lives to 8.5 d and biphasic transformation was observed. Relative to reported faster attenuation rates in soils, trenbolone acetate metabolites are likely more persistent in aqueous systems. Product distributions indicate an enzymatic preference for biotransformation between trendione and 17β-trenbolone. The LC-MS/MS characterization indicates dehydrogenation products as the major detectable products and demonstrates that major structural elements responsible for bioactivity in steroids are likely retained during biotransformation.

Aerobic biotransformation potential of a commercial mixture of naphthenic acids

The biotransformation potential of a commercial naphthenic acid (NA) mixture (NA sodium salt; TCI Chemicals) under aerobic conditions was investigated using mixed aerobic cultures developed under various levels and duration of NA exposure. A culture enriched using the commercial NA mixture as the sole carbon source degraded NAs in a range of NA concentrations, regardless of culture age and the presence of a co-substrate; however, only 28.5% of the NA-carbon was detected as CO2 while 44% was utilized for biomass growth. A fraction of the NA mixture (15-26%) was persistent under all conditions studied. In contrast, a culture fed with a degradable synthetic wastewater only (NA un-amended culture) and another culture fed with the same wastewater and 50 mg NA/L (NA-amended culture), over time lost their ability to degrade NAs. Analysis of the 16S rRNA gene based clone library revealed that 80% of the NA-enriched culture belonged to the γ-Proteobacteria class and was largely dominated by phylotypes most closely related to known NA and hydrocarbon degraders such as Pseudomonas and Microbulbifer. The results of this study indicate that although significant NA degradation is possible, only a small fraction of the NA mixture is completely mineralized to CO2. Further investigation into the biotransformation products and conditions affecting NA biodegradation under realistic refinery and environmental conditions will help to design effective treatment and bioremediation processes.

Degradation of multiwall carbon nanotubes by bacteria

Understanding the environmental transformation of multiwall carbon nanotubes (MWCNTs) is important to their life cycle assessment and potential environmental impacts. We report that a bacterial community is capable of degrading (14)C-labeled MWCNTs into (14)CO2 in the presence of an external carbon source via co-metabolism. Multiple intermediate products were detected, and genotypic characterization revealed three possible microbial degraders: Burkholderia kururiensis, Delftia acidovorans, and Stenotrophomonas maltophilia. This result suggests that microbe/MWCNTs interaction may impact the long-term fate of MWCNTs.

Adsorption, inhibition, and biotransformation of ciprofloxacin under aerobic conditions

The adsorption, inhibition, and biotransformation of the fluoroquinolone antibiotic ciprofloxacin (CIP) under aerobic conditions were investigated in this study. The maximum adsorption capacity and the Langmuir constant were 37.9 mg CIP/g VSS and 37 L/g, respectively. A glucose-fed aerobic culture was inhibited by CIP at 10mg/L or higher and the degree of inhibition increased with increasing CIP concentration. However, the microbial activity recovered to some extent with prolonged incubation under a semi-continuous feeding mode. A low extent of CIP biotransformation was observed in an aerobic, glucose-fed culture derived from poultry litter extract. LC/UV/MS analysis of the biotransformation product showed that only the piperazine ring was oxidized, while the antibiotic quinolone part of CIP was intact.