n- Butanol Production from Acid-Pretreated Jatropha Seed Cake by Clostridium acetobutylicum
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n-Butanol Production from Acid-Pretreated Jatropha Seed Cake by Clostridium acetobutylicum Jasmine Isar & Harshvardhan Joshi & Vidhya Rangaswamy
# Springer Science+Business Media New York 2013
Abstract n-Butanol fermentation using Clostridium strains suffers from low titers due to the inability of the strains to tolerate n-butanol. The current study demonstrates a process to get high titer of n-butanol in a single batch mode from the renewable feedstock jatropha seed cake by employing Clostridium acetobutylicum. Chemical mutagenesis was done for improvement of the strain for better n-butanol tolerance and production. Optimization of the parameters resulted in 13.2 g L−1 of n-butanol in 120 h using acidtreated jatropha seed cake hydrolysate (7 %w/v) in anaerobic sugar medium. The process was scaled up to 15 L level, yielding 18.6 g L−1 of n-butanol in 72 h. The strain was found to be tolerant up to 30 g L−1 n-butanol under optimized conditions. The n-butanol tolerance was accompanied by over-expression of the stress response protein, GroEL, change in fatty acid profile, and ability to accumulate rhodamine 6G in the strain. The study has a significant impact on economically producing n-butanol from biomass. Keywords Butanol tolerance . Jatropha seed cake . Acid pretreatment . Scale up
Introduction n-Butanol is currently produced worldwide at over 1.4 billion gal/year by chemical route. The market demand is expected to increase dramatically if n-butanol can be produced economically from low-cost biomass. Therefore, J. Isar : H. Joshi : V. Rangaswamy (*) Industrial Biotechnology Group, Reliance Life Sciences Pvt. Ltd, Dhirubhai Ambani Life Sciences Centre, R-282, TTC area of MIDC, Thane-Belapur Road, Rabale, Navi Mumbai 400 701, India e-mail: [email protected]
development of processes to produce n-butanol using renewable energy sources such as ligno-cellulosic crops has gained impetus [32]. The economic viability of n-butanol fermentation is governed mainly by three factors: raw material cost, high product titer (achievable by overcoming solvent toxicity), and solvent recovery costs [11, 14] . The raw material issue is being addressed by using various renewable feedstocks for production of n-butanol. The commonly employed feedstocks for n-butanol synthesis are corn stover, corn fiber, and fiber-rich distillers dried grains and solubles [7, 18, 28]. In addition, barley straw hydrolysate [31] and switchgrass hydrolysates [32] have also been exploited for n-butanol production. In this regard, the lignocellulosic feedstock, Jatropha curcas, has been found to be more suitable due to its favorable attributes such as adaptability to varied agroclimatic conditions and soil type, hardy nature, short gestation time of about 3 years, productive life of 50–100 years, not browsed by animals, and drought resistance [21, 22]. Furthermore, jatropha has an upper edge in “food versus fuel” situation as it is a perennial crop and its deep root system helps store carbon, maintain soil quantity and manage water nutrients conser
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