. 2024 Jan 23;90(2):e01090-23. doi: 10.1128/aem.01090-23

TABLE 1.

Operational performance of thermophilic chemostats during the steady operation period^a

Chemostat name	ATL	ATH	PTL	PTH	BTL	BTH	VTL	VTH
Carbon source	Acetate	Acetate	Propionate	Propionate	Butyrate	Butyrate	Isovalerate	Isovalerate
Dilution rate (day⁻¹)	0.025	0.05	0.025	0.05	0.025	0.05	0.025	0.05
HRT (day)	40	20	40	20	40	20	40	20
Inflow concentration (mg·L⁻¹)	20,000	20,000	16,444	16,444	14,667	14,667	13,600	13,600
Gas production rate (mL·L⁻¹·day⁻¹)	115 ± 22	294 ± 67	103 ± 17	383 ± 43	155 ± 28	396 ± 35	143 ± 37	365 ± 18
CH₄ content (%)	58 ± 4	60 ± 5	62 ± 2	63 ± 3	66 ± 2	73 ± 4	67 ± 4	76 ± 6
H₂ partial pressure (Pa)	0.8 ± 0.4	1.4 ± 0.6	2.9 ± 1.2	3.1 ± 1.3	2.3 ± 1.4	2.9 ± 1.3	2.0 ± 1.2	2.5 ± 0.9
pH	8.04 ± 0.14	7.85 ± 0.14	7.95 ± 0.14	7.78 ± 0.14	7.78 ± 0.08	7.63 ± 0.11	7.84 ± 0.14	7.66 ± 0.10
Outflow TOC (mg·L⁻¹)	139 ± 83	132 ± 78	84 ± 49	118 ± 46	87 ± 74	123 ± 91	84 ± 49	114 ± 44
Formate (mg·L⁻¹)^b	ND	ND	ND	ND	ND	ND	ND	ND
Acetate (mg·L⁻¹)	11 ± 22	12 ± 35	6 ± 8	2 ± 4	31 ± 47	27 ± 69	23 ± 53	20 ± 20
Propionate (mg·L⁻¹)	0	0	11 ± 13	15 ± 48	~1.0	~1.0	~1.0	~1.0
Butyrate (mg·L⁻¹)	0	0	0	0	~1.0	~1.0	~1.0	~1.0
Valerate (mg·L⁻¹)	0	0	0	0	0	0	~1.0	~1.0
Iso-valerate (mg·L⁻¹)	0	0	0	0	0	0	~1.0	~1.0
SS (g·L⁻¹)	0.421 ± 0.08	0.543 ± 0.14	0.468 ± 0.11	0.68 ± 0.07	1.43 ± 0.49	1.44 ± 0.38	1.35 ± 0.44	1.38 ± 0.25
VSS (g·L⁻¹)	0.308 ± 0.07	0.392 ± 0.11	0.352 ± 0.10	0.513 ± 0.07	0.62 ± 0.21	0.65 ± 0.18	0.57 ± 0.21	0.67 ± 0.19

^{^a}

HRT, hydraulic retention time; TOC, total organic carbon; SS, suspended solid; VSS, volatile suspended solid; ND, not detected. The operational parameters (e.g., pH, gas production rate, CH₄ content, etc.) were the averages (mean ± SD, n > 30) during the steady-state period in ATL (day 100–550), ATH (day 80–550), PTL (day 100–650), PTH (day 300–450), BTL (day 100–650), BTH (day 300–650), VTL (day 150–650), and ATL (day 300–650) chemostats (Fig. S2). The steady state was defined as the operational parameters (i.e., biogas production, pH, TOC, VSS, and concentrations of VFAs) being relatively stable.

^{^b}

Formate concentration was below the detective limit (10 mg L⁻¹) of the high-performance liquid chromatography.