In situ butanol recovery fermentation has been intensively studied as an effective alternative to conventional butanol production, which is limited due to the cellular toxicity of butanol. However, the low biocompatibility of adsorbents often leads to failure of in situ recovery fermentations. In this study, Clostridium beijerinckii NCIMB 8052 was cultured in flasks without shaking and in situ recovery fermentation was performed by using an adsorbent L493. The amounts of acetone, butanol, and ethanol (ABE) increased by 34.4 % in the presence of the adsorbent. In contrast, cell growth and production of organic acids and ABE were retarded in the 7-L batch fermentations with in situ butanol recovery. Cell damage occurred in the fermentor upon agitation in the presence of the adsorbent, unlike in static flask cultures with in situ recovery. Ex situ recovery fermentation using circulation of fermentation broth after mid-exponential phase of cell growth was developed to avoid adsorbent-cell incompatibility. No apparent cell damage was observed and 25.7 g/L of ABE was produced from 86.2 g/L glucose in the fed-batch mode using 7 L fermentors. Thus, ex situ recovery fermentation with C. beijerinckii is effective for enhancing butanol fermentation.

Background. The utilization of expanded-criteria donors (ECDs) has increased to overcome donor shortages. Unfortunately, the discard rate has also increased, especially in ECDs with acute kidney injury (AKI). We evaluated the outcomes of kidney transplantation in ECDs and standard-criteria donors (SCDs) with and without AKI.Methods. We reviewed the medical records of patients who underwent kidney transplantation. We used the AKI definition published by the Kidney Disease: Improving Global Outcomes group and reviewed the demographic characteristics of donors and recipients. We analyzed transplantation outcomes.Results. Twenty-seven patients underwent kidney transplantation from ECDs with AKI (n = 6) or without AKI (n = 5) and SCDs with AKI (n = 6) or without AKI (n = 10). Initial creatinine and estimated glomerular filtration rate (eGFR) were not significantly different between the groups. The incidence of delayed graft function was highest in ECDs with AKI (n = 3; 36.4%), but this was not a significantly difference. There was no difference in the last creatinine and eGFR in ECDs with AKI (1.32 mg/dL, 58.7 mL/min/1.73 m(2)), ECDs without AKI (1.67 mg/dL, 44.2 mL/min/1.73 m(2)), SCDs with AM (0.94 mg/dL, 81.5 mL/min/1.73 m(2)) and SCDs without AKI (0.97 mg/dL, 81.8 mL/min/1.73 m(2)).Conclusions. As the donor pool is extended to ECDs, young transplant surgeons may increasingly face decisions regarding ECDs with AKI or allocation failure. There is no consensus regarding discard criteria. However, if the donor showed initially normal creatinine levels or if dual-kidney transplantation can be performed, young transplant surgeons should not hesitate to use ECDs with AKI or allocation failure.

This paper proposes a model-based optimization strategy for a fermentation process coupled with an ex situ butanol recovery-by-adsorption (termed "ESBR-by-adsorption" hereafter) process used for continuous biobutanol production. The ESBR-by-adsorption system exhibits cyclic dynamic behavior caused by the periodic switching of the adsorption column for its renewal. Since performance of such a system is largely determined by its dynamic behavior seen after converging to Cyclic Steady State (CSS), the optimization strategy should search for the optimal operating condition leading to the most profitable CSS. For the CSS optimization, we select key optimization variables and define the objective function and constraints. The resulting CSS optimization problem is strongly nonconvex, largely due to the various nonlinearities in the objective function and constraints, e.g., those in the kinetics of the ABE fermentation and adsorption. To alleviate the numerical convergence problem associated with nonconvex optimization problems, we adopt an initialization strategy of identifying a feasible solution region and a "good" initial guess through a coarse grid search. With the initialization strategy, two CSS optimization approaches, "sequential" and "simultaneous," are examined for the system. With the model and simulation, performances of the two approaches are compared with respect to varying qualities of the initial guess to propose an effective practical CSS optimization strategy for the ESBR-by-adsorption system. The optimized continuous production'by the ESBR-byadsorption system showed significantly improved volumetric productivity of butanol, 5.5- and 3.7-fold increases respectively over the batch fermentation or semibatch fermentation with in situ product recovery.

To reduce butanol toxicity, adsorptive fermentation has been extensively studied. In this study, SP850 was systematically selected as an optimal adsorbent showing high butanol selectivity. In the flask culture involving in situ butanol recovery fermentation using Clostridium acetobutylicum ATCC 824 and the adsorbent, production of acetone, butanol, and ethanol (ABE) increased by 46.8%. An acid crash, however, occurred in the ex situ recovery fermentation using SP850. This problem was solved by homologous expression of the adhE1 gene in the ATCC 824 strain. During the ex situ recovery fermentation by the adhE-overexpressing strain, 34.2 g/L of ABE was produced from 132.8 g/L of glucose. In the 146-h continuous mode of ex situ fermentation, the strain produced 205.6 g/L of ABE (146.9 g/L of butanol) from 605.3 g/L of glucose. Our results indicate that proper selection of an adsorbent and strain engineering for the ex situ recovery fermentation is effective at enhancing butanol fermentation. (C) 2015 Elsevier Ltd. All rights reserved.

A dynamic model for a fermentation process equipped with an ex situ butanol recovery (termed "ESBR" hereafter) system: is proposed for continuous production of biobutanol. Since the proposed ESBR system integrates a,fermenter with a stirred-tank-type adsorption column, the dynamic model includes kinetic Models for both the fermentation (the Monod/Luedelcing-Piret model) and the adsorption (the extended Langmuir Model). Parameters in the kinetic models are initially determined using data from batch and fed batch fermentation experiments with in situ butanol recovery (ISBR). The initially developed model is then used to find a feasible operating condition for an experimental ESBR system, and its parameter values are further tuned using experimental data from the proposed ESBR system for accurate predictions in the butanol and glucose concentration range seen in the ESBR operation. The approach to improving the Model accuracy consists of two steps: (1) identifying the critical parameters by performing a sensitivity analysis and (2) re-estimating the,Selected parameters using data obtained during cyclic operation of the proposed,ESBR System. Accordingly, the developed model based on the kinetics for both,fermentation and adsorption can describe and predict the behavior of the proposed ESBR,system. Thus, the proposed systematic approach provides a reliable platform for the optimal scale-up design and control studies of the ESBR system.

Biobutanol is considered to be a promising choice for renewable fuel due to its high energy content, low volatility, and low water solubility. However, the production of biobutanol through fermentation is complicated by the fact that butanol inhibits the microorganism's cell growth and therefore the butanol production when its concentration in the fermentation broth reaches a certain critical level. In order to raise the volumetric productivity to a commercially acceptable level, produced biobutanol needs to be separated out as the fermentation is on-going. In this study, a continuous extractive fermentation process integrated with an ex-situ adsorption recovery process is studied to overcome this limitation. Switching of the adsorption column upon the saturation yields a continuous process with a cyclic steady state behavior. A dynamic model for the integrated process is developed and an optimization is performed based on the cyclic steady state analysis in order to design an optimal operation strategy that satisfies given requirements.

An imbalance of electron in an intramolecular electron transfer pathway was identified as the central factor causing inefficient degradation of lignin by the lignin peroxidase H8 from Phanerochaete chrysosporium (LiPH8). It was elucidated that dimeric lignins or monolignolic analogs containing free-hydroxyl phenolic groups were not only favorable substrates for the reduction of LiPH8 but also strong inhibitors depressing the enzymatic degradation of lignin. The data collectively demonstrated that disturbing the interaction between the free OH group on the phenolic structure and the surface active sites around Trp171 caused the primary deficiency in electron transport between Trp171 and the heme site, which severely inhibited the efficiency of lignin biodegradation by LiPH8/H2O2.

To produce biobutanol, fermentation processes using clostridia that mainly produce acetone, butanol and ethanol are used. In this work, a dynamic model describing the metabolic reactions in an acetone-butanol-ethanol (ABE)-producing clostridium, Clostridium acetobutylicum ATCC824, was proposed. To estimate the 58 kinetic parameters of the metabolic network model with experimental data obtained from a batch fermentor, we used an efficient optimization method combining a genetic algorithm and the Levenberg-Marquardt method because of the complexity of the metabolism of the clostridium. For the verification of the determined parameters, the developed metabolic model was evaluated by experiments where genetically modified clostridium was used and the initial concentration of glucose was changed. Consequently, we found that the developed kinetic model for the metabolic network was considered to describe the dynamic metabolic state of the clostridium sufficiently. Thus, this dynamic model for the metabolic reactions will contribute to designing the clostridium as well as the fermentor for higher productivity.

For curbing the severe inhibition and toxicity of 1-butanol in a fermentor, which stand as one of the major hurdles on the way to commercialization of biobutanol production processes, an extractive fermentation process that can remove metabolites during the ferementation can be an effective solution. Among various separation techniques, adsorption using poly(styrene-co-divinylbenzene) adsorbent resin is an effective and energy-efficient technique that holds much promise. In this paper, we have investigated the adsorption-and-desorption characteristics of the fermentation metabolites to aid the design of a new fermentation process equipped with an in situ or ex-situ butanol recovery capability. Specifically, the Langmuir equation and Ideal Adsorption Solution theory (IAST) have been used for developing an adsorption isotherm model, based on which a kinetic model of the adsorption process is developed. For the parameter estimation of the adsorption model, experiments have been carried out with a batch type slurry adsorption process processing a multiple-component mixture containing acetone, ethanol, 1-butanol, acetic acid, and butyric acid. It is subsequently confirmed that the adsorption model developed with data from the experiments using the model broth adsorption can accurately predict the adsorption behavior of the actual fermentation broth. To ensure the practical applicability of the adsorption process, desorption experiments of the adsorbent resin have also been performed. It is found that approximately 95% of the adsorbates on the adsorbent can be recovered using 140 degrees C steam with the steam-to-adsorbent mass ratio of 1. This study on the adsorption-and-desorption characteristics is expected to contribute to designing a large-scale extractive fermentor for biobutanol production.

ABE (acetone-butanol-ethanol) was produced through alkaline pre-hydrolysis, enzymatic saccharification, and fermentation using yellow poplar as a raw material. In alkaline pre-hydrolysis, 51.1% of the biomass remained as a residue. In the main woody components, the degrees of lignin and xylan removal were 94.3 and 62.0%, respectively. A yield of 80.9% for cellulose-to-glucose and 81.2% for xylan-to-xylose were obtained by enzymatic hydrolysis. The sugar composition of enzymatic hydrolysate was 95.1 g/L of glucose and 21.4 g/L of xylose. The enzymatic hydrolysate also contained 0.5 g/L of acetic acid and 0.5 g/L of total phenolics. Furfural and 5-hydroxymethylfurfural (5-HMF) were not detected in this hydrolysate. The yellow poplar hydrolysate (YPH) from enzymatic saccharification was used for the production of ABE using Clostridium acetobutylicum and C. beijerinckii. In YPH fermentation, C. acetobutylicum produced 18.1 g/L total ABE (productivity 0.38 g/L h, and yield 0.42), and C. beijerinckii produced 12.1 g/L (productivity 0.25 g/L h, and yield 0.37). Although the ABE productivity by C. beijerinckii was slightly low, the general performance of ABE fermentation in YPH was similar to or higher than those reported previously. Therefore, alkaline pre-hydrolysis could be a very effective pretreatment step prior to enzymatic hydrolysis.

ABSTRACT Butanol is an important industrial solvent and advanced biofuel that can be produced by biphasic fermentation by Clostridium acetobutylicum . It has been known that acetate and butyrate first formed during the acidogenic phase are reassimilated to form acetone-butanol-ethanol (cold channel). Butanol can also be formed directly from acetyl-coenzyme A (CoA) through butyryl-CoA (hot channel). However, little is known about the relative contributions of the two butanol-forming pathways. Here we report that the direct butanol-forming pathway is a better channel to optimize for butanol production through metabolic flux and mass balance analyses. Butanol production through the hot channel was maximized by simultaneous disruption of the pta and buk genes, encoding phosphotransacetylase and butyrate kinase, while the adhE1 D485G gene, encoding a mutated aldehyde/alcohol dehydrogenase, was overexpressed. The ratio of butanol produced through the hot channel to that produced through the cold channel increased from 2.0 in the wild type to 18.8 in the engineered BEKW(pPthlAAD ** ) strain. By reinforcing the direct butanol-forming flux in C. acetobutylicum , 18.9 g/liter of butanol was produced, with a yield of 0.71 mol butanol/mol glucose by batch fermentation, levels which are 160% and 245% higher than those obtained with the wild type. By fed-batch culture of this engineered strain with in situ recovery, 585.3 g of butanol was produced from 1,861.9 g of glucose, with the yield of 0.76 mol butanol/mol glucose and productivity of 1.32 g/liter/h. Studies of two butanol-forming routes and their effects on butanol production in C. acetobutylicum described here will serve as a basis for further metabolic engineering of clostridia aimed toward developing a superior butanol producer. IMPORTANCE Renewable biofuel is one of the answers to solving the energy crisis and climate change problems. Butanol produced naturally by clostridia has superior liquid fuel characteristics and thus has the potential to replace gasoline. Due to the lack of efficient genetic manipulation tools, however, strain improvement has been rather slow. Furthermore, complex metabolic characteristics of acidogenesis followed by solventogenesis in this strain have hampered development of engineered clostridia having highly efficient and selective butanol production capability. Here we report for the first time the results of systems metabolic engineering studies of two butanol-forming routes and their relative importances in butanol production. Based on these findings, a metabolically engineered Clostridium acetobutylicum strain capable of producing butanol to a high titer with high yield and selectivity could be developed by reinforcing the direct butanol-forming flux.