Abstract:Microbial cells cultivation is not only the origin, but also the foundation of microbiology. Researches in microbiology can only be carried out when the microbial cells can be cultured. However, conventional microbial cell cultivation is not only time consuming and labour intensive, but human error is also inevitable. Recent years, automated, modularised microbial cells micro-cultivation systems with small volume, good controllability, and equipped with real-time monitoring system have attracted great attention in microbiology. This review presents the state-of-the-art micro-cultivation systems which are implemented in microbial cells cultivation. The key development, applications of various system classified based on their construction, and the prospects of micro-cultivation system are discussed and insights into them are also provided.

Abstract:Cell-penetrating peptides (CPPs) are short peptides that can penetrate the cell membrane or tissue barrier. CPPs can deliver a variety of biomacromolecules, such as proteins, RNA and DNA, into cells to produce intracellular functional effects. Endocytosis and direct penetration have been suggested as the two major uptake mechanisms for CPPs-mediated cargo delivery. Compared with other non-natural chemical molecules-based delivery reagents, the CPPs have better biocompatibility, lower cytotoxicity, are easily degraded after cargo delivery, and can be fused and recombined expressed with bioactive proteins. Because of these advantages, the CPPs have become an important potential tool for delivery of developing drugs which targets intracellular factors. As a novel delivery tool, the CPPs also show promising application prospects in biomedical researches. This review summarized recent advances regarding the classification characteristics, the cellular uptake mechanisms and therapeutic application potentials of CPPs.

Abstract:With the rapid development of antibody genetic engineering, bispecific antibody technology has been advanced. They are capable of binding two or more different epitopes simultaneously, thus offering specific advantages over natural monoclonal antibodies in immunotherapy. Bispecific antibodies have been successfully used in cancer therapy (e.g. melanoma, Hodgkin’s lymphoma, liver cancer, and stomach cancer)?and?inflammation therapy (e.g. rheumatoid arthritis, psoriasis and Crohn’s disease), but are still in their early stage for viral immunotherapy. In this study, we reviewed the research progress of bispecific antibodies for immunotherapy of virus infections, especially those with good effects in vivo and in vitro, to provide references for the research and development of bispecific antibodies for antivirus treatment.

Abstract:Salidroside, as one of the main active ingredients of Rhodiala plant, has the effects of anti-hypoxia, anti-radiation, anti-fatigue, anti-tumor, hypoglycemia and improving immunity. With the increasing demand for salidroside and the decreasing of plant resources, microbial production of salidroside has attracted much attention due to its advantages of short period and easy controlling. At present, microbial production of salidroside is still at the basic research stage. In order to make it easier for researchers to understand the advances of microbial synthesis of salidroside, the biosynthesis pathways, uridine diphosphate glucosyltransferases, wild strain/natural enzymes and engineered strain/recombinant enzymes were reviewed.

Abstract:Alpha-keto acid is a bifunctional organic compound containing both carboxyl and ketone groups, and widely applied in the industries of food, pharmaceutical and cosmetics. Based on the demand of eco-friendly process, safety and sustainable development, production of α-keto acids by enzymatic conversion technology has been paid more and more attention. In this article, we review the status of α-keto acids biosynthesis from three aspects: enzymatic screening, enzymatic modification and optimization of enzymatic conversion conditions. Meanwhile, we also indicate future research directions for further improving α-keto acids production．

Abstract:Rolling circle amplification is a rapid, sensitive and isothermal single-stranded DNA amplification technique that can be used with staining or probes to amplify the detection signal. This technology has been widely used in biological detection and other aspects. The present paper introduces how to design rolling circle amplification, summarize its application in the detection of pathogens, nucleic acid tumor markers, proteins, biological small biomolecules, and viruses in recent years and prospects for future development.

Abstract:Yeast cell wall plays an important role in the establishment and maintenance of cell morphology upon the cell wall stress. The cell wall of yeast consists of β-glucans, mannoproteins and chitin. The composition and structure remodel due to cell wall stress. Brewer’s yeast cell wall exhibits stress response during long-term acclimation in order to adapt to environmental changes. This paper reviews the composition and structure of yeast cell wall and the molecular mechanisms of cell wall remodeling and signal pathway regulation.

Abstract:Sulfated compounds are widely present in cytoplasm, on cell surface, and in extracellular matrix. These compounds play important roles in cell development, differentiation, immune response, detoxication, and cell signal transduction. 3￠-Phosphoadenosine-5￠-phosphosulfate (PAPS) is the universal sulfate group donor for the biosynthesis of sulfated compounds. Up to now, the synthesis of PAPS is still too expensive for industrial applications. This review focuses on the recent progress of PAPS production and summaries the application of PAPS, particularly in the production of glucosinolate, heparin, condroitin sulfate, and oxamniquine production.

Abstract:1,3-1,4-β-glucanase (E.C.3.2.1.73) is an important industrial enzyme which cleave β-glucans into oligosaccharides through strictly cutting the β-1,4 glycosidic bonds in 3-O-substituted glucopyranose units. Microbial 1,3-1,4-β-glucanase belongs to retaining glycosyl hydrolases of family 16 with a jellyroll β-sandwich fold structure. The present paper reviews the industrial application and protein engineering of microbial β-glucanases in the last decades and forecasts the research prospects of microbial β-glucanases.

Abstract:L-tyrosine is one of three aromatic amino acids that are widely used in food, pharmaceutical and chemical industries. The transport system engineering provides an important research strategy for the metabolic engineering of Escherichia coli to breed L-tyrosine producing strain. The intracellular transport of L-tyrosine in E. coli is mainly regulated by two distinct permeases encoded by aroP and tyrP genes. The aroP and tyrP gene knockout mutants were constructed by CRISPR-Cas technique on the basis of L-tyrosine producing strain HGXP, and the effects of regulating transport system on L-tyrosine production were investigated by fermentation experiments. The fermentation results showed that the aroP and tyrP knockout mutants produced 3.74 and 3.45 g/L L-tyrosine, respectively, which were 19% and 10% higher than that of the original strain. The optimum induction temperature was determined to be 38 °C. Fed-batch fermentation was carried out on a 3-L fermentor. The L-tyrosine yields of aroP and tyrP knockout mutants were further increased to 44.5 and 35.1 g/L, respectively, which were 57% and 24% higher than that of the original strain. The research results are of great reference value for metabolic engineering of E. coli to produce L-tyrosine.

Abstract:Naringenin is a natural flavonoid compound with anti-inflammatory, anti-oxidation, anti-viral, anti-atherosclerosis and other pharmacological activities. It is also an important precursor of other flavonoid synthesis and with great value of application. At present, the production of flavonoids such as naringenin by microbial methods has a low yield due to imbalance of metabolic pathways, which greatly limits its industrial application. In this study, a naringenin-producing strain of Saccharomyces cerevisiae Y-01 was used in the research object. The expression levels of 4-coumaric acid: CoA ligase (4CL), chalcone synthase (CHS) and chalcone isomerase (CHI) were controlled by promoter and copy numbers to investigate the quantitative effect of key enzyme expression level on the accumulation level of target products. The results showed that the correlation between naringenin production and 4CL or CHI expression was not significant while there was a positive correlation with the expression level of CHS. Strain Y-04 with high yield of naringenin was obtained by regulating the expression level of chs gene, and the yield was increased by 4.1-folds compared with the original strain Y-01. This study indicated that CHS is a key regulatory target of naringenin synthesis. Rational regulation of CHS expression can significantly promote the accumulation of naringenin. The related results provide an important theoretical reference for the use of metabolic engineering to strengthen microbial synthesis of important flavonoids such as naringenin.

Abstract:In a one-step fermentation system of vitamin C production with Gluconobacter oxydans and Ketogulonicigenium vulgare, a functional module of α-lipoic acid biosynthesis was constructed in G. oxydans. The engineered G. oxydans was co-cultured with K. vulgare to enhance the growth and 2-keto-L-gulonic acid (2-KGA) production of K. vulgare. This one-step fermentation system alleviated the growth inhibition during the mono-culture of K. vulgare and strengthened the interaction between the two bacteria. Moreover, the yield of vitamin C precursor (2-KGA) increased to 73.34 g/L (the control group was 59.09 g/L), and the conversion of D-sorbitol to 2-KGA increased to 86.0%. This study provides a new idea for further optimizing the one-step fermentation system of vitamin C production.

Abstract:Leaf water potential of peanut subjected to drought stress is positively related to the oil content of peanut kernels. The aim of this study was to directly screen the high oil mutants of peanut and create the new peanut varieties using hydroxyproline as water potential regulator. In vitro mutagenesis was carried out with the embryonic leaflets of peanut variety Huayu 20 as explants and pingyangmycin as a mutagen added into the somatic embryo formation medium. The formed somatic embryos were successively transferred to somatic embryo germination and selection medium containing 6 mmol/L hydroxyproline (at –2.079 MPa water potential ) to induce regeneration and directionally screen high oil content mutants. After that, these plantlets were grafted and transplanted to the experimental field and 132 high oil mutants with oil content over 55% were obtained from the offspring of regenerated plants. Finally, among them, the oil contents of 27 lines were higher than 58% and of 2 lines were higher than 60%. A new peanut variety Yuhua 9 with high yield and oil content was bred from the regenerated plant progenies combining the pedigree breeding method. The yield was 14.0% higher than that of the control cultivar in the testing new peanut varieties of Liaoning province, and also it has passed the national registration of non-major crop varieties. Yuhua 9 with an oil content of 61.05%, which was 11.55 percentage points higher than that of the parent Huayu 20, was the peanut cultivar with the highest oil content in the world. The result showed that it was an effective way for directional breeding of high oil peanut varieties by means of the three-step technique including in vitro mutagenesis, directional screening by reducing water potential in medium and pedigree selection of regenerated plant progenies.

Abstract:Biogenic amines (BAs) are low molecular weight organic compounds that present in fermented foods. Large amount of ingested biogenic amines can cause allergy or significant symptoms. Reduction of BAs by enzymatic reaction in fermented foods is one of the most efficient methods for removal of biohazard compounds and assurance food safety. In this study, the multicopper oxidase (MCO) gene in the genome of Lactobacillus fermentum was successfully cloned in Escherichia coli BL21 and expressed at 484 U/L. The recombinant MCO was purified by the immobilized metal affinity chromatography method. The optimal reaction temperature and pH for this enzyme was detected to be 50 °C and 3.5. The Km and Vmax values of the recombinant MCO was determined to be 1.30 mmol/L and 7.67×10-2 mmol/(L·min). Moreover, this MCO dramatically degrades histamine and tyramine by 51.6% and 40.9%, and can degrade other BAs including tryptamine, phenylethylamine, putrescine, cadaverine and spermidine, and was found to be tolerant to 18% (W/V) NaCl. The recombinant MCO is also capable of degrading BAs in soy sauce. The degradation rate of total BAs in soy sauce reaches 10.6% though a relatively low level of enzyme (500 U/L) is used. Multicopper oxidase has the potential to degrade biogenic amines in fermented foods, which lays a foundation for the further application of this kind of food enzymes.

Abstract:Tumor-specific gene mutations might generate suitable neoepitopes for cancer immunotherapy that are highly immunogenic and absent in normal tissues. The high heterogeneity of the tumor genome poses a big challenge for precision cancer immunotherapy. Mutations characteristic of each tumor can help to distinguish it from other tumors. Based on these mutations’ characteristic, it is possible to develop immunotherapeutic strategies for specific tumors. In this study, a tumor neoantigen prediction scheme was proposed, in which both the intracellular antigen presentation process and the ability to bind with extracellular MHC molecule were taken into consideration. The overall design is meritorious and may help reduce the cost for validation experiments compared with conventional methods. This strategy was tested with several cancer genome datasets in the TCGA database, and a number of potential tumor neoantigens were predicted for each dataset. These predicted neoantigens showed tumor type specificity and were found in 20% to 70% of cancer patients. This scheme might prove useful clinically in future.

Abstract:Gene therapy is a rapidly developing field. The most widely used technique for foreign gene transfer is lentiviral-mediated gene therapy. Lentiviral vector has been developed from the first generation to the third generation in terms of safety. The preparation of lentiviruses with high titer remains difficult. In this study, a Fibra-Cel sheet carrier was used as an HEK293T cell carrier matrix, and several sterile cell culture spinners were combined and cultured on a roller bottle machine to scale up the adherent cells. The virus titer was maximized by screening the factors to optimize the lentivirus titer in the third-generation lentivirus packaging process one by one. Fibra-Cel sheet vector was successfully used as the matrix of HEK293T cell adhesion to culture adherent cells at large scale. The optimal conditions for large-scale preparation of the third-generation lentivirus by bottle roller were screened and three batches of lentiviruses were produced on pilot scale. The production time of lentivirus was shortened from 120 hours to 54 hours from plasmid transfection to virus collection; in terms of cost, a rolling bottle machine was used instead of a bioreactor, leading to lower cost and no need for repeated sterilization during the whole process. The safe, effective and low-cost operation of successful production will provide a technical base for the large-scale preparation of lentivirus and thus lay a firm foundation for its clinical application.

Abstract:Pichia pastoris is one of the most convenient and widely used heterologous protein expression systems. To further improve its ability to express heterologous proteins, we developed a high-throughput P. pastoris screening method based on droplet microfluidic and demonstrated the method by screening and obtaining mutants with enhanced xylanase expression and secretion abilities. We used PCR (Polymerase Chain Reaction) amplification to obtain a fusion fragment of xylanase xyn5 gene and green fluorescent protein gfp gene, and cloned this fragment into pPIC9K, the expression vector of Pichia pastoris, to construct the plasmid pPIC9K-xyn5-gfp that recombined the DNA fragments of xylanase and green fluorescent protein. After this plasmid entered P. pastoris GS115 by electroporation, the P. pastoris SG strain that could express xylanase and green fluorescent protein was obtained. The above-said strains were then mutagenized by atmospheric room temperature plasma and subsequently encapsulated to form single-cell droplets. After 24-hour cultivation of the droplets, microfluidic screening was carried out to obtain the mutant strain with high xylanase expression for further construction and screening of the next mutagenesis library. After five rounds of droplet microfluidic screening, a highly productive strain P. pastoris SG-m5 was obtained. The activity of the expressed xylanase was 149.17 U/mg, 300% higher than that of those expressed by the original strain SG. This strain’s ability to secrete heterologous protein was 160% higher than that of the original strain. With a screening throughput of 100 000 strains per hour, the high-throughput P. pastoris screening system based on single-cell droplet microfluidic developed by the present study screens a library with million strains in only 10 hours and consumes only 100 μL of fluorescent reagent, thus reducing the reagent cost by millions of times compared with the traditional microplate screening and more importantly, providing a novel method to obtain P. pastoris with high abilities to express and secret heterologous proteins by efficient and low-cost screening.

Abstract:Based on the transcriptome analysis data of a Bacillus licheniformis, a novel bidirectional promoter was identified from the strain and its transcriptional strength was analyzed. The expression level of a Bacillus clausii derived alkaline protease gene driven by the bidirectional promoter was studied by using the known strong constitutive promoter pShuttle-09 as a control. Three recombinant expression vectors and the corresponding recombinant bacteria were constructed. Under the control of the new promoter pLA and its reverse promoter pLB, the alkaline protease expression level respectively reached 164 U/mL and 111 U/mL. The results indicated that the transcription strength of pLA was significantly higher than that of pShuttle-09 and pLB, and both the pLA and pLB promoters could initiate the expression of the alkaline protease. Thus, it provides a new expression element for the heterogenous genes in Bacillus sp. and a new idea for the co-expression of two genes in one prokaryotic strain.

Abstract:Docosahexaenoic acid (DHA) has many unique physiological functions such as promoting the development of brain and retina in infants. Therefore, it is widely applied to food, pharmacy, breeding and other industries. To obtain engineered strains of Aurantiochytrium limacinum SR21 suitable for industrial application with increased lipid and DHA production, we designed a simple, fast, accurate and high-throughput screening method based on Nile red staining of oil droplets. First, ultraviolet C (UVC) mutagenesis was used to generate a random mutant library of A. limacinum. Second, screening conditions were optimized including staining conditions of Nile red and the sorting criterion. Thereby, three putative high-lipid mutants (D03432, D05106 and D01521) were selected from the mutant library containing 3 648 mutated clones. The three mutants grew faster and produced higher amounts of lipids and DHA compared to wild type (WT). In 100 mL cultures, the lipid content of D03432 and D05106 mutants reached 64.74% and 63.13% of dry cell weight respectively, whereas the wild strain exhibited only 43.19%. DHA yield in these two mutants were even 2.26-fold and 2.37-fold higher than that of the wild strain. Experiment with 5 L fermentor further confirmed that D03432 and D05106 mutants had better performance than the wild strain on DHA yield (45.51% and 66.46% more than that of the wild strain, respectively), and demonstrated their high potential for industrial application. This work not only generated several high-DHA content mutants with high potential for industrial use, but also provided vital guidance for high-throughput screening of lipid hyper-accumulating mutants in other oil-producing microorganisms.

Abstract:The trehalose synthase (ScTreS) gene from Streptomyces coelicolor was successfully cloned and heterologously expressed in Escherichia coli BL21(DE3). The protein purified by Ni-NTA affinity column showed an apparent molecular weight (MW) of 62.3 kDa analyzed by SDS-PAGE. The optimum temperature of the enzyme was 35 °C and the optimum pH was 7.0; the enzyme was sensitive to acidic conditions. By homologous modeling and sequence alignment, the enzyme was modified by site-directed mutagenesis. The relative activities of the mutant enzymes K246A and A165T were 1.43 and 1.39 times that of the wild type, an increased conversion rate of 14% and 10% respectively. To optimize the synthesis conditions of trehalose, the mutant strain K246A was cultivated in a 5-L fermentor and used for whole-cell transformation. The results showed that with the substrate maltose concentration of 300 g/L at 35 °C and pH 7.0, the highest conversion rate reached 71.3%, and the yield of trehalose was 213.93 g/L. However, when maltose concentration was increased to 700 g/L, the yield of trehalose can reach 465.98 g/L with a conversion rate of 66%.