Tailoring physical and chemical microenvironments by polyether-amine in blended membranes for efficient CO2 separation

Xia Lv,Xueqin Li,Lu Huang,Siyuan Ding,Yin Lv,Jinli Zhang 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.3

Pebax® MH 1657 (Pebax)-based blend membranes with different polyether-amine (PEA) loadings were designed and fabricated for efficient CO2 separation. The CO2 separation performance of Pebax/PEA blend membranes was greatly improved in comparison with that of pure membranes. This was mainly because the introduced PEA tailored the physical and chemical microenvironments in blend membranes. Specifically, PEA was a liquid-like additive, which was beneficial to reduce the mass transfer resistance of gases and increase CO2 permeability. Meanwhile, PEA contained amino groups that acted as mobile carriers to tailor the chemical microenvironment in blend membranes. The mobile carriers preferentially reacted reversibly with CO2 molecules, facilitating CO2 transport in membranes. Compared with CO2/CH4 separation performance of pure Pebax membrane, CO2 permeability and CO2/CH4 separation factor of Pebax/PEA-3 increased by 144.8% and 29.4%, respectively. This study suggests that PEA is a promising membrane material for tailoring the physical and chemical microenvironments in blend membranes for efficient CO2 separation.

Biocatalytic Production of Glucosamine from N-Acetylglucosamine by Diacetylchitobiose Deacetylase

( Zhu Jiang ),( Xueqin Lv ),( Yanfeng Liu ),( Hyun-dong Shin ),( Jianghua Li ),( Guocheng Du ),( Long Liu ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.11

Glucosamine (GlcN) is widely used in the nutraceutical and pharmaceutical industries. Currently, GlcN is mainly produced by traditional multistep chemical synthesis and acid hydrolysis, which can cause severe environmental pollution, require a long prodution period but a lower yield. The aim of this work was to develop a whole-cell biocatalytic process for the environment-friendly synthesis of glucosamine (GlcN) from N-acetylglucosamine (GlcNAc). We constructed a recombinant Escherichia coli and Bacillus subtilis strains as efficient whole-cell biocatalysts via expression of diacetylchitobiose deacetylase (Dac_ph) from Pyrococcus furiosus. Although both strains were biocatalytically active, the performance of B. subtilis was better. To enhance GlcN production, optimal reaction conditions were found: B. subtilis whole-cell biocatalyst 18.6 g/l, temperature 40°C, pH 7.5, GlcNAc concentration 50 g/l and reaction time 3 h. Under the above conditions, the maximal titer of GlcN was 35.3 g/l, the molar conversion ratio was 86.8% in 3-L bioreactor. This paper shows an efficient biotransformation process for the biotechnological production of GlcN in B. subtilis that is more environmentally friendly than the traditional multistep chemical synthesis approach. The biocatalytic process described here has the advantage of less environmental pollution and thus has great potential for largescale production of GlcN in an environment-friendly manner.

Combinatorial Fine-Tuning of Phospholipase D Expression by Bacillus subtilis WB600 for the Production of Phosphatidylserine

( Tingting Huang ),( Xueqin Lv ),( Jianghua Li ),( Hyun-dong Shin ),( Guocheng Du ),( Long Liu ) 한국미생물 · 생명공학회 2018 Journal of microbiology and biotechnology Vol.28 No.12

Phospholipase D has great commercial value due to its transphosphatidylation products that can be used in the food and medicine industries. In order to construct a strain for use in the production of PLD, we employed a series of combinatorial strategies to increase PLD expression in Bacillus subtilis WB600. These strategies included screening of signal peptides, selection of different plasmids, and optimization of the sequences of the ribosome-binding site (RBS) and the spacer region. We found that using the signal peptide amyE results in the highest extracellular PLD activity (11.3 U/ml) and in a PLD expression level 5.27-fold higher than when the endogenous signal peptide is used. Furthermore, the strain harboring the recombinant expression plasmid pMA0911-PLD-amyE-his produced PLD with activity enhanced by 69.03% (19.1 U/ml). We then used the online tool \RBS Calculator v2.0 to optimize the sequences of the RBS and the spacer. Using the optimized sequences resulted in an increase in the enzyme activity by about 26.7% (24.2 U/ml). In addition, we found through a transfer experiment that the retention rate of the recombinant plasmid after 5 generations was still 100%. The final product, phosphatidylserine (PS), was successfully detected, with transphosphatidylation selectivity at 74.6%. This is similar to the values for the original producer.

Enhanced 2,5-Furandicarboxylic Acid (FDCA) Production in Raoultella ornithinolytica BF60 by Manipulation of the Key Genes in FDCA Biosynthesis Pathway

( Haibo Yuan ),( Yanfeng Liu ),( Xueqin Lv ),( Jianghua Li ),( Guocheng Du ),( Zhongping Shi ),( Long Liu ) 한국미생물 · 생명공학회 2018 Journal of microbiology and biotechnology Vol.28 No.12

The compound 2,5-furandicarboxylic acid (FDCA), an important bio-based monomer for the production of various polymers, can be obtained from 5-hydroxymethylfurfural (HMF). However, efficient production of FDCA from HMF via biocatalysis has not been well studied. In this study, we report the identification of key genes that are involved in FDCA synthesis and then the engineering of Raoultella ornithinolytica BF60 for biocatalytic oxidation of HMF to FDCA using its resting cells. Specifically, previously unknown candidate genes, adhP3 and alkR, which were responsible for the reduction of HMF to the undesired product 2,5- bis(hydroxymethyl)furan (HMF alcohol), were identified by transcriptomic analysis. Combinatorial deletion of these two genes resulted in 85.7% reduction in HMF alcohol formation and 23.7% improvement in FDCA production (242.0 mM). Subsequently, an aldehyde dehydrogenase, AldH, which was responsible for the oxidation of the intermediate 5-formyl-2-furoic acid (FFA) to FDCA, was identified and characterized. Finally, FDCA production was further improved by overexpressing AldH, resulting in a 96.2% yield of 264.7 mM FDCA. Importantly, the identification of these key genes not only contributes to our understanding of the FDCA synthesis pathway in R. ornithinolytica BF60 but also allows for improved FDCA production efficiency. Moreover, this work is likely to provide a valuable reference for producing other furanic chemicals.

Construction of amphiphilic networks in blend membranes for CO2 separation

Jiangnan Wang,Xia Lv,Lu Huang,Long Li,Xueqin Li,Jinli Zhang 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.1

Blend membranes have attracted great attention because they can combine the advantages of different polymers. To investigate the effect of amphiphilic polymer on the separation performance of blend membranes, a series of blend membranes were designed and fabricated by blending an amphiphilic polymer of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) into poly(ether-block-amide) (Pebax) polymer for CO2 separation. For the as-prepared Pebax/PEDOT:PSS blend membranes, the interconnected CO2-philic networks were constructed by hydrophilic anionic chains of PSS− for accelerating CO2 transport. Meanwhile, non-CO2-philic networks were constructed by the hydrophobic cationic chains of PEDOT+, which distributed around the PSS− chains to provide low friction diffusion for CO2. Therefore, the amphiphilic polymer of PEDOT:PSS was an excellent material for improving CO2 separation performance of blend membranes. The results showed that the Pebax/PEDOT:PSS blend membranes were endowed with excellent CO2 separation performance. Pebax/PEDOT:PSS blend membrane demonstrated the optimal separation performance with a CO2 permeability of 440.2±3.3 Barrer and a CO2/CH4 separation factor of 28±0.6. This study indicates that introducing the amphiphilic polymer into the blend membranes is an efficient strategy for gas separation.

Combinatorial Methylerythritol Phosphate Pathway Engineering and Process Optimization for Increased Menaquinone-7 Synthesis in Bacillus subtilis

Taichi Chen,Hongzhi Xia,Shixiu Cui,Xueqin Lv,Xueliang Li,Yanfeng Liu,Jianghua Li,Guocheng Du,Long Liu 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.5

Vitamin K2 (menaquinone) is an essential vitamin existing in the daily diet, and menaquinone-7 (MK- 7) is an important form of it. In a recent work, we engineered the synthesis modules of MK-7 in Bacillus subtilis, and the strain BS20 could produce 360 mg/l MK-7 in shake flasks, while the methylerythritol phosphate (MEP) pathway, which provides the precursor isopentenyl diphosphate for MK-7 synthesis, was not engineered. In this study, we overexpressed five genes of the MEP pathway in BS20 and finally obtained a strain (BS20DFHG) with MK-7 titer of 415 mg/l in shake flasks. Next, we optimized the fermentation process parameters (initial pH, temperature and aeration) in an 8-unit parallel bioreactor system consisting of 300-ml glass vessels. Based on this, we scaled up the MK-7 production by the strain BS20DFHG in a 50-l bioreactor, and the highest MK-7 titer reached 242 mg/l. Here, we show that the engineered strain BS20DFHG may be used for the industrial production of MK-7 in the future.