6400 calorimeter

All food and feces labeled with brilliant green dye (used in the intervention) were collected, mixed well, and lyophilized. 24-hour urine from the intervention day was collected and underwent direct lyophilization. Lyophilization was performed at -50°C using an instrument (SJIA-5FE, ShuangJia Instrument, Ningbo, China). Calories were measured by using bomb calorimetry according to the published protocol (29 (link)) (Parr 6400 Calorimeter, PARR Instrument Co., Moline, IL). To minimize the error of measurements, all samples were measured repeatedly. If the difference between repeated samples > 50 Cal, measurements were repeated until the difference < 50 cal. We averaged two qualified measurements as the final calories of each sample. Food and fecal protein concentration were determined by the Kjeldahl method, fat concentration was determined by the Soxhlet method, and carbohydrates concentration was calculated by subtracting the protein, fat, water, and ash from the total weight of the sample.

Diets or feces were ground to pass through a 0.42-mm sieve and thoroughly mixed before analysis. Diets and feces were analyzed for DM (method 930.15; AOAC [24 ]), CP (method 984.13; AOAC [24 ]), ether extract (EE; method 920.39; AOAC [24 ]), neutral (NDF) [25 (link)] and acid detergent fiber (ADF; method 973.18; AOAC [24 ]). GE of diets, feces or in vitro undigestible residue was measured using an automatic isoperibol oxygen bomb calorimeter (Parr 6400 Calorimeter; Parr Instrument Company, Moline, IL, USA).

A low-rank coal sample was collected from Pingshuo power generation plant in Shanxi Province, China. Proximate analysis and ultimate analysis of the coal sample were performed using a thermogravimetric analyzer (TGA-701, LECO) and an elemental analyzer (vario Macro CHNS, Elementar), respectively, and the calorific value was determined by an adiabatic bomb calorimetry (Parr 6400 Calorimeter, Parr). The results obtained are summarized in Table 2. Additionally, the chemical compositions of the coal ash were determined by X-ray fluorescence (XRF) spectrometer (S4-Explorer, Bruker) and the results are detailed in Table 2. The coal sample was first dried for 24h at 105 ^oC and then crushed and ground to a size smaller than 150 um.
Industrial steel slags were acquired from Shougang Corporation in Beijing, China, the chemical compositions of which were measured by XRF (S4-Explorer, Bruker) and displayed in Table 2. The slag was first crushed into small particles after drying, and then thoroughly mixed with the coal powder using a ball grinder for the subsequent gasification. Three samples were prepared using the foregoing materials, i.e., a raw steel slag sample (S0), a raw coal sample (S1) and a mixture with the mass ratio of coal sample to steel slags of 1:1 (S2), respectively.

In the short-term HFD study, fecal samples from three groups were collected for 24 h following 1 week of HFD feeding. Samples from five mice in each group were combined, and the fecal microbiota composition was analyzed by Illumina sequencing performed by GenomicWorks (GenomicWorks, Daejeon, Korea) as described previously^{33 (link)–36 (link)}. Briefly, PCR amplification was performed with extracted DNA using primers targeting the V3–V4 regions of the 16S rRNA gene. The amplified products were purified with a QIAquick PCR purification kit (Qiagen, Valencia, CA) and assessed on a Bioanalyzer 2100 (Agilent, Palo Alto, CA) using a DNA 7500 chip. Sequencing was carried out with an Illumina MiSeq Sequencing System according to the manufacturer’s instructions (Illumina, San Diego, CA). To measure fecal exergy excretion, feces were collected during the last 48 h, and calorie content in dried feces was analyzed by bomb calorimetry using a Parr 6400 Calorimeter (Parr, Moline, IL).