Process development and optimisation of lactic acid purification using electrodialysis

Pilot Scale for Production and Purification of Lactic Acid from Ceratonia siliqua L. (Carob) Bagasse

The bioconversion of lignocellulose and organic waste bagasse to lactic acid (LA) is an important alternative process requiring valorization as a potentially viable method in the production of pure LA, to be utilized for various purposes. Carob (Ceratonia siliqua L.) biomass was used for the production of LA, using a thermophilic Bacillus coagulans isolate, cultivated in a batch pilot scale of 35 L fermenters without yeast extract supplementation, and operated for 50 h. During the fermentation process, most of the degradable sugar was consumed within 35 h and resulted in the production of 46.9 g/L LA, with a calculated LA yield of 0.72 g/g sugars and productivity at the log phase of 1.69 g/L/h. The use of LA for different industrial applications requires high purity; therefore, a downstream process (DSP) consisting of different purification stages was used, enabling us to reach up to 99.9% (w/w) product purity, which indicates that the process was very effective. The overall almost pure L-LA yield of the DSP was 56%, which indicates that a considerable amount of LA (46%) was lost during the different DSP stages. This is the first study in which carob biomass bagasse has been tested on a pilot scale for LA production, showing the industrial feasibility of the fermentation process.

Design and Economic Assessment of Alternative Evaporation Processes for Poly-Lactic Acid Production

In this work, alternative evaporation processes for PLA production were designed with economic assessment. The suggested processes are the multiple-effect evaporation (MEE) process and thermal vapor recompression (TVR)-assisted evaporation process. First, the MEE process can efficiently reuse waste heat by additional column installation, thereby reducing the steam energy consumption. The proposed MEE process involves five columns, and after the evaporation in each column, the waste heat of the emitted vapor is reused to heat steam in the reboiler of the next column. Second, the suggested TVR-assisted evaporation process utilizes an additional steam ejector and recovers waste heat from the emitted vapor by increasing the pressure using high-pressure driving steam at the steam ejector. Each alternative process was modeled to predict the steam energy consumption, and to determine the cost-optimal process; the total annualized cost (TAC) of each alternative process was calculated as evaluation criteria. In the simulation results, the alternative processes using MEE and TVR reduced the steam consumption by 71.36% and 89.97%, respectively, compared to the conventional process. As a result of economic assessment, the cost-optimal process is the alternative process using TVR and the TAC can be decreased by approximately 90%.

Low-waste fermentation-derived organic acid production by bipolar membrane electrodialysis—an overview

Organic acids, e.g, citric acid, fumaric acid, lactic acid, malic acid, pyruvic acid and succinic acid, have important role in the food industry and are potential raw materials for the sustainable chemical industry. Their fermentative production based on renewable raw materials requires innovatively designed downstream processing to maintain low environmental impact and resource efficiency throughout the production process. The application of bipolar membranes offers clean and effective way to generate hydrogen ions required for free acid production from its salt. The water dissociation reaction inside the bipolar membrane triggered by electric field plays key role in providing hydrogen ion for the replacement of the cations in organic acid salts. Combined with monopolar ion-exchange membranes in a bipolar membrane electrodialysis process, material flow can be separated beside the product stream into additional reusable streams, thus minimizing the waste generation. This paper focuses on bipolar membrane electrodialysis applied for organic acid recovery from fermentation broth.

Frontiers of Membrane Desalination Processes for Brackish Water Treatment: A Review

Climate change, population growth, and increased industrial activities are exacerbating freshwater scarcity and leading to increased interest in desalination of saline water. Brackish water is an attractive alternative to freshwater due to its low salinity and widespread availability in many water-scarce areas. However, partial or total desalination of brackish water is essential to reach the water quality requirements for a variety of applications. Selection of appropriate technology requires knowledge and understanding of the operational principles, capabilities, and limitations of the available desalination processes. Proper combination of feedwater technology improves the energy efficiency of desalination. In this article, we focus on pressure-driven and electro-driven membrane desalination processes. We review the principles, as well as challenges and recent improvements for reverse osmosis (RO), nanofiltration (NF), electrodialysis (ED), and membrane capacitive deionization (MCDI). RO is the dominant membrane process for large-scale desalination of brackish water with higher salinity, while ED and MCDI are energy-efficient for lower salinity ranges. Selective removal of multivalent components makes NF an excellent option for water softening. Brackish water desalination with membrane processes faces a series of challenges. Membrane fouling and scaling are the common issues associated with these processes, resulting in a reduction in their water recovery and energy efficiency. To overcome such adverse effects, many efforts have been dedicated toward development of pre-treatment steps, surface modification of membranes, use of anti-scalant, and modification of operational conditions. However, the effectiveness of these approaches depends on the fouling propensity of the feed water. In addition to the fouling and scaling, each process may face other challenges depending on their state of development and maturity. This review provides recent advances in the material, architecture, and operation of these processes that can assist in the selection and design of technologies for particular applications. The active research directions to improve the performance of these processes are also identified. The review shows that technologies that are tunable and particularly efficient for partial desalination such as ED and MCDI are increasingly competitive with traditional RO processes. Development of cost-effective ion exchange membranes with high chemical and mechanical stability can further improve the economy of desalination with electro-membrane processes and advance their future applications.

Comparison of Different Lactobacilli Regarding Substrate Utilization and Their Tolerance Towards Lignocellulose Degradation Products

Fermentative lactic acid production is currently impeded by low pH tolerance of the production organisms, the successive substrate consumption of the strains and/or the requirement to apply purified substrate streams. We identified Lactobacillus brevis IGB 1.29 in compost, which is capable of producing lactic acid at low pH values from lignocellulose hydrolysates, simultaneously consuming glucose and xylose. In this study, we compared Lactobacillus brevis IGB 1.29 with the reference strains Lactobacillus brevis ATCC 367, Lactobacillus plantarum NCIMB 8826 and Lactococcus lactis JCM 7638 with regard to the consumption of C5- and C6-sugars. Simultaneous conversion of C5- and C6-monosaccharides was confirmed for L. brevis IGB 1.29 with consumption rates of 1.6 g/(L h) for glucose and 1.0 g/(L h) for xylose. Consumption rates were lower for L. brevis ATCC 367 with 0.6 g/(L h) for glucose and 0.2 g/(L h) for xylose. Further trials were carried out to determine the sensitivity towards common toxic degradation products in lignocellulose hydrolysates: acetate, hydroxymethylfurfural, furfural, formate, levulinic acid and phenolic compounds from hemicellulose fraction. L. lactis was the least tolerant strain towards the inhibitors, whereas L. brevis IGB 1.29 showed the highest tolerance. L. brevis IGB 1.29 exhibited only 10% growth reduction at concentrations of 26.0 g/L acetate, 1.2 g/L furfural, 5.0 g/L formate, 6.6 g/L hydroxymethylfurfural, 9.2 g/L levulinic acid or 2.2 g/L phenolic compounds. This study describes a new strain L. brevis IGB 1.29, that enables efficient lactic acid production with a lignocellulose-derived C5- and C6-sugar fraction.

Selective Electrochemical Conversion of Glycerol to Glycolic Acid and Lactic Acid on a Mixed Carbon-Black Activated Carbon Electrode in a Single Compartment Electrochemical Cell

In recent years, the rapid swift increase in world biodiesel production has caused an oversupply of its by-product, glycerol. Therefore, extensive research is done worldwide to convert glycerol into numerous high added-value chemicals i.e., glyceric acid, 1,2-propanediol, acrolein, glycerol carbonate, dihydroxyacetone, etc. Hydroxyl acids, glycolic acid and lactic acid, which comprise of carboxyl and alcohol functional groups, are the focus of this study. They are chemicals that are commonly found in the cosmetic industry as an antioxidant or exfoliator and a chemical source of emulsifier in the food industry, respectively. The aim of this study is to selectively convert glycerol into these acids in a single compartment electrochemical cell. For the first time, electrochemical conversion was performed on the mixed carbon-black activated carbon composite (CBAC) with Amberlyst-15 as acid catalyst. To the best of our knowledge, conversion of glycerol to glycolic and lactic acids via electrochemical studies using this electrode has not been reported yet. Two operating parameters i.e., catalyst dosage (6.4-12.8% w/v) and reaction temperature [room temperature (300 K) to 353 K] were tested. At 353 K, the selectivity of glycolic acid can reach up to 72% (with a yield of 66%), using 9.6% w/v catalyst. Under the same temperature, lactic acid achieved its highest selectivity (20.7%) and yield (18.6%) at low catalyst dosage, 6.4% w/v.

Electro-membrane processes for organic acid recovery

With an increase in the organic acid requirement, the production of organic acids has been increased over the years. To achieve cost-effective production of organic acids, efficient recovery processes are needed. Electro-membrane processes, including electrodialysis (ED), electrometathesis (EMT), electro-ion substitution (EIS), electro-electrodialysis (EED), electrodialysis with bipolar membrane (EDBM), and electrodeionization (EDI), are promising technologies for the recovery of organic acids. In the electro-membrane processes, organic acids are separated from water and other impurities based on the electro-migration of ions through ion-exchange membranes. These processes can recover various types of organic acids from the fermentation broth with high recovery yield and low energy consumption. In addition, the integration of fermentation and the electro-membrane process can improve the acid recovery with lower byproduct concentration and energy consumption.

With an increase in the organic acid requirement, the publication of organic acids recovery has been increased over the years.

Review on rosmarinic acid extraction, fractionation and its anti-diabetic potential

Rosmarinic acid is a bioactive phytochemical that can be found in many herbs as ethnomedicines. It possesses remarkable pharmacological activities, and thus leading to its exploration as a therapeutic drug in diabetes treatment recently. This article reviews the extraction and fractionation techniques for plant-based natural rosmarinic acid and its anti-diabetic potential based on literature data published in journals, books, and patents from 1958 to 2017. Factors affecting the performance of rosmarinic acid extraction and fractionation such as operating temperature, time, solvent to sample ratio and eluent system are compiled and discussed in detail. The inhibitory action of rosmarinic acid against sugar digestive enzymes, and protective action towards pancreatic β-cell dysfunction and glucolipotoxicity mediated oxidative stress are also critically reviewed. The optimal parameters are largely dependent on the applied extraction and fractionation techniques, as well as the nature of plant samples. Previous studies have proven the potent role of rosmarinic acid to control plasma glucose level and increase insulin sensitivity in hyperglycemia. Although rosmarinic acid is readily absorbed by human body, its mechanism after consumption is remained unclear. Intensive studies should be well planned to determine the dosage and toxicity level of rosmarinic acid for efficacy and safe consumption.

Extractive Fermentation of Lactic Acid in Lactic Acid Bacteria Cultivation: A Review

Lactic acid bacteria are industrially important microorganisms recognized for their fermentative ability mostly in their probiotic benefits as well as lactic acid production for various applications. Nevertheless, lactic acid fermentation often suffers end-product inhibition which decreases the cell growth rate. The inhibition of lactic acid is due to the solubility of the undissociated lactic acid within the cytoplasmic membrane and insolubility of dissociated lactate, which causes acidification of cytoplasm and failure of proton motive forces. This phenomenon influences the transmembrane pH gradient and decreases the amount of energy available for cell growth. In general, the restriction imposed by lactic acid on its fermentation can be avoided by extractive fermentation techniques, which can also be exploited for product recovery.

Fermentative utilization of coffee mucilage using Bacillus coagulans and investigation of down-stream processing of fermentation broth for optically pure l(+)-lactic acid production

In this study, mucilage, a residue from coffee production, was investigated as substrate in fermentative l(+)-lactic acid production. Mucilage was provided as liquid suspension consisting glucose, galactose, fructose, xylose and sucrose as free sugars (up to 60gL(-1)), and used directly as medium in Bacillus coagulans batch fermentations carried out at 2 and 50L scales. Using mucilage and 5gL(-1) yeast extract as additional nitrogen source, more than 40gL(-1) lactic acid was obtained. Productivity and yield were 4-5gL(-1)h(-1) and 0.70-0.77g lactic acid per g of free sugars, respectively, irrespective the scale. Similar yield was found when no yeast extract was supplied, the productivity, however, was 1.5gL(-1)h(-1). Down-stream processing of culture broth, including filtration, electrodialysis, ion exchange chromatography and distillation, resulted in a pure lactic acid formulation containing 930gL(-1)l(+)-lactic acid. Optical purity was 99.8%.

Membrane processing technology in the food industry: food processing, wastewater treatment, and effects on physical, microbiological, organoleptic, and nutritional properties of foods

Membrane processing technology (MPT) is increasingly used nowadays in a wide range of applications (demineralization, desalination, stabilization, separation, deacidification, reduction of microbial load, purification, etc.) in food industries. The most frequently applied techniques are electrodialysis (ED), reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF). Several membrane characteristics, such as pore size, flow properties, and the applied hydraulic pressure mainly determine membranes' potential uses. In this review paper the basic membrane techniques, their potential applications in a large number of fields and products towards the food industry, the main advantages and disadvantages of these methods, fouling phenomena as well as their effects on the organoleptic, qualitative, and nutritional value of foods are synoptically described. Some representative examples of traditional and modern membrane applications both in tabular and figural form are also provided.

Ion-exchange membranes in chemical synthesis – a review

The applicability of ion-exchange membranes (IEMs) in chemical synthesis was discussed based on the existing literature. At first, a brief description of properties and structures of commercially available ion-exchange membranes was provided. Then, the IEM-based synthesis methods reported in the literature were summarized, and areas of their application were discussed. The methods in question, namely: membrane electrolysis, electro-electrodialysis, electrodialysis metathesis, ion-substitution electrodialysis and electrodialysis with bipolar membrane, were found to be applicable for a number of organic and inorganic syntheses and acid/base production or recovery processes, which can be conducted in aqueous and non-aqueous solvents. The number and the quality of the scientific reports found indicate a great potential for IEMs in chemical synthesis.

High titer L-lactic acid production from corn stover with minimum wastewater generation and techno-economic evaluation based on Aspen plus modeling

Technological potentials of l-lactic acid production from corn stover feedstock were investigated by experimental and techno-economic studies. An optimal performance with 104.5 g/L in l-lactic acid titer and 71.5% in overall yield from cellulose in corn stover to l-lactic acid using an engineered Pediococcus acidilactici strain were obtained by overcoming several technical barriers. A rigorous Aspen plus model for l-lactic acid production starting from dry dilute acid pretreated and biodetoxified corn stover was developed. The techno-economic analysis shows that the minimum l-lactic acid selling price (MLSP) was $0.523 per kg, which was close to that of the commercial l-lactic acid produced from starch feedstock, and 24% less expensive than that of ethanol from corn stover, even though the xylose utilization was not considered. The study provided a prototype of industrial application and an evaluation model for high titer l-lactic acid production from lignocellulose feedstock.

A platform technology of recovery of lactic acid from a fermentation broth of novel substrate Zizyphus oenophlia

Lactic acid, a biologically derived compound, exists ubiquitously in nature. Its existence ranges from human being to microorganisms. Having paramount industrial significance, lactic acid should be highly pure, devoid of any contaminants. Hence, development of minimum steps of platform technologies to purify it needs urgent attention. The article proposed a novel and simple process for separation of lactic acid from a potential substrate Zizyphus oenophlia, based on ion exchange chromatography. The process herein involves two steps of purification; firstly a weak anion exchange resin was used to separate lactic acid from other anions present in the broth. This was followed by use of strong cation exchanger which washes out the target molecule (lactic acid) while trapped other cations present in the solution. The selected ion exchangers were Amberlite IRA 96 and Amberlite IR 120. Amberlite IRA 96 retained the lactic acid from the broth while washing away other anions. Maximum binding capacity of the resin was found to 210.46 mg lactic acid/g bead. After the simple two-step purification process, the purity of lactic acid improves up to 99.17 % with a recovery yield of 98.9 %. Upon characterization, formation of only levo rotatory form of lactic acid confirms its easy metabolism by the human system, thus triggering its application towards biomaterial sector.

Biocatalyst development for lactic acid production at acidic pH using inter-generic protoplast fusion

Acid tolerance ofL. delbrueckiiMut Uc-3 has been improved using an inter-generic protoplast fusion approach. The fusant was further treated with UV mutagenesis which generated a mutant with improved lactic acid production in acidic environment.

Nuclear localization of Haa1, which is linked to its phosphorylation status, mediates lactic acid tolerance in Saccharomyces cerevisiae

Improvement of the lactic acid resistance of the yeast Saccharomyces cerevisiae is important for the application of the yeast in industrial production of lactic acid from renewable resources. However, we still do not know the precise mechanisms of the lactic acid adaptation response in yeast and, consequently, lack effective approaches for improving its lactic acid tolerance. To enhance our understanding of the adaptation response, we screened for S. cerevisiae genes that confer enhanced lactic acid resistance when present in multiple copies and identified the transcriptional factor Haa1 as conferring resistance to toxic levels of lactic acid when overexpressed. The enhanced tolerance probably results from increased expression of its target genes. When cells that expressed Haa1 only from the endogenous promoter were exposed to lactic acid stress, the main subcellular localization of Haa1 changed from the cytoplasm to the nucleus within 5 min. This nuclear accumulation induced upregulation of the Haa1 target genes YGP1, GPG1, and SPI1, while the degree of Haa1 phosphorylation observed under lactic acid-free conditions decreased. Disruption of the exportin gene MSN5 led to accumulation of Haa1 in the nucleus even when no lactic acid was present. Since Msn5 was reported to interact with Haa1 and preferentially exports phosphorylated cargo proteins, our results suggest that regulation of the subcellular localization of Haa1, together with alteration of its phosphorylation status, mediates the adaptation to lactic acid stress in yeast.

Simultaneous production of 3-hydroxypropionic acid and 1,3-propanediol from glycerol using resting cells of the lactate dehydrogenase-deficient recombinant Klebsiella pneumoniae overexpressing an aldehyde dehydrogenase

In the present study, the lactate dehydrogenase-deficient (ldhA(-)) recombinant Klebsiella pneumoniae overexpressing an ALDH (KGSADH) was developed and the co-production of 3-HP and PDO from glycerol by this recombinant under resting cell conditions was examined. The new recombinant did not produce any appreciable lactate, which seriously inhibits the production of 3-HP and PDO. The final titers of 3-HP and PDO by the ldhA(-) recombinant strain at 60 h were 252.2 mM and 308.7 mM, respectively, which were improved by approximately 30% and 50%, respectively, compared to those by the counterpart recombinant strain, which was the wild type for ldhA. In addition, after deleting ldhA, the cumulative yield on glycerol and specific production rate of these two metabolites (3-HP and PDO) were enhanced by 41.4% and 52%, respectively.

Electro-extractive fermentation for efficient biohydrogen production

Electrodialysis, an electrochemical membrane technique, was found to prolong and enhance the production of biohydrogen and purified organic acids via the anaerobic fermentation of glucose by Escherichia coli. Through the design of a model electrodialysis medium using cationic buffer, pH was precisely controlled electrokinetically, i.e. by the regulated extraction of acidic products with coulombic efficiencies of organic acid recovery in the range 50-70% maintained over continuous 30-day experiments. Contrary to previous reports, E. coli produced H(2) after aerobic growth in minimal medium without inducers and with a mixture of organic acids dominated by butyrate. The selective separation of organic acids from fermentation provides a potential nitrogen-free carbon source for further biohydrogen production in a parallel photofermentation. A parallel study incorporated this fermentation system into an integrated biohydrogen refinery (IBR) for the conversion of organic waste to hydrogen and energy.

Lactic acid production from lignocellulose-derived sugars using lactic acid bacteria: overview and limits

Lactic acid is an industrially important product with a large and rapidly expanding market due to its attractive and valuable multi-function properties. The economics of lactic acid production by fermentation is dependent on many factors, of which the cost of the raw materials is very significant. It is very expensive when sugars, e.g., glucose, sucrose, starch, etc., are used as the feedstock for lactic acid production. Therefore, lignocellulosic biomass is a promising feedstock for lactic acid production considering its great availability, sustainability, and low cost compared to refined sugars. Despite these advantages, the commercial use of lignocellulose for lactic acid production is still problematic. This review describes the "conventional" processes for producing lactic acid from lignocellulosic materials with lactic acid bacteria. These processes include: pretreatment of the biomass, enzyme hydrolysis to obtain fermentable sugars, fermentation technologies, and separation and purification of lactic acid. In addition, the difficulties associated with using this biomass for lactic acid production are especially introduced and several key properties that should be targeted for low-cost and advanced fermentation processes are pointed out. We also discuss the metabolism of lignocellulose-derived sugars by lactic acid bacteria.

Genome-shuffling improved acid tolerance and l-lactic acid volumetric productivity in Lactobacillus rhamnosus

Genome shuffling is an efficient approach for the rapid improvement of industrially important microbial phenotypes. Here we improved the acid tolerance and volumetric productivity of an industrial strain Lactobacillus rhamnosus ATCC 11443 by genome shuffling. Five strains with subtle improvements in pH tolerance and volumetric productivity were obtained from the populations generated by ultraviolet irradiation and nitrosoguanidine mutagenesis, and then they were subjected for recursive protoplast fusion. A library that was more likely to yield positive colonies was created by fusing the lethal protoplasts obtained from both ultraviolet irradiation and heat treatments. After three rounds of genome shuffling, four strains that could grow at pH 3.6 were obtained. We observed 3.1- and 2.6-fold increases in lactic acid production and cell growth of the best performing at pH 3.8, respectively. The maximum volumetric productivity was 5.77+/-0.05 g/lh when fermented with 10% glucose under neutralizing condition with CaCO(3), which was 26.5+/-1.5% higher than the wild type.

A new process for the continuous production of succinic acid from glucose at high yield, titer, and productivity

A novel three stages continuous fermentation process for the bioproduction of succinic acid at high concentration, productivity and yield using A. succiniciproducens was developed. This process combined an integrated membrane-bioreactor-electrodialysis system. An energetic characterization of A. succiniciproducens during anaerobic cultured in a cell recycle bioreactor was done first. The very low value of Y(ATP) obtained suggests that an ATP dependent mechanism of succinate export is present in A. succiniciproducens. Under the best culture conditions, biomass concentration and succinate volumetric productivity reach values of 42 g/L and 14.8 g/L.h. These values are respectively 28 and 20 times higher compared to batch cultures done in our laboratory. To limit end-products inhibition on growth, a mono-polar electrodialysis pilot was secondly coupled to the cell recycle bioreactor. This system allowed to continuously remove succinate and acetate from the permeate and recycle an organic acids depleted solution in the reactor. The integrated membrane-bioreactor-electrodialysis process produced a five times concentrated succinate solution (83 g/L) compared to the cell recycle reactor system, at a high average succinate yield of 1.35 mol/mol and a slightly lower volumetric productivity of 10.4 g/L.h. The process combined maximal production yield to high productivity and titer and could be economically viable for the development of a biological route for succinic acid production.