Abstract:Improvement of the productivity of industrial strains is an important field in micro-biology, because wild-type strains isolated from nature usually produce only a low level of antibiotics. Although random screening and simple rational screening are still effective without using genomic information, they are always time- and labor-consuming. With the broad application of recombinant DNA technology, protoplast fusion and X-omics, novel methods and strategies such as metabolic engineering, genome shuffling, system biology and system biotechnology, ribosome engineering, epigenetic modification are being exploited for the industry microbiology. In this review, we will focus on the progress of these novel methods and strategies for strain improvement in recent years.

Abstract:Interferons (IFNs) are natural proteins produced by wide variety of cells in response to viral infection or other biological inducers, and they execute diversified functions as antiviral defense, immune activation and cell growth regulation. Four genes encoding porcine interferons (PoIFN), PoIFN-α, PoIFN-γ, PoIFN-αγ or PoIFN-ω, were cloned and sequenced. The four types of porcine interferon genes were subcloned into the pET-His vector, and expressed in Escherichia coli Rosetta (DE3). The recombinant products were purified and renaturalized from inclusion bodies to obtain a native state of well biological activity. Antiviral activity assays for porcine interferons were performed and evaluated by standard procedures in following cell/virus test systems: Marc-145/PRRSV, Marc-145/VSV, PK-15/VSV, Vero/VSV or MDBK/VSV. The data showed that both PoIFN-α and PoIFN-αγ demonstrated significant antiviral activities, and the titer of them against PRRSV was up to 108 U/mg. PoIFN-γ had approximately half or one-thirds antiviral activity of PoIFN-α. PoIFN-ω showed inconspicuous antiviral activity.

Abstract:To evaluate the immune responses of recombinant Lactobacillus casei 393 expressing Porcine Epidemic Diarrhea Viral (PEDV) N protein as oral vaccine, n gene of PEDV was subcloned into the expression vector pPG-1, and then transformed into L. casei 393 by electroporation, resulting in recombinant strain pPG-1-n/L. casei 393.The recombinant strains were induced to express interest protein, which was detected by Western blotting, immunofluorescence microscopy and the whole bacteria ELISA. And then BALB/C mice were used as an animal model immunized with recombinant strains by oral administration, and the immune efficacy was analyzed. The recombinant PEDV N protein showed the antigenic specificity, and was located on the bacterial cell walls of pPG-1-n transformed L. casei. The results of ELISA showed that the mice immunized with recombinant strains could produce remarkable special sIgA level in the feces, and high level of anti-PEDV N protein IgG in the serum (P<0.01), but the induced antibodies in serum did not demonstrated neutralizing effect. Statistical significant difference was observed among the spleen lymphocyte proliferation index (LPI) among the immunization groups of mice and control groups. And there was significant increase of IFN-γ and IL-4 contents in the supernatant of spleen cell culture in immunized group. In conclusion, the oral immunizations with recombinant L. casei 393 can induce significant specific mucosal PEDV N-specific IgA response as well as serum IgG responses, and can evoke both mucosal immune and system immune responses.

Abstract:We amplified dhbC gene from the siderophore producing bacterium CAS15 by PCR. After ligated the PCR product to pMD18-T vector and then sequenced, we obtained a 1197 bp fragment. The blast result showed that the nucleotide acids of dhbC gene (Accession No. FJ194456) of CAS15 shared 99.7% identity with that of dhbC gene of Bacillus subtilis (GenBank Accession No. Z99120), and was predicted to encode a 43.8 kD polypeptide with 398 amino acid residues. We cloned the dhbC gene into expression vector pET-30a(+) and then transformed into Escherichia coli BL21(DE3) via calcium chloride transformation method, and obtained the recombinant E. coli BL21(DE3)/pET-30a-dhbC. Induced by 1 mmol/L IPTG, the fusion protein 6His-DhbC, a 48.8 kD polypeptide was successfully expressed mainly in soluble form in E. coli BL21(DE3), and the amount reached highest at 30oC for 4 h. According to the N-terminal fusion 6 His-tag, we purified the recombinant polypeptide by Ni2+ metal affinity chromatography and finally identified it by Western blotting. The result indicated that the recombinant DhbC had the antigenicity to rabbit anti-his-tag polyclonal antibody, which provides the basis for the study of practical utilization in production and the biocontrol mechanism of B. subtilis. Finally, we deleted dhbC gene by gene knockout and then retransformed it into the dhbC gene-delected mutant, which confirmed that dhbC gene play an important role in siderophore biosynthesis.

Abstract:The promoter of mitochondria-localized small heat shock protein gene in Lycopersicon esculentum (Lehsp23.8) is characterized as strongly heat-inducible. In this study, to determine how the expression of Lehsp23.8 is regulated, we conducted five expression vectors carrying the gus gene driven by the 5￠ deletion products of the Lehsp23.8 promoter. The corresponding transgenic tobacco plants were generated via Agrobacterium tumefaciens-mediated transformation. Transgenic plants were identified by PCR and Southern blotting analysis. GUS activities under heat-shock conditions were characterized in transgenic tobacco plants. After heat shock, obvious GUS staining was detected in the leaves, shoots, roots, flowers and fruits of the transgenic tobacco plants. The result of fluorometric GUS assays in leaves showed that the heat-induced GUS activity of the 565 bp promoter was the strongest, while that of the 255 bp promoter was the lowest. Deletion analysis shows that the smallest promoter fragment (-255 to -23 bp) is sufficient for heat induction. It also indicates that the sequences between -255 bp and -565 bp serve as enhancers, while the sequences between -565 bp and -871 bp can repress the heat-induced activity of the Lehsp23.8 promoter.

Abstract:We isolated a new strain of endophytic Pseudomonas G5 from the stems of Chinese parsley (Coriandrum sativum L.), and it is tentatively identified as Pseudomonas aurantiaca according to analysis of the entire substrate utilization profiles using BIOLOG MicrostationTM system (BIOLOG, Inc, Hayward CA). An array of evidence established that many Gram-negative bacteria employ Quorum sensing (QS) system to regulate gene expression in response to cell density using small diffusible signal molecules, N-acyl homoserine lactones (AHLs), and control diverse phenotypic traits in plant-associated bacteria. In this study, we showed that Pseudomonas sp. strain G5 can produce several types of AHLs at a detectable level using Thin Layer Chromatography (TLC) analysis combined with bioreporter Chromobacterium violaceum CV026 bioassay, and N-hexanoyl-homoserine lactone (HHL, C6-HSL) with Rf value 0.4 is the major signal molecule. Furthermore, we have identified its quorum sensing system composed of PhzI and PhzR by cloning and sequencing of phzI-phzR. PhzI is responsible for synthesis of AHLs signal molecules, and PhzR is a transcriptional regulator. Finally, we heterologously expressed the recombinant plasmid pMD-phzIR in Escherichia coli JM109 and verified it using C. violaceum CV026 bioassay. The phylogenetic analysis using MEGA4 revealed highly similarities exist among the phzIR homologs, suggesting it is evolutionary well conserved in the genus Pseudomonas.

Abstract:We isolated a high efficient antifungal strain A02 from forest soil in a suburb of Beijing. The result of polyphasic taxonomy confirmed that strain A02 belongs to Streptomyces lydicus. The fermented broth of the strain presented a stable and strong inhibiting activity against many plant pathogenic fungi. The purpose of this study was to ascertain the substance base of the antifungal activity of strain A02. We extracted the antifungal metabolite of A02 by using column chromatography with X-5 macroporous resin and 200 mesh silica gel respectively, and then purified it by LC-9101 recycling preparative HPLC with a SP-120-15 column (JAIGEL-ODS-AP). An active compound with purity over 99.845% was finally obtained. The chemical structure of the active compound was determined with spectroscopy methods, including ultraviolet spectrometry, infrared spectrometry, high resolution mass spectrometry and nuclear magnetic resonance. According to the analysis results, we identified the active compound as a tetraene macrolide antibiotic with the molecular weight of 665, the molecular formula C33H47NO13 and the same chemical structure as natamycin. Our research revealed a new biosynthetic function for S. lydicus to produce natamycin, and an expanding application field for natamycin to be used for the control of fungal plant diseases.

Abstract:Ansamycins, such as rifamycin and ansamitocin, usually consist of a group of structural similar components. Geldanamycin, a benzenic ansamycin, has been found to consist of four structural similar components. We analyzed the geldanamycin (GDM) preparation from Streptomyces hygroscopicus 17997 by LC-ESI(+)-MS/MS, and discovered five novel and one known GDM analogues in trace amounts. Based on the ESI(+)-MS/MS spectra of these GDM analogues, and the present understanding of GDM biosynthesis, we proposed the possible chemical structures of these GDM analogues. Three novel GDM analogues, all having the same molecular formula of C29H42N2O10, were GDM biosynthetic derivatives with one of the three C-C double bonds between C2-C3, C4-C5 and C8-C9 in GDM changed to mono-hydroxylated C-C single bond. The other two novel GDM analogues, having the same molecular formula of C28H38N2O8, were 17(or 12, or 4)-desmethoxylgeldanamycin and 4,5-dihydro-10,11-dehydrate-17-desmethyl-17-hydroxylgeldanamycin, respectively. The known GDM analogue, having the molecular formula of C29H42N2O9, was 4, 5-dihydrogeldanamycin, an intermediate in GDM biosynthesis. The discovery of novel GDM analogues provided us new insights in understanding the biosynthetic details of GDM, and clues of obtaining GDM derivatives by gene-disruption and combinatorial biosynthesis.

Abstract:The plasmodium of Physarum polycephalum is a suitable eukaryotic cell for cell cycle investigation, but there is no compatible transient expression system for the plasmodium. Using the promoter and terminator of ardC actin of Physarum polycephalum substituted the CMV IE and SV40 polyA of plasmid pDsRed1-N1, using cassette PardC-MCS-DsRed1-TardC substituted the cassette PardC-hph-TardC of plasmid pTB38, we constructed plasmids pXM1 and pXM2 for transient expression of red fluorescent protein (RFP) in Physarum polycephalum respectively. After reconstituting the transcription elongation factor homologous gene (pelf1) of Physarum polycephalum into the pXM2, we generated a plasmid pXM2-pelf1. After the plasmid pXM1, pXM2 and pXM2-pelf1 were electroporated into the plasmodium of Physarum polycephalum, we observed optimum RFP and PELF1-RFP expression under fluoroscope and confocal microscope between 24-48 h after electroporation, and found that ELF1-RFP expression was accumulated in nucleus of microplasmodium, the optimum electroporation parameters were 40 V/cm electric field, 1 ampere current, and 70 ms electric shock time. The results suggest that this expression system is qualified for transient expression of specific protein in plasmodium of Physarum polycephalum.

Abstract:Using response surface method, we optimized the medium for the asymmetric whole cell biotransformation by Candida tropicalis 104. This strain was used for microbial reduction of 1-[3,5-bis(trifluoromethyl)phenyl] ethanone to (S)-1-[3,5-bis(trifluoromethyl)phenyl] alcohol, with enantiomeric excess(e.e.) reached more than 99.9%. Fractional factorial design was used to evaluate the effects of medium components on carbonyl reductase activity of Candida tropicalis 104. Yeast extract, glucose and NH4Cl were the most important factors among six tested variables that influence the enzyme activity for the biotransformation process. Based on the experimental results, the path of steepest ascent was undertaken to approach the optimal region of these factors. Central composite design and response surface analysis were subsequently employed for further optimization. The optimal medium for Candida tropicalis 104 was composed of (in g/L): glucose 47.14, yeast extract 13.25, NH4Cl 2.71, MgSO4·7H2O 0.4, KH2PO4 1, K2HPO4 1. Under the optimum conditions, the maximum enzyme activity of 852.75 U/L in theory and 851.13 U/L in the experiment were obtained, with an increase of 65.2% compared to the original medium components.

Abstract:Using lipase segregation agar containing trioleoylglycerol, we obtained 18 lipase positive clones by screening from a metagenome library of dairy rumen microflora containing 15 360 clones. The average insert size of lipase positive clones was about 60 kb. Lipase enzyme activity analysis by p-NPP method indicated that Lipase6, Lipase7 and Lipase8 had higher lipolytic activities to substrates of p-nitrophenyl palmitate (C16), p-nitrophenyl alaurate (C12) and p-nitrophenyl palmitate (C16) respectively. The optimum pH of Lipase 6, Lipase 7 and Lipase 8 were 7.5. The halflife period of Lipase 8 with the value of 15 min in 70oC decreased with the increase of temperature. In conclusion, the lipases screened in this study had different substrates specificity and good thermo stability, which laid a basis for large-scale industrial application.

Abstract:We used genetic methods to get a mutational spt15 gene from the recombinant strain Saccharomyces cerevisiae YPH499-3, screened by global transcription machinery engineering (gTME) approach. We transformed the gene into the original strain Saccharomyces cerevisiae YPH499 using the vector pYX212, then got a new recombinant strain. We studied the characteristic of this strain and found that it could metabolize xylose and co-ferment xylose and glucose. Under the fermentation condition of 30oC, 200 r/min, 72 h , the utilization ratio of xylose was 82.0%, with 32.4% of ethanol yield when the carbon source in the media was 50 g/L xylose, while the utilization ratio of xylose and glucose was 80.4% and 100% respectively, with the 31.4% of ethanol yield when the carbon source was 50 g/L glucose/xylose (1:1). Meanwhile, the concentration of the by-product xylitol was very low. This study demonstrates the effect which the forward mutation of spt15 gene makes to the co-fermentation of xylose and glucose to ethanol by Saccharomyces cerevisiae.

Abstract:We studied the effects of Catharsius molossus (a Chinese medicinal insect) on the cell growth, fermentation kinetics of key bioactive substances and anti-cancer activity of Ganoderma lucidum in submerged fermentation. The results showed that C. molossus at all the tested concentrations had no stimulatory effect on the cell growth. However, addition of C. molossus at 5 g/L lead to significant effects on the fermentation kinetics of polysaccharides and triterpenoids of G. lucidum, and at 7th day in fermentation process, the yields of polysaccharides and triterpenoids reached 2.81 g/L and 539.0 mg/L, respectively, while they were 2.25 g/L and 428.2 mg/L in control. In vivo anti-cancer studies showed that the inhibitory rates of control fermented G. lucidum (CFG) and a combination of water extract from C. molossus and CFG on the developed tumor (Heps) in mice were 41.61% and 42.24%, respectively. Moreover, the inhibitory rate of the G. lucidum fermented with C. molossus (GFC) reached 57.21%, which was enhanced 37.49%, compared to the inhibitory rate of the control fermented G. lucidum. These results suggest that supplementation of C. molossus in submerged fermentation of G. lucidum lead to a significant enhancement of the anti-cancer activity of cultured G. lucidum.

Abstract:We studied the effect of initial pH and substrate concentrations on the conversion of xylose to hydrogen by Clostridium butyrium T4 at pH 5.0?8.5 and substrate concentrations 5?40 g/L. The cumulative hydrogen volume and the specific hydrogen production rate increased and then decreased with increasing initial pH or substrate concentrations. At initial pH 6.5 and substrate concentration 20 g/L, the cumulative hydrogen production and the specific hydrogen production rate reached the maximum value of 4.26 L/L and 18.86 mmol-H2/h g-DCW (dry cell weight).

Abstract:To improve mass transfer and enhance the yield for C1,2 biodehydrogenation of steroid 11β-hydroxyl medroxyprogesterone, we carried out the dehydrogenation reaction of 11β-hydroxyl medroxyprogesterone in an oil-in-water (O/W) microemulsion by Arthrobacter simplex UR016. We studied the effects of system composition, dehydrogenation temperature and substrate concentration on microbial transformation. We formulated a suitable O/W microemulsion system with Arthrobacter simplex UR016 culture broth as aqueous phase, 10 g/L of edible oil as oil phase, 4 g/L of Tween-80 and 7% (V/V) alcohol as surfactant and cosurfactant. The optimal dehydrogenation temperature was 33°C. The results showed that in Tween-80/alcohol/edible oil/water microemulsion system, the hydrophobic steroid was solubilised and diffused effectively, with the maximum conversion rate of 88.6% at 46 h under 4 g/L substrate concentration, an increase of 66.2% compared to that in aqueous system. The C1,2 biodehydrogenation of 11b-hydroxyl medroxyprogesterone is more efficient in water-edible oil microemulsion system than in aqueous system.

Abstract:The purpose of the study is to use O. intermedium DN2 to degrade nicotine in tobacco extracts for making reconstituted tobacco. Firstly, we studied the effects of various factors on degradation of nicotine in the extracts by strain DN2. When we added 0.1% yeast extract into the extracts, adjusted its pH value to 7.0 by ammonia solution, inoculated 15% cultures and maintained fermentation temperature of 30°C, the degradation rate of nicotine by strain DN2 was the fastest. Furthmore, under these conditions, we studied the degradation rates of nicotine in three fed batches culture which carried out in a 30-L reactor, the result showed that the average degradation rate of nicotine by strain DN2 was 140.55 mg/L/h, which was much higher than that reported in other studies. These results indicated that strain DN2 may be useful for reducing nicotine content of reconstituted tobacco.

Abstract:We reviewed the fermentation for dihydroxyacetone production. Microbial fermentation is better for dihydroxyacetone production as compared to chemical methods. Gluconobacter oxydans was recognized as the most important strain for industrial production of dihydroxyacetone. The dihydroxyacetone yield is associated with many factors such as substrate, product, oxygen and biomass concentration. Repeated fed-batch fermentation and immobilization fermentation were recognized as the most potential process in various fermentation mode. Construction of recombinant microorganism and optimization of process are future directions of dihydroxyacetone production.

Abstract:Microorganisms in nature have rich variety, whose sizes are from nano scale to micro scale. Therefore, microbes can be used as natural “building blocks” in nano/micro multi-level fabrication processes. At present, most of the bio-manufacturing methods do not apply to direct control of living microbes. Their microbiological global functions and superiorities are not available. In this paper, two novel nano/micro bio-fabrication approaches, micro-fluidic control method and magnetic control method have been established. The living microbes could be manipulated to form micro-scaled patterns or to move orientedly. By these approaches, living microbes are taken as nano/micro robots. We could employ their specific biological functions and regulate their controllable self-assembly, which is expected to design and create a series of new special functional materials and devices.

Abstract:We studied the effects of several medicinal insects on biosynthesis of polysaccharides from Ganoderma lucidum in submerged culture. The results showed that the medicinal insect, Catharsius molossus at 5 g/L significantly promoted the biosynthesis of intracellular polysaccharides (IPS) and extracellular polysaccharides (EPS) of G. lucidum, and compared with control, IPS and EPS yields markedly enhanced from (1.93 ± 0.09) g/L to (2.41 ± 0.12) g/L and (520.3 ± 20.2) mg/L to (608.9 ± 20.2) mg/L, respectively (P < 0.05). Both IPS and EPS consisted of five kinds of components, and IPS-1 and EPS-1 were the major components of IPS and EPS, respectively. Further separation studies showed that IPS-1 was made up of three single compounds, while EPS-1 was made up of two single compounds. There were no new components in both IPS and EPS obtained from G. lucidum in submerged culture by the addition of the insect, C. molossus, suggesting the biosynthetic pathways of the major components of IPS and EPS had not been changed.

Abstract:We used reverse transcriptase polymerase chain reaction (RT-PCR) and rapid amplification of cDNA end (RACE) techniques to obtain the full-length cDNA of b-mannanase (EC 3.2.1.78) from Armillariella tabescens EJLY2098 (an edible fungus). Sequence analysis of the 1481 bp full-length cDNA encoding 445 amino acid residues indicated that the gene contained two structural domains, cellulose-binding domains (CBD) and glycoside hydrolase family 5 (GHF5) domains, other than the conserved b-mannanase domain. Thus, we classified this gene as a member of glycoside hydrolase family 5. Next, we cloned a 1308 bp fragment encoding the b-mannanase mature peptide (re-atMAN47) into the expression vector pPICZaA and expressed it in Pichia pastoris. The yield was 440 mg/L. Enzyme activity reached a maximum of 1.067 IU/mL after 72 h of methanol induction. The re-atMAN47 had an optimal temperature of 60oC and an optimal pH of 5.5. It manifested broad thermostability from 30oC~65oC, and was stable between pH 4.5~7.0. This study represents the ?rst record of a β-mannanase from Armillariella tabescens EJLY2098 and provides a new source of carbohydrate hydrolysis enzyme with good biosafety, thermostability and wide pH stability. It is a good approach for the industrial needs of feed, food and pharmaceutical manufacturers.

Abstract:Functional improvement to one component of the cellulase, endo-b-1, 4-glucanase, has been a focus of the recent research in this area. We report here the saturation mutagenesis of the active site of an endoglucanase (CfEG) from termite Coptotermes formosanus. First, three dimensional structure of CfEG was built via homology modeling by using a close-related (79% homology in sequence) endo-b-1,4-glucanase (NtEG, PDB id=1ks8) from higher termite Nasutitermes takasagoensis as a template. Second, we identified three corresponding amino acid positions at the active site of CfEG by structural superposition onto NtEG. These three putative amino acids for the active site of CfEG, i.e., Asp53, Asp56 and Glu411, were subjected to saturation mutagenesis using degenerate primers. Among the mutants, Asp53Glu and Asp56Cys showed somewhow higher activities than the wildtype, with the latter having more than 3-fold decrease in Km. Double mutation Asp53Leu/Asp56Ile showed nearly 2-fold increase in specific activity and in the same time 2-fold decrease in Km. Saturation mutagenesis to the position Glu411 produced no active mutant, even changing Glu411 explicitly into its similar amino acids such as Glu411Asp and Glu411Gln could not result in any active mutant. These imply that position Glu411 could be extremely important and therefore indispensable for CfEG functionality.

Abstract:To explore the effect of coculturing actinomycetes with Bacillus subtilis on the production of bioactive secondary metabolites, we studied the difference between fermentation products of monocultures and the corresponding cocultures of 22 actinomycetes by antimicrobial assay and HPLC-PDA analysis. We selected Streptomyces strain FXJ2.014 with high bioactivity for further analysis and found additional metabolites in fermentation extracts of cocultures of strains FXJ2.014, FXJ1.296 and AS 4.1252 respectively with B. subtilis. Quinomycin A was the main bioactive metabolite produced by the monoculture of strain FXJ2.014, while a new quinomycin-like component named FXJ2.014-HB was produced when strain FXJ2.014 was cocultured with B. subtilis. Further tests of antimicrobial and antitumor activities indicated that FXJ2.014-HB and Quinomycin A had significant differences in terms of bioactivity. Moreover, the inhibitory activity of FXJ2.014-HB to a variety of tumor cell lines was weaker than the highly toxic Quinomycin A, indicating its potential to be an antibiotic with low cell toxicity. In conclusion, coculture can be used as a promising approach to discover bioactive secondary metabolites from actinomycetes.

Abstract:We used immobilized lipase from Candida sp. 99-125 to produce fatty acid methyl esters (FAMEs) from crude oil and methanol. We studied the effects of phospholipids on activity of immobilized lipase, reaction velocity, stability of immobilized lipase and the stability of immobilized lipase in crude and refined oil. Results showed that the activity of the lipase immersed in petroleum ether with 1% phospholipids dropped more quickly than the lipase in petroleum ether without phospholipids. When soybean oil was used without phospholipids as material, the FAMEs yield of 15 min was 26.2%, whereas the yield decreased to 12.4% when there were 5% phospholipids in the soybean oil. However when the phospholipids content was below 1%, the stability of the lipase did not change obviously. The lipase was stable when used to catalyze crude soybean oil and crude jatropha oil, after 10 cycles the FAMEs yield was still above 70%. This lipase showed great potential for industrial production of biodiesel from crude oil.

Abstract:Candida glycerinogenes WL2002-5 (C. g) is an important industrial strain for glycerol production. To further improve glycerol production, we reconstructed a binary vector pCAM3300-zeocin-CgGPD1, introduced it to Agrobacterium tumefaciens LBA4404 by electroporation, and then transformed the T-DNA harboring the CgGPD1 to Candida glycerinogenes by Agrobacterium tumefaciens-mediated transformation (ATMT). After 96 h fermentation with glucose as the substrate, we screened a transformant named C.g-G8 with high glycerol production. Compared with the wild strain, the glucose consumption rate of C.g-G8 and the glycerol production were 12.97% and 18.06% higher, respectively. During the fermentation, the activity of glycerol-3-phosphate dehydrogenase of C.g-G8 was 27.55% higher than that of the wild strain. The recombinant Candida glycerinogenes with high glycerol production was successful constructed by ATMT method.