Consolidated bioprocessing (CBP) is a multi-step process in a bioreactor, which completes hydrolase production, enzymatic hydrolysis, and microbial fermentation. It is considered to be the most promising process for the production of second-generation biofuels because of its simple steps and low cost. Due to the complexity of lignocellulose degradation and the butanol synthesis pathway, few wild microorganisms can directly utilize lignocellulose to synthesize butanol. With the development of synthetic biology, single-bacterium directly synthesizes butanol using lignocellulose by introducing a butanol synthesis pathway in the cellulolytic Clostridium. However, there are still some problems such as heavy metabolic load of single bacterium and low butanol yield. Co-culture can relieve the metabolic burden of single bacterium through the division of labor in different strains and can further improve the efficiency of butanol synthesis. This review analyzes the recent research progress in the synthesis of biobutanol using lignocellulose by consolidated bioprocessing from both the single-bacterium strategy and co-culture strategy, to provide a reference for the research of butanol and other biofuels.
1-Butanol ; Biofuels ; Butanols ; Fermentation ; Lignin/metabolism*

The products concentrations in traditional acetone-butanol (AB) fermentation are too low that large amount of energy has to be consumed in the distillation and product recovery process. Aiming at direct utilization of the fermentation products, in this study, optimization of property-improved biodiesel manufacturing process coupled with AB extractive fermentation was conducted, under the condition of using the biodiesel originated from waste cooking oil as the extractant and high concentrated corn flour medium. The effect of biodiesel/broth volume ratio, waste supernatant recycle ratio, and electronic carrier addition on the major process performance index was carefully investigated. Under the optimized condition, the biodiesel quality was improved with the cetane value increased from 51.4 to 54.4; "actual butanol yield" reached to a level of 18%, and waste supernatant recycle ratio exceeded 50%. In this way, elimination of energy-consuming product recovery process and realization of "energy-saving & waste minimization" industrial production target advocated by the state government, could be potentially expected.
Bioelectric Energy Sources ; Butanols ; chemistry ; Fermentation ; Gasoline ; Zea mays ; metabolism

In industrial fermentation processes, bacteria have to adapt environmental stresses. Sometimes, such a self-adaption does not work and will cause fermentation failures, although such adaptation also can generate unexpected positive effects with improved fermentation performance. Our review introduces cell self-adaption to environmental variations or stress, process optimization based on such self-adaptions, with heterologous proteins production by Pichia pastoris and butanol fermentation as examples. Our review can sever as reference for fermentation optimization based on cell self-adaption.
Adaptation, Physiological ; Butanols ; metabolism ; Environment ; Fermentation ; Pichia ; cytology ; metabolism

Nine compounds were isolated from the n-butanol extract of the aerial parts of Polygala sibirica by various column chromatographic methods. Their structures were identified by MS and NMR spectroscopic data as sibiricaxanthone F (1), amentoflavone (2), linarin (3), zigu-glucoside I (4), 3, 6'-disinapoyl sucrose (5), tenuifoliside A (6), 2, 4, 4-trimethyl-3-formyl-6-hy-droxy-2, 5-cyclohexadien-1-one (7), lanierone (8), and aralia cerebroside (9) , respectively. Compounds 2, 3, 4, 7, 8 were isolated from the genus Ploygala for the first time, and compound 9 was firstly isolated from the title plant.
Butanols ; chemistry ; Drugs, Chinese Herbal ; chemistry ; Plant Components, Aerial ; chemistry ; Polygala ; 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

1,2,4-Butanetriol (BT) is an important non-natural chemical with a variety of industrial applications. A recombinant Escherichia coli biosynthesizing BT from D-xylose was constructed by heterologously expressing xdh and mdlC, and knocking out competing pathway genes including xylA, xylB, yjhE, yagH and ycdW. To optimize BT synthesis pathway, the third catalytic step that catalyzes the decarboxylation reaction of 3-deoxy-D-glycero-pentulosonic acid was identified as a potential bottleneck. Consequently, 2-keto acid decarboxylases from three different microorganisms were screened, and the kivD gene from Lactococcus lactis was found to increase BT titer by 191%. The improved strain BW-025 reached a final BT titer of 2.38 g/L under optimized transformation conditions. Attempts on synthetic pathway optimization were also made by fine-tuning the expression levels of each enzyme involved in the whole pathway based on BW-025. As a result, an xdh overexpressed recombinant strain, BW-074 was finally generated, with 48.62% higher BT production than that of BW-025.
Butanols ; metabolism ; Escherichia coli ; metabolism ; Gene Knockout Techniques ; Genetic Engineering ; Industrial Microbiology ; methods ; Metabolic Networks and Pathways

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

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

A mixture of fructose and glucose was developed to simulate the hydrolysate of Jerusalem artichoke tubers, the fructose-based feedstock suitable for butanol production. With the initial pH of 5.5 without regulation during mixed-sugar fermentation, as high as 23.26 g/L sugars were remained unconverted, and butanol production of 5.51 g/L were obtained. Compared with either glucose or fructose fermentation, the early termination of mixed-sugar fermentation might be caused by toxic organic acids and the low pH. When the pH of the fermentation system was controlled at higher levels, it was found that sugars utilization was facilitated, but less butanol was produced due to the over-accumulation of organic acids. On the other hand, when the pH was controlled at lower levels, more sugars were remained unconverted, although butanol production was improved. Based on these experimental results, a stage-wise pH regulation strategy, e.g., controlling the pH of the fermentation system at 5.5 untill the OD620 reached 1.0, and then the pH control was removed, was developed, which significantly improved the fermentation performance of the system, with only 2.05 g/L sugars unconverted and 10.48 g/L butanol produced.
Acetone ; metabolism ; Butanols ; metabolism ; Fermentation ; Fructose ; metabolism ; Glucose ; metabolism ; Helianthus ; metabolism ; Hydrogen-Ion Concentration

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