Soy molasses as fermentation substrate for production of butanol using Clostridium beijerinckii BA101

Spray-dried soy molasses (SDSM) contains the sugars dextrose, sucrose, fructose, pinitol, raffinose, verbascose, melibiose, and stachyose. Of the 746 g kg⁻¹ total sugars in SDSM, 434 g kg⁻¹ is fermentable using Clostridium beijerinckii BA101. SDSM was used to produce acetone, butanol, and ethanol (ABE) by C. beijerinckii BA101 in batch cultures. Using 80 g l⁻¹ SDSM, 10.7 g l⁻¹ ABE was produced in P2 medium. Higher concentrations of SDSM resulted in poor solvent production due to the presence of excessive salt and inhibitory components. C. beijerinckii BA101 in SDSM at 80 g l⁻¹ concentration produced 22.8 g l⁻¹ ABE when supplemented with 25.3 g l⁻¹ glucose. SDSM contains 57.4 g kg⁻¹ mineral ash and 2% tri-calcium phosphate. Tri-calcium phosphate up to 43.1 g l⁻¹ was not inhibitory and at a tri-calcium phosphate concentration of 28.8 g l⁻¹, the culture produced more solvents (30.1 g l⁻¹) than the control experiment (23.8 g l⁻¹). In contrast, sodium chloride was a strong inhibitor of C. beijerinckii BA101 cell growth. At a concentration of 10 g l⁻¹ sodium chloride, a maximum cell concentration of 0.6 g l⁻¹ was achieved compared to 1.7 g l⁻¹ in the control experiment. The effects of two salts on specific growth rate constant (μ) and specific rate of ABE production (ν) for C. beijerinckii BA101 were examined. Journal of Industrial Microbiology & Biotechnology (2001) 26, 290–295. Received 20 September 2000/ Accepted in revised form 16 February 2001     

Butanol production by Clostridium beijerinckii. Part I: use of acid and enzyme hydrolyzed corn fiber

Fermentation of sulfuric acid treated corn fiber hydrolysate (SACFH) inhibited cell growth and butanol production (1.7 ± 0.2 g/L acetone butanol ethanol or ABE) by Clostridium beijerinckii BA101. Treatment of SACFH with XAD-4 resin removed some of the inhibitors resulting in the production of 9.3 ± 0.5 g/L ABE and a yield of 0.39 ± 0.015. Fermentation of enzyme treated corn fiber hydrolysate (ETCFH) did not reveal any cell inhibition and resulted in the production of 8.6 ± 1.0 g/L ABE and used 24.6 g/L total sugars. ABE production from fermentation of 25 g/L glucose and 25 g/L xylose was 9.9 ± 0.4 and 9.6 ± 0.4 g/L, respectively, suggesting that the culture was able to utilize xylose as efficiently as glucose. Production of only 9.3 ± 0.5 g/L ABE (compared with 17.7 g/L ABE from fermentation of 55 g/L glucose-control) from the XAD-4 treated SACFH suggested that some fermentation inhibitors may still be present following treatment. It is suggested that inhibitory components be completely removed from the SACFH prior to fermentation with C. beijerinckii BA101. In our fermentations, an ABE yield ranging from 0.35 to 0.39 was obtained, which is higher than reported by the other investigators.     

Production of acetone,butanol and ethanol by Clostridium beijerinckii BA101 and in situ recovery by gas stripping

We examined the effect of gas-stripping on the in situ removal of acetone, butanol, and ethanol (ABE) from batch reactor fermentation broth. The mutant strain (Clostridium beijerinckii BA101) was not affected adversely by gas stripping. The presence of cells in the fermentation broth affected the selectivities of ABE. A considerable improvement in the productivity and yield was recorded in this work in comparison with the non-integrated process. In an integrated process of ABE fermentation-recovery using C. beijerinckii BA101, ABE productivities and yield were improved up to 200 and 118%, respectively, as compared to control batch fermentation data. In a batch reactor C. beijerinckii BA101 utilized 45.4 g glucose l^–1 and produced 17.7 g total ABE l^–1, while in the integrated process it utilized 161.7 g glucose l^–1 and produced total ABE of 75.9 g l^–1. In the integrated process, acids were completely converted to solvents when compared to the non-integrated process (batch fermentation) which contained residual acids at the end of fermentation. In situ removal of ABE by gas stripping has been reported to be one of the most important techniques of solvent removal. During these studies we were able to maintain the ABE concentration in the fermentation broth below toxic levels.     

Continuous solvent production by Clostridium beijerinckii BA101 immobilized by adsorption onto brick

The performance of a continuous bioreactor containing Clostridium beijerinckii BA101 adsorbed onto clay brick was examined for the fermentation of acetone, butanol, and ethanol (ABE). Dilution rates from 0.3 to 2.5 h^–1 were investigated with the highest solvent productivity of 15.8 g l^–1 h^–1 being obtained at 2.0 h^–1. The solvent yield at this dilution rate was found to be 0.38 g g^–1 and total solvent concentration was 7.9 g l^–1. The solvent yield was maximum at 0.45 at a dilution rate of 0.3 h^–1. The maximum solvent productivity obtained was found to be 2.5 times greater than most other immobilized continuous and cell recycle systems previously reported for ABE fermentation. A higher dilution rate (above 2.0 h^–1) resulted in acid production rather than solvent production. This reactor was found to be stable for over 550 h. Scanning electron micrographs (SEM) demonstrated that a large amount of C. beijerinckii cells were adsorbed onto the brick support.     

ABE production from corn: a recent economic evaluation

This article details an economic assessment of butanol production from corn using the newly developed hyper-butanol-producing strain of Clostridium beijerinckii BA101. Butanol is produced in batch reactors and recovered by distillation. For a plant with 153,000 metric tons of acetone, butanol, and ethanol (ABE) production capacity, the production equipment cost and total working capital cost is US$33.47×10⁶ and US$110.46×10⁶, respectively. Based on a corn price (C _p) of US$79.23 ton⁻¹ (US$2.01 bushel⁻¹), an ABE yield of 0.42 (g ABE/g glucose) butanol price is projected to be US$0.34 kg⁻¹. An improved yield of 0.50 will reduce this price to US$0.29 kg⁻¹. Assumptions, such as by-product credit for gases and complete conversion of corn steep liquor (CSL) to fermentation by-products, have been taken into consideration. An increased price of corn to US$197.10 ton⁻¹ would result in a butanol price of US$0.47 kg⁻¹. A grass-rooted plant would result in a butanol price of US$0.73 kg⁻¹ (C _p US$79.23 ton⁻¹). In a worst case scenario, the price of butanol would increase to US$1.07 kg⁻¹ (C _p 197.10 ton⁻¹ for a grass-rooted plant and assuming no credit for gases). This is based on the assumption that corn price would not increase to more than US$197.10 ton⁻¹. Journal of Industrial Microbiology & Biotechnology (2001) 27, 292–297. Received 12 September 2000/ Accepted in revised form 12 January 2001     

Continuous acetone-butanol-ethanol (ABE) fermentation using immobilized cells of Clostridium acetobutylicum in a packed bed reactor and integration with product removal by pervaporation

An integrated solvent (ABE) fermentation and product removal process was investigated. A stable solvent productivity of 3.5 g/L h was achieved by using cells of Clostridium acetobutylicum immobilized onto a packed bed of bonechar, coupled with continuous product removal by pervaporation. Using a concentrated feed solution containing lactose at 130g/L, a lactose value of 97.9% was observed. The integrated fermentation and product removal system, with recycling of the treated fermentor effluent containing only low amount of solvents (/but lactose and acids), leads to only low acid losses. Therefore, most of the acids are converted to solvents, and this results in a high solvent yield of 0.39 g solvents/g lactose utilized. The pervaporation system provided a high product removal rate even at low solvent concentrations. A solvent membrane flux of 7.1 g/m(2) h with a selectivity of 5 was achieved during these investigations. The system proved to be very reliable.     

Butanol production by hypersolvent-producing mutant Clostridium beijerinckii BA101 in corn steep water medium containing maltodextrin

Clostridium beijerinckii NCIMB 8052 parent strain and BA101, a hypersolvent-producing mutant, fermented 6% (w/v) glucose, maltodextrin, maltose or xylose in a medium containing corn steep water (CSW) to produce butanol. Batch fermentation in an unoptimized 6% (w/v) maltodextrin plus 1.6% solids CSW medium demonstrated that C. beijerinckii NCIMB 8052 and BA101 produced 10.7 g butanol/L and 14.5 g butanol/L, respectively.