Pervaporation of ethanol from lignocellulosic fermentation broth

Separation techniques for manufacturing fruit spirits: From traditional distillation to advanced pervaporation process

Separation process is one of the key processes in the production of fruit spirits, including the traditional distillation method and the new pervaporation membrane method. The separation process significantly determines the constituents and proportions of compounds in the fruit spirit, which has a significant impact on the spirit quality and consumer acceptance. Therefore, it is important and complex to reveal the changing rules of chemical substances and the principles behind them during the separation process of fruit spirits. This review summarized the traditional separation methods commonly used in fruit spirits, covering the types, principles, and corresponding equipment of distillation methods, focused on the enrichment or removal of aroma compounds and harmful factors in fruit spirits by distillation methods, and tried to explain the mechanism behind it. It also proposed a new separation technology for the production of fruit spirits, pervaporation membrane technology, summarized its working principle, operation, working parameters, and application in the production of fruit spirits, and outlined the impact of the separation method on the production of fruit spirits based on existing research, focusing on the separation of flavor compounds, sensory qualities, and hazard factors in fruit spirits, along with a preliminary comparison with distillation. Finally, according to the current researches of the separation methods and the development requirement of the separation process of fruit spirits, the prospect of corresponding research is put forward, in order to propose new ideas and development directions for the research in this field.

Manifestation of Triploid Heterosis in the Root System after Crossing Diploid and Autotetraploid Energy Willow Plants

Successful use of woody species in reducing climatic and environmental risks of energy shortage and spreading pollution requires deeper understanding of the physiological functions controlling biomass productivity and phytoremediation efficiency. Targets in the breeding of energy willow include the size and the functionality of the root system. For the combination of polyploidy and heterosis, we have generated triploid hybrids (THs) of energy willow by crossing autotetraploid willow plants with leading cultivars (Tordis and Inger). These novel Salix genotypes (TH3/12, TH17/17, TH21/2) have provided a unique experimental material for characterization of Mid-Parent Heterosis (MPH) in various root traits. Using a root phenotyping platform, we detected heterosis (TH3/12: MPH 43.99%; TH21/2: MPH 26.93%) in the size of the root system in soil. Triploid heterosis was also recorded in the fresh root weights, but it was less pronounced (MPH%: 9.63-19.31). In agreement with root growth characteristics in soil, the TH3/12 hybrids showed considerable heterosis (MPH: 70.08%) under in vitro conditions. Confocal microscopy-based imaging and quantitative analysis of root parenchyma cells at the division-elongation transition zone showed increased average cell diameter as a sign of cellular heterosis in plants from TH17/17 and TH21/2 triploid lines. Analysis of the hormonal background revealed that the auxin level was seven times higher than the total cytokinin contents in root tips of parental Tordis plants. In triploid hybrids, the auxin-cytokinin ratios were considerably reduced in TH3/12 and TH17/17 roots. In particular, the contents of cytokinin precursor, such as isopentenyl adenosine monophosphate, were elevated in all three triploid hybrids. Heterosis was also recorded in the amounts of active gibberellin precursor, GA19, in roots of TH3/12 plants. The presented experimental findings highlight the physiological basics of triploid heterosis in energy willow roots.

Bioethanol Production from Lignocellulosic Biomass-Challenges and Solutions

Regarding the limited resources for fossil fuels and increasing global energy demands, greenhouse gas emissions, and climate change, there is a need to find alternative energy sources that are sustainable, environmentally friendly, renewable, and economically viable. In the last several decades, interest in second-generation bioethanol production from non-food lignocellulosic biomass in the form of organic residues rapidly increased because of its abundance, renewability, and low cost. Bioethanol production fits into the strategy of a circular economy and zero waste plans, and using ethanol as an alternative fuel gives the world economy a chance to become independent of the petrochemical industry, providing energy security and environmental safety. However, the conversion of biomass into ethanol is a challenging and multi-stage process because of the variation in the biochemical composition of biomass and the recalcitrance of lignin, the aromatic component of lignocellulose. Therefore, the commercial production of cellulosic ethanol has not yet become well-received commercially, being hampered by high research and production costs, and substantial effort is needed to make it more widespread and profitable. This review summarises the state of the art in bioethanol production from lignocellulosic biomass, highlights the most challenging steps of the process, including pretreatment stages required to fragment biomass components and further enzymatic hydrolysis and fermentation, presents the most recent technological advances to overcome the challenges and high costs, and discusses future perspectives of second-generation biorefineries.

Triploid Hybrid Vigor in Above-Ground Growth and Methane Fermentation Efficiency of Energy Willow

Hybrid vigor and polyploidy are genetic events widely utilized to increase the productivity of crops. Given that bioenergy usage needs to be expanded, we investigated triploid hybrid vigor in terms of the biology of biomass-related willow traits and their relevance to the control of biomethane production. To produce triploid hybrid genotypes, we crossed two female diploid Swedish cultivars (Inger, Tordis) with two male autotetraploid willow (Salix viminalis) variants (PP-E7, PP-E15). Field studies at two locations and in two successive years recorded considerable midparent heterosis (MPH%) in early shoot length that ranged between 11.14 and 68.85% and in the growth rate between 34.12 and 97.18%. The three triploid hybrids (THs) developed larger leaves than their parental cultivars, and the MPH% for their CO2 assimilation rate varied between 0.84 and 25.30%. The impact of hybrid vigor on the concentrations of plant hormones in these TH genotypes reflected essentially different hormonal statuses that depended preferentially on maternal parents. Hybrid vigor was evinced by an elevated concentration of jasmonic acid in shoot meristems of all the three THs (MPH:29.73; 67.08; 91.91%). Heterosis in auxin-type hormones, such as indole-3-acetic acid (MPH:207.49%), phenylacetic acid (MPH:223.51%), and salicylic acid (MPH:27.72%) and benzoic acid (MPH:85.75%), was detectable in the shoots of TH21/2 plants. These hormones also accumulated in their maternal Inger plants. Heterosis in cytokinin-type hormones characterized the shoots of TH3/12 and TH17/17 genotypes having Tordis as their maternal parent. Unexpectedly, we detected abscisic acid as a positive factor in the growth of TH17/17 plants with negative MPH percentages in stomatal conductance and a lower CO2 assimilation rate. During anaerobic digestion, wood raw materials from the triploid willow hybrids that provided positive MPH% in biomethane yield (6.38 and 27.87%) showed negative MPH in their acid detergent lignin contents (from -8.01 to -14.36%). Altogether, these insights into controlling factors of above-ground growth parameters of willow genotypes support the utilization of triploid hybrid vigor in willow breeding to expand the cultivation of short rotation energy trees for renewable energy production.

Energy Harvesting/Storage and Environmental Remediation via Hot Drinks Wastes

Providing energy and materials are considered one most important issue in the world. Produce and storage energy and also, prepare chemical substances from disposable biomass materials have been widely developed in recent decades to decrease environmental pollutions and production costs. The waste of hot drinks including coffee wastes and tea wastes have considerable potentials to provide energy and different chemical substances. Also, hazardous materials (especially aqueous ions) can be absorbed via hot drinks wastes to protect the environment against perilous pollutants. The low-cost and benign hot drinks wastes including tea wastes and coffee grounds and also the pyrolyzed of them as the hot drinks waste biochar materials have been widely used to produce and store green energies and also, absorb hazardous materials. Production and storage energy and environmental remediation in these sustainable procedures not only reduce the cost of energy but also protect the environment.

Membranes for bioethanol production by pervaporation

BACKGROUND

Bioethanol as a renewable energy resource plays an important role in alleviating energy crisis and environmental protection. Pervaporation has achieved increasing attention because of its potential to be a useful way to separate ethanol from the biomass fermentation process.

RESULTS

This overview of ethanol separation via pervaporation primarily concentrates on transport mechanisms, fabrication methods, and membrane materials. The research and development of polymeric, inorganic, and mixed matrix membranes are reviewed from the perspective of membrane materials as well as modification methods. The recovery performance of the existing pervaporation membranes for ethanol solutions is compared, and the approaches to further improve the pervaporation performance are also discussed.

CONCLUSIONS

Overall, exploring the possibility and limitation of the separation performance of PV membranes for ethanol extraction is a long-standing topic. Collectively, the quest is to break the trade-off between membrane permeability and selectivity. Based on the facilitated transport mechanism, further exploration of ethanol-selective membranes may focus on constructing a well-designed microstructure, providing active sites for facilitating the fast transport of ethanol molecules, hence achieving both high selectivity and permeability simultaneously. Finally, it is expected that more and more successful research could be realized into commercial products and this separation process will be deployed in industrial practices in the near future.

In situ product recovery techniques aiming to obtain biotechnological products: A glance to current knowledge

Biotechnology and bioengineering techniques have been widely used in the production of biofuels, chemicals, pharmaceuticals, and food additives, being considered a "green" form of production because they use renewable and nonpolluting energy sources. On the other hand, in the traditional processes of production, the target product obtained by biotechnological routes must undergo several stages of purification, which makes these processes more expensive. In the past few years, some works have focused on processes that integrate fermentation to the recovery and purification steps necessary to obtain the final product required. This type of process is called in situ product recovery or extractive fermentation. However, there are some differences in the concepts of the techniques used in these bioprocesses. In this way, this review sought to compile relevant content on considerations and procedures that are being used in this field, such as evaporation, liquid-liquid extraction, permeation, and adsorption techniques. Also, the objective of this review was to approach the different configurations in the recent literature of the processes employed and the main bioproducts obtained, which can be used in the food, pharmaceutical, chemical, and/or fuel additives industry. We intended to elucidate concepts of these techniques, considered very recent, but which emerge as a promising alternative for the integration of bioprocesses.

Cell Factories for Industrial Production Processes: Current Issues and Emerging Solutions

Despite all the progresses made by metabolic engineering, still only a few biotechnological processes are running at an industrial level. In order to boost the biotechnological sector, integration strategies as well as long-term views are needed. The aim of the present review is to identify the main drawbacks in biotechnological processes, and to propose possible solutions to overcome the issues in question. Novel cell factories and bioreactor design are discussed as possible solutions. In particular, the following microorganisms: Yarrowia lipolytica, Trichosporon oleaginosus, Ustilago cynodontis, Debaryomyces hansenii along with sequential bioreactor configurations are presented as possible cell factories and bioreactor design solutions, respectively.

Overview of Alternative Ethanol Removal Techniques for Enhancing Bioethanol Recovery from Fermentation Broth

This study aims at reviewing the alternative techniques for bioethanol recovery, highlighting its advantages and disadvantages, and to investigate the technical challenges facing these alternatives to be widely used. The findings showed that the integration of these techniques with the fermentation process did not meet a large acceptance in the industrial sector. The majority of conducted studies were mainly focusing on ethanol recovery from aqueous standard solution rather than the investigation of these techniques performance in fermentation-separation coupled system. In this context, pervaporation has received more attention as a promising alternative to distillation. However, some challenges are facing the integration of these techniques in the industrial scale as the fouling problem in pervaporation, the toxicity of solvent in liquid extraction, energy consumption in vacuum fermentation. It was also found that there is a lack of the technical economic analysis for these techniques which may limit the spread of its application in the large scale. Currently, hybrid systems integrating distillation with other alternative techniques are considered as an innovative solution to reduce the high cost of the distillation process and the low separation efficiency of the alternatives techniques.

Effects of by-products of fermentation of banana pseudostem on ethanol separation by pervaporation

In this work, we performed recovery of ethanol from a fermentation broth of banana pseudostem by pervaporation (PV) as a lower-energy-cost alternative to traditional separation processes such as distillation. As real fermentation systems generally contain by-products, it was investigated the effects of different components from the fermentation broth of banana pseudostem on PV performance for ethanol recovery through commercial flat sheet polydimethylsiloxane (PDMS) membrane. The experiments were compared to a binary solution (ethanol/water) to determine differences in the results due to the presence of fermentation by-products. A real fermented broth of banana pseudostem was also used as feed for the PV experiments. Seven by-products from fermented broth were identified: propanol, isobutanol, methanol, isoamyl alcohol, 1-pentanol, acetic acid, and succinic acid. Moreover, the residual sugar content of 3.02 g/L¹ was obtained. The presence of methanol showed the best results for total permeate flux (0.1626 kg·m^-2 ·h^-1 ) and ethanol permeate flux (0.0391 kg·m^-2 ·h^-1 ) during PV at 25°C and 3 wt% ethanol, also demonstrated by the selectivity and enrichment factor. The lowest total fluxes of permeate were observed in the experiments containing the acids. Better permeance of 0.1171 from 0.0796 kg·m^-2 ·h^-1 and membrane selectivity of 9.77 from 9.30 were obtained with real fermentation broth than with synthetic solutions, possibly due to the presence of by-products in the multicomponent mixtures, which contributed to ethanol permeation. The results of this work indicate that by-products influence pervaporation of ethanol with hydrophobic flat sheet membrane produced from the fermented broth of banana pseudostem.

Lignocellulosic bioethanol production: prospects of emerging membrane technologies to improve the process – a critical review

To meet the worldwide rapid growth of industrialization and population, the demand for the production of bioethanol as an alternative green biofuel is gaining significant prominence. The bioethanol production process is still considered one of the largest energy-consuming processes and is challenging due to the limited effectiveness of conventional pretreatment processes, saccharification processes, and extreme use of electricity in common fermentation and purification processes. Thus, it became necessary to improve the bioethanol production process through reduced energy requirements. Membrane-based separation technologies have already gained attention due to their reduced energy requirements, investment in lower labor costs, lower space requirements, and wide flexibility in operations. For the selective conversion of biomasses to bioethanol, membrane bioreactors are specifically well suited. Advanced membrane-integrated processes can effectively contribute to different stages of bioethanol production processes, including enzymatic saccharification, concentrating feed solutions for fermentation, improving pretreatment processes, and finally purification processes. Advanced membrane-integrated simultaneous saccharification, filtration, and fermentation strategies consisting of ultrafiltration-based enzyme recycle system with nanofiltration-based high-density cell recycle fermentation system or the combination of high-density cell recycle fermentation system with membrane pervaporation or distillation can definitely contribute to the development of the most efficient and economically sustainable second-generation bioethanol production process.

Kinetic model of continuous ethanol fermentation in closed-circulating process with pervaporation membrane bioreactor by Saccharomyces cerevisiae

Unstructured kinetic models were proposed to describe the principal kinetics involved in ethanol fermentation in a continuous and closed-circulating fermentation (CCCF) process with a pervaporation membrane bioreactor. After ethanol was removed in situ from the broth by the membrane pervaporation, the secondary metabolites accumulated in the broth became the inhibitors to cell growth. The cell death rate related to the deterioration of the culture environment was described as a function of the cell concentration and fermentation time. In CCCF process, 609.8 g L(-1) and 750.1 g L(-1) of ethanol production were obtained in the first run and second run, respectively. The modified Gompertz model, correlating the ethanol production with the fermentation period, could be used to describe the ethanol production during CCCF process. The fitting results by the models showed good agreement with the experimental data. These models could be employed for the CCCF process technology development for ethanol fermentation.

Inhibition effect of secondary metabolites accumulated in a pervaporation membrane bioreactor on ethanol fermentation of Saccharomyces cerevisiae

The secondary metabolites accumulated in a pervaporation membrane bioreactor during ethanol fermentation were mostly composed of acetic acid, lactic acid, propionic acid, citric acid, succinic acid and glycerol. The inhibition effect of these compounds at a broad concentration range was studied through ethanol fermentation by Saccharomyces cerevisiae. An increasing concentration of the secondary metabolites led to longer lag time and a reduction of cell growth. The specific cell growth rate, cell yield, ethanol productivity were only 0.061 h(-1), 0.024, 0.47 g L(-1) h(-1) respectively, when the medium contained 3.12 g of acetic acid, 10.23 g of lactic acid, 2.72 g of propionic acid, 1.35 g of citric acid, 2.26 g of succinic acid and 49.25 g of glycerol per liter (a concentration level in pervaporation membrane bioreactor at later fermentation period). By increasing pH of the medium to 6.0-8.0, the inhibition of these secondary metabolites could be greatly relieved.

Current challenges in commercially producing biofuels from lignocellulosic biomass

Biofuels that are produced from biobased materials are a good alternative to petroleum based fuels. They offer several benefits to society and the environment. Producing second generation biofuels is even more challenging than producing first generation biofuels due the complexity of the biomass and issues related to producing, harvesting, and transporting less dense biomass to centralized biorefineries. In addition to this logistic challenge, other challenges with respect to processing steps in converting biomass to liquid transportation fuel like pretreatment, hydrolysis, microbial fermentation, and fuel separation still exist and are discussed in this review. The possible coproducts that could be produced in the biorefinery and their importance to reduce the processing cost of biofuel are discussed. About $1 billion was spent in the year 2012 by the government agencies in US to meet the mandate to replace 30% existing liquid transportation fuels by 2022 which is 36 billion gallons/year. Other countries in the world have set their own targets to replace petroleum fuel by biofuels. Because of the challenges listed in this review and lack of government policies to create the demand for biofuels, it may take more time for the lignocellulosic biofuels to hit the market place than previously projected.

Enhanced ethanol fermentation in a pervaporation membrane bioreactor with the convenient permeate vapor recovery

A continuous and closed-circulating fermentation (CCCF) system with a pervaporation membrane bioreactor was built for ethanol fermentation without a refrigeration unit to condense the permeate vapor. Two runs of experiment with a feature of complete and continuous coupling of fermentation and pervaporation were carried out, lasting for 192h and 264h, respectively. The experimental measurement indicated that the enhanced fermentation could be achieved with additional advantages of convenient permeate recovery and energy saving of the process. During the second experiment, the average cell concentration, glucose consumption rate, ethanol productivity, ethanol yield and total ethanol amount produced reached 19.8gL(-1), 6.06gL(-1)h(-1), 2.31gL(-1)h(-1), 0.38, and 609.8gL(-1), respectively. During the continuous fermentation process, ethanol removal in situ promoted the cell second growth obviously, but the accumulation of the secondary metabolites in the broth became the main inhibitor against the cell growth and fermentation.