An efficient aqueous two phase systems using dual inorganic electrolytes to separate 1,3-propanediol from the fermented broth

Continuous and autonomous-flow separation of laccase enzyme utilizing functionalized aqueous two-phase system with computer vision control

Downstream processing of biomolecules, particularly therapeutic proteins and enzymes, presents a formidable challenge due to intricate unit operations and high costs. This study introduces a novel cysteine (cys) functionalized aqueous two-phase system (ATPS) utilizing polyethylene glycol (PEG) and potassium phosphate, referred as PEG-K3PO4/cys, for selective extraction of laccase from complex protein mixtures. A 3D-baffle micro-mixer and phase separator was meticulously designed and equipped with computer vision controller, to enable precise mixing and continuous phase separation under automated-flow. Microfluidic-assisted ATPS exhibits substantial increase in partition coefficient (Kflow = 16.3) and extraction efficiency (EEflow = 88 %) for laccase compared to conventional batch process. Integrated and continuous-flow process efficiently partitioned laccase, even in low concentrations and complex crude extracts. Circular dichroism spectra of laccase confirm structural stability of enzyme throughout the purification process. Eventually, continuous-flow microfluidic bioseparation is highly useful for seamless downstream processing of target biopharmaceuticals in integrated and autonomous manner.

Advances for Biorefineries: Glycerol Hydrogenolysis to 1,3-Propylene Glycol

Humanity’s growing dependence on non-renewable resources and the ensuing environmental impact thus generated have spurred the search for alternatives to replace chemicals and energy obtained from petroleum derivatives. Within the group of biofuels, biodiesel has managed to expand worldwide at considerable levels, going from 20 million tn/year in 2010 to 47 million tn/year in 2022, boosting the supply of glycerol, a by-product of its synthesis that can be easily used as a renewable, clean, low-cost raw material for the manufacture of products for the chemical industry. The hydrogenolysis of glycerol leads to the production of glycols, 1,2-propylene glycol (1,2-PG) and 1,3-propylene glycol (1,3-PG). In particular, 1,3-PG has the highest added value and has multiple uses including its application as an additive in the polymer industry, the manufacture of cosmetics, cleaning products, cooling liquids, etc. This review focuses on the study of the hydrogenolysis of glycerol for the production of 1,3-PG, presenting the main reaction mechanisms and the catalysts employed, both in liquid and vapor phase. Engineering aspects and the effect of the operating variables to achieve maximum yields are discussed. Finally, studies related to the stability and the main deactivation mechanisms of catalytic systems are presented.

Production of Propanediols through In Situ Glycerol Hydrogenolysis via Aqueous Phase Reforming: A Review

Production of 1,2-propanediol and 1,3-propanediol are identified as methods to reduce glycerol oversupply. Hence, glycerol hydrogenolysis is identified as a thermochemical conversion substitute; however, it requires an expensive, high-pressure pure hydrogen supply. Studies have been performed on other potential thermochemical conversion processes whereby aqueous phase reforming has been identified as an excellent substitute for the conversion process due to its low temperature requirement and high H2 yields, factors which permit the process of in-situ glycerol hydrogenolysis which requires no external H2 supply. Hence, this manuscript emphasizes delving into the possibilities of this concept to produce 1,2-propanediol and 1,3-propanediol without “breaking the bank” with expenses. Various heterogenous catalysts of aqueous phase reforming (APR) and glycerol hydrogenolysis were identified, whereby the combination of a noble metal, support, and dopant with a good amount of Brønsted acid sites are identified as the key factors to ensure a high yield of 1,3-propanediol. However, for 1,2-propanediol, a Cu-based catalyst with decent basic support is observed to be the key for good yield and selectivity of product. The findings have shown that it is possible to produce high yields of both 1,2-propanediol and 1,3-propanediol via aqueous phase reforming, specifically 1,2-propanediol, for which some of the findings achieve better selectivity compared to direct glycerol hydrogenolysis to 1,2-propanediol. This is not the case for 1,3-propanediol, for which further studies need to be conducted to evaluate its feasibility.

Metabolic Engineering and Regulation of Diol Biosynthesis from Renewable Biomass in Escherichia coli

As bulk chemicals, diols have wide applications in many fields, such as clothing, biofuels, food, surfactant and cosmetics. The traditional chemical synthesis of diols consumes numerous non-renewable energy resources and leads to environmental pollution. Green biosynthesis has emerged as an alternative method to produce diols. Escherichia coli as an ideal microbial factory has been engineered to biosynthesize diols from carbon sources. Here, we comprehensively summarized the biosynthetic pathways of diols from renewable biomass in E. coli and discussed the metabolic-engineering strategies that could enhance the production of diols, including the optimization of biosynthetic pathways, improvement of cofactor supplementation, and reprogramming of the metabolic network. We then investigated the dynamic regulation by multiple control modules to balance the growth and production, so as to direct carbon sources for diol production. Finally, we proposed the challenges in the diol-biosynthesis process and suggested some potential methods to improve the diol-producing ability of the host.

Green and Efficient Extraction of Polysaccharide and Ginsenoside from American Ginseng (Panax quinquefolius L.) by Deep Eutectic Solvent Extraction and Aqueous Two-Phase System

In this study, a green and effective extraction method was proposed to extract two main compounds, ginsenosides and polysaccharides, from American ginseng by combining deep eutectic solvents (DESs) with aqueous two-phase systems. The factors of type of DESs, water content in DESs, the solid–liquid ratio, extraction temperature, and extraction time were studied in the solid–liquid extraction. Then, the aqueous two-phase system (DESs-ethylene oxide–propylene oxide (EOPO)) and salty solution exchange (EOPO-salty solution) was applied for the purification of polysaccharides. The content of the polysaccharides and ginsenosides were analyzed by the anthrone–sulfuric acid method and HPLC method, which showed that the extraction efficiency of deep eutectic solvents (DESs) was better than conventional methods. Moreover, the antioxidant activities of ginseng polysaccharides and their cytotoxicity were further assayed. The advantages of the current study are that, throughout the whole extraction process, we avoided the usage of an organic reagent. Furthermore, the separated green solvent DESs and EOPO could be recovered and reused for a next cycle. Thus, this study proposed a new, green and recyclable extraction method for extracting ginsenosides and polysaccharides from American ginseng.

High yield recovery of 2,3-butanediol from fermented broth accumulated on xylose rich sugarcane bagasse hydrolysate using aqueous two-phase extraction system

Downstream processing of chemicals obtained from fermentative route is challenging and cost-determining factor of any bioprocess. 2,3-Butanediol (BDO) is a promising chemical building block with myriad applications in the polymer, food, pharmaceuticals, and fuel sector. The current study focuses on the recovery and purification of BDO produced (68.2 g/L) from detoxified xylose-rich sugarcane bagasse hydrolysate by a mutant strain of Enterobacter ludwigii. Studies involving screening and optimization of aqueous-two phase system (ATPS) revealed that 30% w/v (NH₄)₂SO₄ addition to clarified fermented broth facilitated BDO extraction in isopropanol (0.5 v/v), with maximum recovery and partition coefficient being 97.9 ± 4.6% and 45.5 ± 3.5, respectively. The optimized protocol was repeated with unfiltered broth containing 68.2 g/L BDO, cell biomass, and unspent protein, which led to the partitioning of 66.7 g/L BDO, 2.0 g/L xylose and 9.0 g/L acetic acid into organic phase with similar BDO recovery (97%) and partition coefficient (45).

Recent Developments in Solvent-Based Fluid Separations

The most important developments in solvent-based fluid separations, separations involving at least one fluid phase, are reviewed. After a brief introduction and discussion on general solvent trends observed in all fields of application, several specific fields are discussed. Important solvent trends include replacement of traditional molecular solvents by ionic liquids and deep eutectic solvents and, more recently, increasing discussion around bio-based solvents in some application fields. Furthermore, stimuli-responsive systems are discussed; the most significant developments in this field are seen for CO₂-switchable and redox-responsive solvents. Discussed fields of application include hydrocarbons separations, carbon capture, biorefineries, and metals separations. For all but the hydrocarbons separations, newly reported electrochemically mediated separations seem to offer exciting new windows of opportunities.

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.

Klebsiella pneumoniae-A Useful Pathogenic Strain for Biotechnological Purposes: Diols Biosynthesis under Controlled and Uncontrolled pH Levels

Despite being a well-known human pathogen, Klebsiella pneumoniae plays a significant role in the biotechnology field, being considered as a microbial cell factory in terms of valuable chemical biosynthesis. In this work, Klebsiella pneumoniae DSMZ 2026 was investigated for its potential to biosynthesize 1,3-propanediol (PDO) and 2,3-butanediol (BDO) during batch fermentation under controlled and uncontrolled pH levels. The bacterial strain was cultivated at a bioreactor level, and it was inoculated in 2 L of specific mineral broth containing 50 g/L of glycerol as the main carbon source. The process was conducted under anaerobic conditions at 37 °C and 180 RPM (rotations per minute) for 24 h. The effect of pH oscillation on the biosynthesis of PDO and BDO was investigated. Samples were taken every 3 h and specific tests were performed: pH measurement, main substrate consumption, PDO and BDO production. The cell morphology was analyzed on both solid and liquid media. After 24 h of cultivation, the maximum concentrations of PDO and BDO were 28.63 ± 2.20 g/L and 18.10 ± 1.10 g/L when the pH value was maintained at 7. Decreased concentrations of PDO and BDO were achieved (11.08 ± 0.14 g/L and 7.35 ± 0.00 g/L, respectively) when the pH level was not maintained at constant values. Moreover, it was identified the presence of other metabolites (lactic, citric, and succinic acids) in the cultivation media at the beginning of the process, after 12 h and 24 h of cultivation.

Application of thermo-separating aqueous two-phase system in extractive bioconversion of polyhydroxyalkanoates by Cupriavidus necator H16

Polyhydroxyalkanoates (PHAs), a family of biodegradable and renewable biopolymers show a huge potential as an alternative to conventional plastics. Extractive bioconversion (in situ product recovery) is a technique that integrates upstream fermentation and downstream purification. In this study, extractive bioconversion of PHAs from Cupriavidus necator H16 was performed via a thermo-separating aqueous two-phase system to reduce the cost and environmental impacts of PHAs production. Key operating parameters, such as polymer concentration, temperature, and pH, were optimized. The strategy achieved a yield and PF of 97.6% and 1.36-fold, respectively at 5% EOPO 3900 concentration, 30 °C fermentation temperature and pH 6. The PHAs production process was also successfully scaled up in a 2 L bioreactor. To the best of our knowledge, this is the first report on extractive fermentation of PHAs from Cupriavidus necator utilizing a thermo-separation system to achieve a better productivity and purity of the target product.

Process optimization and kinetic analysis of malic acid production from crude glycerol using Aspergillus niger

In the present work, optimization of crude glycerol fermentation to produce malic acid by using Aspergillus niger was investigated using response surface methodology and artificial neural network. Kinetic investigation of bioconversion of crude glycerol into malic acid using Aspergillus niger was studied using Monod, Mosser, and Haldane-Andrew models. Crude glycerol concentration, initial pH and yeast extract concentration were found to be significant compounds affecting malic acid production by Aspergillus niger. Both dry cell weight and malic acid titre were found decreased with increase in crude glycerol concentration. Haldane-Andrew model gave the best fit for the production of malic acid from crude glycerol with µ_max of 0.1542 h^-1. The maximum malic acid production obtained under optimum conditions was 92.64 + 1.54 g/L after 192 h from crude glycerol using Aspergillus niger.