Aiyong He

Butanol production from hemicellulosic hydrolysate of corn fiber by a Clostridium beijerinckii mutant with high inhibitor-tolerance

A Clostridium beijerinckii mutant RT66 with considerable inhibitor-tolerance obtained by continuous culture was used for butanol production from non-detoxified hemicellulosic hydrolysate of corn fiber treated with dilute sulfuric acid (SAHHC). In fed-batch fermentation, 1.8L of diluted SAHHC containing 10 g/L of reducing sugar was provided during the acidogenic phase and 0.2L of concentrated SAHHC containing 300 g/L of reducing sugar was provided during the solventogenic phase. The mutant produced a total amount of solvents of 12.9 g/L, which consisted of 3.1 g/L of acetone, 9.3 g/L of butanol and 0.5 g/L of ethanol. A solvent yield of 0.35 g/g sugar and a productivity of 0.18 g/L h in 72 h were achieved. The remarkable inhibitor-tolerance of C. beijerinckii RT66 demonstrates that this may be an excellent strain for butanol production from ligocellulosic materials.

Butanol production from acid hydrolyzed corn fiber with Clostridium beijerinckii mutant

Sulfuric acid treated corn fiber hydrolysate (SACFH) inhibited cell growth and the production of butanol (4.7±0.2 g/L) by Clostridium beijerinckii IB4 in P2 medium. Optimal medium components were determined using fractional factorial design. NH4HCO3, FeSO4·7H2O and CaCO3 were demonstrated to be significant components in the production of butanol. The Box-Behnken design and a corresponding quadratic model were used to predict medium components (NH4HCO3 1.96 g/L, FeSO4·7H2O 0.26 g/L and CaCO3 3.15 g/L) and butanol yield (9.5 g/L). The confirmation experiment, under the predicted optimal conditions, yielded a butanol level of 9.5±0.1g/L. This study indicates that the Box-Behnken design is an effective approach for screening the optimal medium components required for the production of butanol. It also demonstrates that SACFH, which has high levels of inhibitors such as furan and phenolic compounds, may be used as a renewable carbon source in the production of biofuels.

Efficient carbon dioxide utilization and simultaneous hydrogen enrichment from off-gas of acetone-butanol-ethanol fermentation by succinic acid producing Escherichia coli.

The off-gas from acetone-butanol-ethanol (ABE) fermentation was firstly used to be CO2 source (co-substrate) for succinic acid production. The optimum ratio of H2/CO2 indicated higher CO2 partial pressures with presence of H2 could enhance C4 pathway flux and reductive product productivity. Moreover, when an inner recycling bioreactor was used for CO2 recycling at a high total pressure (0.2Mpa), a maximum succinic acid concentration of 65.7g·L(-1) was obtained, and a productivity of 0.76g·L(-1)·h(-1) and a high yield of 0.86g·g(-1) glucose were achieved. Furthermore, the hydrogen content was simultaneously enriched to 92.7%. These results showed one successful attempt to reuse the off-gas of ABE fermentation which can be an attractive CO2 source for succinic acid production.

Ultrasound-assisted D-tartaric acid whole-cell bioconversion by recombinant Escherichia coli

d-Tartaric acid has wide range of application in the pharmaceutical industry and scarcely exists in nature. In this study, cis-epoxysuccinate hydrolase (CESH)-containing Escherichia coli was used to perform whole-cell bioconversion of cis-epoxysuccinate (CES) to D-tartaric acid and the catalytic efficiency was investigated by ultrasound treatment. The bioconversion rate of CES sodium reached 70.36% after 60 min treated after ultrasound, which is 3-fold higher than that in the control. The specific rate could be further improved by 2-fold after 5 repeated batches compared with the first one, however, the specific rate gradually decreased with the increase of repeat batches (>5 batches). The CESH from Bordetella sp. BK-52 was a typical Michaelis-Menten enzyme with Vmax and Km values of 28.17 mM/h/g WCW (wet of cell weight) and 30.18 mM, respectively. The process for the d-tartaric acid bioconversion, which consisted of 102.31 g/L CES sodium, 8.78 mg/mL whole cell and ultrasound power of 79.36 W, is further optimized using response surface methodology. The specific rate finally reached 194.79 ± 1.78 mM/h/g WCW under the optimal conditions. Furthermore, the permeability of inner and outer membrane was improved approximately 1.6 and 1.4-fold after ultrasound treatment, respectively, which may be a crucial factor for improvement of the bioconversion efficiency.