ReviewProcess operation performance of PDMS membrane pervaporation coupled with fermentation for efficient bioethanol production☆
Introduction
The transportation sector worldwide is almost entirely dependent on petroleum-based fuels and it is responsible for over than 50% of the world oil consumption [1]. It is predicted that motor vehicles account for more than 19% of global carbon dioxide emissions and 70% of global carbon monoxide emissions [1], [2]. Bioethanol with carbon neutral, derived from a renewable biomass, is considered an important way of progress for improving air quality, limiting greenhouse gas emissions, and finding new energetic resources. As a transportation fuel, ethanol has a higher octane number, higher flame speeds, broader flammability limits, and higher heats of vaporization [1], [2]. Ethanol could be combined and blended with petrol within unmodified spark-ignition engines or burned in its pure form within modified spark-ignition engines [3].
Batch, fed-batch and continuous operations are three fermentation modes [4]. Batch fermentation is the simplest operation mode. During the process, nothing is added after inoculation except possibly acid or alkali for culture pH control. The yeast cells works in initial high substrate concentration and final high ethanol concentration. Yeast cells work at low substrate concentration with an increasing ethanol concentration during the course of fed-batch fermentation process. The major advantage of fed-batch over batch fermentation is the ability to prolong culture life time, reach the maximum viable cell concentration and allow a higher concentration of accumulative fermentation product. Continuous fermentation can be performed in different kinds of bioreactors with stirred tank reactors in single or series. In the process, feed containing substrate, culture medium and other required nutrients, is pumped continuously into an agitated vessel. Continuous fermentation can give a higher productivity than batch fermentation and the highest productivities can be achieved at low dilution rates.
During the above fermentation processes, the accumulation of ethanol in the broth inhibits the cell growth and fermentation, leading to low ethanol productivity, low ethanol concentration in the broth, and large amount of wastewater treatment. In the subsequent process, a lot of energy is consumed for product recovery from the broth. Ethanol fermentation is a biochemical reaction process controlled by product concentration, and ethanol accumulated in the broth has a serious inhibition effect on fermentation. During conventional fermentation process without ethanol in situ removal from broth, the cell metabolic activity would be weaken leading to the decrease of ethanol productivity with ethanol accumulation. The inhibition of ethanol on yeast began to appear, if ethanol concentration in the broth reaching 60 g·L−1–80 g·L−1. The final ethanol concentration can hardly reach 140 g·L−1 during batch fermentation [5]. Several separation technologies, including gas stripping, extraction, adsorption, distillation and pervaporation, have been explored for ethanol removal in situ from the broth during fermentation to meet the requirement of reducing the cost of ethanol recovery [6], [7].
Pervaporation is one of the most promising approaches for the recovery of alcohols from fermentation broths [8]. It is simple, nontoxic to cells, and potentially less energy consuming than distillation [9]. The feed or fermentation broth is forced flowing on one side of the membrane, and a gaseous phase permeate would be released. In order to supply a driven force between the membrane upstream and downstream sides, a vacuum or sweep gas less common is exerted at the other side of the membrane. Polydimethylsiloxane (PDMS) is the current benchmark hydrophobic material for ethanol pervaporation, since it has good stability and nice tolerance to the organic solvent [10], [11]. Ethanol in situ removal by pervaporation can reduce ethanol concentration in the broth, relieve inhibition, prolong culture time and enhance fermentation process. In recent years, several reviews have provided the state-of-the-art of the membrane material and fabrication for bioalcohol pervaporation [8], [12]. The operation performance of the integrated process is of great importance, since it could provide significant information for process design and regulation. However, so far there is no review focused on the operation performance of the integrated process. The main objective of this review is to provide the recent insights about the operation performance of PDMS membrane pervaporaiton coupled with ethanol fermentation for bioethanol production, which includes the separation performance of PDMS membrane, ethanol fermentation performance with in situ removal and subsequent processing on the downstream of the membrane.
Section snippets
Mass transfer steps and model
The mass transfer of ethanol from the upstream of the membrane to the downstream of the membrane during pervaporation could be included four steps, as shown in Fig. 1: (1) transferred through a liquid boundary layer by convective mass transfer, and ethanol concentration in liquid bulk (cb) was decreased to the concentration in liquid boundary layer (cbm) at interface of liquid boundary layer/membrane; (2) sorpted into the upstream surface of the membrane, and ethanol concentration was increased
Enhanced fermentation performance
The schematic diagram of fermentation coupled with PDMS membrane pervaporation is illustrated in Fig. 3. Compared with conventional batch fermentation or continuous stirring tank reactor (CSTR) operation, there are five advantages for ethanol fermentation coupled with pervaporation: increase of ethanol productivity, increase of cell density, continuous operation for a long time, reduction of the amount of wastewater treatment and energy consumption required for subsequent purification [36], [62]
Purification for fuel grade ethanol
In general, ethanol concentration on the downstream of the PDMS membrane is in the range of 20 wt% and 40 wt% [41]. Ethanol concentration on membrane downstream could not meet the requirement of fuel grade ethanol, since ethanol concentration must be over 99.5 wt% for fuel grade ethanol. Distillation would be the common approach to increase ethanol concentration to the azeotropic point (95.5 wt%). However, distillation is energy extensive since liquid evaporation and vapor condensation are
Conclusions and Perspectives
PDMS membrane pervaporation coupled with fermentation is a promising process for bioethanol production. Solution-diffusion model is the most common theory for the description of ethanol mass transfer from the upstream to the downstream of the membrane. In order to increase the mechanical strength of the PDMS membrane, several polymer and inorganic materials, such as Cellulose acetate (CA), Polyamide (PA), Polysulfone (PSF), Polyetherimide (PEI) and ceramics can be used as the supported layer
References (78)
- et al.
Recent trends in global production and utilization of bio-ethanol fuel
Appl. Energy
(2009) - et al.
Production of liquid biofuels from renewable resources
Prog. Energy Combust.
(2011) - et al.
Challenges and opportunities in improving the production of bio-ethanol
Prog. Energy Combust.
(2015) - et al.
Fuel ethanol production: Process design trends and integration opportunities
Bioresour. Technol.
(2007) - et al.
Hydrolysis kinetics of inulin by imidazole-based acidic ionic liquid in aqueous media and bioethanol fermentation
Chem. Eng. Sci.
(2016) - et al.
Hybrid membranes for pervaporation separations
J. Membr. Sci.
(2017) - et al.
Pervaporative separation of bioethanol using a polydimethylsiloxane/polyetherimide composite hollow-fiber membrane
Bioresour. Technol.
(2012) - et al.
Effects of polydimethylsiloxane (PDMS) molecular weight on performance of PDMS/ceramic composite membranes
J. Membr. Sci.
(2011) - et al.
Manipulation of confined structure in alcohol-permselective pervaporation membranes
Chin. J. Chem. Eng.
(2017) - et al.
A predictive mass transfer model for aroma compounds recovery by pervaporation
J. Food Eng.
(2009)
Computational fluid dynamics modeling of mass transfer for aroma compounds recovery from aqueous solutions by hydrophobic pervaporation
J. Food Eng.
A simplified solution-diffusion theory in pervaporation: the total solvent volume fraction model
J. Membr. Sci.
Mass transfer in pervaporation: The key component approximation for the solution-diffusion model
Desalination
Performance study of pervaporation in a microfluidic system for the removal of acetone from water
Chem. Eng. J.
Pervaporation — Importance of concentration polarization in the extraction of trace organics from water
J. Membr. Sci.
Effect of boundary-layer mass-transfer resistance in the pervaporation of dilute organics
J. Membr. Sci.
The influence of support layer structure on mass transfer in pervaporation of composite PDMS–PSF membranes
Chem. Eng. J.
Composite PDMS membrane with high flux for the separation of organics from water by pervaporation
J. Membr. Sci.
Sonication-enhanced in situ assembly of organic/inorganic hybrid membranes: Evolution of nanoparticle distribution and pervaporation performance
J. Membr. Sci.
Enhanced flux of polydimethylsiloxane membrane for ethanol permselective pervaporation via incorporation of MIL-53 particles
J. Membr. Sci.
Dynamically formed inner skin hollow fiber polydimethylsiloxane/polysulfone composite membrane for alcohol permselective pervaporation
Chem. Eng. J.
Fabrication of high silicalite-1 content filled PDMS thin composite pervaporation membrane for the separation of ethanol from aqueous solutions
J. Membr. Sci.
Pervaporation of ethanol produced from banana waste
Waste Manag.
Energy efficient of ethanol recovery in pervaporation membrane bioreactor with mechanical vapor compression eliminating the cold traps
Bioresour. Technol.
PDMS mixed matrix membranes containing hollow silicalite sphere for ethanol/water separation by pervaporation
J. Membr. Sci.
Preparation and characterization of ZSM-5/PDMS hybrid pervaporation membranes: Laboratory results and pilot-scale performance
Sep. Purif. Technol.
ZIF-67 filled PDMS mixed matrix membranes for recovery of ethanol via pervaporation
Sep. Purif. Technol.
Ethanol fermentation integrated with PDMS composite membrane: An effective process
Bioresour. Technol.
Enhanced ethanol recovery of PDMS mixed matrix membranes with hydrophobically modified ZIF-90
Sep. Purif. Technol.
Pervaporation of ethanol/water mixture by organophilic nano-silica filled PDMS composite membranes
Desalination
Improved performance of PDMS/ceramic composite pervaporation membranes by ZSM-5 homogeneously dispersed in PDMS via a surface graft/coating approach
Chem. Eng. J.
Integration of ethanol removal using carbon nanotube (CNT)-mixed membrane and ethanol fermentation by self-flocculating yeast for antifouling ethanol recovery
Process Biochem.
Improved ethanol recovery through mixed-matrix membrane with hydrophobic MAF-6 as filler
Sep. Purif. Technol.
Fabrication and characterization of micro-patterned PDMS composite membranes for enhanced ethanol recovery
J. Membr. Sci.
Pervaporation of alcoholic beverages—The coupling effects between ethanol and aroma compounds
J. Membr. Sci.
Kinetic model of continuous ethanol fermentation in closed-circulating process with pervaporation membrane bioreactor by Saccharomyces cerevisiae
Bioresour. Technol.
Influence of fermentation by-products on the purification of ethanol from water using pervaporation
Bioresour. Technol.
Effect of the microfiltration phase on pervaporation of ethanol produced from banana residues
Pervaporation of ethanol from lignocellulosic fermentation broth
Bioresour. Technol.
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2022, Materials Today: ProceedingsCitation Excerpt :When compared to integrated pervaporization technology, external arranged pervaporization has better cleaning capacities and a higher efficiency [72]. Fan et al., [80] suggested that a high concentration of ethanol in fermentation broth has a negative effect on the microorganisms present in the broth, and thus it is critical to continuously separate ethanol from the fermentation broth. As a result, membrane pervaporation in combination with fermentation is a promising technique for addressing the issue of ethanol concentration in fermentation broth.
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2021, Renewable EnergyCitation Excerpt :The improvement of the integrated pervaporation and new proposals for bioreactors have been reported. Fan et al. [276–278] proposed replacing cold traps with mechanical vapor compression, which ensured a 50% reduction in energy consumption during ethanol recovery. Cai et al. [279] developed a two-step pervaporation system (see Fig. 7) to increase the ABE production and reduce the energy consumption for solvent recovery.
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Supported by the National Natural Science Foundation of China (Nos. 20176030, 20276041, 20776088, 21808144), China Postdoctoral Science Foundation (No. 2016M592710), Fundamental Research Funds for the Central Universities (No. 20822041B4013) and Key Laboratory of Development and Application of Rural Renewable Energy, MOA, China (No. 18H0491).