Synergistic efficacy of ultrasound and ammonium persulfate in inactivating Escherichia coli O157:H7 in buffered peptone water and orange juice.

This study investigated the synergistic effects of ammonium persulfate (PS) and ultrasound (US) on the inactivation of Escherichia coli O157:H7 in buffered peptone water (BPW) and orange juice products. A comprehensive assessment of PS concentrations ranging from 1 to 300 mM, considering not only the statistical significance but also the reliability and stability of the experimental outcomes, showed that 150 mM was the optimal PS concentration for the inactivation of E. coli O157:H7. Additionally, US output intensities varying from 30 % to 60 % of the maximum US intensity were evaluated, and 50 % US amplitude was found to be the optimal US condition. A 50 % amplitude setting on the sonicator corresponds to half of its maximum displacement, approximately 60 µm, based on a maximum amplitude of 120 µm. The inactivation level of E. coli O157:H7 was significantly enhanced by the combined treatment of PS and US, compared to each treatment of PS and US alone. In the BPW, a 10-min treatment with the combination of PS and US resulted in a significant synergistic inactivation, achieving up to a log reduction of 3.86 log CFU/mL. Similarly, in orange juice products, a 5-min treatment with the combination of PS and US yielded a significant synergistic inactivation, with a reduction reaching 5.90 log CFU/mL. Although the treatment caused a significant color change in the sample, the visual differences between the treated and non-treated groups were not pronounced. Furthermore, the combined treatment in orange juice demonstrated significantly enhanced antimicrobial efficacy relative to BPW. Despite identical 5-min treatment periods, the application in orange juice resulted in a substantially higher log reduction of E. coli O157:H7, achieving 7.16 log CFU/mL at a reduced PS concentration of 30 mM, whereas the same treatment in BPW yielded only a 2.89 log CFU/mL reduction at a PS concentration of 150 mM, thereby highlighting its significantly superior antimicrobial performance in orange juice. The mechanism underlying microbial inactivation, induced by the combined treatment of PS and US, was identified as significant cell membrane damage. This damage is mediated by sulfate radicals, generated through the sono-activation of persulfate. In addition, the low pH of orange juice, measured at 3.7, is likely to have further deteriorated the E. coli O157:H7 cells compared to BPW (pH 7.2), by disrupting their cell membranes, proton gradients, and energy metabolism. These findings underscore the effectiveness of PS and US integration as a promising approach for non-thermal pasteurization in the food industry. Further research is needed to optimize treatment parameters and fully explore the practical application of this technique in large-scale food processing operations. Sensory evaluation and nutritional assessment are also necessary to address the limitations of PS.

Aspergillus oryzae-Fermented Wheat Peptone Enhances the Potential of Proliferation and Hydration of Human Keratinocytes through Activation of p44/42 MAPK.

Identifying materials contributing to skin hydration, essential for normal skin homeostasis, has recently gained increased research interest. In this study, we investigated the potential benefits and mechanisms of action of Aspergillus oryzae-fermented wheat peptone (AFWP) on the proliferation and hydration of human skin keratinocytes, through in vitro experiments using HaCaT cell lines. The findings revealed that compared to unfermented wheat peptone, AFWP exhibited an improved amino acid composition, significantly (p < 0.05) higher DPPH scavenging capability and cell proliferation activity, and reduced lipopolysaccharide-induced NO production in RAW 264.7 cells. Furthermore, we separated AFWP into eleven fractions, each ≤2 kDa; of these, fraction 4 (AFW4) demonstrated the highest efficacy in the cell proliferation assay and was found to be the key component responsible for the cell proliferation potential and antioxidant properties of AFWP. Additionally, AFW4 increased the expression of genes encoding natural moisturizing factors, including filaggrin, transglutaminase-1, and hyaluronic acid synthase 1-3. Furthermore, AFW4 activated p44/42 MAPK, but not JNK and p38 MAPK, whereas PD98059, a p44/42 MAPK inhibitor, attenuated the beneficial effects of AFW4 on the skin, suggesting that the effects of AFW4 are mediated via p44/42 MAPK activation. Finally, in clinical studies, AFW4 treatment resulted in increased skin hydration and reduced trans-epidermal water loss compared with a placebo group. Collectively, these data provide evidence that AFW4 could be used as a potential therapeutic agent to improve skin barrier damage induced by external stresses.

Improvement of tacrolimus production in Streptomyces tsukubaensis by mutagenesis and optimization of fermentation medium using Plackett-Burman design combined with response surface methodology.

OBJECTIVE: This study was conducted to enhance the production of tacrolimus in Streptomyces tsukubaensis by strain mutagenesis and optimization of the fermentation medium. RESULTS: A high tacrolimus producing strain S. tsukubaensis FIM-16-06 was obtained by ultraviolet mutagenesis coupled with atmospheric and room temperature plasma mutagenesis.Then, nine variables were screened using Plackett-Burman experimental design, in which soluble starch, peptone and Tween 80 showed significantly affected tacrolimus production. Further studies were carried out employing central composite design to elucidate the mutual interaction between the variables and to work out optimal fermentation medium composition for tacrolimus production. The optimum fermentation medium was found to contain 61.61 g/L of soluble starch, 20.61 g/L of peptone and 30.79 g/L of Tween 80. In the optimized medium, the production of tacrolimus reached 1293 mg/L in shake-flask culture, and reached 1522 mg/L while the scaled-up fermentation was conducted in a 1000 L fermenter, which was about 3.7 times higher than that in the original medium. CONCLUSIONS: Combining compound mutation with rational medium optimization is an effective approach for improving tacrolimus production, and the optimized fermentation medium could be efficiently used for industrial production.

Waste soybean frying oil for the production, extraction, and characterization of cell-wall-associated lipases from Yarrowia lipolytica.

The lipolytic yeast Yarrowia lipolytica produces cell-wall-associated lipases, namely Lip7p and Lip8p, that could have interesting properties as catalyst either in free (released lipase fraction-RLF) or cell-associated (cell-bound lipase fraction-CBLF) forms. Herein, a mixture of waste soybean frying oil, yeast extract and bactopeptone was found to favor the enzyme production. Best parameters for lipase activation and release from the cell wall by means of acoustic wave treatment were defined as: 26 W/cm2 for 1 min for CBLF and 52 W/cm2 for 2 min for RLF. Optimal pH and temperature values for lipase activity together with storage conditions were similar for both the free enzyme and cell-associated one: pH 7.0; T = 37 °C; and > 70% residual activity for 60 days at 4, - 4 °C and for 15 days at 30 °C.

Peptone from casein, an antagonist of nonribosomal peptide synthesis: a case study of pedopeptins produced by Pedobacter lusitanus NL19.

Novel natural products are urgently needed to address the worldwide incidence of bacterial resistance to antibiotics. Extreme environments are a major source of novel compounds with unusual chemical structures. Pedobacter lusitanus NL19 is a new bacterial species that was isolated from one such environment and which produces compounds with potent activity against relevant microorganisms in the clinical, food, veterinary and aquaculture areas. The production of antimicrobials by P. lusitanus NL19 was identified in tryptic soy agar (TSA), but not in its equivalent broth (TSB). It was observed that in TSB medium a high concentration of casein peptone (PC) repressed the production of antibacterial compounds. HPLC, MS and MS/MS spectra with de novo sequencing revealed that the bioactivity of P. lusitanus NL19 was due to the production of pedopeptins. Hence, biosynthesis of pedopeptins is inhibited by high concentrations of PC in the broth medium. Furthermore, a nonribosomal peptide synthetase (NRPS) gene cluster was identified in the genome of NL19 encoding the biosynthesis of the peptides. qPCR analysis confirmed that the transcription of these genes is repressed in cells cultivated in high concentrations of PC. It is shown that pedopeptins are nonribosomal peptides with a broad-spectrum activity, including against Gram-positive and Gram-negative bacteria and yeasts.

Bacterial cellulose as an oleaginous yeast cell carrier for soybean oil refinery effluent treatment and pyrolysis oil production.

Bacterial cellulose produced from soybean oil refinery effluent is a good immobilization carrier because of the large pores in its fiber network, its high water-holding capacity, and its good biocompatibility. In this study, it was applied to immobilization of oleaginous yeasts for treating soybean oil refinery effluent. The immobilization percentage reached 50%, and the removal of chemical oxygen demand and oil content reached 92.1% and 93.1%, respectively, during dynamic immobilization using a mass percentage of bacterial cellulose of 30% and an immobilization time of 24 h, which were significantly higher than those of free oleaginous yeasts or yeasts immobilized by bacterial cellulose from rich medium. The immobilized oleaginous yeasts facilitated the recovery of the yeasts and effectively treated three batches of soybean oil refinery effluent. The immobilized oleaginous yeasts recovered after soybean oil refinery effluent treatment were pyrolyzed to produce bio-oil, which contributed to more alkanes and a higher calorific value of bio-oil in the pyrolysis products as compared to those of free oleaginous yeasts. As bacterial cellulose used as an oleaginous yeast cell carrier is produced from soybean oil refinery effluent, no waste of immobilization materials is involved and an efficient waste-into-oil bioprocess is developed.

Evaluation of peptones from chicken waste as a nitrogen source for micro-organisms.

In this study, chicken peptone was produced by hydrolysing inedible parts derived from chickens using endo-protease and exo-protease. The usefulness of chicken peptone as a nutrient source for bacteria was evaluated in comparison with other commercially produced peptones (animal, soy and casein-derived peptone). Escherichia coli and Bacillus subtilis were used as test strains to determine the effect of peptones from different sources on their growth ability. Both bacteria were successfully cultured in chicken peptone solution, which is similar to peptone solution containing commercial peptones apart from animal peptone. In chemical analysis, chicken peptone contained 12·0% nitrogen; this was similar to the nitrogen content from other commercial peptone sources, except for the 9·0% nitrogen found in soy peptones. The molecular weight of the peptone was determined by gel filtration chromatography, and those of all peptone, except animal-derived peptone, were found to be <5000 Da. In addition, when B. subtilis was cultured in a medium containing chicken peptone, it was shown that the protease activity was highest as compared with other commercial peptones. From these results, it is suggested that chicken peptone can be utilized for microbial culture, and this is an effective method to reuse chicken waste.

Biotechnological Valorization of Food Marine Wastes: Microbial Productions on Peptones Obtained from Aquaculture By-Products.

Based on a biotechnological strategy, in the present work several peptones are produced from the Alcalase hydrolysis (0.1-0.2% v/w, 56-64 °C, pH 8.27-8.98, 3 h) and thermal processing (105 °C, 60 min) of wastes generated from the industrial processing of turbot, salmon, trout, seabream and seabass. These peptones were included (in the range of 2.6-11 g/L of soluble protein) as main source of organic nitrogen (protein substrates) in low-cost media for the culture of lactic acid bacteria (LAB), marine probiotic bacteria (MPB) and ubiquitous Gram+ bacteria. In most cases, batch fermentations conducted in aquaculture peptone media led to the best growth, metabolic productions and yields. Nevertheless, no significant differences between aquaculture peptones and commercial media were generally observed. Kinetic parameters from a logistic equation and used for cultures modeling were applied with the purpose of comparing the bioproduction outcomes. In economical terms, the validity of the aquaculture peptones as substitutives of the peptones (meat extract, casitone, etc.) from commercial media was also compared. The decreasing of the costs for LAB bioproductions ranged between 3-4 times and the growth costs of MPB and Gram+ bacteria were improved more than 70 and 15 times, respectively, in relation to those found in control commercial media.

Optimization of extracellular lipase production by halotolerant Bacillus sp. VITL8 using factorial design and applicability of enzyme in pretreatment of food industry effluents.

The effect of macro and micronutrients of media components on lipase production by Bacillus sp. VITL8 was investigated using classical as well as statistical methods. Initially, the carbon source, nitrogen source, inducer and metal ions that affect lipase production were selected using the classical approach. Subsequently, selected nutrients along with other key factors (such as pH, agitation rate, gum acacia and tween 80) were investigated using Placket Burman design. Finally, three significant factors, viz., olive oil, peptone and tween 80 were studied using a 22 full factorial central composite design. Under optimized condition [6% (v/v) of olive oil, 0.7% peptone, 0.9% tween 80 and 25 h of incubation], the enzyme production was found to be 2.2 times higher with an overall enzyme production of 325.0 ± 1.4 U mL-1. Laboratory scale experiment proved that the enzyme could be utilized for pretreatment of food industry effluent rich in fat and oil (dairy, bakery and poultry). The enzyme was capable of hydrolyzing more than 50% of the initial fat present in all these effluents and enabled the reduction in the levels of biological oxygen demand (BOD) and chemical oxygen demand (COD) of the effluent samples. The study thus reveals the utility of the lipase produced by the halotolerant bacterium Bacillus sp. VITL8 in the pretreatment of industrial effluents contaminated with oil and fat.HighlightsLipase production was enhanced by 2.2-fold using statistical methodsOne of the few reports on lipase production by a halotolerant bacterium, especially by Bacillus sp.Production of 325.0 ± 1.4 U mL-1 lipase within 25 h by a halotolerant bacteriumPretreatment of food industry effluents using Bacillus sp. VITL8 lipaseImprovement in effluent quality within 8 h of treatment.

Enhancing nitrobenzene biodegradation in aquatic systems: Feasibility of using plain soil as an inoculant and effects of adding ascorbic acid and peptone.

Nitrobenzene (NB) is recalcitrant to microbial biodegradation due to the electron-deficient character of the nitro group (NO2-). Prior work has found that the reductant could enhance NB biodegradation by providing excess electron donors. However, the existing theory couldn't explain the increase-and-decrease pattern of the NB biodegradation rate with an increase in a reductant concentration. Our results suggest that the reductant affects NB biodegradation by two mechanisms: the available electron donors and the stimulation or inhibition of biomass growth, which are linked by a pseudo-first-order reaction kinetics. In addition, the results showed that directly inoculating the plain soil into the aquatic system and then allowing the synergistic effect of the organic reductant (ascorbic acid) and the substrate (peptone) enhance NB biodegradation. Employing the new method, 200 mg L-1 NB was transformed in 72 h. GC-MS analysis detected two novel intermediate metabolites, indicating that NB was degraded into aniline and further transformed into acetanilide and 9-octadecenamide before its mineralization. This study sheds light on how to exploit the synergistic effects of the availability of excess electron donors and biomass growth by controlling the reductant and a substrate in the right concentration range (e.g., ascorbic acid < 0.8 mgL-1 + peptone).

Tryptone-stabilized gold nanoparticles induce unipolar clustering of supernumerary centrosomes and G1 arrest in triple-negative breast cancer cells.

Gold nanoparticles of different sizes, shapes, and decorations exert a variety of effects on biological systems. We report a novel mechanism of action of chemically modified, tryptone-stabilized gold nanoparticles (T-GNPs) in the triple-negative breast cancer (TNBC) cell line, MDA-MB-231. The T-GNPs, synthesized using HAuCl4.3H2O and tryptone and characterized by an assortment of spectroscopy techniques combined with high-resolution electron microscopy, demonstrated strong antiproliferative and anti-clonogenic potential against MDA-MB-231 cells, arresting them at the G1 phase of the cell cycle and promoting apoptosis. The molecular mechanism of action of these particles involved induction of unipolar clustering and hyper amplification of the supernumerary centrosomes (a distinctive feature of many tumour cells, including TNBC cells). The clustering was facilitated by microtubules with suppressed dynamicity. Mass spectrometry-assisted proteomic analysis revealed that the T-GNP-induced G1 arrest was facilitated, at least in part, by downregulation of ribosome biogenesis pathways. Due to the presence of supernumerary centrosomes in many types of tumour cells, we propose chemical induction of their unipolar clustering as a potential therapeutic strategy.

[Determination of nine B vitamins in peptone using ultra high performance liquid chromatography-tandem mass spectrometry].

A method using ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the determination of nine B vitamins in peptone. The samples were extracted with water. The analytes were separated on a Syncronis C18 column (100 mm×2.1 mm, 1.7 µm). The nine B vitamins were detected by ESI-MS/MS under the multiple reaction monitoring (MRM) mode, and the analysis was completed in 8 min. Quantification analysis was performed by using the external standard method. The correlation coefficients (R2) of the nine B vitamins in their linear ranges were greater than 0.999. The limits of detection were 0.09-1.67 µg/L. The relative standard deviations of the method were less than 3% (n=6). The mean recoveries of the nine B vitamins were 80.2%-103.9% at different spiked levels. The method is simple, accurate and sensitive, and is suitable for the determination of the nine B vitamins in peptone.

Perturbation of tubulin structure by stellate gold nanoparticles retards MDA-MB-231 breast cancer cell viability.

Gold nanoparticles (GNPs) of different sizes and shapes have been investigated extensively for their therapeutic potential against several diseases including cancer. However, the mechanisms with which they affect the cells are yet to be fully comprehended. In this study, we report the strong antiproliferative potential of novel, star-shaped ("stellate") GNPs that target tubulin-the building-block protein of the cytoskeletal filaments called microtubules-and disrupt microtubule network integrity. The stellate GNPs ("sGNPs") were synthesized from tryptone-stabilized GNPs ("tGNPs") and characterized by various spectroscopy methods combined with high-resolution transmission electron microscopy. Among a panel of cancer cell lines tested, they showed strong antiproliferative and anti-clonogenic efficacy against MDA-MB-231 cells. The antiproliferative mechanism of the sGNPs involves perturbation of the secondary and tertiary conformation of tubulin as evidenced by far-UV circular dichroism and anilinonaphthalene sulphate-binding assays. The structural perturbation of tubulin retarded its assembly competence as evidenced by polymer mass analysis and electron microscopy imaging of tubulin assembled in vitro and by immunofluorescence visualization of the cellular microtubules. The treated cells also induced cell cycle arrest at G1 phase. Taken together, our data suggest that sGNPs are potent, tubulin-targeted antiproliferative particles that can be evaluated further for their anticancer potential.

Effects of medium composition on the growth and lipid production of microplasmodia of Physarum polycephalum.

Physarum polycephalum is a plasmodial slime mold. One of the trophic stages in the life cycle of this organism is a plasmodium. In submerged culture, plasmodia are fragmented into microplasmodia. The latter both lack cell walls and are capable of rapid growth. There has been limited information on the effects of medium composition on the growth and lipid accumulation of microplasmodia. In this study, optimization of medium components by response surface methodology showed that tryptone and yeast extract concentrations had the most significant effects on lipid and biomass production; significant synergistic interactions between glucose and tryptone concentration on these responses were also recorded. The optimal medium was composed of 20 g/L of glucose, 6.59 g/L of tryptone, and 3.0 g/L of yeast extract. This medium yielded 13.86 g/L of dry biomass and 1.97 g/L of lipids. These amounts are threefold higher than those of the American Type Culture Collection (ATCC) medium. In addition, biomass and lipid production reached maximal values between only 4 and 5 days. Fatty acid compositions analysis by gas chromatography-mass spectrometer (GC-MS) revealed that P. polycephalum lipids consisted mainly of oleic acid (40.5%), linoleic acid (10%), and octadecynoic (15.8%). This is the first report on the fatty acid composition of P. polycephalum microplasmodia. These results suggest that the biomass of microplasmodia could be used as a source of material for direct conversion into biodiesel because of the absence of cell walls or it could also be used as a supplemental source of beneficial fatty acids for humans, albeit with some further evaluation needed.

Efficacy of neutralizing buffered peptone water for recovery of Salmonella, Campylobacter, and Enterobacteriaceae from broiler carcasses at various points along a commercial immersion chilling process with peroxyacetic acid.

In 2016, USDA-Food Safety and Inspection Service began using a neutralizing buffered peptone water (nBPW) to rinse broiler carcasses for Salmonella and Campylobacter performance standard testing. The nBPW contains standard buffered peptone water (BPW) with compounds to neutralize residual antimicrobials that may be transferred from the carcass to the sample rinsate. However, a direct comparison of nBPW and BPW on carcasses commercially treated with antimicrobials has not been conducted. On 3 replicate days in a commercial broiler processing plant, an immersion chilling biomap using whole carcass rinse samples taken prior to any chilling treatment (30), after pre-chill treatment (30), after primary chill (30), after secondary chill (30), after post-chill treatment (50), and after post-chill treatment without the pre-chill treatment (49) were tested. Carcasses were rinsed with either BPW (without neutralizer) or nBPW. Rinsates were sampled for Salmonella and Campylobacter prevalence and both Enterobacteriaceae (EB) prevalence and counts. No significant differences were observed between sampling sites or rinse media for Salmonella due to an overall low prevalence (4 positive/219 samples). Campylobacter prevalence significantly decreased from prior to chilling (93%) to after all chilling steps (47%) as anticipated (P < 0.0001); however, overall significantly fewer Campylobacter positive carcasses were detected when nBPW was used (55%) in comparison to BPW (70%, P = 0.0258). Both EB prevalence and counts significantly decreased (both P < 0.0001) from prior to chilling (100%, 2.35 log10 CFU/mL) through after all chilling steps (52%, 0.47 log10 CFU/mL). The use of nBPW versus BPW did not impact EB prevalence; however, samples rinsed with nBPW had significantly higher overall counts (1.26 vs. 1.00 log10 CFU/mL, P = 0.0134). The results from this study indicate that the use of a PAA pre-chill treatment did not significantly impact bacteria recovery following all chilling steps. The use of nBPW was effective in neutralizing residual PAA in carcass rinsates when sampling for EB counts; however, nBPW may lessen the ability to detect Campylobacter in these same samples.

Medium composition optimization, structural characterization, and antioxidant activity of exopolysaccharides from the medicinal mushroom Ganoderma lingzhi.

To contribute towards effective exploitation and utilization of natural antioxidants, response surface methodology (RSM) was employed to optimize the medium composition for the production of exopolysaccharides from the medicinal mushroom Ganoderma lingzhi (GLEPS). An optimal medium for GLEPS production was gave through Plackett-Burman design, path of steepest ascent, and Box-Behnken design as follows: glucose (59.62 g/L), yeast extract (10.03 g/L), CaCO3 (0.2 g/L), thiamine (45.13 mg/L), KH2PO4 (1.0 g/L), peptone (1.5 g/L), Tween 80 (10.26 mL/L), ZnSO4 (0.3 g/L), mannitol (1.5 g/L), MgSO4 (0.5 g/L), and aspartate (8.86 g/L). The GLEPS yield obtained was 3.57 ±â€¯0.21 g/L-3.16-fold higher than that produced in basal medium alone. The resulting GLEPS rich in uronic acid, d-mannose, l-rhamnose, and d-glucose, was a heteropolysaccharide with high-molecular weights (475,000 kDa and 21.6 kDa, 87.97%). It was demonstrated that the GLEPS with higher carbohydrate and uronic acid contents exhibited strong in vitro antioxidant activities via radical scavenging, reductive capacity, and chelation of transition metal catalysis. These findings indicated that RSM is an efficient tool to predict the composition of culture medium required for maximizing GLEPS yield, and GLEPS had potent antioxidant activities and could be explored as a novel natural antioxidant in functional food or medicine.

Chicken feather peptone: A new alternative nitrogen source for pigment production by Monascus purpureus.

Peptones are accepted as one of the most favourable nitrogen sources supporting pigment synthesis in Monascus purpureus. The present study was performed to test the feasibility of chicken feather peptone (CFP) as nitrogen source for pigment production from M. purpureus ATCC16365. CFP was compared with fish peptone (FP) and protease peptone (PP) in order to elucidate its effectiveness on pigment production. CFP was prepared from waste feathers using hydrolysis (KOH) and neutralization (H2SO4) methods. The protein content of CFP was determined as 67.2 g/100 g. Optimal concentrations of CFP and glucose for pigment production were determined as 3 and 20 g/L, respectively. A medium pH of 5.5 and an incubation period of 7-days were found to be more favourable for pigment production. In CFP, PP and FP media, yellow pigment absorbances were 2.819, 2.870 and 2.831, red pigment absorbances were 2.709, 2.304 and 2.748, and orange pigment absorbances were 2.643, 2.132 and 2.743, respectively. Sugar consumption and mycelia growth showed the similar trends in CFP, FP and PP media. This study indicates that the peptone from chicken feathers may be a good nutritional substrate for pigment production from M. purpureus.

Tryptone-stabilized gold nanoparticles target tubulin and inhibit cell viability by inducing an unusual form of cell cycle arrest.

Gold nanoparticles have been investigated extensively for their molecular mechanisms of action and anticancer potential. We report a novel, tubulin-targeted antiproliferative mechanism of action of tryptone-stabilized gold nanoparticles (TsAuNPs). TsAuNPs, synthesized using HAuCl4·3H2O and tryptone and characterized by a variety of spectroscopic methods and transmission electron microscopy, were found to be inhibitory to viability of human pancreatic (PANC-1), cervical (HeLa), and breast (MDA-MB-231) cancer cell lines in a concentration-dependent manner, with highest efficacy against PANC-1 cells. The particles strongly inhibited the clonogenic propagation of PANC-1 cells. TsAuNPs-mediated inhibition of cell viability involved an unusual mode of cell cycle arrest (arrest at both G0/G1 phase and S-phase) followed by apoptosis. In vitro, TsAuNPs bound purified tubulin, competitively inhibited anilinonaphthalene sulfonate binding to tubulin, and suppressed tubulin assembly. In cells, tubulin-TsAuNPs interactions were manifested as a disrupted microtubule network, defective reassembly of cold-disassembled microtubules, and induction of tubulin acetylation. Our data indicate that TsAuNPs inhibit cell viability by inducing differential cell cycle arrest possibly through disrupted dynamicity of cellular microtubules.

A Simple Defined Medium for the Production of True Diketopiperazines in Xylella fastidiosa and Their Identification by Ultra-Fast Liquid Chromatography-Electrospray Ionization Ion Trap Mass Spectrometry.

Diketopiperazines can be generated by non-enzymatic cyclization of linear dipeptides at extreme temperature or pH, and the complex medium used to culture bacteria and fungi including phytone peptone and trypticase peptone, can also produce cyclic peptides by heat sterilization. As a result, it is not always clear if many diketopiperazines reported in the literature are artifacts formed by the different complex media used in microorganism growth. An ideal method for analysis of these compounds should identify whether they are either synthesized de novo from the products of primary metabolism and deliver true diketopiperazines. A simple defined medium (X. fastidiosa medium or XFM) containing a single carbon source and no preformed amino acids has emerged as a method with a particularly high potential for the grown of X. fastidiosa and to produce genuine natural products. In this work, we identified a range of diketopiperazines from X. fastidiosa 9a5c growth in XFM, using Ultra-Fast Liquid Chromatography coupled with mass spectrometry. Diketopiperazines are reported for the first time from X. fastidiosa, which is responsible for citrus variegated chlorosis. We also report here fatty acids from X. fastidiosa, which were not biologically active as diffusible signals, and the role of diketopiperazines in signal transduction still remains unknown.

Statistical optimization for the production of recombinant cold-adapted superoxide dismutase in E. coli using response surface methodology.

Cold-adapted superoxide dismutase (SOD) with higher catalytic activity at lower temperature has great amount of applications in many aspects as an industrial enzyme. The application of recombinant enzyme in gene engineering and microbial fermentation technology is an effective way to obtain high-yield product. In this study, to obtain the recombinant SOD in E. coli (rPsSOD) with the highest activity, the Box-Behnken design was first applied to optimize the important parameters (lactose, tryptone and Tween-80) affecting the activity of rPsSOD. The results showed that the optimal fermentation conditions were Tween-80 (0.047%), tryptone (6.16 g/L), lactose (11.38 g/L). The activity of rPsSOD was 71.86 U/mg (1.54 times) as compared with non-optimized conditions. Such an improved production will facilitate the application of the cold-adapted rPsSOD.