Search

In this paper, the different applications of butyric acid and its current and future production status are highlighted, with a particular emphasis on the biofuels industry. As such, this paper discusses different issues regarding butyric acid fermentations and provides suggestions for future improvements and their approaches.

The effects of the hydraulic retention time (HRT=8, 10, 12 or 16.7 h) and glucose concentration (30, 40 or 50 g/L) on the production of hydrogen and butyrate by an immobilized Clostridium tyrobutyricum culture, grown under continuous culturing conditions, were evaluated. With 30 g/L glucose, the higher HRTs tested led to greater butyrate concentrations in the culture, i.e., 9.3 g/L versus 12.9 g/L with HRTs of 8 h and 16.7 h, respectively. In contrast, higher biogas and hydrogen production rates were generally seen when the HRT was lower. Experiments with different glucose concentrations saw a significant amount of glucose washed out when 50 g/L was used, the highest being 22.7 g/L when the HRT was 16.7 h. This study found the best conditions for the continuous production of hydrogen and butyric acid by C. tyrobutyricum to be with an HRT of 12 h and a glucose concentration of 50 g/L, respectively.

Objective: To produce butyric acid from red algae such as Gelidium amansii in which galactose is a main carbohydrate, microorganisms utilizing galactose and tolerating inhibitors in hydrolysis including levulinic acid and 5-hydroxymethylfurfural (HMF) are required. Results: A newly isolated bacterium, Clostridium sp. S1 produced butyric acid not only from galactose as the sole carbon source but also from a mixture of galactose and glucose through simultaneous utilization. Notably, Clostridium sp. S1 produced butyric acid and a small amount of acetic acid with the butyrate:acetate ratio of 45.4:1 and it even converted acetate to butyric acid. Clostridium sp. S1 tolerated 0.5-2 g levulinic acid/l and recovered from HMF inhibition at 0.6-2.5 g/l, resulting in 85-92 % butyric acid concentration of the control culture. When acid-pretreated G. amansii hydrolysate was used, Clostridium sp. S1 produced 4.83 g butyric acid/l from 10 g galactose/l and 1 g glucose/l. Conclusion: Clostridium sp. S1 produces butyric acid from red algae due to its characteristics in sugar utilization and tolerance to inhibitors, demonstrating its advantage as a red algae-utilizing microorganism. [ABSTRACT FROM AUTHOR]

ABE (acetone-butanol-ethanol) was produced through alkaline pre-hydrolysis, enzymatic saccharification, and fermentation using yellow poplar as a raw material. In alkaline pre-hydrolysis, 51.1% of the biomass remained as a residue. In the main woody components, the degrees of lignin and xylan removal were 94.3 and 62.0%, respectively. A yield of 80.9% for cellulose-to-glucose and 81.2% for xylan-to-xylose were obtained by enzymatic hydrolysis. The sugar composition of enzymatic hydrolysate was 95.1 g/L of glucose and 21.4 g/L of xylose. The enzymatic hydrolysate also contained 0.5 g/L of acetic acid and 0.5 g/L of total phenolics. Furfural and 5-hydroxymethylfurfural (5-HMF) were not detected in this hydrolysate. The yellow poplar hydrolysate (YPH) from enzymatic saccharification was used for the production of ABE using Clostridium acetobutylicum and C. beijerinckii. In YPH fermentation, C. acetobutylicum produced 18.1 g/L total ABE (productivity 0.38 g/L h, and yield 0.42), and C. beijerinckii produced 12.1 g/L (productivity 0.25 g/L h, and yield 0.37). Although the ABE productivity by C. beijerinckii was slightly low, the general performance of ABE fermentation in YPH was similar to or higher than those reported previously. Therefore, alkaline pre-hydrolysis could be a very effective pretreatment step prior to enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Abstract: The production of butanol from thin stillage by Clostridium pasteurianum DSM 525 was evaluated in the paper. At initial pH values ranging from 5.0 to 7.0 C. pasteurianum DSM 525 produced 6.2–7.2g/L of butanol utilizing glycerol in thin stillage as the main carbon source, with yields of 0.32–0.44g butanol produced/g glycerol consumed, which are higher than previously reported yields (e.g., 0.14–0.31g butanol/g glycerol, ). Lactic acid in the thin stillage acted as a buffering agent, maintaining the pH of the medium within a range of 5.7–6.1. Lactic acid was also utilized along with glycerol, enhancing butanol production (6.5g/L butanol vs. 8.7g/L butanol with 0 and 16g/L lactic acid, respectively). These results demonstrate the feasibility of cost-effective butanol production using thin stillage as a nutrient-containing medium with a pH buffering capacity. [Copyright &y& Elsevier]

We determined the potential of three mechanical pulverizers—a continuous ball mill (CBM), an air classifier mill (ACM), and a high-speed mill (HSM)—in the continuous pretreatment of corn stover. The mean diameters of the pulverized biomasses were not significantly different in the three cases, and the glucose yields from the CBM-, ACM-, and HSM-pulverized samples were 29%, 49%, and 44%, respectively. The energy requirements and process capacities for the ACM and HSM were similar. We conclude that the ACM and HSM could be used in the continuous pretreatment of corn stover and would be useful in biofuel production. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The first attempt to produce caproic acid by M. hexanoica with s-HF/MBRs. • Caproic acid of 10.08 g L−1 was produced with the fastest productivity of 0.69 g L−1 h−1. • The s-HF/MBRs showing potentials on caproic acid production by co-culture process. Abstract In this study, a coculture bioprocess was developed with Clostridium strains producing butyric acid and Megasphaera hexanoica producing caproic acid from the butyric acid. The two bacterial strains were each cultivated in two submerged hollow-fiber membrane bioreactors (s-HF/MBRs), separately. Each fermentation broth was filtered through the membrane modules, and the filtered broth was either interchanged on another reactor or obtained sequentially through. Using s-HF/MBRs, the caproic acid concentration increased to 10.08 g L−1, with the fastest productivity of 0.69 g L−1 h−1, which higher than that previously reported. [ABSTRACT FROM AUTHOR]

Lignocellulosic degradation compounds, especially phenolic compounds, inhibit the fermentation of Clostridium strains. In this study, a simple in situ detoxification method using a surfactant was developed for butyric acid production by Clostridium tyrobutyricum ATCC25755. Tween 80, a non-ionic surfactant, was chosen to sequester inhibitors by forming micelles, consequently preventing direct contact of inhibitors with cell membranes. When Tween 80 was added during fermentation, butyric acid production was significantly enhanced in the presence of hydrophobic phenolics such as p -coumaric acid (0 vs. 3.1 g/L butyric acid) and ferulic acid (2.2 vs. 4.6 g/L butyric acid) even at 0.016 g/L of Tween 80 (corresponding to the critical micelle concentration). Lignin, a polyphenol compound in lignocellulose, was also detoxified by Tween 80. When Tween 80 was added to acid-pretreated rice straw hydrolysate, butyric acid production significantly increased (0.1 vs. 8.7 g/L butyric acid), thus verifying detoxification effect of Tween 80 on lignocellulosic hydrolysate. [ABSTRACT FROM AUTHOR]

Abstract: Clostridium sp. BS-1 produces hexanoic acid as a metabolite using galactitol and enhanced hexanoic acid production was obtained by in situ extractive fermentation with Clostridium sp. BS-1 under an optimized medium composition. For medium optimization, five ingredients were selected as variables, and among them yeast extract, tryptone, and sodium butyrate were selected as significant variables according to a fractional factorial experimental design, a steepest ascent experimental design, and a Box–Behnken experimental design. The optimized medium had the following compositions in modified Clostridium acetobutyricum (mCAB) medium: 15.5gL−1 of yeast extract, 10.13gL−1 of tryptone, 0.04gL−1 of FeSO4·7H2O, 0.85gL−1 of sodium acetate, and 6.47gL−1 of sodium butyrate. The predicted concentration of hexanoic acid with the optimized medium was 6.98gL−1, and this was validated experimentally by producing 6.96gL−1 of hexanoic acid with Clostridium sp. BS-1 under the optimized conditions. In situ extractive fermentation for hexanoic acid removal was then applied in a batch culture system with the optimized medium and 10% (v/v) alamine 336 in oleyl alcohol as an extractive solvent. The pH of the culture in the extractive fermentation was maintained at 5.4–5.6 by an acid balance between production and retrieval by extraction. During a 16 day culture, the hexanoic acid concentration in the solvent increased to 32gL−1 while it was maintained in a range of 1–2gL−1 in the medium. The maximum rate of hexanoic acid production was 0.34gL−1 h−1 in in situ extractive fermentation. [Copyright &y& Elsevier]

• Caproic acid was produced from the hydrolysate of Jerusalem artichoke (JA). • Megasphaera elsdenii T81 utilized fructose and glucose in the hydrolysate of JA. • The hydrolysate of JA increased carbon consumption and caproic acid production. • Value-added chemical production using inexpensive feedstocks was evaluated. Caproic acid (CA) was produced by Megasphaera elsdenii T81 with Jerusalem artichoke tubers (JA) as a feedstock. More CA was produced under the medium with the acid hydrolysate of JA than the comparative medium with a carbon composition similar to that of JA. CA was produced up to 13.0 g/L and 0.52 g/L/h with extractive fermentation using a mixed solvent of alamine 336 in oleyl alcohol at 37 °C. The JA cost to produce 1 ton of CA is only 505 USD, which is much lower than that required for purchasing sucrose (860 USD) in CA production. As a result of the analysis performed using SuperPro Designer, including the cost of distillation to obtain pure CA, the estimated production cost for CA from dry JA is 1869 USD/ton CA at the production scale of 2000 ton/year, which is lower than the current market price for petroleum-derived CA (~2500 USD/ton). [ABSTRACT FROM AUTHOR]