Jaoon Y.H. Kim

Enhanced detoxification of organophosphates using recombinant Escherichia coli with co-expression of organophosphorus hydrolase and bacterial hemoglobin

A significantly improved, recombinant Escherichia coli has been developed to degrade the toxic organophosphorus compound, Paraoxon, to non-toxic materials by co-expression of organophosphorus hydrolase (OPH) under trc promoter and Vitreoscilla hemoglobin (VHb) under O2dependent nar promoter. VHb-expressing whole cells had significant enhancement of OPH activity (48%, 18.7 vs. 27.8 unit l−1) and bioconversion efficiency Vmax/Km (44%, 0.14 vs. 0.2 min−1) compared to VHb-free system.

Production of biohydrogen by recombinant expression of [NiFe]-hydrogenase 1 in Escherichia coli

BackgroundHydrogenases catalyze reversible reaction between hydrogen (H2) and proton. Inactivation of hydrogenase by exposure to oxygen is a critical limitation in biohydrogen production since strict anaerobic conditions are required. While [FeFe]-hydrogenases are irreversibly inactivated by oxygen, it was known that [NiFe]-hydrogenases are generally more tolerant to oxygen. The physiological function of [NiFe]-hydrogenase 1 is still ambiguous. We herein investigated the H2 production potential of [NiFe]-hydrogenase 1 of Escherichia coli in vivo and in vitro. The hya A and hya B genes corresponding to the small and large subunits of [NiFe]-hydrogenase 1 core enzyme, respectively, were expressed in BL21, an E. coli strain without H2 producing ability.ResultsRecombinant BL21 expressing [NiFe]-hydrogenase 1 actively produced H2 (12.5 mL H2/(h·L) in 400 mL glucose minimal medium under micro-aerobic condition, whereas the wild type BL21 did not produce H2 even when formate was added as substrate for formate hydrogenlyase (FHL) pathway. The majority of recombinant protein was produced as an insoluble form, with translocation of a small fraction to the membrane. However, the membrane fraction displayed high activity (~65% of total cell fraction), based on unit protein mass. Supplement of nickel and iron to media showed these metals contribute essentially to the function of [NiFe]-hydrogenase 1 as components of catalytic site. In addition, purified E. coli [NiFe]-hydrogenase 1 using his6-tag displayed oxygen-tolerant activity of ~12 nmol H2/(min·mg protein) under a normal aeration environment, compared to [FeFe]-hydrogenase, which remains inactive under this condition.ConclusionsThis is the first report on physiological function of E. coli [NiFe]-hydrogenase 1 for H2 production. We found that [NiFe]-hydrogenase 1 has H2 production ability even under the existence of oxygen. This oxygen-tolerant property is a significant advantage because it is not necessary to protect the H2 production process from oxygen. Therefore, we propose that [NiFe]-hydrogenase can be successfully applied as an efficient biohydrogen production tool under micro-aerobic conditions.

Improved production of biohydrogen in light-powered Escherichia coli by co-expression of proteorhodopsin and heterologous hydrogenase

BackgroundSolar energy is the ultimate energy source on the Earth. The conversion of solar energy into fuels and energy sources can be an ideal solution to address energy problems. The recent discovery of proteorhodopsin in uncultured marine γ-proteobacteria has made it possible to construct recombinant Escherichia coli with the function of light-driven proton pumps. Protons that translocate across membranes by proteorhodopsin generate a proton motive force for ATP synthesis by ATPase. Excess protons can also be substrates for hydrogen (H2) production by hydrogenase in the periplasmic space. In the present work, we investigated the effect of the co-expression of proteorhodopsin and hydrogenase on H2 production yield under light conditions.ResultsRecombinant E. coli BL21(DE3) co-expressing proteorhodopsin and [NiFe]-hydrogenase from Hydrogenovibrio marinus produced ~1.3-fold more H2 in the presence of exogenous retinal than in the absence of retinal under light conditions (70 μmole photon/(m2·s)). We also observed the synergistic effect of proteorhodopsin with endogenous retinal on H2 production (~1.3-fold more) with a dual plasmid system compared to the strain with a single plasmid for the sole expression of hydrogenase. The increase of light intensity from 70 to 130 μmole photon/(m2·s) led to an increase (~1.8-fold) in H2 production from 287.3 to 525.7 mL H2/L-culture in the culture of recombinant E. coli co-expressing hydrogenase and proteorhodopsin in conjunction with endogenous retinal. The conversion efficiency of light energy to H2 achieved in this study was ~3.4%.ConclusionHere, we report for the first time the potential application of proteorhodopsin for the production of biohydrogen, a promising alternative fuel. We showed that H2 production was enhanced by the co-expression of proteorhodopsin and [NiFe]-hydrogenase in recombinant E. coli BL21(DE3) in a light intensity-dependent manner. These results demonstrate that E. coli can be applied as light-powered cell factories for biohydrogen production by introducing proteorhodopsin.

Production of biohydrogen by heterologous expression of oxygen-tolerant Hydrogenovibrio marinus [NiFe]-hydrogenase in Escherichia coli

Oxygen sensitivity of hydrogenase is a critical issue in efficient biological hydrogen production. In the present study, oxygen-tolerant [NiFe]-hydrogenase from the marine bacterium, Hydrogenovibrio marinus, was heterologously expressed in Escherichia coli, for the first time. Recombinant E. coli BL21 expressing H. marinus [NiFe]-hydrogenase actively produced hydrogen, but the parent strain did not. Recombinant H. marinus hydrogenase required both nickel and iron for biological activity. Compared to the recombinant E. coli [NiFe]-hydrogenase 1 described in our previous report, recombinant H. marinus [NiFe]-hydrogenase displayed 1.6- to 1.7-fold higher hydrogen production activity in vitro. Importantly, H. marinus [NiFe]-hydrogenase exhibited relatively good oxygen tolerance in analyses involving changes of surface aeration and oxygen proportion within a gas mixture. Specifically, recombinant H. marinus [NiFe]-hydrogenase produced ∼7- to 9-fold more hydrogen than did E. coli [NiFe]-hydrogenase 1 in a gaseous environment containing 5-10% (v/v) oxygen. In addition, purified H. marinus [NiFe]-hydrogenase displayed a hydrogen evolution activity of ∼28.8 nmol H₂/(minmg protein) under normal aerobic purification conditions. Based on these results, we suggest that oxygen-tolerant H. marinus [NiFe]-hydrogenase can be employed for in vivo and in vitro biohydrogen production without requirement for strictly anaerobic facilities.

Enhancement of Mussel Adhesive Protein Production in Escherichia coli by Co‐expression of Bacterial Hemoglobin

Mussel adhesive proteins (MAPs) have been considered as potential underwater and medical bioadhesives. Previously, we reported a functional expression of recombinant MAP hybrid fp‐151, which is a fusion protein with six type 1 (fp‐1) decapeptide repeats at each type 5 (fp‐5) terminus, with practical properties in Escherichia coli. In the present work, we introduced the Vitreoscilla hemoglobin (VHb) co‐expression strategy to enhance the production levels of hybrid fp‐151 since VHb has been successfully used for efficient oxygen utilization in several expression systems, including E. coli. In both batch‐type flask and fed‐batch‐type bioreactor cultures, we found that co‐expression of VHb conferred higher cell growth and hybrid fp‐151 production. Its positive effects were significantly increased in high cell density bioreactor cultures as the microaerobic environment was more quickly and severely formed. We obtained a ∼1.9‐fold higher (∼1 g/L) production of MAP fp‐151 from VHb co‐expressing cells in fed‐batch bioreactor cultures as compared to that from VHb non‐expressing cells. Collectively and regardless of the culture type, VHb co‐expression strategy was successful in enhancing the production of recombinant mussel adhesive proteins in the E. coli expression system.

Expression and N-glycan analysis of human 90K glycoprotein in Drosophila S2 cells

Human 90K (h90K; Mac-2-binding protein) glycoprotein is a potential pharmaceutical due to its inhibitory activity against cancer metastasis and expansion. Here, h90K glycoprotein was produced in insect Drosophila S2 cell system, and its N-glycan pattern was analyzed. A plasmid encoding h90K gene, fused with a hexahistidine tag under the control of Drosophila metallotionein promoter, was stably transfected into S2 cells. After copper sulfate induction, transfected S2 cells secreted recombinant h90K at a good expression level of 28mg/L in a 150-mL spinner flask culture. The purified recombinant h90K showed an apparent molecular weight of ∼78kDa which was much smaller than that (∼97kDa) of the natural h90K. Because de-N-glycosylated h90K appeared at ∼60kDa protein band, it was suggested that the recombinant h90K from S2 cells has small N-glycans with about half the molecular weight (∼18kDa) of N-glycans of the natural h90K. Through detail analyses using high-performance liquid chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, the S2-derived recombinant h90K was confirmed that it has simple paucimannosidic structures containing two or three mannose residues with core fucose as the major (∼79%) N-glycans.