Table 2.
Solvent and acid yields of C. pasteurianum DSM 525 (WT) and its various mutant derivatives when grown in bioreactors on either glucose or glycerol as the carbon source. Mutants were: C. pasteurianum DSM 525-H1Δrex (Δrex, CRG5522); C. pasteurianum DSM 525-H1Δhyd (Δhyd, CRG5528), and; C. pasteurianum DSM 525-H1ΔdhaBCE (ΔdhaBCE, CRG5534). Abbreviations used: butanol (BuOH), ethanol (EtOH), 1,3-propanediol (PDO), solvents (EtOH, BuOH, PDO), acids (acetate, butyrate, lactate). Carbon recovery was calculated by assuming 3.5 g/l dry-weight per 10 OD values (Sarchami et al., 2016), carbon dioxide desorption as described by Percheron et al. (1995) and the assumption that 46.2% of dry-weight is carbon (Papoutsakis and Meyer, 1985). The carbon fraction of yeast extract was neglected. *Fermentation of ΔdhaBCE was undertaken in serum bottles along with a wild type control.
| Carbon source |
60 g/l glycerol |
60 g/l glucose |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Medium |
Biebl plus 1 g/l yeast extract |
2x YT* |
Biebl |
|||||||
| Strain | Δrex | Δhyd | WT | ΔdhaBCE | WT | Δrex | Δhyd | ΔdhaBCE | WT | |
| Growth characteristics | ||||||||||
| Specific growth rate [h−1] | 0.32±0.04 | 0.35±0.01 | 0.42±0.01 | 0.39±0.00 | 0.40±0.00 | 0.15±0.02 | 0.11±0.01 | 0.13±0.03 | 0.16±0.03 | |
| Doubling time [min] | 135±15 | 119±3 | 100±1 | 106±1 | 105±0 | 90±9 | 103±10 | 85±4 | 81±12 | |
| Max. OD | 15.0±0.5 | 17.5±0.6 | 15.3±0.3 | 4.38±0.12 | 4.48±0.01 | 34.9±1.0 | 36.2±0.1 | 34.8±2.5 | 34.3±2.7 | |
| Carbon recovery [%] | 88.9±2.7 | 91.4±1.3 | 90.5±4.4 | 114.4±6.0 | 127.8±5.4 | 70.7±14.3 | 83.5±15.0 | 72.3±13.9 | 73.3±14.9 | |
| Selectivity [M/M] | ||||||||||
| BuOH/Solvents | 0.516±0.002 | 0.312±0.003 | 0.289±0.024 | 0.862±0.002 | 0.795±0.001 | 0.703±0.015 | 0.729±0.021 | 0.635±0.027 | 0.563±0.051 | |
| Yield [M/M] | ||||||||||
| BuOH/C-Source | 0.250±0.005 | 0.166±0.004 | 0.142±0.003 | 0.399±0.019 | 0.431±0.021 | 0.124±0.034 | 0.156±0.029 | 0.041±0.008 | 0.031±0.003 | |
| EtOH/C-Source | 0.053±0.006 | 0.102±0.001 | 0.037±0.000 | 0.064±0.002 | 0.066±0.003 | 0.055±0.018 | 0.061±0.017 | 0.025±0.007 | 0.026±0.008 | |
| PDO/C-Source | 0.182±0.000 | 0.265±0.005 | 0.317±0.034 | 0.000±0.000 | 0.046±0.002 | n.a. | n.a. | n.a. | n.a. | |
| Solvents/C-Source | 0.484±0.011 | 0.533±0.007 | 0.496±0.030 | 0.463±0.021 | 0.542±0.026 | 0.179±0.052 | 0.217±0.046 | 0.066±0.016 | 0.057±0.001 | |
| Acids/C-Source | 0.050±0.006 | 0.106±0.000 | 0.114±0.008 | 0.122±0.009 | 0.136±0.004 | 0.567±0.129 | 0.567±0.153 | 0.686±0.156 | 0.708±0.177 | |