Abstract:

Abstract:[Objective] To screen probiotic Lactobacillus as candidate strains for healthy yoghurt. [Methods] Lactobacilli isolated from healthy human feces and Milk Tofu were tested and screened by tolerance to simulated gastric juice. Probiotic potential was determined based on resistance to simulated gastrointestinal juice and bile salts, antibacterial activity, and cholesterol degradation ability. [Results] Results show that 41 bacterial strains with dissolved calcium were obtained from the Lactobacillus isolation medium. Five strains with high tolerance to low pH and simulated gastric juice were selected from the screened strains and identified by 16S rRNA gene sequencing. Three strains were Lactobacillus, named as Lactobacillus plantarum (LpMT-3), Lactobacillus plantarum (LpMT-5) and Lactobacillus salivarius (LsAF-7). These three Lactobacillus strains exhibited higher tolerance to simulated gastric juice than the commercially available LGG (Lactobacillus rhamnosus GG). After the Lactobacillus strains were transferred to intestinal juice for 26 h, survival rate of LpMT-5 was stable at approximately 45%, lower than LGG (49%). The three Lactobacillus strains displayed higher tolerance to bile salt than LGG when the concentration of bile salt was 0.10%. LpMT-3 and LsAF-7 were still alive when the concentration of bile salt was increased to 0.20%. All the three strains exhibited antibacterial activity, especially to Enterococcus faecalis, followed by Staphylococcus aureus, and the least inhibition effect to Escherichia coli and Salmonella. All three Lactobacillus strains also showed cholesterol-reducing ability. [Conclusion] Three strains of Lactobacillus could be taken as the strains to further develop new probiotic products and health yogurt.

Abstract:

Abstract:[Objective] The objective of this study is to isolate and identify a novel bacterial strain capable of selectively desulfurizing CX-DBT, and then to determine its desulfurizing pathway and optimize the culture condition. [Methods] CX-DBT was used as the sole sulfur resource to enrich the bacterial cultures, and then GC-MS was used to determine CX-DBT desulfurizing pathway by analyzing the metabolic productions. The new culture, strain JDZX13, was identified based on the morphological, physiological and biochemical properties, and 16S rRNA gene sequence profiles. Single factor test and orthogonal design method were performed to determine the optimal biodesulfurizaio conditions. [Results] The new strain JDZX13 belonged to Gordonia sp. and named as Gordonia sp. JDZX13 (KP993297), which could selectively desulfurize CX-DBT by “4S pathway”. The optimum operating conditions were found as 15 g/L of sucrose, 2 g/L of NH4Cl, 0.1 g/L of MgCl2, 1 mL of metal solution, at pH 7.0 and 35 °C. [Conclusion] A bacterial strain JDZX13 was successfully isolated and identified with the utilization of CX-DBT by “4S pathway”. After a serial optimizations, the cell growth and desulfurizing capability were further enhanced. This result would be an important reference for further exploring the petroleum biodesulfurization technology.

Abstract:[Objective] We selected Simmondsia chinensis (Jojoba) fatty acyl-CoA reductase Jojoba FAR for heterologous expression in Komagataella pastoris strain GS115 to produce fatty alcohol by fermentation. [Methods] Gene encoding this fatty acyl-CoA reductase was amplified from plasmid pRL105 and cloned into the plasmid pGAPZαA; the recombinant expression plasmid was transformed into K. pastoris GS115 by electrotransformation. We detected fatty alcohol from positive transformant by GC-MS. [Results] We constructed a recombinant K. pastoris GS115 strain pGAPZ-far-GS115 that produced fatty alcohols in flask fermentation. Afterwards, a fed-batch fermentation was used for further verification. And the engineered strain produced 134.74 mg/L fatty alcohols with a productivity of 1.22 mg/(L·h). [Conclusion] Our findings prove the possibility to produce fatty alcohol in K. pastoris GS115, provide the potential for industrial production of fatty alcohol by K. pastoris.

Abstract:[Objective] The lipase gene of Aurantiochytrium sp. PKU#SW7 was cloned and expressed in Escherichia coli, and the lipase enzymatic properties were characterized. [Methods] Sequence of lipase gene was identified with transcriptome data (Liu, et al; unpublished data). The recombinant plasmid pET30-lip was over expressed in Rosetta(DE3) by auto-induced and dual temperature control strategy. The recombinant lipase (LIP) was purified with Ni-Agarose His affinity chromatography and the enzymatic properties were further determined. [Results] A length of 873 bp lipase gene was obtained (GenBank accession number: KT305964). The optimal temperature and pH for lipase hydrolytic activity on p-NPB were 40 °C and pH 8.0, respectively. The LIP activity was increased to about 130% after treated by Ca2+ and Co2+ for 30 min. No significant inhibition of LIP activity was observed by methanol treatment. Under the optimal conditions, the LIP specific activities for p-NPP and p-NPB were 70.0±3.1 U/mg and 102.5±2.6 U/mg. [Conclusion] The LIP of Aurantiochytrium sp. PKU#SW7 possess favorable characteristics and meets the basic requirements of biodiesel catalyst.

Abstract:[Objective] In order to optimize the cultivation conditions of the Schizochytrium sp. 20888 to increase DHA yield. [Methods] The effects of cultivation time, carbon and nitrogen sources and their concentrations and culture temperature on the cell growth, cellular lipid and DHA contents were studied. A series of “one-factor-at-a-time” experiments and orthogonally designed tests were carried out. The biomass was tested as dried weight, the lipid content was tested by Soxhlet extraction and the DHA content was determined by gas chromatography. [Results] The optimal cultivation time was 4 d, the proper temperature was 23 °C, and the optimal medium formula was as following (g/L): glucose 65, glycerol 80, peptone 6, yeast extract 4, sodium glutamate 8. [Conclusion] Optimal cultivation conditions for DHA production were obtained successfully. Under the optimal conditions, the DHA yield was reached to 33.68%.

Abstract:[Objective] In order to solve the environmental pollution problem caused by long chain petroleum hydrocarbons, we selected biosurfactant-producing strain that can degrade oil efficiently. [Methods] Six glycolipid-producing strains were isolated from grape skins by using oil-plate and blood-plate method. Oil-spreading test was conducted to test emulsifying ability of the strains. Strain K6 was selected out by detecting emtl gene sequence related to mannosylerythritol lipids synthesis. Morphological, physiological and molecular phylogenic studies were conducted to identify strain K6. The metabolites of strain K6 were characterized by TLC and HPLC. [Results] Strain K6 that produced mannosylerythritol lipids was identified as Pseudozyma churashimaensis. Moreover, its degradation rate of petroleum hydrocarbons could reach 70.17%. [Conclusion] Strain K6 has the ability to produce glycolipid biosurfactant and degrade petroleum hydrocarbons, which shows a practical significance on restoring the petroleum-contaminated environment.

Abstract:[Objective] To fully demonstrate the bacterial diversity in radiation polluted soils from the Northwestern China, and investigate effects of radiation pollution on the bacterial community. [Methods] composition and structure of bacterial communities in soils from the control of no radiation pollution and the radiation contaminated in different levels was analyzed based on high-throughput sequencing of the V3 region of the 16S rRNA gene. [Results] A total of 110 348 effective sequences and 17 604 OTUs were obtained, which were classified into 726 genera from 19 phyla and others including 6 candidate phyla and the unclassified in bacteria domain. The result of diversity analysis showed that the radiation pollution resulted in significant change in bacterial community in soils, and led to the improvement of bacterial diversity and richness. The analysis of bacterial composition indicated percent rates of bacteria from phylum Proteobacteria decreased significantly under the radiation stress, while the Actinobacteria increased gradually with the improvement in radiation levels. The proportion of the unclassified, Firmicutes and Acidobacteria rise obviously. Additionally, lots of unclassified genera exist in radiation pollution soils. [Conclusion] it proved extremely rich bacterial diversity in radiation contaminated area and a lot of novel microbial resources which need to further discover.

Abstract:[Objective] To analyze the influence of precipitation on the total bacteria and microbial community composition in coastal waters. [Methods] Water samples were collected from three stations in Qinhuang Dao west beach before and after rainfalls in August 2014. Total and culturable bacterial species were enumerated using fluorescence microscope and plate counting methods, respectively. Culturable bacterial species were identified using molecular approach and the microbial community structure was analyzed. [Results] Total and culturable bacterial species were 5.6×109 cfu/L and 8.3×107 cfu/L before rainfall, 9.2×109 cfu/L and 2.1×108 cfu/L after rainfalls. Among the culturable bacteria, Proteobacteria is the mostly dominant bacterial phylum (80% before rainfall, 73% after rainfall), followed by Bacteroides (12% before rainfall, 13% after rainfall) and Firmicute (7% before rainfall, 11% afer rainfall). Enterobacter spp. (21 strains), Marinobacter spp. (13 strains), Arcobacter spp. (13 strains), Pseudomonas spp. (10 strains), Bacillus spp. (10 strains) and Vibrio spp. (6 strains) were dominant species before rainfall. Enterobacter spp. (22 strains), Marinobacter spp. (21 strains), Bacillus spp. (14 strains), Acinetobacter spp. (11 strains), Pseudomonas spp. (9 strains) and Arcobacter spp. (5 strains) were dominant species after rainfall. [Conclusion] Precipitation has significant impact on total number of bacteria. Clearly, precipitation significantly shaped the bacterial community structure in the coastal waters.

Abstract:[Objective] An endophytic fungus SG17 was isolated from the root of Myricaria laxiflora before flooding. In order to explore the antioxidant capacity and the possible material foundation, bio-identification, antioxidant confirmation and phenolic acids analysis were conducted here. [Methods] The internal transcribed spacer (ITS) of nrDNA was sequenced, and a total antioxidant kit was used to measure the capacity with the positive control of Vitamin C. Furthermore, High performance liquid chromatography (HPLC) and thin layer chromatography (TLC) were applied to analyze the natural phenolic compounds from the fermentation broth. [Results] The antioxidant capacity of SG17 was extraordinarily high, and the extract of the fermentation liquid was 31.86% as high as the same content of vitamin C. ITS sequence and BLAST analysis indicated that SG17 would be Aspergillus fumigates, and this conclusion was further proved by morphological characterization. The contents of phenolic acids were rich in the fermentation broth, in which gallic acid could be detected by HPLC, and a compound with the same UV spectrum as chlorogenic acid was found both by HPLC and TLC. [Conclusion] The endophyte SG17, an Aspergillus fumigatus, had much higher antioxidant activity than reported before, and could be explored as a potential antioxidant resource in the future.

Abstract:[Objective] To investigate PBSX-like defective prophages resident in 39 Bacillus subtilis strains preserved in China Center for Type Culture Colletion (CCTCC). [Methods] B. subtilis strains were induced with mitomycin C, yielding cell lysate supernatants. Agarose gel electrophoresis was used to detect the existence of 13 kb DNA fragments in cell lysate supernatants. Cell lysate supernatants were mixed with PBSX-sensitive strain, B. subtilis W23 to determine the killing activity against W23. Phage-like particles in the cell lysate supernatants were examined with transmission electron microscopy. [Results] Cell lysate supernatants of 24 strains were detected to have 13 kb DNA fragments, and had killing activity against W23. They were defined as PBSX lysogenic bacteria. 1 strain’s lysate supernatants possessed 13 kb DNA fragments, but had no killing activity against W23. 5 strains’ lysate supernatants displayed killing activity against W23 although 13 kb DNA fragments were not detected in them. 9 strains’ lysate supernatants did not have 13 kb DNA fragments, as well as had no killing activity against W23. Among the 9 strains, 3 strains’ lysate supernatants were detected to have phage-like particles distinguished with PBSX. [Conclusion] Among the 39 B. subtilis strains, 61.5% are PBSX lysogenic bacteria. Industrial strains and wild strains isolated from soil collected from Shennongjia harbor various phage-like particles distinguished from PBSX. Results in this paper provide more theory evidences for further uncovering the function of PBSX on host bacteria.

Abstract:[Objective] To isolate and identify lactate-utilizing bacteria from human gut, and investigate thier metabolic traits of lactate. [Methods] We used Hungate roll tube technique to isolate anaerobic bacteria with lactate as substrate, and then identified the strain based on morphologies, biochemical reaction and 16S rRNA gene. Then, in vitro fermentation system was used to assess the metabolic traits of lactate and its cross-feeding with lactic acid bacteria. [Results] We verified that lactate was generally utilized by human microflora. We obtained a lactate-utilizing bacterium, belonging to Veillonella, that efficiently consumed more than 50 mmol/L lactate within 24 h, and mainly generated acetate and propionate. Furthermore, it ameliorated the lactate accumulation when co-cultured with lactic acid bacteria Enterococcus. [Conclusion] Our results suggest that this strain could be used as potential probiotics with lactic acid bacteria to cooperate the dynamics of lactate in the hind gut.

Abstract:[Objective] Diversity of fungal endophytes associated with Juglans regia was studied. [Methods] Fungal endophytes from different seasons, habitats and parts of Juglans regia were isolated by tissue expand method. Strains were classified by morphology and similarity of internal transcribed spacer (ITS) sequence by ClustalX 2.0. Composition, diversity and preference of fungal endophytes were analyzed by the colonization frequency (CF), isolation rate (IR), isolation frequency (IF), Shannon-Wiener biodiversity index (H′). [Results] In total 1 450 fungal endophytes were isolated from Juglans regia and classified into 47 genera. Among them, Alternaria (20.00%), Fusarium (8.34%), Saccharomyces (8.14%) were the dominant genera. The diversity of fungal endophytes and Evenness index (E) were maximum in 2-yesr-old twig, Shanyang, spring with Shannon-Wiener index 1.15, 1.42, 1.92 and evenness 0.36, 0.42, 0.54, respectively. [Conclusion] There was some difference in diversity of fungal endophytes isolated from different parts, habitats, season of Juglans regia. Meanwhile, the similarity coefficient and evenness show that the fungal endophytes isolated from Juglans regia were relatively stable.

Abstract:[Objective] To study the effects of cultivation substrate using fruit tree branches on Ganoderma lucidum quality characteristics. [Methods] The agronomic traits of strain JINDI G. lucidum cultivated with apple/peach/pear branches were analyzed. In addition, the nutritional composition and the content of polysaccharides and the function improving sleep were measured and evaluated. [Results] The growth rate of G. lucidum mycelia cultivated with three fruit branches was significantly lower than that in the conventional substrate as control (P<0.05), and 7–13 days was prolonged to mycelia grow. And the yield decline of G. lucidum in the fruit branch group, to a certain extent, has been found. There were no significant differences in the contents of nutrients in between each group, while the content of the mineral elements in the G. lucidum cultivated with three fruit branches were much higher than control. The content of polysaccharide of G. lucidum in the fruit branch group was lower compared with control. While all group can effectively prolong the pentobarbital sodium sleeping time of mice, and the pear branches group shorten sleep latency accomplied with 60% of sleep rate. [Conclusion] The yield and content of polysaccharide of G. lucidum cultivated with fruit branches were decreased differently with poor agronomic traits. But the pear branches can effectively improve sleeping. It was feasible to use fruit branches for G. lucidum cultivation after the optimization of substrate formula.

Abstract:[Objective] Pathogen isolation, identification, and drug sensitivity test were performed on Rana catesbeiana that were suffering from skin ulcers in order to provide references to effectively prevent and control skin ulcers disease. [Methods] Pathogens, separated from the heart, liver and nidus of dying Rana catesbeiana infected by skin ulcers with the use of routine separation methods, were identified through artificial infection test, API 20E biochemical identification system, and 16S rRNA gene sequence analysis. Then, drug sensitivity test was conducted using paper diffusion method. [Results] One superior strain (NWG20141026), isolated from Rana catesbeiana infected by skin ulcers, exhibited strong pathogenicity to Rana catesbeiana by Artificial infection test. Through API 20E biochemical identification and 16S rRNA gene sequence analysis, it was found that the strain was Proteus vulgaris. The results from drug sensitivity test showed that phathogen of skin ulcer were highly sensitive to 7 medicines, such as florfenicol, tetracycline, doxycycline, nalidixic acid, sulfisoxazole, enrofloxacin, and erythrocin. [Conclusion] Skin ulcer disease, caused by Proteus vulgaris, could be treated by florfenicol, tetracycline, doxycycline, nalidixic acid, and sulfisoxazole.

Abstract:[Objective] To obtain the polyclonal antibody against SpaA pilin subunit from Lactobacillus rhamnosus, and study its species specificity. [Methods] The spaA of Lactobacillus rhamnosus GG (LGG) was amplified by PCR and cloned into plasmid pET-28α(+). The resultant plasmid was transformed into Escherichia coli BL21(DE3), and the recombinant SpaA was expressed by IPTG induction and purified by Ni-NTA column. The purified protein was used to immunize the BALB/c mice for raising polyclonal antibody. The SpaA presence in 18 Lactic acid bacteria (LAB) strains belonging to 12 species was detected by indirect whole-cell ELISA, Western and Dot-blot assays. [Results] The recombinant SpaA was obtained with molecular mass of 36 kD as expected. The antibody against SpaA was generated with titer of 1:12 800. Western analysis showed that the antibody can specifically react with the native SpaA. Among 18 LAB strains, all of Lactobacillus rhamnosus, Lactobacillus casei and Lactobacillus paracasei strains showed positive reactions in the spaA-PCR and RT-PCR detection, while only 3 strains of Lactobacillus rhamnosus showed positive reactions with SpaA antibody in whole-cell ELISA and Dot-blot, and none of the other strains had obvious cross reaction with SpaA antibody. [Conclusion] Although SpaA encoding gene was highly homologous among Lactobacillus rhamnosus, Lactobacillus casei and Lactobacillus paracasei species, SpaA protein was uniquely expressed and cell surface-exposed in Lactobacillus rhamnosus. The SpaA antibody obtained in this study provide a useful tool for further immunomagnetic separation and pilin function investigation of highly adhesive Lactobacillus rhamnosus strains.

Abstract:[Objective] To compare oral microbial diversity between periodontitis patients and healthy people by analyzing the saliva microbial community structure in the same region with same nationality. [Methods] We collected 10 saliva samples from 10 subjects (5 from periodontitis patients, 5 from healthy people) and marked DP (Dongxiang periodontitis patients) and DH (Dongxiang healthy people). Saliva samples’ DNA was extracted and the 16S ribosomal RNA gene clone library was constructed. The sequencing results were analyzed by software such as MOTHUR, MEGA 4.0, and ClustalX 3.0. [Results] A total of 115 OTUs (DP 60; DH 75) were obtained and all OTUs were classified into 6 phyla and 27 genera. TM7 was the unique dominant phyla in DP group. The dominant genera in DP group only included: Fusobacterium, Porphyromonas, Peptostreptococcus, TM7_genera. [Conclusion] There is a certain difference of oral microbial community structure between Dongxiang periodontitis and healthy people. The roles of Fusobacterium, Peptostreptococcus, TM7_genera in oral cavity of periodontitis patients may deserve further study.

Abstract:[Objective] Essential oil (EO) composition of Coreopsis tinctoria Nutt., together with The their anti-Cryptococcus activity and influence on the cell membrane of Cryptococcus neoformans present study were evaluated in this study. [Methods] EO from Coreopsis tinctoria Nutt. was extracted team distillation and the main chemical components of it was identified by GC-MS. The micro-dilution method was used in acquiring the minimal inhibitory concentration (MIC). The cell weight of C. neoformans and germ tube germination of C. neoformans were also determined to evaluate the anti-C. neoformans activity in vitro. The effect on membrane permeabilization was measured by monitoring the influx of Propidium iodide (PI) using flow cytometry and further verified through the inhibition of ergosterol synthesis in the cell membrane. [Results] The MIC value of EO against C. neoformans was 0.781 μL/mL. Cell weight and germ tube germination of C. neoformans were inhibited in a dose-dependent manner. As shown in the results ergosterol production was reduced and propidium iodide penetrated C. neoformans through a lesion in its cell membrane upon treatment with EO. [Conclusion] Inhibitory effect of EO against C. neoformans relying on the cell membrane lesion.

Abstract:Tens of thousands of prokaryotic species/strains have been found and taxonomically designated since the first publication around 340 years ago. Especially in recent years, with the rapid development of molecular biology, numerous emerging taxa have been identified and designated. There is an imminent calling for a systematic summary of the known microorganisms and make appropriate revision of Chinese nomenclature what scientists have revealed, classified and Latinized. This paper tended to summarize the Chinese-Latin bilingual nomenclature for approximate more than 1 500 species in over 350 genera and more than 1 200 species in over 120 genera suffixed with -bacter and -bacterium, respectively, based on their characteristics and arrangement of biotope, morphology including motility, shape and dimension, biochemisty, and taxonomic domain position, i.e. Bacteria or Archaea. Expecting it contribute to promote the development of microorganism taxonomy in China and abroad, and to improve international communication and cooperation.

Abstract:Quorum sensing is a cell-cell signaling process that many bacteria use to regulate gene expression by synthesizing small signaling molecules called autoinducers as a function of the density of the population. Most autoinducers are species-specific, however, one autoinducer called autoinducer-2 (AI-2) is produced and detected by many species of bacteria and utilized in interspecies communication. Quantitative determination of AI-2 is essential for exploring the bacterial AI-2-related physiological and biochemical processes. However, there is no standardized method for the quantification of AI-2. Thus, this paper reviews the methods of determination of AI-2 and addresses the need in further research.

Abstract:Essential oils, a series of aromatic oily liquids extracted from aromatic plants, are fine natural antimicrobial materials. Essential oils have many advantages in the antimicrobial aspect: (1) have strong and broad range of antimicrobial activity; (2) have a fumigating characteristic and aromatic odor; (3) be natural and environmental friendly; (4) easy to be extracted from wide sources. Based on these advantages, essential oils have great potential applications in the antimicrobial field. In this paper, we overviewed the latest progress of researching about essential oils from several aspects, such as the distribution and chemical composition, the antibacterial and antifungal activity, as well as relationship between the chemical compositions and antimicrobial activity. This review could promote the application of essential oils in broad antimicrobial field and provide a reference for the scientists engaged in the research of essential oils.

Abstract:Nuclear energy plays an important role in relieving the energy shortage and reducing the emission of greenhouse gas, however, the adverse effect caused by radioactive wastes impedes the development of nuclear energy. Kineococcus radiotolerans is a gram positive bacterium isolated from nuclear waste polluted environment and can survive under harsh conditions, such as radiation, strong alkali, high salinity, drought, high concentration of mental ions, high osmotic pressure, and high chemical toxicity. It can be potentially used in environmental bioremediation and medical studies. The current status on its physicochemical characteristics, radio-resistance, anti-oxidation, resistance to chemical toxicity is reviewed in this paper.

Abstract:Klebsiella pneumoniae is an important opportunistic pathogen and the rate of its nosocomial infection rises continuously. It has brought difficulties to therapy. Efflux pumps’ overexpression has been recently recognized as one of the most important mechanisms of drug resistance displayed by K. pneumoniae. The most important developments were introduced in this review, including the latest progress on the drug resistant profile of K. pneumoniae caused by efflux pumps, and the molecular structure and genetic regulation of efflux pumps. The inhibitors of efflux pumps and the roles of traditional Chinese medicine on drug resistant K. pneumoniae were also adressed in this review to provide some guides to treat infectious diseases caused by drug resistant pathogens.

Abstract:Protein is one of the most important biological macromolecules. In the protein translocation system, many proteins, after being synthesized in the ribosome, will enter their corresponding subcellular organelles through the endoplasmic reticulum or plasma membrane to play a important role in biological functions. There are three pathways for protein secretion, which are Sec pathway, Tat pathway and SRP pathway. In this paper, we present a basic transport pathway of protein, and mainly introduce the translocation mediated by the signal recognition particle. We summarize the composition and function of the signal recognition particle and its receptor respectively, and also make a brief explanation about the regulation pathway. What’s more, we introduce the relevant YidC membrane protein family, and we also have a new insight into the existent of the signal recognition particle regulatory system.

Abstract:Recent development of molecular biology and high-throughput sequencing (next generation sequencing, NGS) technologies make our deeper understanding possible for the giant panda gut flora, both in the community structure and function. Studies have found that the giant panda’s intestinal flora plays an important role in the host immunity, digestion and metabolism, which could be affected by many factors including the digestive tract structure, diet, season and age. This article reviews the progress of intestinal bacterial community structure and biological characteristics of the giant panda, and discusses the future research directions.

Abstract:1,3-dihydroxyacetone (DHA) is a kind of important chemical raw materials and pharmaceutical intermediates. It is widely used in cosmetics, pharmaceutical, food and other fields. Therefore, it is important to carry out studies on the production of DHA. Biotransformation of glycerol to DHA is the main method for industrial production of DHA. However, there exists substrate and product inhibition, and dissolved oxygen limitation during the production process. In this paper, the progress of DHA biosynthetic pathway, strain improvement, common production process, separation and extraction methods are summarized. In order to improve the strain productivity, it is important to optimize the metabolic pathway and production process, simplify the separation and purification routes in the future.

Abstract:L-Arginine, a semi-essential amino acid, plays an important role in the metabolism of human life. It has a wide and expanding application in industry with a fast growing market demand. Currently, the main method of production of L-Arginine is microbial fermentation. To develop microbial strains with high productivity and stability, the most effective method is to optimize the L-Arginine producing strains. And fortunately, metabolic engineering method can be used to screen the efficient L-Arginine producing strains, and has obtained the certain success. In this mini-review, the metabolic pathway and regulatory mechanism of L-Arginine biosynthesis in microorganisms were analyzed, and the strategies for metabolic engineering the efficient L-Arginine producing strains were summarized．Furthermore, the prospects of future research about the stability of L-Arginine engineering strains and the expansions of substrate utilization were discussed.

Abstract:[Objective] One of the genetic manipulation restriction factors in Bacillus coagulansis the absence of an efficient and reproducible transformation method. This study optimized the concentrations of the osmoticums, sorbitol and mannitol, in the growth, electroporationand recovery media and other conditions to improved the transformation efficiency of B. coagulans P4-102B. [Methods] To optimize the conditions for electroproation of B. coagulans P4-102B, a shuttle vector for E. coli and B. coagulans pNW33N was used. Factors including growth phase, competent cell density, electroporation buffer, re-growth medium were investigated. [Results] Results showed that the electro-transformation efficiency under high osmolarity was higher than that under the low osmolarity and the stability of electro-transformation efficiency was enhance. The highest transformation efficiency of 2.7×102 cfu/μg DNA in strain P4-102B was obtained under the optimized conditions: growth OD600 0.8, electro-transformation buffer SMG [(0.5 mol/L sorbitol, 0.5 mol/L mannitol and glycerol 10% (w/v)], 1 mm cuvette, electro-transformation field strength 14 kV/cm and pulse constant for 5 ms, re-growth medium RGM (LB with 0.5 mol/L sorbitol and 0.38 mol/L mannitol). [Conclusion] High osmolarity improved the stabitity and reproducibility of electro-transformation and obtained a high electro-transformation efficiency.