Discovery of a reductase-producing strain recombinant E. coli CCZU-A13 using colorimetric screening and its whole cell-catalyzed biosynthesis of ethyl (R)-4-chloro-3-hydroxybutanoate

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.

New model compounds for the efficient colorimetric screening of medium chain length polyhydroxyalkanoate (mcl-PHA) depolymerases reveal mechanism of activity

Plastic pollution presents a significant environmental problem contributing to increased CO2 emissions and persistently accumulation in ecosystems. Biobased polymers, like polyhydroxyalkanoates (PHAs), offer a part of a solution with their biodegradability and reduced carbon footprint. However, effective end-of-life strategies, such as controlled enzymatic depolymerization, are crucial for sustainability, relying on efficient PHA depolymerases (PHAases). Here we describe the synthesis of two new chromogenic compounds derived from polyhydroxyoctanoate (PHO) and their application in a continuous, quantitative spectrophotometric assay for PHO depolymerase and other medium chain lengths PHAase activity within 10 min. These substrates allow activity measurement at temperatures above 45 °C, simplifying the comparison of PHAases and aiding enzymatic degradation progress. The study also explores enzyme specificity and identifies key amino acids involved in PHO recognition by PfPHOase. The 3-hydroxyoctanoyl moieties of both compounds were found to bind specifically to a groove formed by the amino acids Phe96, Phe125, Ile171, and Val230, which are highly conserved in known mcl-PHA depolymerases.

Drug metabolite synthesis by immobilized human FMO3 and whole cell catalysts

Background

Sufficient reference standards of drug metabolites are required in the drug discovery and development process. However, such drug standards are often expensive or not commercially available. Chemical synthesis of drug metabolite is often difficulty due to the highly regio- and stereo-chemically demanding. The present work aims to construct stable and efficient biocatalysts for the generation of drug metabolites in vitro.

Result

In this work, using benzydamine as a model drug, two easy-to-perform approaches (whole cell catalysis and enzyme immobilization) were investigated for the synthesis of FMO3-generated drug metabolites. The whole cell catalysis was carried out by using cell suspensions of E. coli JM109 harboring FMO3 and E. coli BL21 harboring GDH (glucose dehydrogenase), giving 1.2 g/L benzydamine N-oxide within 9 h under the optimized conditions. While for another approach, two HisTrap HP columns respectively carrying His₆-GDH and His₆-FMO3 were connected in series used for the biocatalysis. In this case, 0.47 g/L benzydamine N-oxide was generated within 2.5 h under the optimized conditions. In addition, FMO3 immobilization at the C-terminal (membrane anchor region) significantly improved its enzymatic thermostability by more than 10 times. Moreover, the high efficiency of these two biocatalytic approaches was also confirmed by the N-oxidation of tamoxifen.

Conclusions

The results presented in this work provides new possibilities for the drug-metabolizing enzymes-mediated biocatalysis.

Electronic supplementary material

The online version of this article (10.1186/s12934-019-1189-7) contains supplementary material, which is available to authorized users.

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.

Carbonyl group-dependent high-throughput screening and enzymatic characterization of diaromatic ketone reductase

We have developed a carbonyl group-dependent colorimetric method for assay of carbonyl reductases using inexpensive 2,4-dinitrophenylhydrazine (DNPH).

Biosynthesis of 1,2-dihydroxydibenzofuran by magnetically immobilized cells of Escherichia coli expressing phenol hydroxylase in liquid-liquid biphasic systems

Escherichia coli cells expressing phenol hydroxylase (designated as PHIND) were used to biosynthesize 1,2-dihydroxydibenzofuran (1,2-dihydroxyDBF) from dibenzofuran (DBF). The pathway of DBF biotransformation by strain PHIND was proposed, in which DBF was initially monohydroxylated at C-1 and C-4 positions to produce 1- and 4-hydroxyDBF, then underwent successive hydroxylation to yield 1,2- and 3,4-dihydroxyDBF, of which 1,2-dihydroxyDBF was identified for the first time. Magnetically immobilized cells of strain PHIND in biphasic systems with dodecane as the solvent presented highest biosynthesis activity for 1,2-dihydroxyDBF, which was a 6.5-fold improvement compared to biosynthesis in aqueous system. The recycling experiments demonstrated that magnetically immobilized cells exhibited higher biosynthesis activity for 1,2-dihydroxyDBF than that by nonmagnetically immobilized cells during five cycles in biphasic systems. These works support the development of an efficient biosynthesis process using magnetically immobilized cells in biphasic systems and provide a promising technique for improving the productivity in 1,2-dihydroxyDBF biosynthesis.

Improved biosynthesis of ethyl (S)-4-chloro-3-hydroxybutanoate by adding L-glutamine plus glycine instead of NAD+ in β-cyclodextrin-water system

To reduce dependence on the expensive cofactor and effectively biotransform ethyl 4-chloro-3-oxobutanoate, L-glutamine and glycine were found to enhance the content of intracellular NADH and the reductase activity. Adding the mixture of 200 mM of L-glutamine and 500 mM of glycine to the reaction media, a 1.67-fold of reductase activity was increased over the control without the addition of the two compounds. Moreover, β-cyclodextrin (0.4 mol β-cyclodextrin/mol ethyl 4-chloro-3-oxobutanoate) was also added into this reaction media, and the biocatalytic activity of the whole-cell biocatalyst of Escherichia coli CCZU-K14 was increased by 1.34-fold than that without β-cyclodextrin. In this β-cyclodextrin-water media containing L-glutamine (200 mM) plus glycine (500 mM), ethyl (S)-4-chloro-3-hydroxybutanoate (>99% ee) could be obtained from 3000 mM ethyl 4-chloro-3-oxobutanoate in the yield of 98.0% after 8h. All the positive features demonstrate the potential applicability of the bioprocess for the large-scale production of ethyl (S)-4-chloro-3-hydroxybutanoate.

Biosynthesis of ethyl (S)-4-chloro-3-hydroxybutanoate with an NADH-dependent reductase (ClCR) discovered by genome data mining using a modified colorimetric screening strategy

An NADH-dependent reductase (ClCR) was discovered by genome data mining. After ClCR was overexpressed in E. coli BL21, recombinant E. coli CCZU-T15 with high reductase activity and excellent stereoselectivity for the reduction of ethyl 4-chloro-3-oxobutanoate (COBE) into ethyl (S)-4-chloro-3-hydroxybutanoate [(S)-CHBE] was screened using a modified high-throughput colorimetric screening strategy. After the reaction optimization, a highly stereoselective bioreduction of COBE into (S)-CHBE (>99% ee) with the resting cells of E. coli CCZU-T15 was successfully demonstrated in toluene-water (50:50, v/v) biphasic system. Biotransformation of 1000 mM COBE for 24 h in the biphasic system, (S)-CHBE (>99% ee) could be obtained in the high yield of 96.4%. Significantly, E. coli CCZU-T15 shows high potential in the industrial production of (S)-CHBE (>99% ee).