Abstract
BackgroundAcetone–butanol–ethanol fermentation has been studied for butanol production. Alternatively, to achieve acetone-free butanol production, use of clostridium strains producing butanol and 1,3-propanediol (1,3-PDO) from glycerol, natural and engineered isopropanol–butanol–ethanol (IBE) producers has been attempted; however, residual 1,3-PDO and acetone, low IBE production by natural IBE producers, and complicated gene modification are limitations.ResultsHere, we report an effective isopropanol and butanol (IB) fermentation using a newly isolated Clostridium sp. A1424 capable of producing IB from various substrates with a small residual acetone. Notably, this strain also utilized glycerol and produced butanol and 1,3-PDO. After 46.35 g/L of glucose consumption at pH 5.5-controlled batch fermentation, Clostridium sp. A1424 produced 9.43 g/L of butanol and 13.92 g/L of IB at the productivity of 0.29 and 0.44 g/L/h, respectively, which are the highest values in glucose-based batch fermentations using natural IB producers. More interestingly, using glucose–glycerol mixtures at ratios ranging from 20:2 to 14:8 led to not only acetone-free and 1,3-PDO-free IB fermentation but also enhanced IB production along with a much higher butanol content (butanol/isopropanol ratio of 1.81 with glucose vs. 2.07–6.14 with glucose–glycerol mixture). Furthermore, when the mixture of glucose and crude glycerol at the ratio of 14:8 (total concentration of 35.68 g/L) was used, high butanol/isopropanol ratio (3.44) and butanol titer (9.86 g/L) were achieved with 1.4-fold enhanced butanol yield (0.28 g/g) and productivity (0.41 g/L/h) compared to those with glucose only at pH 5.5.ConclusionsA newly isolated Clostridium sp. A1424 was able to produce butanol and isopropanol from various carbon sources. The productivity and titer of butanol and total alcohol obtained in this study were higher than the previously reported results obtained using other natural IB producers. Use of the mixture of glucose and glycerol was successful to achieve acetone-free, 1,3-PDO-free, and enhanced IB production with higher yield, productivity, and selectivity of butanol compared to those with glucose only, providing great advantages from the perspective of carbon recovery to alcohols. This notable result could be accomplished by isolating an effective IB producer Clostridium sp. A1424 as well as by utilizing glucose–glycerol mixtures.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0650-7) contains supplementary material, which is available to authorized users.
Highlights
Acetone–butanol–ethanol fermentation has been studied for butanol production
Butanol production has been investigated with non-acetone producing Clostridium pasteurianum, which is capable of producing butanol and 1,3-propanediol (1,3-PDO) from glycerol [10,11,12,13,14]
The results presented here suggest that the use of the high isopropanol and butanol (IB) producing strain Clostridium sp
Summary
To achieve acetone-free butanol production, use of clostridium strains producing butanol and 1,3-propanediol (1,3-PDO) from glycerol, natural and engineered isopropanol–butanol–ethanol (IBE) producers has been attempted; residual 1,3-PDO and acetone, low IBE production by natural IBE producers, and complicated gene modification are limitations. Acetone accounting for 20–30% of ABE production is considered as an undesirable product because of its corrosiveness and poor fuel properties [1]. For this reason, there has been much effort to reduce or eliminate the production of acetone by interrupting the acetone pathway using genetic manipulation. Butanol production has been investigated with non-acetone producing Clostridium pasteurianum, which is capable of producing butanol and 1,3-propanediol (1,3-PDO) from glycerol [10,11,12,13,14]. Attempts have been made to decrease the production of 1,3-PDO using a chemically mutated strain [15] and using a mixture of glucose and glycerol as substrates [16, 17]; but a certain amount of 1,3-propanediol was still produced
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
