Polyethyleneimine-grafted collagen fiber as a carrier for cell immobilization

Understanding the mechanism of polyethyleneimine-mediated cell disintegration and protein extraction in E. coli: The role of floc network formation and PEI molecular weight

Cell disintegration and protein extraction are crucial steps in downstream process development for biopharmaceuticals produced in E. coli. In this study, we explored the extraction mechanism of polyethyleneimine (PEI) at the cellular level and characterized the floc network that is formed upon PEI addition by Focused Beam Reflectance Measurement and Dispersion Analyzer. PEI disintegrates the cells by detachment of the outer membrane allowing protein to diffuse into the interspace of the flocs. Protein release into the supernatant occurs by diffusion out of the floc network. We could show that the type and concentrations of PEIs with varying molecular weight determines the floc properties and thus the extraction efficiency. We could demonstrate why optimal conditions, using 70 kDa PEI at 0.25 g/g cell dry mass, lead to efficient extraction while at suboptimal conditions extraction is almost negligible. Our findings provide valuable insights into the relationship between floc properties and PEI-driven protein extraction, with potential applications in bioprocessing and biotechnology.

Polyethyleneimine modified activated carbon for high-efficiency adsorption of copper ion from simulated wastewater

In this study, activated carbon (AC) was chemically activated using sodium hydroxide (NaOH), and polyethyleneimine (PEI) was grafted onto the AC using glutaraldehyde as a cross-linking agent. Then the modified AC was applied to treat water samples containing copper ions (Cu²⁺). Preparation of AC-NaOH@PEI. The grafted AC was characterized, demonstrating that the specific surface area of material decreased from 959.3 to 556.9 m²/g. The ζ-potential changed from -27.2 to 10.4 mV, and the presence of a distinct flocculation on the surface of the AC was observed via scanning electron microscopy. The results demonstrated that PEI was successfully grafted onto the surface of AC. Furthermore, the adsorption results indicated that the Cu²⁺ adsorption capacity of AC-NaOH@PEI was greatly enhanced with increasing PEI loading. The adsorption amount of Cu²⁺ by the grafted AC-NaOH@PEI-200 increased from 20.02 to 47.8 mg/g. In addition, the adsorption of Cu²⁺ by AC-NaOH@PEI was a pH dependent process. At a pH of 6, the maximum removal rate reached 93%. The adsorption process is better described by the Langmuir and quasi-second order adsorption models, signifying that the adsorption of Cu²⁺ on AC@PEI consists of monolayer adsorption and chemisorption. After four adsorption-desorption cycles, AC@PEI exhibited high adsorption capacity for Cu²⁺, indicating that it has good regeneration ability. It is a promising adsorbent material.

Isolation and identification of Zalaria sp. Him3 as a novel fructooligosaccharides-producing yeast

AIMS

This study aimed at obtaining a novel fructooligosaccharides (FOS)-producing yeast, which was different from conventional FOS producers, Aureobasidium spp.

METHODS AND RESULTS

Strain Him3 was newly isolated from a Japanese dried sweet potato as a FOS producer. The strain exhibited yeast-like cells and melanization on the potato dextrose agar medium, and formed very weak pseudomycelia on the yeast extract polypeptone dextrose agar medium. Based on the internal transcribed spacer (ITS) region of ribosomal DNA and a partial β-tubulin gene sequences, the strain Him3 was identified as Zalaria sp. The β-fructofuranosidase (FFase) produced by strain Him3 was localized on the cell surface (CS-FFase) as well as in the culture broth (EC-FFase). The FOS production yields by CS-FFase and EC-FFase from 50% sucrose were 63.8% and 64.6%, respectively, to consumed sucrose after the reaction for 72 h.

CONCLUSIONS

We successfully isolated a novel black yeast, Zalaria sp. Him3, with effective capacity for FOS production. Phylogenetic analysis revealed that strain Him3 was distantly related with the conventional FOS producers, Aureobasidium spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

Since FFase of strain Him3 demonstrated high production yields of FOS, it could be applied to novel industrial production of FOS, which is different from conventional methods.

Immobilization of recombinant Escherichia coli cells expressing glucose isomerase using modified diatomite as a carrier for effective production of high fructose corn syrup in packed bed reactor

To improve the operational stability of glucose isomerase in E. coli TEGI-W139F/V186T, the immobilized cells were prepared with modified diatomite as a carrier and 74.1% activity of free cells was recovered after immobilization. Results showed that the immobilized cells still retained 86.2% of the initial transformational activity after intermittent reused 40 cycles and the yield of D-fructose reached above 42% yield at 60 °C. Moreover, the immobilized cells were employed in the continuous production of High Fructose Corn Syrup (HFCS) in a recirculating packed bed reactor for 603 h at a constant flow rate. It showed that the immobilized cells exhibited good operational stability and the yield of D-fructose retained above 42% within 603 h. The space-time yield of high fructose corn syrup reached 3.84 kg L^-1 day^-1. The investigation provided an efficient immobilization method for recombinant cells expressing glucose isomerase with higher stability, and the immobilized cells are a promising biocatalyst for HFCS production.