coli

In-Situ Biocatalytic Production of Trehalose with Autoinduction Expression of Trehalose Synthase

We developed an in-situ biocatalytic process that couples autoinduction expression of trehalose synthase (TreS) and whole-cell catalysis for trehalose production. With lactose as the autoinducer, the activity of recombinant TreS in recombinant Escherichia coli was optimized through a visualization method, which resulted in a maximum value of 12 033 ± 730 U/mL in pH-stat fed-batch fermentation mode. Meanwhile, the permeability of the autoinduced E. coli increased significantly, which makes it possible to be directly used as a whole-cell biocatalyst for trehalose production, whereby the byproduct glucose can also act as an extra carbon source. In this case, the final yield of trehalose was improved to 90.5 ± 5.7% and remained as high as 83.2 ± 5.0% at the 10th batch, which is the highest value achieved using recombinant TreS. Finally, an integrated strategy for trehalose production was established, and its advantages compared to the traditional mode have been summarized.

Upscale production of a recombinant cyclodextrin glycosyltransferase from Paenibacillus macerans in Escherichia coli

Cyclodextrin glucanotransferase (CGTase) is an important enzyme with multiple functions in starch utilization. In the present study, a fermentation process for the production of CGTase from Escherichia coli harboring the recombinant plasmid pET28b(+)-CGTase was investigated and optimized. The optimal fermentation and expression conditions were 10.0 g/L glycerol, 20.0 g/L tryptone, and 10.0 g/L yeast extract with an initial pH of 7.0, an IPTG concentration of 0.1 mM and an induction temperature of 28 °C for 10 h. The resulting CGTase activity reached up to 36.4 U/L and was 2.1-fold higher than before optimization. Under these optimal fermentation conditions, the up-scaled fermentation was carried out in a 500-L fermentor, and a CGTase activity of 45.2 U/L was achieved. This study provides a foundation for the industrial production of CGTase.

High efficiency preparation and characterization of intact poly(vinyl alcohol) dehydrogenase from Sphingopyxis sp.113P3 in Escherichia coli by inclusion bodies renaturation

Poly(vinyl alcohol) dehydrogenase (PVADH, EC 1.1.99.23) is an enzyme which has potential application in textile industry to degrade the poly(vinyl alcohol) (PVA) in waste water. Previously, a 1,965-bp fragment encoding a PVADH from Sphingopyxis sp. 113P3 was synthesized based on the replacement of the rare codons in Escherichia coli (E. coli). In this work, the deduced mature PVADH (mPVADH) gene of 1,887 bp was amplified by polymerase chain reaction (PCR) and inserted into the site between NcoI and HindIII in pET-32a(+). The constructed recombinant plasmid was transformed into E. coli Rosetta (DE3). In shake flask, the fusion protein of thioredoxin (Trx)-mPVADH was expressed precisely; however, Trx-mPVADH was found to accumulate mainly as inclusion bodies. After isolating, dissolving in buffer containing urea, purification, dialysis renaturation, and digesting with recombinant enterokinase/His (rEK/His), the bioactive mPVADH fragments were obtained with protein concentration of 0.56 g/L and enzymatic activity of 194 U/mL. The K m and V max values for PVA 1799 were 2.33 mg/mL and 15.7 nmol/(min·mg protein), respectively. (1)H-NMR and infrared (IR) spectrum demonstrated that its biological function was oxidizing hydroxyl groups of PVA 1799 to form diketone, and PVA 1799 could be degraded completely by successive treatment with mPVADH and oxidized PVA hydrolase (OPH).