Carbon and Nutrients from Organic Residues Modulate the Dynamics of Prokaryotic and Fungal Communities

Inputs of carbon (C) and nutrients from organic residues may select specific microbes and shape the soil microbial community. However, little is known about the abiotic filtering of the same residues with different nutrient concentrations applied to the soil. In our study, we explored how applying organic residue, vinasse, as fertilizer in its natural state (V) versus its concentrated form (CV) impacts soil microbiota. We conducted two field experiments, evaluating soil prokaryotic and fungal communities over 24 and 45 days with vinasse (V or CV) plus N fertilizer. We used 16S rRNA gene and ITS amplicon sequencing. Inorganic N had no significant impact on bacterial and fungal diversity compared to the control. However, the varying concentrations of organic C and nutrients in vinasse significantly influenced the soil microbiome structure, with smaller effects observed for V compared to CV. Prokaryotic and fungal communities were not correlated (co-inertia: RV coefficient = 0.1517, p = 0.9708). Vinasse did not change the total bacterial but increased the total fungal abundance. A higher C input enhanced the prokaryotic but reduced the fungal diversity. Our findings highlight vinasse's role as an abiotic filter shaping soil microbial communities, with distinct effects on prokaryotic and fungal communities. Vinasse primarily selects fast-growing microorganisms, shedding light on the intricate dynamics between organic residues, nutrient concentrations, and soil microbes.

Gas chromatography-mass spectrometric determination of organic acids by ion pair liquid extraction followed by in-situ butylation from aqua feed samples

A rapid and sensitive analytical method was developed to quantitatively determine organic acids (OAs) from fish feed samples extracted by ion-pair (IP) solvent extraction, followed by in-situ butylation and gas chromatography-mass spectrometric (GC-MS) analysis. The extraction of OAs was carried out with acetonitrile containing 10 mM tetrabutylammonium hydroxide (TBAH), and the analytes were derivatized to their butyl esters in the injection port of the GC-MS system. The developed method was validated in the range of 1-5000 ng/g, with recoveries ranging from 93-117%. The limit of detection (LOD) and limit of quantification (LOQ) of the method was 1-5 ng/g and 2-10 ng/g, respectively, yielding good linearity (R² > 0.9990) and precision with a relative standard deviation less than 10%. The proposed method was successfully applied to analyze OAs in sinking and floating fish feed samples. The analyzed samples showed the presence of benzoic, succinic, fumaric, glutaric, adipic, and phthalic acids in sinking feed samples; and benzoic, succinic, adipic, phthalic acids in floating feed samples, respectively.

[Determination of eight organic residues in ion exchange resins by headspace gas chromatography]

An analytical method based on headspace gas chromatography was developed for the determination of eight organic residues in ion exchange resins, methyl isopropyl ketone, methyl butyrate, 3-pentanone, 1,3-diethyl benzene, 1,4-diethyl benzene, dichloroethane, 1,3-dichlorobenzene, and methyl methacrylate. The organic residues in different types of resins were studied to provide a basis for the safe use of ion-exchange resins in food and medicine. The main factors (chromatographic column, equilibrium temperature, equilibrium time, flow rate, etc.) that affect the accuracy and sensitivity of the eight organic residues were investigated during instrument analysis. The extraction solvent and chromatographic conditions for the samples were optimized. According to the extraction efficiencies of methyl benzene, methyl alcohol and dimethyl sulfoxide, 2.0 g of the sample was extracted with dimethyl sulfoxide under ultrasonic conditions at 20 ℃. A DB-23 chromatographic column (60 m×0.32 mm×0.25 μm) and hydrogen flame ionization detector (FID) were selected for the GC method, and good separation and quantitative results were obtained for the eight organic residues. The process and conditions are summarized as follows. The equilibration time of the headspace sampler was 30 min, and the equilibrium temperature was 80 ℃. The temperature of the sampler was 240 ℃, while that of the FID detector was 300 ℃, with nitrogen being used as the carrier gas. The programmed temperature of the column was maintained at 60 ℃ for 16 min, then increased to 200 ℃ at a heating rate of 20 ℃/min, and maintained at this level for 2 min. The flow rate was 1.2 mL/min for detection. The external standard method was utilized for quantitative analysis. Good linear relationships were observed for the eight organic residues, and the correlation coefficients (R²) were all above 0.999 in the mass concentration range of 0.02-200 mg/L. The limits of detection (LODs) were 0.0050-0.0375 ng/g. The average recoveries for the eight organic residues were in the range of 82.3% to 109.2% at three spiked levels, and the relative standard deviation (RSD, n=6) was 1.06% to 4.16%. Eleven types of resin samples were detected by this method, and a certain amount of organic compounds were observed in the resin samples. The methyl methacrylate content in the methacrylate resin XAD761 was 414.4 μg/g, while that in the styrene resin LX-69B was as high as 470.8 μg/g. As opposed to traditional analytical methods, the present method has high sensitivity, good accuracy, and precision, with simple operation without derivatization or the need for acid-base treatment of the sample to reduce contamination. This method can be used to simultaneously detect a variety of organic residues in ion-exchange resins, so that the detection efficiency is significantly improved.