Partitioning of butanol and other fermentation broth components in phosphonium and ammonium-based ionic liquids and their toxicity to solventogenic clostridia

Novel Methods Using an Arthrobacter sp. to Create Anaerobic Conditions for Biobutanol Production from Sweet Sorghum Juice by Clostridium beijerinckii

Biobutanol can be produced by Clostridia via an acetone–butanol–ethanol (ABE) fermentation under strictly anaerobic conditions. Oxygen-free nitrogen (OFN) gas is typically used to create anaerobic conditions for ABE fermentations. However, this method is not appropriate for large-scale fermentations as it is quite costly. The aim of this work was to study the feasibility of butanol production from sweet sorghum juice (SSJ) by Clostridium beijerinckii TISTR 1461 using various methods to create anaerobic conditions, i.e., growth of a strictly aerobic bacterium, an Arthrobacter sp., under different conditions and a chemical method using sodium dithionite (SDTN) to consume residual oxygen. SSJ containing 60 g/L of total sugar supplemented with 1.27 g/L of (NH4)2SO4 was used as a substrate for butanol production. The results showed that 0.25 mM SDTN could create anaerobic conditions, but in this case, C.beijerinckii TISTR 1461 could produce butanol at a concentration (PB) of only 8.51 g/L with a butanol productivity (QB) of 0.10 g/L·h. Arthrobacter sp. BCC 72131 could also be used to create anaerobic conditions. Mixed cultures of C.beijerinckii TISTR 1461 and Arthrobacter sp. BCC 72131 created anaerobic conditions by inoculating the C.beijerinckii 4 h after Arthrobacter. This gave a PB of 10.39 g/L with a QB of 0.20 g/L·h. Comparing butanol production with the control treatment (using OFN gas to create anaerobic conditions, yielding a PB of 9.88 g/L and QB of 0.21 g/L·h) indicated that using Arthrobacter sp. BCC 72131 was an appropriate procedure for creating anaerobic conditions for high levels of butanol production by C. beijerinckii TISTR 1461 from a SSJ medium.

Development of novel hydrophilic ionic liquid membranes for the recovery of biobutanol through pervaporation

This paper aims to develop novel hydrophilic ionic liquid membranes using pervaporation for the recovery of biobutanol. Multiple polyvinyl alcohol (PVA) membranes based on three commercial ionic liquids with different loading were prepared for various experimental trials. The ionic liquids selected for the study include tributyl (tetradecyl) phosphonium chloride ([TBTDP][Cl]), tetrabutyl phosphonium bromide ([TBP][Br]) and tributyl methyl phosphonium methylsulphate ([TBMP][MS]). The synthesized membranes were characterized and tested in a custom-built pervaporation set-up. All ionic liquid membranes showed better results with total flux of 1.58 kg/m²h, 1.43 kg/m²h, 1.38 kg/m²h at 30% loading of [TBP][Br], [TBMP][MS] and [TBTDP][Cl] respectively. The comparison of ionic liquid membranes revealed that by incorporating [TBMP]MS to PVA matrix resulted in a maximum separation factor of 147 at 30 wt% loading combined with a relatively higher total flux of 1.43 kg/m²h. Density functional theory (DFT) calculations were also carried out to evaluate the experimental observations along with theoretical studies. The improved permeation properties make these phosphonium based ionic liquid a promising additive in PVA matrix for butanol-water separation under varying temperature conditions.

Using poly(vinyldodecylimidazolium bromide) for the in-situ product recovery of n-butanol

The mitigation of end-product inhibition during the biosynthesis of n-butanol is demonstrated for an in-situ product recovery (ISPR) system employing a poly(ionic liquid) (PIL) absorbent. The thermodynamic affinity of poly(vinyldodecylimidazolium bromide) [P(VC₁₂ ImBr)] for n-butanol, acetone and ethanol versus water was measured at conditions experienced in a typical acetone-ethanol-butanol (ABE) fermentation. In addition to providing a high n-butanol partition coefficient (PC = 6.5) and selectivity (α_BuOH/water = 46), P(VC₁₂ ImBr) is shown to be biocompatible with Saccharomyces cerevisiae and Clostridium acetobutylicum. Furthermore, the diffusivity of n-butanol in a hydrated PIL provides absorption rates that support ISPR applications. Using a 5 wt% PIL phase fraction relative to the aqueous phase mass, P(VC₁₂ ImBr) improved the volumetric productivity of a batch ABE ISPR process by 31% relative to a control fermentation. The concentration of n-butanol in the P(VC₁₂ ImBr) phase was sufficient to increase the alcohol concentration from 1.5 wt% in the fermentation medium to 25 wt% in the saturated PIL, thereby facilitating downstream n-butanol recovery.

In situ biobutanol recovery from clostridial fermentations: a critical review

Butanol is a precursor of many industrial chemicals, and a fuel that is more energetic, safer and easier to handle than ethanol. Fermentative biobutanol can be produced using renewable carbon sources such as agro-industrial residues and lignocellulosic biomass. Solventogenic clostridia are known as the most preeminent biobutanol producers. However, until now, solvent production through the fermentative routes is still not economically competitive compared to the petrochemical approaches, because the butanol is toxic to their own producer bacteria, and thus, the production capability is limited by the butanol tolerance of producing cells. In order to relieve butanol toxicity to the cells and improve the butanol production, many recovery strategies (either in situ or downstream of the fermentation) have been attempted by many researchers and varied success has been achieved. In this article, we summarize in situ recovery techniques that have been applied to butanol production through Clostridium fermentation, including liquid-liquid extraction, perstraction, reactive extraction, adsorption, pervaporation, vacuum fermentation, flash fermentation and gas stripping. We offer a prospective and an opinion about the past, present and the future of these techniques, such as the application of advanced membrane technology and use of recent extractants, including polymer solutions and ionic liquids, as well as the application of these techniques to assist the in situ synthesis of butanol derivatives.

Utilization of Ionic Liquids in Lignocellulose Biorefineries as Agents for Separation, Derivatization, Fractionation, or Pretreatment

Ionic liquids (ILs) can play multiple roles in lignocellulose biorefineries, including utilization as agents for the separation of selected compounds or as reaction media for processing lignocellulosic materials (LCM). Imidazolium-based ILs have been proposed for separating target components from LCM biorefinery streams, for example, the dehydration of ethanol-water mixtures or the extractive separation of biofuels (ethanol, butanol) or lactic acid from the respective fermentation broths. As in other industries, ILs are potentially suitable for removing volatile organic compounds or carbon dioxide from gaseous biorefinery effluents. On the other hand, cellulose dissolution in ILs allows homogeneous derivatization reactions to be carried out, opening new ways for product design or for improving the quality of the products. Imidazolium-based ILs are also suitable for processing native LCM, allowing the integral benefit of the feedstocks via separation of polysaccharides and lignin. Even strongly lignified materials can yield cellulose-enriched substrates highly susceptible to enzymatic hydrolysis upon ILs processing. Recent developments in enzymatic hydrolysis include the identification of ILs causing limited enzyme inhibition and the utilization of enzymes with improved performance in the presence of ILs.