Reduced catabolic protein expression in Clostridium butyricum DSM 10702 correlate with reduced 1,3-propanediol synthesis at high glycerol loading

AMB Express

Table 3 C. butyricum growth parameters, with aqueous and gaseous end-product concentrations for low (170 mM) vs high (620 mM) initial glycerol concentrations after 20 hours of fermentation

Parameter/Glycerol Concentration	170 mM	620 mM
C Balance	1.05	1.08
Specific Growth Rate (h⁻¹) ^a	0.175	0.113
Substrate utilization (%)	92.1	28.3
Y PDO/s (mol /mol)	0.51 ± 0.01	0.55 ± 0
PDO (g/L h)	0.31 ± 0.01	0.16 ± 0.01
PDO (g/L)	6.15 ± 0.13	3.13 ± 0.11
Y Buty/s (mol /mol)	0.18 ± 0	0.22 ± 0.01
Buty (g/L)	2.46 ± 0.05	1.28 ± 0.37
Y Acet/s (mol /mol)	0.02 ± 0	0
Acet (g/L)	0.23 ± 0.02	0.04 ± 0
Y H₂/s (mol /mol)	0.13 ± 0.02	0.19 ± 0.01
H₂ (mmol/L)	20.84 ± 3.29	32.47 ± 4.76
Y CO₂/s (mol /mol)	0.47 ± 0.08	0.60 ± 0.01
CO₂ (mmol/L)	74.76 ± 12.84	100.58 ± 3.42

^aGrowth rate was calculated from the increase in number of cells with time during the exponential phase. Carbon recovery was calculated from the ratio of (carbon out)/(carbon in) where the formula C₄H₇O₂N (Zeng et al., [1993]) was used for C. butyricum biomass; Y, Yield; PDO, 1,3-PDO; Buty, butyrate; Acet, acetate. Three independent biological replicates were used for each experiment.