Three ways for protein aggregation and the control strategies / 生物工程学报

Protein aggregation is a critical issue in the production of biopharmaceuticals. During protein production, transport and storage, various factors can lead to protein aggregation. With the in-depth study, different ways of protein aggregation and various influencing factors were identified. This includes physical and chemical factors, translation modifications and protein structure. Since protein aggregation exerts major impact on the activity and homogeneity of proteins, it is of great importance to study the ways of protein aggregation and how to control it to obtain high-quality proteins. The review focuses on three ways of protein aggregation, namely 3D domain swapping, salt bridge formation, and oxidative stress, as well as methods to control protein aggregation during protein production, transport and storage. This may facilitate reducing the loss caused by the formation of protein aggregation and improving the purity and homogeneity of protein in research and commercial production.

High level secretory expression of recombinant human tissue factor in Pichia pastoris / 中国生化药物杂志

Objective To construct a eukaryotic expression vector in Pichia pastoris containing human tissue factor( hTF) gene,in order to achieve high level secretory expression in extracellular.Methods Expression plasmid, pGAPZaA-hTF, was constructed by inserting the synthesized sequence encoding human extracellular tissue factor into yeast expression vector pGAPZaA and transformed into Pichia pastoris SMD1168H with electroporation.Having been selected by Zeocin, transformants containing hTF cDNA were expressed in YPD, extracellular proteins were detected by SDS-PAGE and confirmed by Western bolt.Results Successfully constructed the recombinant pGAPZaA-hTF expression system in Pichia pastoris.SDS-PAGE showed that the molecular weight of the expression product was about 37 -40 kDa.Western-blot indicated that it was human extracellular tissue factor.The crude yield of total protein in medium was up to 1 g/L, more than 80% of which was hTF.Conclusion Truncated rTF gene is expressed in Pichia pastoris and the active products are secreted into the medium which have the same activation as the native TF.

High level expression of recombinant human fibrinogen in Pichia pastoris / 中国生化药物杂志

Objective To construct a eukaryotic expression vector in Pichia pastoris containing human fibrinogen gene, in order to achieve high level secretory expression in extracellular.Methods Expression plasmid,pGAPZαA-FGB-FGG-FGA-AOX1,was constructed by inserting the synthesized sequence encoding human fibrinogen(FGA, FGB,FGG) and then introduced into Pichia pastoris SMD1168H by electroporation.Transformants were availably screened by Zeocin resistance,the expression of recombinant protein was identified by SDS-PAGE and Western blot analysis, the protein yield was tested by ELISA assay.After ultrafiltration and purification, the biological activity of protein was detected.Results The crude yield of human fibrinogen in Pichia pastoris supernatant reached 15 mg/L in flask and the biological aggregation activity was determined.Conclusion The human fibrinogen gene was obtained and successfully expressed in Pichia pastoris and the active products were secreted into the medium.

High level expression of α-CGTase and optimize biotransformation conditions of AA-2 G / 中国生化药物杂志

Objective To construct a prokaryotic expression vector in BL21 to secretorily expressα-Cyclodextrin Glycosyltransferase(α-CGTase). Methods α-CGT gene was amplified from Bacillus macerens genome by PCR.pET26b and α-CGT gene were connected after digested with Nco I, Xho I respectivly, and then transformed into Escherichia coli BL21 strain.α-CGTase was expressed in fermentation culture medium and AA-2G was prepared by using α-CGTase, VC and starch.Results α-CGTase was expressed secretorily and the enzyme activity was up to 120 U/mL.AA-2G was prepared by the biotransformation of VC and starch using α-CGTase which proved to be correct by HPLC.Conclusion AA-2G was prepared by using self-madeα-CGTase, after optimized the preparation conditions the yield of AA-2G was 17.46 g/L, and the conversion rate reached 58.2%(mg/mg).

Research progress on Nisin biosynthesis and breeding of high-yield strains / 中国生化药物杂志

Nisin, produced by several strains in the growth process of Lactococcus lactis, is a natural antimicrobial polypeptide.Now, Nisin has served as an effective and safe food additive extensively used in food industry in many countries and regions because of its excellent antimicrobial activity.However, the current production of Nisin is largely fermented by lactobacillus and its industrialized production still can not meet enormous market needs, therefore establishing reasonably high-yield Nisin strains is of great significance.This review mainly summarizes the development pathway of molecule based on the functional expression of Nisin biosynthetic genes and regulation of gene expression, and also the study status on high Nisin-producing strains which provides practical foundation for further study on expected strains as well as some useful guidance for large-scale industrialized production of Nisin.

Rsearch progress on breeding of pullulan high-yield strain without melanin / 中国生化药物杂志

Pullulan is a linear glucosic polysaccharide produced by the polymorphic fungus Aureobasidium Pullulans, which has long been applied for various applications in medical and food industry due to its security, stability and low adhesive ability.At present, the two problems in restricting pullulan industrial production are the low polysaccharide production and melanin secreted which is hard to erase completely, giving the following process some problem.As a starting point, this review article collects and analyzes the progress on the breeding of pullulan high-yield strain without melanin in recent years, in order to find more efficient strains breeding methods, laying a foundation for further breeding of pullulan high-yield strain without melanin.

Construction of tissue-engineered cartilage with cross-linked sodium hyaluronate as scaffold materials in vitro / 中国组织工程研究

BACKGROUND:Tissue engineering provides new ideas and approaches for repair of cartilage defects. OBJECTIVE:To develop a complete set of solutions for construction of tissue engineered cartilagein vitro, with chondrocytes as seed cels and cross-linked sodium hyaluronate as scaffold materials. METHODS: New Zealand rabbit articular chondrocytes were isolated, counted, and then cultured and passaged to prepare cellsuspension. Toluidine blue staining, RT-PCR and immunocytochemistry were exerted to evaluate the cultured cels. Chondrocytes were seeded and co-cultured with cross-linked sodium hyaluronate scaffold for 21 days. Then, RNA was isolated for RT-PCR, and frozen sections were prepared for morphological observation and immunohistochemistry study. RESULTS AND CONCLUSION:The chondrocytes could adhere to the cross-linked sodium hyaluronate scaffold and aggregate, growing between fibers or adhering to the scaffold in a monolayer manner. The transcripts of cartilage specific aggrecan gene and colagen type II alpha 1 gene and cartilage specific protein colagen type II were expressed in cel-scaffold complexes to maintain the phenotype of chondrocytes. Cel-scaffold complexes co-cultured in vitro can form cartilage extracelular matrix, by which tissue engineered cartilage is expected to be obtained.