Efficacy of tri-n-octylamine, tri-n-butyl phosphate and di-(2-ethylhexyl) phosphoric acid for reactive separation of protocatechuic acid

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 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.