BIOTECHNOLOGY & BIOTECHNOLOGICAL EQUIPMENT

Effect of hydrophilic polymers on the wettability, static and dynamic, of solid substrate covered by confluent monolayer of air-damaged SIRC cells
Eftimov P, Stefanova N, Lalchev Z and Georgiev GA
The aim of this study was to evaluate the possible implementation of hydrophilic polymers as recovery agents in air-damaged corneal cells. The sessile bubble technique was implemented to measure the wetting properties of four selected polymers: hydroxyethyl cellulose (HEC), sodium chondroitin sulphate (SCS), hydroxypropyl-methylcellulose (HPMC) and poloxamer F127 (PO12), at equilibrium conditions and in the case of advancing and receding contact angle. For testing the wetting properties of the polymers, glass slides covered with a confluent monolayer of Statens Seruminstitut rabbit cornea (SIRC) cells were used. HEC showed best properties for a broad concentration range, as the polymer showed capability to maintain low values of the static (equilibrium) contact angle (average static contact angle - 36.07˚, compared to average static compact angles of HPMC - 38.44˚, PO12 - 38.92˚ and SCS - 37.85˚), i.e. better wettability. Sessile bubble technique provides quick, relatively simple and reliable approach for testing surface properties of the listed polymers. The nature of the surface damage produced by the exposition of SIRC cells was used as a plausible model of evaporative dry eye syndrome, and thus the results may have clinical implementation.
Toxigenic profiles and trinucleotide repeat diversity of species isolated from banana fruits
Alghuthaymi MA and Bahkali AH
Infesting species isolated from banana fruit samples were identified and quantified by morphological, mycotoxicological and molecular tools. A total of 19 isolates were obtained: was most predominant (26%), followed by (16%), (16%), (10.5%), (10.5%), (10.5%) and (5%). Fumonisin B1, deoxynivalenol and zearalenone contents were assayed by high-performance liquid chromatography (HPLC). Seventeen isolates, belonging to , , , , , and spp., produced mycotoxins when cultured on rice medium. Fumonisin was produced by all of the studied isolates, except , at a concentration of over 1 μgmL. isolates 4 and 5 and isolate 3 were the most potent producers of deoxynivalenol. We compared the 19 isolates based on the bands amplified by 10 microsatellite primers. Of these, seven primers, (TCC)5, (TGG)5, (GTA)5, (ATG)5, (TAC)5, (TGC)5 and (TGT)5, yielded a high number of bands and different mean number of alleles. The similarity level between isolates was calculated using a simple matching coefficient. Dendrograms were constructed by the unweighted pair-group method with arithmetical averages (UPGMA). Two main clusters were observed. The interspecific genetic similarity between spp. isolates was between 40% and 58% and the intraspecific similarity from 58% to 100%, indicating a high degree of genetic diversity in the tested isolates. Some unexpected genetic similarities were observed among the isolates, indicating non-agreement between morphological and molecular identification of the isolates.
Severe pre-eclampsia complicated by HELLP syndrome alterations in the structure of the umbilical cord (morphometric and immunohistochemical study)
Balsak D, Togrul C, Ekinci C, Cavus Y, Tahaoglu AE, Deveci E, Gül T, Karaman E, Ekinci A and Sakar N
The aim of this study was to evaluate the morphometric and immunohistochemistry in umbilical cords from patients with severe pre-eclampsia with and without haemolysis, elevated liver enzymes and low platelets (HELLP) syndrome. The patient and control groups were similar according to baseline obstetric characteristics. White blood cell count in patients with HELLP syndrome and the control group was significantly increased among patients with HELLP syndrome ( < 0.001). Morphometric examination and endothelial core length were significantly different between the groups. In the umbilical cord cross-section of the HELLP group, endothelial cell degeneration in the vessel wall and basement membrane thickening were observed. In the muscle layer of blood vessels, the following disorders were found: increased collagen fibres in the muscle cell, hyperplasia and separation of muscle fibres as well as edema in the intermediate connective tissue. Immunohistochemical analysis showed that endothelial cells, basal membrane and fibroblast cells in the HELLP group expressed high levels of CD44. Vessel wall and amniotic epithelial basement membrane thickening were observed in the HELLP group. Matrix metalloproteinase 9 (MMP9) was expressed. Fibroblast and smooth muscle cells were fusiform and showed a positive reaction to immunohistochemical staining of -actin smooth muscle.
Distribution patterns of carbohydrates in murine glycocalyx
Pavlova V, Paunova-Krasteva T, Stoitsova S and Nikolova E
Enterocytes are unique cells governing an array of processes. They are covered by the gut glycocalyx, which is an extraneous carbohydrate-rich coat and an integral part of the plasma membrane. The intestinal glycocalyx and secreted mucins constitute a glycosylated milieu which has a number of physiological and protective functions. One of the important functions of the glycocalyx is its barrier function against microbial adherence to different membrane glycolipids. Thus, the glycocalyx is an important part of the mucosal immune system in newborns. The aim of our study was to identify the carbohydrates in the small bowel glycocalyx of Balb/c mice at different ages. We used plant lectins with different sugar specificities. Fluorescein-labelled lectins binding different carbohydrate moieties were detected using confocal laser scanning microscopy. Biotinilated lectins were used for transmission electron microscopy observations of the constituents of the gut glycocalyx at different periods of postnatal development in mice. Different carbohydrate moieties that were identified in the murine intestinal glycocalyx followed different distribution patterns and characteristics. Carbohydrates present on the mucus surface depended on tissue localization, cell type and stage of development. The distribution and mucins glycosylation could be of interest in analysing the response of the mucosal barrier to intestinal pathogens causing infection or inflammation.
Frequency of the common promoter polymorphism in a population from central Bulgaria
Tacheva T, Chelenkova P, Dimov D, Petkova R, Chakarov S and Vlaykova T
Matrix metalloproteinases (MMPs) are a family of highly homologous extracellular Zn-dependent endopeptidases, also known as matrixins. MMP-2 (gelatinase A) and MMP-9 (gelatinase B) are considered to play a key role in a variety of physiological processes as well as in the development and progression of a vast majority of pathological conditions. Most of the genes encoding MMPs, including MMP-2, are highly polymorphic. One of the single nucleotide polymorphisms with functional activity in the promoter region of is the transition (rs243865). The aim of the present study was to evaluate the genotype and allele frequencies of the common promoter polymorphism in in 75 individuals from central Bulgaria and to compare our results with those of other population studies. We found that 76.0% of the randomly enrolled individuals are carriers of the genotype, 17.3% of , and 6.7% of the genotype. The minor allele frequency (MAF) was 15.3%. Interestingly, the obtained genotype frequencies appeared to differ from those of some other Caucasian populations (USA - 55/38/7, MAF 26%; The Netherlands - 52.8/40.5/6.7, MAF 26.9%; Austria - 55.6/35.5/8.9, MAF 27.2%), but were closer to the values of the reported global genotype distribution (75.3/21.3/3.4, MAF 14%).
Evaluation of dentinal defect formation after root canal preparation with two reciprocating systems and hand instruments: an study
Helvacioglu-Yigit D, Aydemir S and Yilmaz A
The purpose of this study was to evaluate the presence of dentinal defects after root canal preparation with hand instruments and two different reciprocating instruments. Sixty freshly extracted mandibular incisor teeth were selected for this study. On the basis of root length, mesiodistal and buccolingual dimensions, the teeth were allocated into three identical experimental groups ( = 15) and one control group ( = 15). The teeth in the control group were left unprepared. The other groups were: stainless steel hand instruments, WaveOne® Primary instruments and RECIPROC® R25 instruments. The reciprocating instruments were used with a reciprocating gentle in-and-out motion in a torque-limited electric motor at the appropriate preset mode. Horizontal sections were made 3, 6 and 9 mm from the apex. Samples were stained with methylene blue and viewed through a stereomicroscope. The presence of dentinal defects (fractures, incomplete cracks and craze lines) and their locations were investigated by two endodontists. These data were analysed statistically by Fisher's exact and chi-square tests. No defects were observed in the unprepared group. All instruments caused dentinal defects, with no significant differences between the instrument systems. All experimental groups demonstrated significantly more defects at the 3-mm level in comparison with the unprepared group ( = 0.032). At the other levels, there was no significant difference between the experimental groups and the control group. The use of hand or reciprocating instruments could induce the formation of dentinal defects during root canal preparation.
Resin cementation of zirconia ceramics with different bonding agents
Tanış MÇ, Akay C and Karakış D
The aim of this study was to evaluate the effects of sandblasting and different chemical bonding agents on shear bond strength of zirconia and conventional resin cement. In this study, 35 zirconia specimens were treated as follows: Group I: control; Group II: sandblasting; Group III: sandblasting + Monobond S; Group IV: sandblasting + Monobond Plus; Group V: sandblasting + Z-Prime Plus. The specimens in each group were bonded with conventional composite resin cement Variolink II. After cementation, specimens were stored in distilled water (at 37 °C) for 24 h and shear test was performed. The highest shear bond strength values were observed in Groups IV and V. The lowest shear bond strength values were observed in Group I. Using 10-methacryloyloxy-decyl dihydrogenphosphate monomer-containing priming agents, e.g. Monobond Plus and Z-PRIME Plus, combined with sandblasting can be an effective method for resin bonding of zirconia restorations.
De novo transcriptome analysis of a medicinal fungi and identification of SSR markers
Huang Y, Wu X, Jian D, Zhan Y and Fan G
The aim of this study was to facilitate gene discovery for functional genome studies and to identify simple sequence repeat (SSR) markers for molecular-assisted selection in . The transcriptome of was sequenced using а high-throughput RNA sequencing system - the Illumina Hiseq 2000. A total of 16,383,818 clean sequencing reads, 35,532 contigs and 25,811 unigenes were postulated. Based on similarity searches with known proteins, 19,350 genes (74.97% of the unigenes) were annotated. In the present research, 19,266, 10,978 and 7831 unigenes were mapped in Nr, Swiss-Prot and clusters of orthologous groups (COG) classifications, respectively. Of all unigenes, 6845 were categorized into three functional groups, namely biological process, cellular components and molecular function and 11,088 were annotated to 108 pathways by searching the Kyoto Encyclopedia of Genes and Genomes pathway database. A total of 1129 SSRs were identified in these unigenes. In addition, 23 candidate genes, potentially involved in sterol biosynthesis, were identified and were worthy of further investigation.
Optimization of carbon source and glucose feeding strategy for improvement of L-isoleucine production by
Wang J, Wen B, Xu Q, Xie X and Chen N
Fed-batch cultivations of L-isoleucine-producing TRFP (SG, -ABA, with a pTHR101 plasmid containing a thr operon and ilvA) were carried out on different carbon sources: glucose, sucrose, fructose, maltose and glycerol. The results indicated that sucrose was the best initial carbon source for L-isoleucine production and then sucrose concentration of 30 g·L was determined in the production medium. The results of different carbon sources feeding showed that the glucose solution was the most suitable feeding media. The dissolved oxygen (DO) of L-isoleucine fermentation was maintained at 5%, 15% and 30% with DO-stat feeding, respectively. The results indicated that when the DO level was maintained at 30%, the highest biomass and L-isoleucine production were obtained. The accumulation of acetate was decreased and the production of L-isoleucine was increased markedly, when the glucose concentration was maintained at 0.15 g·L by using glucose-stat feeding. Finally, the glucose concentration was maintained at 0.10 g·L and the DO level was controlled at approximately 30% during the whole fermentation period, using the combined feeding strategy of glucose-stat feeding and DO feedback feeding. The acetate accumulation was decreased to 7.23 g·L, and biomass and production of L-isoleucine were increased to 46.8 and 11.95 g·L, respectively.
Relationship between vitamin D status and immunosuppressive therapy in kidney transplant recipients
Filipov JJ, Zlatkov BK, Dimitrov EP and Svinarov D
There is a growing body of evidence for the protective role of vitamin D in diabetes mellitus (DM), infection, cancer, cardiovascular disease, immune disorders and kidney function. Considering the reported high prevalence of vitamin D insufficiency among kidney transplant recipients (KTRs), the aim of this study was to assess the influence of immunosuppressive therapy and other factors on vitamin D status in such patients. The study included 289 KTRs (189 males and 100 females) who consented to participate. The first test for 25-hydrohyvitamin D [25(OH)D] was performed by a validated liquid chromatography-tandem mass spectrometry method. Influence of immunosuppressive drugs and previously reported predictors on vitamin D status was assessed by descriptive statistics, univariate and multivariate regression. Our results showed that only 53 patients (18.34%) of the studied KTRs were vitamin D sufficient. In addition to a well expected positive association between serum 25(OH)D and summer blood sampling ( < 0.05) and inverse relationship between vitamin D status and DM, gender (female) and body mass index, serum 25(OH)D was found to be inversely associated with calcineurin inhibitors (CNI) ( < 0.05) and unaffected by other immunosuppressive agents. Our study demonstrated high prevalence of vitamin D insufficiency after kidney transplantation in the studied cohort of patients. Apart from female gender, winter months, DM and overweight, the use of CNI could be considered an additional significant predictor of lower 25(OH)D in Bulgarian KTRs.
Research into acetone removal from air by biofiltration using a biofilter with straight structure plates
Baltrėnas P, Zagorskis A and Misevičius A
The biological air treatment method is based on the biological destruction of organic compounds using certain cultures of microorganisms. This method is simple and may be applied in many branches of industry. The main element of biological air treatment devices is a filter charge. Tests were carried out using a new-generation laboratory air purifier with a plate structure. This purifier is called biofilter. The biofilter has a special system for packing material humidification which does not require additional energy inputs. In order to extend the packing material's durability, it was composed of thermally treated birch fibre. Pollutant (acetone) biodegradation occurred on thermally treated wood fibre in this research. According to the performed tests and the received results, the process of biodestruction was highly efficient. When acetone was passed through biofilter's packing material at 0.08 m s rate, the efficiency of the biofiltration process was from 70% up to 90%. The species of bacteria capable of removing acetone vapour from the air, i.e. (, ), (, ), () and sp., was identified in this study during the process of biofiltration. Their amount in the biological packing material changed from 1.6 × 10 to 3.7 × 10 CFU g.
Effect of BMP-6 on development and maturation of mouse preantral follicles
Wang X, Su L, Pan X, Yao J, Li Z, Wang X and Xu B
The aim of this study was to investigate the effect and mechanism of bone morphogenetic protein-6 (BMP-6) on the growth and maturation of mouse follicles . Preantral follicles isolated from mice were incubated with recombinant human BMP-6 (rhBMP-6) before analysis. BMP-6 expression was detected by immunofluorescence and western blot. Maturation of oocytes was observed microscopically. Estradiol (E) and progesterone (P) levels were measured by enzyme-linked immunosorbent assay. Expression of steroidogenesis-related genes was detected by reverse transcription quantitative polymerase chain reaction. There was a marked increase in the preantral follicles maturation in cells incubated with 50 ng/mL of rhBMP-6 for eight days, compared with the control. The levels of E, P and steroidogenesis-related genes were also significantly increased in granulosa cells and theca cells cultured for 6, 10 and 11 days, respectively. Conversely, the preantral follicle maturing rate was remarkably decreased in cells incubated with 50 ng/mL of rhBMP-6 for day 11, accompanied with reduction in E, P levels and steroidogenesis-related genes levels. Meanwhile, compared with the control, the maturing rate was not significantly different in cells incubated with 100 ng/mL of rhBMP-6 for day 8 or day 11. However, the E levels and its relevant regulation gene expression all increased significantly, while the P content and its relevant regulation gene expression decreased. The results indicate that BMP-6 can promote the maturation of preantral follicles in a concentration and time-dependent manner and may play a role in the regulation of steroid hormone synthesis and/or secretion.
The positive effects of Mn on nitrogen use and surfactin production by ATCC 21332
Huang X, Liu J, Wang Y, Liu J and Lu L
Surfactin, one of the most effective biosurfactants, has great potential in commercial applications. Studies on effective methods to reduce surfactin's production cost are always a hotspot in the research field of biosurfactants. The aim of this study was to reveal the role of Mn in promoting the biosynthesis of surfactin by ATCC 21332, which could arise more targeted suggestions on surfactin yield promotion. In this study, was cultivated in media containing different Mn concentrations. The obtained results showed that the yield of surfactin gradually increased upon Mn addition (0.001 to 0.1 mmol/L) and achieved the maximal production of 1500 mg/L, which reached 6.2-fold of the yield obtained in media without Mn addition. Correspondingly, the usage ratios of ammonium nitrate were improved. When the Mn concentration was higher than 0.05 mmol/L, nitrate became the main nitrogen source, instead of ammonium, indicating that the nitrogen utilization pattern was also changed. An increase in nitrate reductase activity was observed and the increase upon Mn dosage had a positive correlate with nitrate use, and then stimulated secondary metabolic activity and surfactin synthesis. On the other hand, Mn enhanced the glutamate synthase activity, which increased nitrogen absorption and transformation and provided more free amino acids for surfactin synthesis.
Optimization of lipase production on agro-industrial residue medium by (NRLL B-2641) using response surface methodology
Tanyol M, Uslu G and Yönten V
The aim of our research was to explore the most cost-efficient and optimal medium composition for the production of lipase from (NRLL B-2641) culture grown on sunflower oil cake (SuOC) by applying response surface methodology (RSM). The oil cake was used instead of carbon sources. Peptone, ammonium sulphate and the carbon source (SuOC) were the most important factors as it is obligatory for microbial growth. Subsequently, the optimum values for the carbon source, peptone and ammonium sulphate were found to be 11.10% (w/v), 1.18% (w/v) and 0.83% (w/v), respectively. Experiments carried out under optimum conditions revealed a maximum lipase activity of 10.8 U mL, which was achieved after 48 h of fermentation. The obtained results were finally verified with batch experiments carried out under the optimum conditions evaluated and it was demonstrated that the SuOC from agro-industrial residue as substrates can be used as an inexpensive base (carbon source) for the production of lipase by . (NRLL B-2641).
Subclinical hypothyroidism: association with cardiovascular risk factors and components of metabolic syndrome
Pesic MM, Radojkovic D, Antic S, Kocic R and Stankovic-Djordjevic D
The aim of this cross-sectional study was to evaluate the cardiovascular risk in patients with subclinical hypothyroidism (SH) and metabolic syndrome (MetS) components. The study included 60 patients with SH and a control group of 60 healthy volunteers, gender and age matched, with normal thyroid-stimulating hormone (TSH) and free thyroxin (FT4) concentration. The following measurements were made in all participants: TSH, FT4, thyroid peroxidase antibodies, anti-thyroglobulin antibodies, body mass index (BMI), waist circumference, blood pressure, fasting plasma glucose, total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides (TG), TC/HDL cholesterol and LDL/HDL cholesterol ratio, basal insulin level and homeostatic model assessment insulin resistance (HOMA-IR) index. MetS was diagnosed according to the National Cholesterol Education Program Adult Treatment Panel III criteria. The results showed that the following indices were statistically significantly higher in the SH group: BMI ( < 0.05), diastolic blood pressure ( < 0.001), TC ( < 0.05), TG ( < 0.05) and basal insulin level ( < 0.05). Although MetS parameters were present in a higher per cent in the SH group, there was a significantly higher number of patients with hypertension and decreased HDL cholesterol ( < 0.05). More frequently, MetS was diagnosed in SH patients (46.67%) than in the control group (33.33%), although the difference was not statistically significant. These results indicated that the traditional cardiovascular risk factors were more frequently present in SH patients as compared to euthyroid participants. Our results did not confirm significantly higher presence of MetS in SH patients in comparison with euthyroid respondents.
Effect of cyprodinil and fludioxonil pesticides on bovine liver catalase activity
Karadag H and Ozhan F
This study investigated if the use of the pesticides cyprodinil and fludioxonil produced an inhibitory effect on the bovine liver catalase (CAT) activity. It was documented that the activity of the enzyme decreased with increasing concentrations of cyprodinil and fludioxonil from 0 to 500 ppm. At pesticide concentrations of 250 and 500 ppm, the activity of CAT remained unchanged and passed to a steady state. The exposure to cyprodinil in concentrations of 10, 50, 100, 250 and 500 ppm, led to a decrease in the per cent of the CAT enzyme activity calculated as 45.4, 68.0, 73.0, 77.8 and 77.4, respectively. Similarly, the exposure to fludioxonil in concentrations of 10, 50, 100, 250 and 500 ppm, produced the following percentage decrease in the CAT enzyme activity: 20.0, 30.8, 42.8, 46.3 and 45.9, respectively. Cyprodinil inhibited CAT competitively, whereas the mechanism of fludioxonil inhibition over the enzyme was non-competitive.
Degradation kinetics and pathway of phenol by and species
Hasan SA and Jabeen S
This article elucidates that strain (IES--1) is a versatile toxic organic compound degrader. With the degradation of malathion and cypermethrin (studied by other researchers previously), this strain was able to degrade phenol. Two other indigenous soil flora (i.e., sp. (IES-S) and (IES-B)) were also found to be potential phenol degraders. Phenol was degraded with Monod kinetics during growth in nutrient broth and mineral salts medium. Before entering into the growth inhibition phase, strains IES--1, IES-S and IES-B could tolerate up to 400, 700 and 500 mg/L phenol, respectively, when contained in nutrient broth. However, according to the Luong-Levenspiel model, the growth of strains IES--1, IES-S and IES-B would cease at 2000, 2174 and 2190 mg/L phenol, respectively. Strain IES--1 degraded 700, 900 and 1050 mg/L phenol contained in mineral salts medium with the specific rates of 0.034, 0.075 and 0.021 h, respectively. All these strains grew by making clusters when exposed to phenol in order to prevent damages due to high substrate concentration. These strains transformed phenol into catechol, which was then degraded via -cleavage pathway.
LAU 13: a new source of keratinase and its multi-functional biocatalytic applications
Lateef A, Adelere IA and Gueguim-Kana EB
A newly isolated bacterium identified as based on biochemical tests and 16S rRNA analysis and its mutant variant created by exposure to ultraviolet radiation at 254 nm were investigated for keratinolytic activity. The wild-type strain produced 35.4-50.4 U/mL keratinase over a period of 120 h, while the mutant one yielded 64.4-108.5 U/mL keratinase for the same period of 120 h. The optimal conditions for the enzyme activities were pH 7.5 and 40 °C. The mutant and wild-type strain keratinases retained 59% and 54% of their activity after 12 h pretreatment at 40 °C, and 64% and 60% of their activity after 12 h at pH 7.5, respectively. The keratinases showed high substrate specificity for feathers, but low specificity for human and bovine hairs. The enzymes were activated by Na, Ca, Fe and Mg. However, while Mn activated the enzyme from the mutant strain, it inhibited that of the wild type. The mutant and wild-type strain completely degraded whole chicken feathers after 6 and 9 days at 30 ± 2 °C, and also completely dehaired goat skin within 12 and 16 h, respectively, without damage to the skin. Similarly, remarkable destaining of blood-stained cloth occurred within 2-3 h. The obtained results showed an improvement in the properties of the mutant strain for use of the micro-organism or its enzyme as biocatalysts.
Increasing plasmid-based DNA vaccine construct (16 kb pSVK-HBVA) production in XL10-Gold through optimization of media component
Wang Y, Zhang L, Zhang W, Wu H, Zhu XM, Xu YJ, Yan JQ and Yu JY
At present, there are production processes to produce protein by () fermentation. Research on the design and optimization of the plasmid fermentation medium, however, is less advanced. The fermentation medium that is optimized for plasmid DNA production is different from the medium that is optimized for protein production. So, establishing a scientific and rational method to optimize the fermentation medium used for plasmid production is very important. Previously, our laboratory developed a novel therapeutic DNA vaccine (named pSVK-HBVA) for hepatitis B based on the alphavirus replicon, and found that XL10-Gold was the optimal host strain for the production of plasmid pSVK-HBVA. The aim of this study was to establish a scientific and rational method to optimize the fermentation medium used for plasmid production, and investigate the effect of growth medium composition on the production of plasmid pSVK-HBVA harboured in XL10-Gold, as well as to optimize the medium composition. The one-factor-at-a-time experiments demonstrated that Luria-Bertani (LB) was the optimal basic medium. The optimal carbon source and nitrogen source were glycerol and home-made proteose peptone, respectively. Based on the Plackett-Burman (PB) design, proteose peptone, glycerol and NHCl were identified as the significant variables, which were further optimized by the steepest ascent (descent) method and central composite design. Growth medium optimization in 500-mL shake flasks by response surface methodology resulted in a maximum volumetric yield of 13.61 mg/L, which was approximately 2.5 times higher than that obtained from the basic medium (LB).
Complementary annealing mediated by exonuclease: a method for seamless cloning and conditioning site-directed mutagenesis
Sun S, Huang H, Qi YB, Qiu M and Dai ZM
Traditional cut-paste DNA cloning is often limited by the availability of restriction enzyme sites. Here, we described the complementary annealing mediated by exonuclease (CAME), in which the insert or vector fragment is amplified to carry sequences complementary to the other, and both fragments are modified by exonuleases to create directional single-stranded overhangs. The two recessed DNA fragments are joined through complementary strand annealing. The CAME is highly efficient for cloning the DNA of at least 12 kb and single DNA fragment out of a complex DNA sample. Moreover, the application of CAME greatly improved the efficiency of site-directed mutagenesis.
Probiotic and cultural characteristic of strain 4/13 of human origin
Baltova K and Dimitrov Z
within the group is a major species in the human microflora. The potential probiotic properties of a strain of human origin were evaluated. Out of 17 studied strains, 4/13 showed the highest immunomodulatory effect (induction of interferon gamma measured by sandwich enzyme-linked immunosorbent assay) in Balb/c mouse splenocytes and the highest rate of adhesion to Caco-2 human epithelial cells. The strain also reduced the concentration of cholesterol in the growth medium by 65% as compared with the initial concentration (measured spectrophotometrically). These probiotic properties indicate that 4/13 could prove an attractive concentrated adjunct monoculture in the production of new functional foods. To obtain a freeze-dried bacterial concentrate from 4/13, the influence of different culture media, temperatures and pH values on the accumulation of cell biomass was studied. Yoghurt samples were produced using a classical fermentation technology. Freeze-dried concentrated monoculture of 4/13 with over 1 × 10 CFU/g viable cells was added as an adjunct culture together with a starter. The viable 4/13 cells remained above the critical value of 10 CFU/g during storage at 5 °C for the entire 20-day period. Organoleptic tests did not reveal any adverse change in the product taste and aroma of yoghurt samples at the 20th day. In conclusion, 4/13 was selected as having suitable probiotic and cultural characteristics for production of fermented milk products with high nutritional and biological value.