Reactive separation of protocatechuic acid using Tri-n-octyl amine and Di-(2-ethylhexyl) phosphoric acid in Methyl isobutyl ketone

The Sustainable Approach of Process Intensification in Biorefinery Through Reactive Extraction Coupled with Regeneration for Recovery of Protocatechuic Acid

In the current scenario, where environmental degradation, global climate change, and the depletion of petroleum feedstock pose significant challenges, the chemical industry seeks sustainable alternatives for manufacturing chemicals, fuels, and bioplastics. Biorefining processes that integrate biomass conversion and microbial fermentation have emerged as preferred approaches to create value-added compounds. However, commercializing biorefinery products is hindered by dilute concentrations of final products and the demand for high purity goods. To address these challenges, effective separation and recovery procedures are essential to minimize costs and equipment size. This article proposes a biorefinery route for the production of protocatechuic acid (PCA) by focusing on in situ PCA separation and purification from fermentation broth. PCA is a significant phenolic molecule with numerous applications in the pharmaceutical sector for its anti-inflammatory, antiapoptotic, and antioxidant properties, as well as in the food, polymer, and other chemical industries. The chemical approach is predominantly used to produce PCA due to the cost-prohibitive nature of natural extraction techniques. Reactive extraction, a promising technique known for its enhanced extraction efficiency, is identified as a viable strategy for recovering carboxylic acids compared to conventional methods. The extraction of PCA has been explored using various solvents, including natural and conventional solvents, such as aminic and organophosphorous extractants, as well as the potential utilization of ionic liquids as green solvents. Additionally, back extraction techniques like temperature swing and diluent composition swing can be employed for reactive extraction product recovery, facilitating the regeneration of the extractant from the organic phase. By addressing the challenges associated with PCA production and usage, particularly through reactive extraction, this proposed biorefinery route aims to contribute to a more sustainable and environmentally friendly chemical industry. The incorporation of PCA in the biorefinery process allows for the utilization of this valuable compound with diverse industrial applications, thus providing an additional incentive for the development and optimization of efficient separation techniques.

Separation of Mandelic Acid by a Reactive Extraction Method Using Tertiary Amine in Different Organic Diluents

Mandelic acid is a valuable chemical that is commonly used in the synthesis of various drugs, in antibacterial products, and as a skin care agent in cosmetics. As it is an important chemical, various methods are used to synthesize and extract this compound. However, the yields of the used processes is not significant. A dilute aqueous solution is obtained when using several production methods, such as a fermentation, etc. In this study, the reactive extraction of mandelic acid from aqueous solutions using tri-n-octylamine extractant at 298.15 K was investigated. Dimethyl phthalate (DMP), methyl isobutyl ketone (MIBK), 2-octanone, 1-octanol, n-pentane, octyl acetate, and toluene were used as diluents. The batch extraction results of the mandelic acid experiments were obtained for the development of a process design. Calculations of the loading factor (Z), distribution coefficient (D), and extraction efficiency (E%) were based on the experimental data. The highest separation yield was obtained as 98.13% for 0.458 mol.L⁻¹ of tri-n-octylamine concentration in DMP. The overall extraction constants were analyzed for the complex of acid-amine by the Bizek approach, including K₁₁, K₁₂, and K₂₃.

Metabolic and process engineering for microbial production of protocatechuate with Corynebacterium glutamicum

3,4-Dihydroxybenzoate (protocatechuate, PCA) is a phenolic compound naturally found in edible vegetables and medicinal herbs. PCA is of high interest in the chemical industry and has wide potential for pharmaceutical applications. We designed and constructed a novel Corynebacterium glutamicum strain to enable the efficient utilization of d-xylose for microbial production of PCA. Shake flask cultivation of the engineered strain showed a maximum PCA titer of 62.1 ± 12.1 mM (9.6 ± 1.9 g L^-1 ) from d-xylose as the primary carbon and energy source. The corresponding yield was 0.33 C-mol PCA per C-mol d-xylose, which corresponds to 38% of the maximum theoretical yield. Under growth-decoupled bioreactor conditions, a comparable PCA titer and a total amount of 16.5 ± 1.1 g PCA could be achieved when d-glucose and d-xylose were combined as orthogonal carbon substrates for biocatalyst provision and product synthesis, respectively. Downstream processing of PCA was realized via electrochemically induced crystallization by taking advantage of the pH-dependent properties of PCA. This resulted in a maximum final purity of 95.4%. The established PCA production process represents a highly sustainable approach, which will serve as a blueprint for the bio-based production of other hydroxybenzoic acids from alternative sugar feedstocks.

Separation of bio-products by liquid–liquid extraction

Solvent extraction one of the oldest approaches of separation known, remains one of the most well-known methods operating on an industrial scale. With the availability of variety of solvents as well as commercial equipment, liquid–liquid extractions finds applications in fields like chemicals and bio-products, food, polymer, pharmaceutical industry etc. Liquid–liquid extraction process is particularly suitable for biorefinery process (through conversion using microorganisms), featuring mild operational conditions and ease of control of process. The principles, types, equipment and applications of liquid–liquid extraction for bioproducts are discussed. Currently various intensification techniques are being applied in the field of liquid–liquid extraction for improving the process efficiency like hybrid processes, reactive extraction, use of ionic liquids etc, which are gaining importance due to the cost associated with the downstream processing of the fermentation products (20–50% of total production cost).

Reactive extraction: a promising approach to separate protocatechuic acid

3,4-Dihydroxybenzoic acid, commonly known as protocatechuic acid, is a naturally occurring phenolic compound, being the active component of many medicinal and edible plants. The in vitro and in vivo studies of protocatechuic acid conclude that it possesses many pharmacological properties. Protocatechuic acid, present in waste streams of food processing industries, is considered a phenolic pollutant. Owing to its bactericidal properties and in order to maintain the standards of disposal, its removal from the waste streams is necessary. Protocatechuic acid finds applications also in bioplastics, polymers, and also bio-based active films to improve food preservation. Its direct extraction from plant secondary metabolites possesses many difficulties. Recently reports of protocatechuic acid production by several Bacillus species are present in literature. For the retrieval/removal of protocatechuic acid from aqueous streams, methods like adsorption, O₃/UV or H₂O₂/UV, and microbial degradation are in practice. For the retrieval of carboxylic acid from fermentation broths and aqueous streams, reactive extraction by the use of specific extractants has been found to be a most suitable method owing to its several advantages. The present paper is focused on the separation of protocatechuic acid by reactive extraction as a promising approach. The parameters needed for the design such as distribution coefficient, water co-extraction, physical and chemical extraction, effect of initial acid concentration, diluents, extractant, and extractant concentration have been discussed.

Effect of temperature on equilibria for physical and reactive extraction of protocatechuic acid

Owing to its biological and chemical applications, the separation of protocatechuic acid, a polyphenol compound, is of interest to researchers. Extraction studies with initial acid concentration (0.001–0.01 kmol m⁻³) using aminic extractant tri-n-octyl amine (TOA) (0.2287 kmol m⁻³ -1.1436 kmol m⁻³) in diluent octanol at diverse temperature ranges from 288 K - 313 K was done. Parameters like loading ratio, distribution coefficient, equilibrium complexation constant, diffusion coefficient, number of stages necessary for protocatechuic acid counter-current extraction were obtained; this information is useful in designing a process for the in situ separation of the acid from the fermentation broth as well as from the waste streams. The increase in temperature distribution coefficient was found to increase up to the temperature of 303 K and was found to decrease with a further rise in temperature. The entropy and enthalpy values for the reaction at different temperatures were obtained. The highest extraction of 91.1 % and distribution coefficient of 1.14 were obtained at 313 K for an acid concentration of 0.01 kmol m^−3, and TOA concentration of 1.1436 kmol m⁻³ and 4 stages are required for counter-current extraction process for acquiring the required separation efficiency. Development of 1:1 complex of protocatechuic acid and TOA take place as concluded from the values of the loading ratio.