Simultaneous saccharification and fermentation of dilute alkaline-pretreated corn stover for enhanced butanol production by Clostridium saccharobutylicum DSM 13864.

Simultaneous saccharification and fermentation (SSF) process was applied for biobutanol production by Clostridium saccharobutylicum DSM 13864 from corn stover (CS). The key influential factors in SSF process, including corn steep liquor concentration, dry biomass and enzyme loading, SSF temperature, inoculation size and pre-hydrolysis time were optimized. In 5-L bioreactor with SSF process, butanol titer and productivity of 12.3 g/L and 0.257 g/L/h were achieved at 48 h, which were 20.6% and 21.2% higher than those in separate hydrolysis and fermentation (SHF), respectively. The butanol yield reached 0.175 g/g pretreated CS in SSF, representing 50.9% increase than that in SHF (0.116 g/g pretreated CS). This study proves the feasibility of efficient and economic production of biobutanol from CS by SSF.

Techno-economics of carbon preserving butanol production using a combined fermentative and catalytic approach.

This paper presents a novel process for n-butanol production which combines a fermentation consuming carbon dioxide (succinic acid fermentation) with subsequent catalytic reduction steps to add hydrogen to form butanol. Process simulations in Aspen Plus have been the basis for the techno-economic analyses performed. The overall economy for the novel process cannot be justified, as production of succinic acid by fermentation is too costly. Though, succinic acid price is expected to drop drastically in a near future. By fully integrating the succinic acid fermentation with the catalytic conversion the need for costly recovery operations could be reduced. The hybrid process would need 22% less raw material than the butanol fermentation at a succinic acid fermentation yield of 0.7g/g substrate. Additionally, a carbon dioxide fixation of up to 13ktonnes could be achieved at a plant with an annual butanol production of 10ktonnes.

Continuous butanol fermentation from xylose with high cell density by cell recycling system.

A continuous butanol production system with high-density Clostridium saccharoperbutylacetonicum N1-4 generated by cell recycling was established to examine the characteristics of butanol fermentation from xylose. In continuous culture without cell recycling, cell washout was avoided by maintaining pH>5.6 at a dilution rate of 0.26 h(-1), indicating pH control was critical to this experiment. Subsequently, continuous culture with cell recycling increased cell concentration to 17.4 g L(-1), which increased butanol productivity to 1.20 g L(-1) h(-1) at a dilution rate of 0.26 h(-1) from 0.529 g L(-1) h(-1) without cell recycling. The effect of dilution rates on butanol production was also investigated in continuous culture with cell recycling. Maximum butanol productivity (3.32 g L(-1) h(-1)) was observed at a dilution rate of 0.78 h(-1), approximately 6-fold higher than observed in continuous culture without cell recycling (0.529 g L(-1) h(-1)).

Fermentative production of butanol--the academic perspective.

As mobility is a major pillar of World's economic system and burning fuels from fossil resources leads to a dramatic increase in greenhouse gas emissions, the production and use of appropriate biofuels offer at least a partial solution to this problem. Butanol represents a biofuel extender or replacement with properties clearly superior to ethanol (higher mileage, not hygroscopic, usable without engine modifications, not corrosive). In addition, it is a valuable feedstock for the chemical industry. Scientific challenges for an economically competitive fermentation process include employment of cheap carbon sources, not competing with nutrition, a detailed understanding of the metabolic reactions of the biological process, development of appropriately engineered construction strains, and adaption of process technology to modern standards.

Fermentative production of butanol--the industrial perspective.

A sustainable bacterial fermentation route to produce biobutanol is poised for re-commercialization. Today, biobutanol can compete with synthetic butanol in the chemical market. Biobutanol is also a superior biofuel and, in longer term, can make an important contribution towards the demand for next generation biofuels. There is scope to improve the conventional fermentation process with solventogenic clostridia and drive down the production cost of 1-butanol by deploying recent advances in biotechnology and engineering. This review describes re-commercialization efforts and highlights developments in feedstock utilization, microbial strain development and fermentation process development, all of which significantly impact production costs.

Downstream process synthesis for biochemical production of butanol, ethanol, and acetone from grains: generation of optimal and near-optimal flowsheets with conventional operating units.

Manufacturing butanol, ethanol, and acetone through grain fermentation has been attracting increasing research interest. In the production of these chemicals from fermentation, the cost of product recovery constitutes the major portion of the total production cost. Developing cost-effective flowsheets for the downstream processing is, therefore, crucial to enhancing the economic viability of this manufacturing method. The present work is concerned with the synthesis of such a process that minimizes the cost of the downstream processing. At the outset, a wide variety of processing equipment and unit operations, i.e., operating units, is selected for possible inclusion in the process. Subsequently, the exactly defined superstructure with minimal complexity, termed maximal structure, is constructed from these operating units with the rigorous and highly efficient graph-theoretic method for process synthesis based on process graphs (P-graphs). Finally, the optimal and near-optimal flowsheets in terms of cost are identified.

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$33.47x10(6) and US$110.46x10(6), respectively. Based on a corn price (C(p)) of US$79.23 x ton(-1) (US$2.01 x bushel(-1)), an ABE yield of 0.42 (g ABE/g glucose) butanol price is projected to be US$0.34 x kg(-1). An improved yield of 0.50 will reduce this price to US$0.29 x 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 x ton(-1) would result in a butanol price of US$0.47 x kg(-1). A grass-rooted plant would result in a butanol price of US$0.73 x kg(-1) (C(p) US$79.23 x ton(-1)). In a worst case scenario, the price of butanol would increase to US$1.07 x kg(-1) (C(p) 197.10 x 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 x ton(-1).