Effective biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate by supplementation of l-glutamine, d-xylose and β-cyclodextrin in n-butyl acetate–water media

Engineering Alcohol Dehydrogenase for Efficient Catalytic Synthesis of Ethyl (R)-4-Chloro-3-hydroxybutyrate

Ethyl (R)-4-chloro-3-hydroxybutyrate [(R)-CHBE] is an intermediate with high value in medicine and pesticide applications. Alcohol dehydrogenase serves as an excellent biocatalyst during the synthesis of (R)-CHBE. However, the lack of effective engineering methods limits its wider application. In this study, the sequence-modeling-docking-principle (SMDP) method was used to screen enzymes with catalytic activity. Three protein modification strategies were established for the active center, substrate channel, and distal hotspot to enhance the catalytic efficiency of alcohol dehydrogenase LCRIII. Substrate batch replenishment was used to alleviate substrate inhibition. Subsequently, optimal mutant M3 (W151F-S167A-F215Y) was successfully obtained with a specific enzyme activity of 23.00 U/mg and kcat/Km of 11.22 (mM-1·min-1), which were 4.55- and 3.98-fold higher than those of the wild type, respectively. (R)-CHBE was prepared using M3 and GDH at 298.21 g/L (>99% e.e.). This study provides a promising approach for the protein engineering modification of alcohol dehydrogenase and industrial-scale production of (R)-CHBE.

Efficient Synthesis of Chiral Aryl Alcohol with a Novel Kosakonia radicincitans Isolate in Tween 20/L-carnitine: Lysine-Containing Synergistic Reaction System

Chiral trifluoromethyl alcohols as vital intermediates are of great interest in fine chemicals and especially in pharmaceutical synthesis. In this work, a novel isolate Kosakonia radicincitans ZJPH202011 was firstly employed as biocatalyst for the synthesis of (R)-1-(4-bromophenyl)-2,2,2-trifluoroethanol ((R)-BPFL) with good enantioselectivity. By optimizing fermentation conditions and bioreduction parameters in aqueous buffer system, the substrate concentration of 1-(4-bromophenyl)-2,2,2-trifluoroethanone (BPFO) was doubled from 10 to 20 mM, and the enantiomeric excess (ee) value for (R)-BPFL increased from 88.8 to 96.4%. To improve biocatalytic efficiency by strengthening the mass-transfer rate, natural deep-eutectic solvents, surfactants and cyclodextrins (CDs) were introduced separately in the reaction system as cosolvent. Among them, L-carnitine: lysine (C: Lys, molar ratio 1:2), Tween 20 and γ-CD manifested higher (R)-BPFL yield compared with other same kind of cosolvents. Furthermore, based on the excellent performance of both Tween 20 and C: Lys (1:2) in enhancing BPFO solubility and ameliorating cell permeability, a Tween 20/C: Lys (1:2)-containing integrated reaction system was then established for efficient bioproduction of (R)-BPFL. After optimizing the critical factors involved in BPFO bioreduction in this synergistic reaction system, BPFO loading increased up to 45 mM and the yield reached 90.0% within 9 h, comparatively only 37.6% yield was acquired in neat aqueous buffer. This is the first report on K. radicincitans cells as new biocatalyst applied in (R)-BPFL preparation, and the developed Tween 20/C: Lys-containing synergistic reaction system has great potential for the synthesis of various chiral alcohols.

Efficient Valorization of Sugarcane Bagasse into Furfurylamine in Benign Deep Eutectic Solvent ChCl:Gly-Water

Recently, highly efficient production of valuable furan-based chemicals from available and renewable lignocellulosic biomass has attracted more and more attention via a chemoenzymatic route in an environmentally friendly reaction system. In this work, the feasibility of chemoenzymatically catalyzing sugarcane bagasse into furfurylamine with heterogeneous catalyst and ω-transaminase biocatalyst was developed in the deep eutectic solvent (DES) ChCl:Gly-water. Sulfonated Al-Laubanite was firstly synthesized to catalyze sugarcane bagasse to furfural. SEM, BET, XRD, and FT-IR were used to characterize Al-Laubanite. Catalyst Al-Laubanite structure was significantly different from carrier laubanite. High furfural yield (60.9%) was achieved by catalyzing sugarcane bagasse in 20 min at 170 ℃ and pH 1.0 by Al-Laubanite (2.4 wt%) in the presence of ChCl:Gly (20 wt%). Potential catalytic mechanism was proposed under the optimized catalytic condition. In addition, one recombinant E. coli CV harboring ω-transaminase could completely transform biomass-derived furfural to furfurylamine at 40 °C and pH 7.5 using L-alanine as amine donor in ChCl:Gly-water (20:80, wt:wt). This established chemoenzymatic cascade reaction strategy was successfully utilized for valorization of biomass into furan-based chemicals in the benign ChCl:Gly-water system.

Improved Bio-Synthesis of 2,5-bis(hydroxymethyl)furan by Burkholderia contaminans NJPI-15 With Co-substrate

Upgrading of biomass derived 5-hydroxymethylfurfural (HMF) has attracted considerable interest recently. A new highly HMF-tolerant strain of Burkholderia contaminans NJPI-15 was isolated in this study, and the biocatalytic reduction of HMF into 2,5-bis(hydroxymethyl)furan (BHMF) using whole cells was reported. Co-substrate was applied to improve the BHMF yield and selectivity of this strain as well as HMF-tolerant level. The catalytic capacity of the cells can be substantially improved by Mn²⁺ ion. The strain exhibited good catalytic performance at a pH range of 6.0–9.0 and a temperature range of 25°C–35°C. In addition, 100 mM HMF could be reduced to BHMF by the B. contaminans NJPI-15 resting cells in presence of 70 mM glutamine and 30 mM sucrose, with a yield of 95%. In the fed-batch strategy, 656 mM BHMF was obtained within 48 h, giving a yield of 93.7%. The reported utilization of HMF to produce BHMF is a promising industrially sound biocatalytic process.

Enhanced bioreduction synthesis of ethyl (R)-4-chloro-3-hydroybutanoate by alkalic salt pretreatment

In this study, biomass-hydrolysate was used for enhancing the bioreduction of ethyl 4-chloro-3-oxobutanoate (COBE). Firstly, dilute alkalic salt pretreatment was attempted to pretreat bamboo shoot shell (BSS). It was found that enzymatic in situ hydrolysis of 20-50 g/L BSS pretreated with dilute alkalic salts (0.4% Na₂CO₃, 0.032% Na₂S) at 7.5% sulfidity by autoclaving at 110 °C for 40 min gave sugar yields at 59.9%-73.5%. Moreover, linear relationships were corrected on solid recovery-total delignification-sugar yield. In BSS-hydrolysates, xylose and glucose could promote the reductase activity of recombinant E. coli CCZU-A13. Compared with glucose, hydrolysate could increase the reductase activity by 1.35-folds. Furthermore, the cyclohexane-hydrolysate (10:90, v/v) biphasic media containing ethylene diamine tetraacetic acid (EDTA, 40 mM) and l-glutamine (150 mM) was built for the effective biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate [(R)-CHBE] (94.6% yield) from 500 mM COBE. In conclusion, this strategy has high potential for the effective biosynthesis of (R)-CHBE (>99% e.e.).

Chemical-enzymatic conversion of corncob-derived xylose to furfuralcohol by the tandem catalysis with SO42-/SnO2-kaoline and E. coli CCZU-T15 cells in toluene-water media

One-pot synthesis of furfuralcohol from corncob-derived xylose was attempted by the tandem catalysis with solid acid SO₄^2-/SnO₂-kaoline and recombination Escherichia coli CCZU-T15 whole-cells in the toluene-water media. Using SO₄^2-/SnO₂-kaoline (3.5wt%) as catalyst, the furfural yield of 74.3% was obtained from corncob-derived xylose in the toluene-water (1:2, v:v) containing 10mM OP-10 at 170°C for 30min. After furfural liquor was mixed with corncob-hydrolysate from the enzymatic hydrolysis of oxalic acid-pretreated corncob residue, furfural (50.5mM) could be completely biotransformed to furfuralcohol with Escherichia coli CCZU-T15 whole-cells harboring an NADH-dependent reductase (ClCR) in the toluene-water (1:3, v:v) containing 12.5mM OP-10 and 1.6mM glucose/mM furfural at 30°C and pH 6.5. Furfuralcohol was obtained at 13.0% yield based on starting material corncob (100% furfuralcohol yield for bioreduction of furfural step). Clearly, this one-pot synthesis of furfuralcohol strategy shows high potential application for the effective utilization of corncob.

Effective Utilization of Carbohydrate in Corncob to Synthesize Furfuralcohol by Chemical-Enzymatic Catalysis in Toluene-Water Media

In this study, carbohydrates (cellulose plus hemicellulose) in corncob were effectively converted furfuralcohol (FOL) via chemical-enzymatic catalysis in a one-pot manner. After corncob (2.5 g, dry weight) was pretreated with 0.5 wt% oxalic acid, the obtained corncob-derived xylose (19.8 g/L xylose) could be converted to furfural at 60.1% yield with solid acid catalyst SO₄^2-/SnO₂-attapulgite (3.6 wt% catalyst loading) in the water-toluene (3:1, v/v) at 170 °C for 20 min. Moreover, the oxalic acid-pretreated corncob residue (1.152 g, dry weight) was enzymatically hydrolyzed to 0.902 g glucose and 0.202 g arabinose. Using the corncob-derived glucose (1.0 mM glucose/mM furfural) as cosubstrate, the furfural liquor (48.3 mM furfural) was successfully biotransformed to FOL by recombinant Escherichia coli CCZU-A13 cells harboring an NADH-dependent reductase (SsCR) in the water-toluene (4:1, v/v) under the optimum conditions (50 mM PEG-6000, 0.2 mM Zn²⁺, 0.1 g wet cells/mL, 30 °C, pH 6.5). After the bioreduction for 2 h, FAL was completely converted to FOL. The FOL yield was obtained at 0.11 g FOL/g corncob. Clearly, this one-pot synthesis strategy shows high potential application for the effective synthesis of FOL.

One-pot chemo-enzymatic synthesis of furfuralcohol from xylose

Furfuralcohol (FOL) is an important intermediate for the production of lysine, ascorbic acid, and lubricants. It can be used as a hypergolic fuel in rocketry. In this study, it was attempted to synthesize FOL from xylose by tandem catalysis with solid acid SO₄^2-/SnO₂-Montmorillonite and recombination Escherichia coli CCZU-K14 whole cells. Using SO₄^2-/SnO₂-Montmorillonite (3.0wt% dosage) as catalyst, a highest furfural yield of 41.9% was achieved from xylose at 170°C for 20min. Furthermore, Escherichia coli CCZU-K14 whole cells were used for bioconverting furfural to FOL. The optimum biocatalytic reaction temperature, reaction pH, cosubstrate concentration, and substrate concentration were 30°C, 6.5, 1.5mol glucose/mol furfural, and 200mM, respectively. Finally, the yield of FOL from 200mM furfural was achieved to 100% by Escherichia coli CCZU-K14 whole cells after 24h. In conclusion, this strategy show high potential application for the effective synthesis of FOL.

An experimental modeling of trinomial bioengineering- crp, rDNA, and transporter engineering within single cell factory for maximizing two-phase bioreduction

A carbonyl reductase (cr) gene from Candida glabrata CBS138 has been heterologously expressed in cofactor regenerating E. coli host to convert Ethyl-4-chloro-3-oxobutanoate (COBE) into Ethyl-4-chloro-3-hydroxybutanoate (CHBE). The CR enzyme exhibited marked velocity at substrate concentration as high as 363mM with highest turnover number (112.77±3.95s^-1). Solitary recombineering of such catalytic cell reproduced CHBE 161.04g/L per g of dry cell weight (DCW). Introduction of combinatorially engineered crp (crp*, F136I) into this heterologous E. coli host yielded CHBE 477.54g/L/gDCW. Furthermore, using nerolidol as exogenous cell transporter, the CHBE productivity has been towered to 710.88g/L/gDCW. The CHBE production has thus been upscaled to 8-12 times than those reported so far. qRT-PCR studies revealed that both membrane efflux channels such as acrAB as well as ROS scavenger genes such as ahpCF have been activated by engineering crp. Moreover, membrane protecting genes such as manXYZ together with solvent extrusion associated genes such as glpC have been upregulated inside mutant host. Although numerous proteins have been investigated to convert COBE to CHBE; this is the first approach to use engineering triad involving crp engineering, recombinant DNA engineering and transporter engineering together for improving cell performance during two-phase biocatalysis.

Effective asymmetric bioreduction of ethyl 4-chloro-3-oxobutanoate to ethyl (R)-4-chloro-3-hydroxybutanoate by recombinant E. coli CCZU-A13 in [Bmim]PF6-hydrolyzate media

It was the first report that the concentrated hydrolyzates from the enzymatic hydrolysis of dilute NaOH (3wt%)-soaking rice straw at 30°C was used to form [Bmim]PF6-hydrolyzate (50:50, v/v) media for bioconverting ethyl 4-chloro-3-oxobutanoate (COBE) into ethyl (R)-4-chloro-3-hydroxybutanoate [(R)-CHBE] (>99% e.e.) with recombinant E. coli CCZU-A13. Compared with pure glucose, the hydrolyzates could promote both initial reaction rate and the intracellular NADH content. Furthermore, emulsifier OP-10 (20mM) was employed to improve the reductase activity. Moreover, Hp-β-cyclodextrin (0.01mol Hp-β-cyclodextrin/mol COBE) was also added into this bioreaction system for enhancing the biosynthesis of (R)-CHBE from COBE by E. coli CCZU-A13 whole-cells. The yield of (R)-CHBE (>99% e.e.) from 800mM COBE was obtained at 100% in the [Bmim]PF6-hydrolyzate (50:50, v/v) media by supplementation of OP-10 (20mM) and Hp-β-CD (8mM). In conclusion, an effective strategy for the biosynthesis of (R)-CHBE was successfully demonstrated.