Bio-based succinic acid recovery by ion exchange resins integrated with nanofiltration/reverse osmosis preceded crystallization

Recent advances in bio-based production of top platform chemical, succinic acid: an alternative to conventional chemistry

Succinic acid (SA) is one of the top platform chemicals with huge applications in diverse sectors. The presence of two carboxylic acid groups on the terminal carbon atoms makes SA a highly functional molecule that can be derivatized into a wide range of products. The biological route for SA production is a cleaner, greener, and promising technological option with huge potential to sequester the potent greenhouse gas, carbon dioxide. The recycling of renewable carbon of biomass (an indirect form of CO2), along with fixing CO2 in the form of SA, offers a carbon-negative SA manufacturing route to reduce atmospheric CO2 load. These attractive attributes compel a paradigm shift from fossil-based to microbial SA manufacturing, as evidenced by several commercial-scale bio-SA production in the last decade. The current review article scrutinizes the existing knowledge and covers SA production by the most efficient SA producers, including several bacteria and yeast strains. The review starts with the biochemistry of the major pathways accumulating SA as an end product. It discusses the SA production from a variety of pure and crude renewable sources by native as well as engineered strains with details of pathway/metabolic, evolutionary, and process engineering approaches for enhancing TYP (titer, yield, and productivity) metrics. The review is then extended to recent progress on separation technologies to recover SA from fermentation broth. Thereafter, SA derivatization opportunities via chemo-catalysis are discussed for various high-value products, which are only a few steps away. The last two sections are devoted to the current scenario of industrial production of bio-SA and associated challenges, along with the author's perspective.

The Application of the Nanofiltration Membrane NF270 for Separation of Fermentation Broths

The potential for nanofiltration (NF) in removing both relatively low molecular weight (MW) organic species and charged solutes from complex media is noteworthy. The main aim of the current work was to improve understanding of the separation mechanisms of fermentation broths components in the NF process. For this purpose, the experimental investigations were performed using the commercial polyamide NF270 membrane. The feed solution was ultrafiltered 1,3-propanediol (1,3-PD) broths. The separation results were analyzed and discussed in light of the detailed characteristics of both the membrane and the broth components. It has been noted that the membrane ensured the complete 1,3-PD permeability and significant rejection of some feed components. A thorough analysis showed that the retention of carboxylic acids was based on both the Donnan effect and sieve mechanism, according to the following order: succinic acid > lactic acid > acetic acid > formic acid. Indeed, acids retention increased with increasing charged acids ions valency, Stokes radius (rS) as well as MW, and decreasing diffusion coefficient (D). In turn, for ions, the following orders retention was determined: SO42− = PO43− > Cl− and Ca2+ > Na+ > NH4+ ~ K+. It indicated that the ions retention increased with increasing ions charge density, hydrated radius (rH), and hydration energy (Eh). It showed that the separation of the ions was based on the Donnan exclusion, sieving effect, and dielectric exclusion.

Valorization of wastewater to recover value-added products: A comprehensive insight and perspective on different technologies

In recent years, due to rapid globalization and urbanization, the demand for fuels, energy, water and nutrients has been continuously increasing. To meet the future need of the society, wastewater is a prominent and emerging source for resource recovery. It provides an opportunity to recover valuable resources in the form of energy, fertilizers, electricity, nutrients and other products. The aim of this review is to elaborate the scientific literature on the valorization of wastewater using wide range of treatment technologies and reduce the existing knowledge gap in the field of resource recovery and water reuse. Several versatile, resilient environmental techniques/technologies such as ion exchange, bioelectrochemical, adsorption, electrodialysis, solvent extraction, etc. are employed for the extraction of value-added products from waste matrices. Since the last two decades, valuable resources such as polyhydroxyalkanoate (PHA), matrix or polymers, cellulosic fibers, syngas, biodiesel, electricity, nitrogen, phosphorus, sulfur, enzymes and a wide range of platform chemicals have been recovered from wastewater. In this review, the aspects related to the persisting global water issues, the technologies used for the recovery of different products and/or by-products, economic sustainability of the technologies and the challenges encountered during the valorization of wastewater are discussed comprehensively.

The Application of Cellulose Acetate Membranes for Separation of Fermentation Broths by the Reverse Osmosis: A Feasibility Study

Recently, there has been a special research focus on the bioconversion of glycerol to 1,3-propanediol (1,3-PD) due to its significance in the chemical industry. However, the treatment and separation of fermentation broths is a great challenge. Currently, the reverse osmosis (RO) process is a reliable state-of-the-art technique for separation of biological solutions. This study (as the first to do so) investigated the feasibility of separation of 1,3-PD broths with the use of cellulose acetate (CA) membrane by the RO process. The experiments were carried out using the installation equipped with the plate module, under the transmembrane pressure (TMP) and temperature of 1 MPa and 298 K, respectively. It was found that the used membrane was suitable for broth separation. Indeed, it was noted that 1,3-PD, as a target product, migrated through the membrane; meanwhile, other broth components were rejected in various degrees. Moreover, it was proven that retention of carboxylic acids tended to increase with increasing molecular weight, according to the following order: succinic acid > lactic acid > acetic acid > formic acid. With regards to ions, retention degree increased with the increase of ionic radius and decrease of diffusion coefficient. Finally, it was demonstrated that the CA membrane is resistant to irreversible fouling, which has a positive effect on the economic viability of the process.

Technological advancements in valorization of second generation (2G) feedstocks for bio-based succinic acid production

Succinic acid (SA) is used as a commodity chemical and as a precursor in chemical industry to produce other derivatives such as 1,4-butaneidol, tetrahydrofuran, fumaric acid, and bio-polyesters. The production of bio-based SA from renewable feedstocks has always been in the limelight owing to the advantages of renewability, abundance and reducing climate change by CO₂ capture. Considering this, the current review focuses on various 2G feedstocks such as lignocellulosic biomass, crude glycerol, and food waste for cost-effective SA production. It also highlights the importance of producing SA via separate enzymatic hydrolysis and fermentation, simultaneous saccharification and fermentation, and consolidated bioprocessing. Furthermore, recent advances in genetic engineering, and downstream SA processing are thoroughly discussed. It also elaborates on the techno-economic analysis and life cycle assessment (LCA) studies carried out to understand the economics and environmental effects of bio-based SA synthesis.

Expanding the application of ion exchange resins for the preparation of antimicrobial membranes to control foodborne pathogens

Although ion exchange resins (IERs) have been extensively adopted in water treatment, there are no reports on the application thereof for synthesizing antibacterial materials against pathogenic bacteria. The present study is the first in which the ion exchange characteristic of IERs was utilized to introduce silver ions that possess efficient antibacterial properties. The resulting antibacterial materials were incorporated into polylactic acid (PLA) and/or polybutylene adipate terephthalate (PBAT) to prepare antibacterial membranes. XPS spectra revealed the occurrence of in-situ reduction of silver ions to metallic silver, which was preferable since the stability of silver in the materials was improved. EDS mapping analysis indicated that the distribution of silver was consistent with the distribution of sulfur in the membranes, verifying the ion exchange methodology proposed in the present study. To investigate the antibacterial performance of the prepared membranes, zone of inhibition tests and bacteria-killing tests were performed. The results revealed that neither bare polymeric membranes of PLA and PBAT nor IER-incorporated polymeric membranes exhibited noticeable antibacterial activities. In comparison, the antibacterial membranes demonstrated effective and sustainable antibacterial activities against pathogenic bacteria Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The prepared antibacterial membranes exhibited potential in food-related applications such as food packaging to delay food spoilage due to microbial growth.

Advances in downstream processes and applications of biological carboxylic acids derived from organic wastes

Recovering carboxylic acids derived from organic wastes from fermentation broth is challenging. To provide a reference for future study and industrial application, this review summarized recent advances in recovery technologies of carboxylic acids including precipitation, extraction, adsorption, membrane-based processes, etc. Meanwhile, applications of recovered carboxylic acids are summarized as well to help choose suitable downstream processes according to purity requirement. Integrated processes are required to remove the impurities from the complicated fermentation broth, at the cost of loss and expense. Compared with chemical processes, biological synthesis is better options due to low requirements for the substrates. Generally, the use of toxic agents, consumption of acid/alkaline and membrane fouling hamper the sustainability and scale-up of the downstream processes. Future research on novel solvents and materials will facilitate the sustainable recovery and reduce the cost of the downstream processes.