Esterification Of Lactic Acid Research Articles

Influence of Lactic Acid Surface Modification of Cellulose Nanofibrils on the Properties of Cellulose Nanofibril Films and Cellulose Nanofibril-Poly(lactic acid) Composites.

In this study, cellulose nanofibrils (CNFs) were modified by catalyzed lactic acid esterification in an aqueous medium with SnCl2 as a catalyst. Films were made from unmodified and lactic acid-modified CNF without a polymer matrix to evaluate the effectiveness of the modification. Ungrafted and lactic acid-grafted CNF was also compounded with poly(lactic acid) (PLA) to produce composites. Mechanical, water absorption, and barrier properties were evaluated for ungrafted CNF, lactic acid-grafted CNF films, and PLA/CNF composites to ascertain the effect of lactic acid modification on the properties of the films and nanocomposites. FTIR spectra of the modified CNF revealed the presence of carbonyl peaks at 1720 cm−1, suggesting that the esterification reaction was successful. Modification of CNF with LA improved the tensile modulus of the produced films but the tensile strength and elongation decreased. Additionally, films made from modified CNF had lower water absorption, as well as water vapor and oxygen permeability, relative to their counterparts with unmodified CNFs. The mechanical properties of PLA/CNF composites made from lactic acid-grafted CNFs did not significantly change with respect to the ungrafted CNF. However, the addition of lactic acid-grafted CNF to PLA improved the water vapor permeability relative to composites containing ungrafted CNF. Therefore, the esterification of CNFs in an aqueous medium may provide an environmentally benign way of modifying the surface chemistry of CNFs to improve the barrier properties of CNF films and PLA/CNF composites.

Synthesis and characterization of bio catalyst prepared from dairy waste for lactic acid esterification

Abstract Dairy byproduct is known for its valuable chemical and nutritional content possessing high market potential. Notwithstanding, it is tractable to exploit its utilization. The waste generated is organic and having huge energy potential. The objective of current research is to synthesize novel catalyst from a dairy based solid waste called Ghee Residue by chemical activation process and deploy it for the production of iso-butyl lactate. Surface identity of catalyst was furnished using Brunauer-Emmet Teller (BET) method and Fourier Transform Infrared Spectroscopy (FTIR). Effect of variables like reaction time, temperature of reaction and loading of catalyst on lactic acid conversion were studied. In addition to this, reaction kinetics modelling was performed using 2nd order pseudo-homogeneous approach. It was inferred that, both internal as well as external resistance of mass transfer could not offer any influence on overall rate of reaction in this esterification. Optimum condition for esterification reaction was at 368 K with 3% catalyst loading giving the highest conversion around 74%. The energy of activation for the present system using synthesized catalyst was 41.5 kJ/mol and found to be lower in comparison with the other catalysts. Although, the activity of GRC declined gradually less than 10% from the activity of the several reaction cycle.

Ethyl lactate production by reactive distillation – optimization of reaction kinetics and energy efficiency

Background: Ethyl lactate is an environmentally benign solvent, which could substitute petrol-based volatile organic compounds (VOCs) in many applications if production costs are reduced. It is usually produced by the esterification of lactic acid with ethanol – two important chemical building blocks of biorefineries that are available at industrial scale. Reactive distillation is a promising alternative production process, which utilises process intensification to increase energy efficiency and space-time yield by enhancing the reaction kinetics. Methods: In this work, process intensification of ethyl lactate production by means of distillation was analysed with special focus on the efficient separation of water. The feedstock requirements were studied and the process was optimized regarding reaction kinetics in experiments on laboratory level. The preparation of anhydrous starting mixtures for ethyl lactate formation was tested in batch experiments and applied to reactive distillation. The simultaneous distillation was optimized to ensure that the by-product water was separated efficiently and the separation capacity was not limiting the reaction rate. Combined reactive distillation was compared to a serial setup of reactors and distillation steps. Results: It was found that an optimized serial setup can offer similar process intensification at a lower distillate rate compared to simultaneous reactive distillation. Conclusions: The serial setup is more flexible and straight-forward to regulate and scale-up. Based on the experimental results a continuous production process that uses process intensification to reach high ethyl lactate yield and purity was proposed.

Association between the nasopharyngeal microbiome and metabolome in patients with COVID-19

SARS-CoV-2, the causative agent for COVID-19, infect human mainly via respiratory tract, which is heavily inhabited by local microbiota. However, the interaction between SARS-CoV-2 and nasopharyngeal microbiota, and the association with metabolome has not been well characterized. Here, metabolomic analysis of blood, urine, and nasopharyngeal swabs from a group of COVID-19 and non-COVID-19 patients, and metagenomic analysis of pharyngeal samples were used to identify the key features of COVID-19. Results showed lactic acid, l-proline, and chlorogenic acid methyl ester (CME) were significantly reduced in the sera of COVID-19 patients compared with non-COVID-19 ones. Nasopharyngeal commensal bacteria including Gemella morbillorum, Gemella haemolysans and Leptotrichia hofstadii were notably depleted in the pharynges of COVID-19 patients, while Prevotella histicola, Streptococcus sanguinis, and Veillonella dispar were relatively increased. The abundance of G. haemolysans and L. hofstadii were significantly positively associated with serum CME, which might be an anti-SARS-CoV-2 bacterial metabolite. This study provides important information to explore the linkage between nasopharyngeal microbiota and disease susceptibility. The findings were based on a very limited number of patients enrolled in this study; a larger size of cohort will be appreciated for further investigation.

Photochemical Synthesis of Lactic Acid Esters at Ambient Temperature Employing Sulfonically Fuctionalized N/W-Doped Nano-semiconductor.

Appreciating the wide array of applications of lactic acid esters in the flavoring industry as well as in cosmetic and pharmaceutical industries, respectively, their clean and green synthesis gain immense importance. Therefore, traditional ester synthesis processes, involving high-temperature requirements, need to be replaced. A photochemical route has been adopted where visible light illumination was used as the major driving force to synthesize lactic acid esters. This process involves the application of sulfonically functionalized nitrogen/tungsten-doped nanotitania as photocatalysts. These functionalized catalysts efficiently and repeatedly catalyzed the esterification of lactic acid at ambient temperature. The photo-activity of these catalysts is attributed to the presence of a large number of active sulfonate sites on its surface. As per the proposed photochemical mechanism, illumination initiates the electron discharge from the conduction band, which migrates toward absorbed lactic acid through sulfonate sites forming lactic acid radical. This radical in turn attracts the alcohol molecules producing the desired ester. Reaction parameters were optimized to maximize the product yield. The economic validity of the photocatalyst was specked by repetitive experiments, and both the catalysts were found to be efficient even after five reusability cycles. The development of these catalysts can completely replace commercial ester synthesis strategies.

Synthesis of a novel bifunctional mesoporous Ti-SBA-15-SO3H catalyst and studies on their enhanced performance and kinetic modeling of lactic acid esterification reaction with n-butanol

Abstract In the present study, the mesoporous Ti-SBA-15-SO3H catalyst is synthesized by using the sol-gel method. Further, these materials have been characterized by different advanced analytical techniques such as Low angle X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetry/Differential thermal analysis (TG/DTA), N2 adsorption/desorption studies, Fourier transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Temperature-programmed desorption of ammonia (NH3-TPD) and Lactic acid esterification catalytic activity studies. The Ti-SBA-15-SO3H catalyst is found to have a surface area of 457 m2/g, a pore volume of 0.12 cm3/g, a pore diameter of 3.16 nm, and a high acid density of 1.72 mmol/g. The optimum reaction conditions for lactic acid esterification with n-butanol are found to be a 1: 4 M ratio, 3 wt-% catalysts, 115 °C temperature, and 120 min reaction time to obtain 72% conversion. Further, the reusability tests reveal that the spent catalyst can be used for five successive runs without the loss of considerable activity. The pseudo-homogeneous model was able to describe the kinetics of this esterification with negligible error. The activation energy and equilibrium rate constant for Ti-SBA-15-SO3H is found to be Ea = 0.063 KJ/mol and K = 5.019 lit/mol min, respectively, to catalyze the esterification of lactic acid with n-butanol. A plausible mechanism for the catalytic activity is proposed.

New Greener Method for the Preparation of Heteropolyacid Compounds (HPW) Modified with Metallic Tin and Application in the Lactic Acid Esterification Reaction

The main objective of this work was to design an innovative method to prepare heterogeneous heteropolyacid catalysts. The heteropolyacid H3PW12O40 (HPW) was modified with tin(II) by two methodologies: a conventional aqueous ion-exchange (CS) and a redox solid-state (SS). In both cases, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurements evidenced that Keggin structure was preserved. All materials were active in the esterification of lactic acid with several alcohols and a mechanism was proposed. The best results were obtained for octanol and benzyl alcohol, where higher conversion values were obtained. The catalytic activity (turnover frequency, TON) showed an efficient performance for the materials prepared with 4 h of calcination (CS4h and SS4h). However, the catalyst prepared by the SS method was in accordance with the development of environmentally friendly processes.

A green and energy-efficient photocatalytic process for the accelerated synthesis of lactic acid esters using functionalized quantum dots

Sulphonated-grafted-titania quantum dot catalyzed green and energy-efficient photochemical process for the synthesis of valuable lactic acid esters at ambient temperature.

Acyl and oligo(lactic acid) prodrugs for PEG-b-PLA and PEG-b-PCL nano-assemblies for injection

Poly(ethylene glycol)-block-poly(D,L-lactic acid) (PEG-b-PLA) and poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) form nano-assemblies, including micelles and nanoparticles, that increase the water solubility of anticancer drugs for injection. PEG-b-PLA and PEG-b-PCL are less toxic than commonly used organic solvents or solubilizers for injection, such as Cremophor EL® in Taxol®. Formulating paclitaxel in PEG-b-PLA micelles, as Genexol-PM®, permits dose escalation over Taxol®, enhancing antitumor efficacy in breast, lung and ovarian cancers. To expand the repertoire of anticancer drugs for injection, acyl and oligo(lactic acid) ester prodrugs have been synthesized for PEG-b-PLA and PEG-b-PCL nano-assemblies, compatibility, and novel nanomedicines for injection. Notably, acyl and oligo(lactic acid) taxane prodrugs delivered by PEG-b-PLA and PEG-b-PCL nano-assemblies display heightened plasma exposure, reduction in biodistribution into major organs and enhanced tumor exposure in murine tumor models, versus parent anticancer drugs in conventional formulations. As a result, acyl and oligo(lactic acid) ester prodrugs are less toxic and induce durable antitumor responses. In summary, acyl and oligo(lactic acid) ester prodrugs widen the range of anticancer drugs that can be tested safely and effectively by using PEG-b-PLA and PEG-b-PCL nano-assemblies, and they display superior anticancer efficacy over parent anticancer drugs, which are often approved products. Oligo(lactic acid) ester taxane prodrugs are in pre-clinical development as novel drug combinations and immunotherapy combinations for cancer therapy.

Microcontroller Based Automated Reactor for Esterification of Lactic Acid: MATLAB Simulation

ABSTRACT: This paper deals with esterification of lactic acid using sulphonated carbon catalyst in a newly designed microcontroller based automated reactor (MBAR) and the simulation of process parameters using MATLAB programming. The reactor was accompanied with moisture sensor, temperature sensor and solenoid valves in the embedded system. The study of effect of process parameters such as silica gel weight, hot air temperature, molar ratio and conversion of lactic acid on the removal of water, generated during esterification reaction, was performed. Water removal by adsorption using silica gel at each stage of conversion was estimated experimentally as well as with the help of developed, simulated linear equations, using MATLAB. The experimental and MATLAB results were compared and found in close vicinity. The simulation results revealed that an increased water removal is achieved with increasing conversion and molar ratio. The results also validated that increasing the reaction temperature increases the conversion tremendously with a rapid decrease in hot air flow requirement. The uniqueness of newly designed reactor is that the silica bed is operated in rotation in such a way that when one is in operation another is regenerated during its idle time.

Response Surface Methodology and Artificial Neural Networks for Optimization of Catalytic Esterification of Lactic Acid

AbstractResponse surface methodology (RSM) and artificial neural network (ANN) models were employed to study the esterification of lactic acid and isoamyl alcohol. A carbon‐based solid acid catalyst prepared by wet impregnation was used in the esterification reaction. Experimental characterization revealed its potential to serve as catalyst for the esterification reaction. The experiments were performed based on the design of experiments provided by RSM and ANN models. Both models were compared on the basis of prediction efficacies and deviation from actual data. The prediction data results demonstrated that the ANN model gave better prediction efficiency and lower prediction deviation than the RSM model. The ANN model provided a higher coefficient of determination and lower error values than the RSM model. Moreover, the catalyst exhibited a good stability and recyclability up to four reaction cycles.

Effect of the apple cultivar on cloudy apple juice fermented by a mixture of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus fermentum

This study aimed to evaluate the fermentation performance of a mixture of Lactobacillus spp. in cloudy apple juices from nine cultivars. The results showed that cultivar influenced most the properties of the fermented cloudy apple juice. The fermented cloudy apple juices made from Changfu had the highest viable bacterial count and acetic acid contents (6.37 × 108 CFU/mL and 2.67 mg/mL, respectively). It also had higher sensory score, second only to Huaniu. The highest total sugar consumption, utilising fructose, glucose, and sucrose (33.07 mg/mL), was seen with Golden Delicious. Qinguan fermented cloudy apple juice had the highest contents of lactic acid (6.74 mg/mL) and total esters (921.36 μg/L); d-limonene also detected in this fermented cloudy apple juice. Of the nine cultivars examined in this study, Changfu, Qinguan, and Golden Delicious were the most suitable for producing fermented cloudy apple juice with better taste, higher viable count and more intense aroma.

Quantitative analysis of total acidity in aqueous lactic acid solutions by direct potentiometric titration

In aqueous solutions of concentrated lactic acid (>30 wt%), oligomers of lactic acid can produce via the intermolecular esterification of lactic acid, and thus the amount of titratable acidity is often less than that of total acidity. In this paper, the hydrolysis of oligomers of lactic acid was investigated at different temperatures in detail. The experimental results showed that when the content of total acidity is lower than 30 wt% in aqueous lactic acid solutions, the oligomers of lactic acid can been completely hydrolyzed to give monomeric lactic acid and the monomeric lactic acid is stable at temperatures of 8–33 °C, thus the total acidity is equivalent to the titratable acidity and can be determined quantitatively by a direct potentiometric titration. The results for determining total acidities were in good agreement with those obtained from a back titration by a two tailed t-test. Compared with the back titration, the novel method's procedure is simpler and reducing sugars do not interfere with measurements. The relative standard deviation (RSD) was less than 0.7% and 1.1% for the direct potentiometric and back titrations, respectively, which indicated that the direct potentiometric titration has a higher precision.

Study of glycerolysis of lactic acid

Increasing production of a biodiesel industry, will also increase the by-product of the industry, glycerol. Further processes were investigated to get an added value of the byproduct. Glycerol esters of lactic acid and in particulars glycerol monolactate is one of the more value of derivative material from glycerol, which is known as safe, nontoxic and biodegradable emulsifier in food, cosmetics, and pharmaceutical industries. This research aims to study the effect of temperature and reactant ratio to the rate of catalyst free glycerolysis reaction of lactic acid. Experiments were conducted in a three-necked flask equipped with a thermometer, a stirrer and a reflux condenser. The reactions were conducted for 4 hours at 100°C – 140°C while the mole ratios of glycerol to lactate acid were varied 1:1 to 5:1. The conversion of lactic acid to ester increased by increasing the reaction temperature. The results also showed that more glycerol ratio to lactate acid, the higher conversion of the acid was obtained. As of the variables studied, maximum conversion was 86.28% at mole ratio of reactants was 5:1, 140°C within 4 hours. Irreversible homogeneous second order reaction model was suitable with the experimental data.

Effects of initial oxygenation on chemical and aromatic composition of wine in mixed starters of Hanseniaspora vineae and Saccharomyces cerevisiae

The use of Saccharomyces and non-Saccharomyces yeast species as mixed starters has potential advantages over pure culture fermentation due to increased wine complexity based on modification of metabolites of oenological interest. In this work, the effects of initial oxygenation on fermentation performance, chemical and volatile composition of French Colombard wine fermented with Hanseniaspora vineae and Saccharomyces cerevisiae in sequential inoculations were investigated in 1 L flasks. Although dominated by S. cerevisiae at the middle-end of fermentation, initial aeration for 1 day boosted H. vineae populations, and allowed H. vineae to coexist longer with S. cerevisiae in mixed cultures compared to no aeration, and suppressed S. cerevisiae later in the fermentation, which resulted in extended fermentation time. More important, the major fermentation products and volatile compounds were significantly modified by aeration and different from no aeration fermentation. The wines produced by aeration of mixed fermentations were characterized with higher amounts of glycerol, lactic acid and acetate esters, and lower levels of ethanol, higher alcohol and ethyl fatty acid esters. The aeration had more potential to shape the quality of wines and diversify the aromatic characteristics relative to simple mixed inoculation, as indicated by PCA analysis. Our results suggested that the impact of early aeration on yeast physiology extends beyond the aeration phase and influences fermentation activity, chemical and aromatic compounds in the following anaerobic stage. The aeration for a short time during the cell growth stage in mixed fermentation is therefore a potential means to increase the aromatic diversity and quality of wine, possibly providing an alternative approach to meet the expectations of wine consumers for diverse aromatic qualities.

Characterization of E 472 food emulsifiers – determination of bound and free fruit acids, free glycerol and ash content

Emulsifiers of the type E 472 are esters of fruit acids and mono- and diacylglycerols (MAG and DAG), which are used to adjust techno-functional properties in various food products. The most dominant representatives of E 472 emulsifiers are acetic acid esters (E 472a), lactic acid esters (E 472b), citric acid esters (E 472c), and mono- and diacetyl tartaric acid esters (E 472e). For the determination of fruit acids, a high-performance liquid chromatography method with ultraviolet light (HPLC–UV) detection was developed. Free and total fruit acids were determined by reversed phase HPLC–UV analysis of untreated and saponified emulsifier extracts with 20 mM potassium hydrogen phosphate buffer (pH 2.6) as isocratic eluent. Limits of quantitation of 0.08–0.27 g free fruit acid/kg emulsifier and 4–14 g total fruit acid/kg granted a reliable method with recoveries for free and total fruit acids between 80 and 100% with relative standard deviations (%RSD) below 4%. For the quantitation of free glycerol by spectrophotometry, an enzymatic assay was optimized for the analysis of E 472 providing reliable results with %RSD values below 9%. In addition, the ash content of E 472 emulsifiers was determined.

Characterization of E 472 food emulsifiers by high-performance thin-layer chromatography with fluorescence detection and mass spectrometry

Esters of fruit acids including acetic acid and mono- and diacylglycerols (MAG and DAG), also known as E 472 emulsifiers, are used in the food industry as food additives to adjust techno-functional properties like viscosity, emulsion stability and foaming stability in various products, mainly dairy products. Based on the respective acids, E 472 emulsifiers are classified in several categories with acetic acid esters (ACETEM, E 472a), lactic acid esters (LACTEM, E 472b), citric acid esters (CITREM, E 472c), and mono- and diacetyl tartaric acid esters (DATEM, E 472e) as the most prominent representatives. Besides fruit acid esters, E 472 emulsifiers mainly comprise MAG, DAG, triacylglycerols, free fatty acids, free fruit acids and free glycerol in different amounts. Here we present an innovative and sensitive method for the characterization of the composition of E 472 emulsifiers by high-performance thin-layer chromatography with fluorescence detection (HPTLC–FLD). For HPTLC–FLD, technical emulsifiers were simply dissolved and analyzed on HPTLC silica gel plates after a two-fold development and derivatization with primuline, enabling the easy characterization and direct visual comparison of the emulsifier pattern (fingerprint) through the fluorescent lipid components under UV 366 nm. Thus, the HPTLC–FLD fingerprint approach represents a simple tool for the comparison of different samples, batches and categories of E 472. Coupling of HPTLC to mass spectrometry moreover enabled the identification of constituents of interest.

Remarkable effects of deep eutectic solvents on the esterification of lactic acid with ethanol over Amberlyst-15

Deep eutectic solvents (DESs) are widely used in numerous reactions both as a solvent and a catalyst. In this study, different types of DESs were investigated as a supplementary component for Amberlyst-15 to enhance its catalytic activity in the esterification reaction of lactic acid with ethanol. The effects of the following parameters such as DES type, choline chloride: glycerol (ChCl-Gly) (1 : 2) amount, molar ratio of reactants, temperature and agitation rate on the initial rate of reaction and yield of ethyl lactate were investigated. According to the results, DESs alone did not have any catalytic effect on the esterification; however, DESs together with Amberlyst-15 provided a significant increase in the initial rate of reaction and yield. The activation energy of the reaction decreased significantly with the combined use of Amberlyst-15 and ChCl-Gly (1 : 2). Internal and external mass transfer limitations were found to be negligible under optimum reaction conditions.

EFFICIENT LACTAMIDE SYNTHESIS BY FED-BATCH METHOD USING NITRILE HYDRATASE OF RHODOCOCCUS PYRIDINIVORANS NIT-36

Lactamide is used in the synthesis of lactic acid esters and as a solvent in many ecofriendly formulations. Till date lactamide synthesis was accomplished by employing chemical methods involving harsh reaction conditions while the enzyme-based approach ensures high purity lactamide synthesis under ambient environment without the intervention of acid byproducts using lactonitrile as substrate. Nitrile hydratase of Rhodococcus pyridinivorans NIT-36 was expressed by supplementing the growth medium with inducer i.e. lactamide. A 1.7-fold increase in enzyme activity was recorded by double feeding of the inducer. A further two-fold enhancement in enzymatic activity was achieved by the statistical optimization of process parameters for lactamide production by Response Surface Methodology. The substrate, lactonitrile inhibited the enzyme at higher concentrations, hence a fed-batch approach was adopted. The enzyme substrate ratio was standardized and the enzyme completely converted 15 mM of lactonitrile to lactamide in 30 minutes using 2 mg/ml resting cells. The fed-batch was performed at 1 L scale and 100% biotransformation of 360 mM of lactonitrile to lactamide was achieved at 45°C in 720 minutes. The catalytic productivity of 14.5 g/g dcw/h for lactamide formation was finally recorded in the 1 L fed-batch reaction.

Pervaporation Reactor for Enhanced Esterification of Lactic Acid and Isobutyl Alcohol

AbstractThe esterification of lactic acid and isobutyl alcohol to isobutyl lactate and water was intensified. An ex situ pervaporation reactor (PVR) shifted the equilibrium towards the formation of isobutyl lactate. The effects of temperature, molar acid/alcohol ratio, catalyst loading, and ratio of effective membrane area to total reaction volume were investigated with and without a PVR. Lactic acid conversion beyond reaction equilibrium was enhanced with such a reactor. The partial fluxes of the individual components were evaluated for each reaction parameter indicating that the membrane was selective towards separation of water and exhibited a good performance. The performance of the ex situ PVR was studied, which revealed that the water removal rate exceeded the water production rate.