To evaluate the ability of microbial mix-culture fermenting syngas into ethanol, we studied the microbial mix-cultures A-fm 4, G-fm 4, Lp-fm 4 and B-fm 4 obtained by enrichment and compared with Clostridium autoethanogenum DSM10061 with 10% and 25% inoculation size. The results show that, with 10% inoculation size, the ethanol production of A-fm 4, G-fm 4, Lp-fm 4, B-fm 4 and C. autoethanogenum were 349.15, 232.16, 104.25, 79.90 and 26.99 mg/L respectively. With 25% inoculation size, the ethanol production were 485.81, 472.73, 348.58, 272.52 and 242.15 mg/L respectively. Higher inoculation size will increase the production of ethanol. The tested mix-culture exhibited a significant yield advantage compared with the maximum production of C. autoethanogenum reported in the literature (259.64 mg/L). This research provided a practical method to improve ethanol production from syngas.
Bacteria ; classification ; metabolism ; Clostridium acetobutylicum ; metabolism ; Ethanol ; isolation & purification ; metabolism ; Fermentation ; Gases ; metabolism ; Hydrogen ; metabolism

The low butanol concentration of acetone-butanol-ethanol fermentation causes uneconomical product recovery. In this work, the effect of small molecule non-ionic surfactants on butanol fermentation was evaluated, using laboratory stocks of Clostridium acetobutylicum ATCC 824. Non-ionic surfactants substantially increased butanol production when additive amount was higher than 1% (W/W). Butanol concentration reached 16.9 g/L with 5% (W/W) Tween 80 and 100 g/L glucose in a 5 L fermenter. It was found that surfactants micelle solubilization capacity to butanol was very limited, indicating that butanol could hardly enter the surfactants micelle. Butanol production improvement was probably caused by cell surface hydrophobicity change due to surfactants adsorption.
Acetone ; chemistry ; Bioreactors ; Butanols ; chemistry ; Clostridium acetobutylicum ; metabolism ; Ethanol ; chemistry ; Fermentation ; Surface-Active Agents ; chemistry

Butanol production from acid hydrolysate of Jerusalem artichoke juice by Clostridium acetobutylicum L7 was investigated, and it was found that natural components of the hydrolysate were suitable for solvent production with the species. With batch fermentation using the medium containing 48.36 g/L total sugars, 8.67 g/L butanol was produced at 60 h, and the ratio of butanol to acetone to ethanol was 0.58:0.36:0.06, which were similar to the fermentation with fructose as carbon source, but both of these two fermentations were slower than that with glucose as carbon source, indicating the fructose transport of the species might not be effective as that for glucose. When the total sugars of the medium were increased to 62.87 g/L, the residual sugars increased slightly from 3.09 g/L to 3.26 g/L, but butanol production of the fermentation system was improved significantly, with 11.21 g/L butanol produced and the ratio of butanol to acetone to ethanol at 0.64:0.29:0.05, which illustrated that an excess in sugars enhanced the butanol biosynthesis of the species by compromising its acetone production. When the sugar concentration of the medium was further increased, much more sugars were remained unconsumed, making the process economically unfavourable.
Butanols ; metabolism ; Clostridium acetobutylicum ; metabolism ; Fermentation ; Helianthus ; chemistry ; Industrial Microbiology ; methods

Clostridium acetobutylicum, a biofuel-butanol producer, has attracted worldwide interests. Strain improvement is important for the process of biobutanol industrialization where efficient genetic modification systems are essential. In this review, the history of genetic modification systems of C. acetobutylicum was introduced, and the types and principles of these systems and their disadvantages are summarized and analysed. The development of updated genetic modification systems for C. acetobutylicum is also proposed.
Biofuels ; Butanols ; analysis ; metabolism ; Clostridium acetobutylicum ; genetics ; Gene Expression Regulation, Bacterial ; Genetic Engineering ; Genetic Techniques

Clostridium acetobutylicum is an important strain for bio-butanol formation. In recent years, gene-editing technology is widely used for developing the hyper-butanol-production strains. In this study, three genes (cac1251, cac2118 and cac2125) encoding cell division proteins (RodA, DivIVA and DivIB) in C. acetobutylicum were knocked out. The cac2118-knockout strain had changed its cell morphology to spherical-shape during the solventogenesis, and obtained a higher butanol yield of 0.19 g/g, increasing by 5.5%, compared with the wild type strain. The glucose utilization and butanol production of cac1251-knockout strain decreased by 33.9% and 56.3%, compared the with wild type strain, reaching to 47.3 g/L and 5.6 g/L. The cac1251-knockout strain and cac2125-knockout strain exhibited poor cell growth with cell optical density decreased by 40.4% and 38.3%, respectively, compared with that of the wild type strain. The results indicate that cell division protein DivIVA made the differences in the regulation of cell morphology and size. Cell division proteins RodA and DivIB played significant roles in the regulation of cell division, and affected cell growth, as well as solventogenesis metabolism.
Butanols ; Cell Division/genetics* ; Clostridium acetobutylicum/genetics* ; Fermentation ; Gene Knockout Techniques ; Solvents

Solventogenic clostridia are important industrial microorganisms. Optimization of the fermentation performance of solventogenic clostridia, through genetic modification, has always been considered as the main topic involved in solvents production. However, due to the incomplete genetic tools, no research breakthroughs have been achieved. In recent years, with the development of new technologies and methods (e.g. TargeTron gene knockout, large DNA fragment integration method), great progresses have been made towards genetic engineering solventogenic clostridia. In this review, we summarize the development of the genetic tools for solventogenic clostridial species, and simultaneously point out the shortages of the existing technologies in efficiency and comprehensiveness. Therefore, optimization of the existing technologies in gene inactivation in clostridia, such as establishing homologous exchange-based gene deletion and exchange, is still imperative; and in parallel, new genetic tools (e.g. multiplex genome editing, targeted or random multi-copy gene integration) should also be timely developed.
Acetone ; metabolism ; Butanols ; metabolism ; Clostridium ; genetics ; metabolism ; Clostridium acetobutylicum ; genetics ; metabolism ; Clostridium beijerinckii ; genetics ; metabolism ; Ethanol ; metabolism ; Fermentation ; Genetic Engineering ; methods ; Industrial Microbiology ; methods ; Solvents ; metabolism

Sugarcane bagasse modified by polyethylenimine (PEI) and glutaraldehyde (GA) was used as a carrier to immobilize Clostridium acetobutylicum XY16 in the process of butanol production. The effects of chemically modified sugarcane bagasse on batch and repeat-batch fermentations were investigated. Batch fermentation was conducted with an addition of 10 g/L modified sugarcane bagasse and 60 g/L glucose, resulting in a high solvent concentration of 21.67 g/L and productivity of 0.60 g/(L x h) with the treatment of 4 g/L PEI and 1 g/L GA. Compared to the fermentations by free cells and immobilized cells on unmodified sugarcane bagasse, the productivity increased 130.8% and 66.7%, respectively. The fibrous-bed bioreactor also maintained a stable butanol production during repeat-batch fermentations, achieving a maximum productivity of 0.83 g/(L x h) with a high yield of 0.42 g/g.
Batch Cell Culture Techniques ; Bioreactors ; Butanols ; metabolism ; Cells, Immobilized ; Cellulose ; metabolism ; Clostridium acetobutylicum ; metabolism ; Fermentation ; Saccharum ; chemistry

Protein phosphorylation in bacteria is important for signaling and metabolic activity. Clostridium acetobutyicum can synthesize high yield of organic solvent under acidic condition. How solventogenesis is regulated at molecular level in this bacterium, is not clearly elucidated yet. We used two dimensional electrophoresis (2-DE) and mass spectrometry to have a differential analysis of the bacterial proteins from Clostridium acetobutylicum at acedogenic and solventogenic stage. We focused on these iso-spots with similar molecular mass and different pI values. Totally, eight string spots were identified, which displayed significant changes of pI values as well as spot volumes in response to solventogenic development. The data acquired from mass spectrometry demonstrated that all of the iso-spots contained the phosphrylated peptides. Bioinformatic analysis revealed that these proteins partake in the pathways of solvent synthesis.
Bacterial Proteins ; metabolism ; Clostridium acetobutylicum ; genetics ; metabolism ; Electrophoresis, Gel, Two-Dimensional ; Mass Spectrometry ; Phosphorylation ; Proteome ; analysis ; Proteomics ; methods

We used ribosome engineering technology, with which antibiotic-resistant strains are resulted from mutations on microbial ribosome, to screen a high butanol-producing Clostridium strain. A novel mutant strain S3 with high butanol production and tolerance was obtained from the original Clostridium acetobutylicum L7 with the presence of mutagen of streptomycin. Butanol of 12.48 g/L and ethanol of 1.70 g/L were achieved in S3, 11.2% and 50%, respectively higher than the parent strain. The conversion rate of glucose to butanol increased from 0.19 to 0.22, and fermentation time was 9 h shorter. This caused an increase in butanol productivity by 30.5%, reaching 0.24 g/(Lh). The mutant butanol tolerance was increased from 12 g/L to 14 g/L, the viscosity of fermentation broth was dramatically decreased to 4 mPa/s, 60% lower than the parent strain. In addition, the genetic stability of mutant strain S3 was also favorable. These results demonstrate that ribosome engineering technology may be a promising process for developing high butanol-producing strains.
Butanols ; metabolism ; Clostridium acetobutylicum ; drug effects ; genetics ; metabolism ; Fermentation ; Genetic Engineering ; Mutation ; Recombinant Proteins ; biosynthesis ; genetics ; Ribosomes ; genetics ; Streptomycin ; pharmacology

Cell autolysis plays important physiological roles in the life cycle of clostridial cells. Understanding the genetic basis of the autolysis phenomenon of pathogenic Clostridium or solvent producing Clostridium cells might provide new insights into this important species. Genes that might be involved in autolysis of Clostridium acetobutylicum, a model clostridial species, were investigated in this study. Twelve putative autolysin genes were predicted in C. acetobutylicum DSM 1731 genome through bioinformatics analysis. Of these 12 genes, gene SMB_G3117 was selected for testing the in tracellular autolysin activity, growth profile, viable cell numbers, and cellular morphology. We found that overexpression of SMB_G3117 gene led to earlier ceased growth, significantly increased number of dead cells, and clear electrolucent cavities, while disruption of SMB_G3117 gene exhibited remarkably reduced intracellular autolysin activity. These results indicate that SMB_G3117 is a novel gene involved in cellular autolysis of C. acetobutylicum.
Autolysis ; genetics ; Clostridium acetobutylicum ; genetics ; metabolism ; Computational Biology ; Genes, Bacterial ; N-Acetylmuramoyl-L-alanine Amidase ; genetics ; metabolism ; Temperature