Excretory expression of IsPETase in E. coli by an enhancer of signal peptides and enhanced PET hydrolysis.

The PET hydrolase from Ideonella sakaiensis (IsPETase) is efficient for PET degradation, which provides a promising solution for environmental contamination by plastics. This study focuses on improving the excretion of IsPETase from E. coli by signal peptide (SP) engineering. A SP enhancer B1 (MERACVAV) was fused to the N-terminal of commonly-used SP (PelB, MalE, LamB, and OmpA) to mediate excretion of IsPETase. Strikingly, the modified SP B1OmpA, B1PelB, and B1MalE significantly increased the excretion of IsPETase, while IsPETase was basically expressed in periplasmic space without enhancer B1. The excretion efficiency of IsPETase mediated by B1PelB was improved by 62 folds compared to that of PelB. The hydrolysis of PET by crude IsPETase in culture solution was also enhanced. Furthermore, the amount of released MHET/TPA from PET by IsPETase was increased by 2.7 folds with pre-incubation of hydrophobin HFBII. Taken together, this work may provide a feasible strategy for the excretion and application of the IsPETase.

Excretory overexpression of hydrophobins as multifunctional biosurfactants in E. coli.

Hydrophobins are small amphipathic proteins excreted from filamentous fungi that self-assemble into the amphipathic film at hydrophobic/hydrophilic interfaces and can be used in a wide range of biotechnological application such as antimicrobial coatings, biosensors, and drug delivery. Here we describe a simple method for producing functionally active class I and class II hydrophobins in E. coli. The class I hydrophobin EAS (rodlet protein) from Neurospora crassa and class II hydrophobin HFBII from Trichoderma reesei were separately fused with fusion partner Ffu312 (ß-fructofuranosidase truncation with a native signal peptide) and successfully expressed in E. coli. Significantly, fused hydrophobins Ffu312-EAS and Ffu312-HFBII were excreted into the culture medium. The excretory expression of hydrophobins facilitated the correct disulfide-bond formation and simplified the purification. Both fusion hydrophobins reversed the glass surface hydrophilicity, reduced the water surface tension and improved emulsion stability. Ffu312 has little effect on surface coating, water surface tension and emulsion stabilization of hydrophobins. This study may provide an efficient approach for excretory and functional expression of class I and class II hydrophobins in E. coli.

Elucidation of lid open and orientation of lipase activated in interfacial activation by amphiphilic environment.

Lipases have wide applications using as biocatalyst in numerous biotechnological and bioengineering fields, especially function at hydrophobic or amphiphilic interface. Previously, the lipase from Burkholderia ambifaria YCJ01 was significantly activated when immobilized on the amphiphilic environment. In this work, insights into the functional effect of amphiphilic surface on lipase activation are presented by molecular dynamic simulations. The notable open of "lid" (α5 region) and the displacement of "flap" region (α8 region) of the lipase are closely related with the activation mechanism of lipase, which makes the active site accessible. Strikingly, the hydrophobic analysis showed that most of the hydrophobic surface residues of lipase, as an interfacial enzyme, located at the "lid" and "flap" regions make the entry to active site naturally orient to the oil-water interface to achieve enzyme activation. Additionally, the analysis of Rg and hydrogen bonding interaction suggested that the amphiphilic environment benefits to the exposure of hydrophobic regions, especially the "lid" and "flap" regions, and the maintenance of the nonpolar environment of the active site. Observations from this work not only complement the activation mechanism of lipase induced by the amphiphilic environment, but also provide a reference for the engineering of immobilized media for interfacial enzyme.

A novel Ffu fusion system for secretory expression of heterologous proteins in Escherichia coli.

BACKGROUND: The high level of excretion and rapid folding ability of ß-fructofuranosidase (ß-FFase) in Escherichia coli has suggested that ß-FFase from Arthrobacter arilaitensis NJEM01 can be developed as a fusion partner. METHODS: Based on the modified Wilkinson and Harrison algorithm and the preliminary verification of the solubility-enhancing ability of ß-FFase truncations, three ß-FFase truncations (i.e., Ffu209, Ffu217, and Ffu312) with a native signal peptide were selected as novel Ffu fusion tags. Four difficult-to-express protein models; i.e., CARDS TX, VEGFR-2, RVs and Omp85 were used in the assessment of Ffu fusion tags. RESULTS: The expression levels and solubility of each protein were markedly enhanced by the Ffu fusion system. Each protein had a favorable Ffu tag. The Ffu fusion tags performed preferably when compared with the well-known fusion tags MBP and NusA. Strikingly, it was confirmed that Ffu fusion proteins were secreted into the periplasm by the periplasmic analysis and N-amino acid sequence analysis. Further, efficient excretion of HV3 with defined anti-thrombin activity was obtained when it was fused with the Ffu312 tag. Moreover, HV3 remained soluble and demonstrated notable anti-thrombin activity after the removal of the Ffu312 tag by enterokinase. CONCLUSIONS: Observations from this work not only complements fusion technologies, but also develops a novel and effective secretory system to solve key issues that include inclusion bodies and degradation when expressing heterologous proteins in E. coli, especially for proteins that require disulfide bond formation, eukaryotic-secreted proteins, and membrane-associated proteins.