Environmentally-friendly strategy for separation of 1,3-propanediol using biocatalytic conversion

Advances in biosynthesis and downstream processing of diols

Diols are important platform chemicals with a wide range of applications in the fields of chemical and pharmaceutical industries, food, feed and cosmetics. In particular, 1,3-propanediol (PDO), 1,4-butanediol (1,4-BDO) and 1,3-butanediol (1,3-BDO) are appealing monomers for producing industrially important polymers and plastics. Therefore, the commercialization of bio-based diols is highly important for supporting the growth of biomanufacturing for the fiber industry. This review focuses primarily on the microbial production of PDO, 1,4-BDO and 1,3-BDO with respect to different microbial strains and biological routes. In addition, metabolic platforms which are designed to produce various diols using generic bioconversion strategies are reviewed for the first time. Finally, we also summarize and discuss recent developments in the downstream processing of PDO according to their advantages and drawbacks, which is taken as an example to present the prospects and challenges for industrial separation and purification of diols from microbial fermentation broth.

Atomistic molecular dynamics simulation and COSMO-SAC approach for enhanced 1,3-propanediol extraction with imidazolium-based ionic liquids

CONTEXT

1,3-Propanediol (1,3-PDO) is a key chemical in various industries, including pharmaceuticals and material sciences, and is projected to see significant market growth. However, the current challenges in its downstream processing, particularly in terms of cost and efficiency, highlight the need for innovative solutions. Our study delves into using ionic liquids (ILs) as a potential alternative, aiming to address these critical separation challenges more sustainably and efficiently. In this study, we utilized molecular dynamics (MD) simulations and the COSMO-SAC to examine 1,3-propanediol (1,3-PDO) extraction using four imidazolium-based ionic liquids with 1-butyl-3-methylimidazolium [Bmim] cation and with different anions bis(pentafluoroethanesulfonyl)imide [NPF2]-, bis(trifluoromethylsulfonyl)imide [NTF2]-, thiocyanate [SCN]-, and trifluoromethanesulfonate [TFO]-. Molecular dynamics simulations, incorporating analysis of radial distribution functions (RDF) and spatial distribution functions (SDF), revealed that [Bmim][SCN] and [Bmim][TFO] exhibit enhanced interactions with 1,3-PDO. Notably, [Bmim][SCN] formed the most hydrogen bonds, averaging 1.639 per molecule, due to its coordinating [SCN]- anion. This was in contrast to the fewer hydrogen bonds formed by non-coordinating anions in [Bmim][NPF2] and [Bmim][NTF2]. In ternary systems, [Bmim][SCN] and [Bmim][TFO] demonstrated superior selectivity for 1,3-PDO extraction compared to the other ionic liquids, with selectivity values around 29. These findings, supported by COSMO-SAC predictive modeling, highlight the potential of [Bmim][SCN] as a promising candidate for 1,3-PDO extraction, emphasizing the importance of anion selection in optimizing ionic liquid properties for this application.

METHODS

In our study, we employed MD simulations, incorporating the OPLS-AA force field, and COSMO-SAC to investigate the extraction of 1,3-PDO using imidazolium-based ionic liquids: [Bmim][NTF2], [Bmim][NPF2], [Bmim][SCN], and [Bmim][TFO]. The MD simulations were conducted using LAMMPS software, focusing on elucidating the RDF, SDF, and hydrogen bonding. Analysis of the distribution coefficient (β) and selectivity (S) for the ternary mixture was also conducted. These aspects of the simulation were analyzed using TRAVIS and VMD software. Additionally, the COSMO-SAC model was employed to determine the activity coefficients of 1,3-PDO in the ionic liquids, with molecular optimization conducted using Gaussian16 and sigma profile calculations performed using COSMO-SAC.

Strain evolution and novel downstream processing with integrated catalysis enable highly efficient co-production of 1,3-Propanediol and organic acid esters from crude glycerol

Bioconversion of natural microorganisms generally results in a mixture of various compounds. Downstream processing (DSP) which only targets a single product often lacks economic competitiveness due to incomplete use of raw material and high cost of waste treatment for by-products. Here, we show with the efficient microbial conversion of crude glycerol by an artificially evolved strain and how a catalytic conversion strategy can improve the total products yield and process economy of the DSP. Specifically, Clostridium pasteurianum was first adapted to increased concentration of crude glycerol in a novel automatic laboratory evolution system. At m³ scale bioreactor the strain achieved a simultaneous production of 1,3-propanediol (PDO), acetic and butyric acids at 81.21, 18.72 and 11.09 g/L within only 19 h, respectively, representing the most efficient fermentation of crude glycerol to targeted products. A heterogeneous catalytic step was developed and integrated into the DSP process to obtain high-value methyl esters from acetic and butyric acids at high yields. The co-production of the esters also greatly simplified the recovery of PDO. For example, a cosmetic grade PDO (96% PDO) was easily obtained by a simple single-stage distillation process (with an overall yield more than 77%). This integrated approach provides an industrially attractive route for the simultaneous production of three appealing products from the crude glycerol fermentation broth, which greatly improve the process economy and ecology. This article is protected by copyright. All rights reserved.

A novel downstream process for highly pure 1,3-propanediol from an efficient fed-batch fermentation of raw glycerol by Clostridium pasteurianum

An efficient downstream process without prior desalination was developed for recovering 1,3-propanediol (1,3-PDO) with high purity and yield from broth of a highly productive fed-batch fermentation of raw glycerol by Clostridium pasteurianum. After removal of biomass and proteins by ultrafiltration, and concentration by water evaporation, 1,3-PDO was directly recovered from the broth by vacuum distillation with continuous addition and regeneration of glycerol as a supporting agent. Inorganic salts in the fermentation broth were crystallized but well suspended by a continuous flow of glycerol during the distillation process, which prevented salt precipitation and decline of heat transfer. On the other hand, ammonium salt of organic acids were liberated as ammonia gas and free organic acids under vacuum heating. The latter ones formed four types of 1,3-PDO esters of acetic acid and butyric acid, which resulted in yield losses and low purity of 1,3-PDO (< 80%). In order to improve the efficiency of final 1,3-PDO rectification, we examined alkaline hydrolysis to eliminate the ester impurities. By the use of 20% (w/w) water and 2% (w/w) sodium hydroxide, > 99% reduction of 1,3-PDO esters was achieved. This step conveniently provided free 1,3-PDO and the sodium salt of organic acids from the corresponding esters, which increased the 1,3-PDO yield by 7% and prevented a renewed formation of esters. After a single stage distillation from the hydrolyzed broth and a followed active carbon treatment, 1,3-PDO with a purity of 99.63% and an overall recovery yield of 76% was obtained. No wastewater with high-salt content was produced during the whole downstream process. The results demonstrated that the monitoring and complete elimination of 1,3-PDO esters are crucial for the efficient separation of highly pure 1,3-PDO with acceptable yield from fermentation broth of raw glycerol.

Separation and Purification of Biogenic 1,3-Propanediol from Fermented Glycerol through Flocculation and Strong Acidic Ion-Exchange Resin

In the present work, was investigated the separation and purification procedure of the biogenic 1,3-propanediol (1,3-PD), which is a well-known valuable compound in terms of bio-based plastic materials development. The biogenic 1,3-PD was obtained as a major metabolite through the glycerol fermentation by Klebsiella pneumoniae DSMZ 2026 and was subjected to separation and purification processes. A strong acidic ion exchange resin in H⁺ form was used for 1,3-PD purification from the aqueous solution previously obtained by broth flocculation. The eluent volume was investigated considering the removal of the secondary metabolites such as organic acids (acetic, citric, lactic, and succinic acids) and 2,3-butanediol (2,3-BD), and unconsumed glycerol. It was observed that a volume of 84 mL of ethanol 75% loaded with a flow rate of 7 mL/min completely remove the secondary metabolites from 10 mL of concentrated fermented broth, and pure biogenic 1,3-PD was recovered in 128 mL of the eluent.

The design and synthesis of high efficiency adsorption materials for 1,3-propanediol: physical and chemical structure regulation

In this study, a series of polystyrene-divinylbenzene resins with precise physical structure regulation and chemical modification were successfully synthesized. The regulation of Friedel–Crafts reaction conditions resulted in several physical resins with various BET surface areas and pore structures, while the adsorption of 1,3-propanediol revealed that the molecular size and other physical properties exhibited a moderate contribution to the adsorption of hydrophilic compounds. The adsorption processes between 1,3-propanediol and nitrogen, oxygen and boron functional group modified resins were further explored, and boronic acid modified resins named PS-3NB and PS-SBT exhibited higher adsorption capacities than commercial resin CHA-111. The adsorption capacity of PS-3NB and PS-SBT reached 17.54 mg g⁻¹ and 17.23 mg g⁻¹, respectively, which were 37% and 35% higher than that of commercial resin CHA-111. Furthermore, the adsorption mechanism demonstrated that the content of boronic acid, solution pH and adsorbate hydrophobicity were the primary adsorption driving forces. Herein, we provided a method to modify polystyrene-divinylbenzene materials with boronic acid to selectively adsorb hydrophilic polyols via the specific affinity between boronic acid and diol molecule.

Chemically modified materials efficiently captured 1,3-propanediol via the specific affinity between boronic acid and diol.