Steering the product spectrum in high-pressure anaerobic processes: CO2 partial pressure as a novel tool in biorefinery concepts

Table 3 Summary of p-values^a from the aligned rank transform test for the main and interaction effects of elevated partial pressure of CO₂ (pCO₂) or N₂ (pN₂), substrate concentration and addition of external electron donor (formate) in carboxylates production and cell density during Experiment II

Independent factor		pCO₂		Substrate concentration (S/X ratio)	pCO₂		External electron donor
Interaction		pCO₂	pCO₂: substrate concentration (S/X ratio)	Substrate concentration (S/X ratio)	pCO₂	pCO2: external electron donor	External electron donor
Dependent variable	Propionate (mg COD L⁻¹)	0.81	0.94	****	0.78	0.07	0.59
	Butyrate (mg COD L⁻¹)	0.37	****	****	0.62	0.11	0.76
	Acetate (mg COD L⁻¹)	0.25	0.31	0.13	0.31	0.43	0.36
	Succinate (mg COD L⁻¹)	0.22	0.18	0.67	0.26	****	****
	Cell density (cells m L⁻¹)	0.77	0.09	*	0.87	0.75	****

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