A process integration approach for the production of biological iso-propanol, butanol and ethanol using gas stripping and adsorption as recovery methods

In situ Product Recovery of Microbially Synthesized Ethyl Acetate from the Exhaust Gas of a Bioreactor by Membrane Technology

Ethyl acetate is at present exclusively produced from fossil resources. Microbial synthesis of this ester from sugar-rich waste as an alternative is an aerobic process. Ethyl acetate is highly volatile and therefore stripped with the exhaust gas from the bioreactor which enables in situ product recovery. Previous research on microbial formation of ethyl acetate has focused on the kinetics of ester synthesis and in part on the ester stripping, while the separation of the ester from the exhaust gas has hardly been investigated. A mixed matrix membrane was developed consisting of Silikalite-1 embedded in polydimethylsiloxane which was installed in a radial-symmetrical membrane module. Evaluation of the separation of ethyl acetate was based on the analysis of the composition of the feed and retentate gas by mass spectrometry. The separation efficiency of the membrane was first tested with varied flows of artificial exhaust gas, containing defined amounts of ethyl acetate. A model for describing the separation process was parametrized by the measured data and used to design a real separation experiment. Ethyl acetate produced from delactosed whey permeate by Kluyveromyces marxianus DSM 5422 in a stirred bioreactor gassed with 0.5 vvm air was successfully separated from the exhaust gas by membranes; 93.6% of the stripped ester was separated. Liquid ethyl acetate was recovered by cooling the permeate gas to ‒78°C, whereby 99.75% of the condensed organic compounds were ethyl acetate. This study demonstrates for the first time that microbially produced and stripped ethyl acetate can be effectively separated from the exhaust gas of bioreactors by membrane technology to obtain the ester in high yield and purity.

Lignocellulosic biorefineries: A multiscale approach for resource exploitation

Biomass can become the source for chemicals towards a sustainable production system. However, the challenges it presents such as the variety of species, their widespread and sparse availability, and the expensive transportation claims for an integrated approach to design the novel production system. Multiscale approaches have not been properly extended to biorefineryes design and deployment, due to the comprehensive experimental and modelling work they require. A systems perspective provides the systematic framework to analyze the availability and composition of raw materials across regions, how that affects process design, the portfolio of products that can be obtained by evaluating the strong link between the biomass features and the process design. The use of lignocellulosic materials requires for a multidisciplinary work, that must lead to new process engineers with technical competences in biology, biotechnology but also process engineering, mathematics, computer science and social sciences towards a sustainable process/chemical industry.

Isopropanol-butanol-ethanol production by cell-immobilized vacuum fermentation

The Isopropanol-Butanol-Ethanol productivity by solventogenic clostridia can increase when cells are immobilized on low-cost, renewable fibrous materials; however, butanol inhibition imposes the need for dilute sugar solutions (less than40 g/L). To alleviate this problem, the in-situ vacuum product recovery technique was applied to recover IBE in repeated-batch cultivation of Clostridium beijerinckii DSM 6423 immobilized on sugarcane bagasse. Five repeated batch cycles were conducted in a 7-L bioreactor containing P2 medium (∼60 g/L glucose) and bagasse packed in 3D-printed concentric annular baskets. In three cycles, glucose was consumed by 86% on average, the IBE productivity was 0.35 g/L∙h or 30% and 17% higher relative to free- and immobilized (without vacuum)-cell cultures. Notably, the product stream contained 45 g/L IBE. However, the fermentation was unsatisfactory in two cycles. Finally, by inserting a fibrous bed with hollow annuli in a vacuum fermentation, this work introduces the concept of an internal-loop boiling-driven fibrous-bed bioreactor.

Removal of organic matter from wastewater coming from fruit juice production using solar photo-Fenton process

The grape juice production generates an industrial wastewater that has a high concentration of organic matter and several polyphenols, such as ethanol. Therefore, the discharge of this wastewater can produce environmental problems. The aim of this work was to determine the optimal concentration of the reagents involved in a solar photo-Fenton process in the treatment of wastewater coming from juice. The process was analysed in a factorial design, as a function of H2O2 (900, 1000, 1100 mg/L) and Fe2+ (90, 100, 110 mg/L) concentration. The grape juice wastewater presents high organic content (20,500 mg/L COD and 5.4 mg/L polyphenols). Also, the presence of alcohols such ethanol, ethyl acetate and 2-metil-1-propanol was confirmed. The results showed that highest COD (>27%) and polyphenols removal (>36%) were obtained in experiments with 1100 mg H2O2/L and 100 mg Fe2+/L. In treatments with higher COD removal, 2-metil-1-propanol was detected as an intermediate of ethanol oxidation. These results proved that solar photo-Fenton is a suitable approach for treating the refractory organic matter from grape juice.

Precisely Patterned Nanostrand Surface of Cucurbituril[n]-Based Nanofiltration Membranes for Effective Alcohol-Water Condensation

Low concentration alcohols produced by state-of-the-art biological fermentation restrict subsequent purification processes for chemical, pharmaceutical, biofuel, and other applications. Herein, a rarely reported cucurbituril[n] (n = 6, 8) is employed to pattern the thin-film composite membranes with controllable and quantifiable nanostrand structures through a host-guest strategy. The resulting nanofiltration membrane with such morphology is the first report that exhibits excellent separation performance for isopropyl alcohol (IPA) and water, condensing the initial 0.5 wt % IPA aqueous solution to 9.0 wt %. This not only provides a novel strategy for patterning nanostructural morphology but also makes nanofiltration membranes promising for alcohol condensation in the biological fermentation industry that may reduce energy consumption and postprocessing costs.

Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation

Production of butanol for fuel via the conventional Acetone-Butanol-Ethanol fermentation has been considered economically risky because of a potential oversupply of acetone. Alternatively, acetone is converted into isopropanol by specific solventogenic Clostridium species in the Isopropanol-Butanol-Ethanol (IBE) fermentation. This route, although less efficient, has been gaining attention because IBE mixtures are a potential fuel. The present work is dedicated to reviewing past and recent advances in microorganisms, feedstock, and fermentation equipment for IBE production. In our analysis we demonstrate the importance of novel engineered IBE-producing Clostridium strains and cell retention systems to decrease the staggering number of fermentation tanks required by IBE plants equipped with conventional technology. We also summarize the recent progress on recovery techniques integrated with fermentation, especially gas stripping. In addition, we assessed ongoing pilot-plant efforts that have been enabling IBE production from woody feedstock.

Integrated Vacuum Stripping and Adsorption for the Efficient Recovery of (Biobased) 2-Butanol

Biobased 2-butanol offers high potential as biofuel, but its toxicity toward microbial hosts calls for efficient techniques to alleviate product inhibition in fermentation processes. Aiming at the selective recovery of 2-butanol, the feasibility of a process combining in situ vacuum stripping followed by vapor adsorption has been assessed using mimicked fermentation media. The experimental vacuum stripping of model solutions and corn stover hydrolysate closely aligned with mass transfer model predictions. However, the presence of lignocellulosic impurities affected 2-butanol recovery yields resulting from vapor condensation, which decreased from 96 wt % in model solutions to 40 wt % using hydrolysate. For the selective recovery of 2-butanol from a vapor mixture enriched in water and carbon dioxide, silicalite materials were the most efficient, particularly at low alcohol partial pressures. Integrating in situ vacuum stripping with vapor adsorption using HiSiv3000 proved useful to effectively concentrate 2-butanol above its azeotropic composition (>68 wt %), facilitating further product purification.