LCMS-food waste compost FCFS-NEW
Description
(A) Variations in temperature, pH, moisture content, EC, total carbon, total nitrogen, NH4+-N, NO3--N, available phosphorus (P), and available potassium (K). (B) Variations in cellulose, hemicellulose, oil, and lignin. (C) Variations in C/N and GI. (D) Variations in bacterial community diversity and composition during composting. (E) Analysis of metabolite dynamics during composting.
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Temperature sensors (NJSWB-1110, Testo, Shanghai, China) were used to record the temperature. The water extract was obtained by mixing 3 g of fresh sample and 30 mL of deionized water and filtered with filter paper (diameter 150 mm, Quantitative filter paper, BKMAM, Changde, China) to measure the pH, electrical conductivity (EC), and seed germination index (GI). Moisture content was measured by drying fresh samples in an oven (Mechanical Convection Oven, ThermoFisher, Beijing, China) at 105 ℃. An elemental analyzer (PE2400, PerkinElmer, Shanghai, China) was used to determine the total carbon (TC) and total nitrogen (TN) contents. Fresh solid samples were also extracted using 2 M potassium chloride (1:10, weight/volume) (Guo Yao, Beijing, China) to determine the concentrations of ammonium (NH4+-N) and nitrate (NO3--N) using a segmented flow analyzer (Technicon Autoanalyzer System, SPXFLOW, Charlotte, North Carolina, USA). Available phosphorus (P) and available potassium (K) were determined in accordance with a previously reported method (Tabrika et al., 2021), and GI was measured in accordance with a previously reported method (Wang et al., 2022b). Twenty bok choy (Shanghai green) seeds were used for each treatment. The oil content was determined according to a previously reported method (H'ng et al., 2017). The oil content was defined as the mass of organic matter recovered compared with the initial mass of the compost (Liu et al., 2023a) sample and was presented as a percentage. Total organic matter was determined using a loss-on-ignition method by burning the dried sample in a muffle furnace at 550 ℃ for 24 h. Cellulose, hemicellulose, and lignin contents were measured using an adapted version of the method described by Zheng et al. (2021). To completely hydrolyze cellulose and hemicellulose, 0.7 g of air-dried and ground (5 mm sieve) compost samples were boiled with 5 mL of 72 % (v/v) H2SO4 for 4.5 h. The crushed liquid was suction filtered, and the residue was dried to a constant mass at 105 ℃ and weighed as Wl. The dried residue was transformed into a dry porcelain crucible and heated at 650 ℃ for 5 h (W2). The acid-insoluble lignin content was calculated as the difference between Wl and W2. The glucose (C1) and reducing sugar (C2) contents in the filtrate were measured using a Glucose (HK) Assay kit (Sigma-Aldrich, St. Louis, Missouri, USA) and the DNS method (MILLER, 1959), respectively. The use method has completely followed the manufacturer's instructions. The cellulose content was calculated as (0.9/0.96) × C1 × (V/M) × α × 100 %, where 0.9 indicates the molecular mass ratio of monomer hexose to polymer and 0.96 indicates the saccharification coefficient, Cl represents the glucose content (g·L-1), V represents the total volume of the sugar solution (L), M represents the mass of dry matter added to the sample, and α indicates the dilution time. The hemicellulose content was calculated as (0.88/0.93) × (C2 - C1) × (V/M) × α × 100 %.