Nitrogen sources enhance siderophore-mediated competition for iron between potato common scab and late blight causative agents.

How do pathogens affecting the same host interact with each other? We evaluated here the types of microbe-microbe interactions taking place between Streptomyces scabiei and Phytophthora infestans, the causative agents of common scab and late blight diseases in potato crops, respectively. Under most laboratory culture conditions tested, S. scabiei impaired or completely inhibited the growth of P. infestans by producing either soluble and/or volatile compounds. Increasing peptone levels correlated with increased inhibition of P. infestans. Comparative metabolomics showed that production of S. scabiei siderophores (desferrioxamines, pyochelin, scabichelin, and turgichelin) increased with the quantity of peptone, thereby suggesting that they participate in the inhibition of the oomycete growth. Mass spectrometry imaging further uncovered that the zones of secreted siderophores and of P. infestans growth inhibition coincided. Moreover, either the repression of siderophore production or the neutralization of their iron-chelating activity led to a resumption of P. infestans growth. Replacement of peptone by natural nitrogen sources such as ammonium nitrate, sodium nitrate, ammonium sulfate, and urea also triggered siderophore production in S. scabiei. Interestingly, nitrogen source-induced siderophore production also inhibited the growth of Alternaria solani, the causative agent of the potato early blight. Overall, our work further emphasizes the importance of competition for iron between microorganisms that colonize the same niche. As common scab never alters the vegetative propagation of tubers, we propose that S. scabiei, under certain conditions, could play a protective role for its hosts against much more destructive pathogens through exploitative iron competition and volatile compound production.

Xylitol biosynthesis enhancement by Candida tropicalis via medium, process parameter optimization, and co-substrate supplementation.

The present study examines the impact of nitrogen sources (yeast extract, ammonium sulfate peptone, ammonium nitrate, urea, and sodium nitrate), salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, 0.3 g/L CaCl2), trace elements solution (0.1 g/L CuSO4, 0.1 g/L FeSO4, 0.02 g/L MnCl2, 0.02 g/L ZnSO4), operational parameters (temperature, aeration, agitation, initial pH and xylose concentration) and co- substrate supplementation (glucose, fructose, maltose, sucrose, and glycerol) on xylitol biosynthesis by Candida tropicalis ATCC 13803 using synthetic xylose. The significant medium components were identified using the Plackett Burman design followed by central composite designs to obtain the optimal concentration for the critical medium components in shaker flasks. Subsequently, the effect of operational parameters was examined using the One Factor At a Time method, followed by the impact of five co-substrates on xylitol biosynthesis in a 1 L bioreactor. The optimal media components and process parameters are as follows: peptone: 12.68 g/L, yeast extract: 6.62 g/L, salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, and 0.3 g/L CaCl2): 1.23 X (0.62 g/L, 0.62 g/L, and 0.37 g/L respectively), temperature: 30 °C, pH: 6, agitation: 400 rpm, aeration: 1 vvm, and xylose: 50 g/L. Optimization studies resulted in xylitol yield and productivity of 0.71 ± 0.004 g/g and 1.48 ± 0.018 g/L/h, respectively. Glycerol supplementation (2 g/L) further improved xylitol yield (0.83 ± 0.009 g/g) and productivity (1.87 ± 0.020 g/L/h) by 1.66 and 3.12 folds, respectively, higher than the unoptimized conditions thus exhibiting the potential of C. tropicalis ATCC 13803 being used for commercial xylitol production.

Bidirectional fermentation of Monascus and Mulberry leaves enhances GABA and pigment contents: establishment of strategy, studies of bioactivity and mechanistic.

Bidirectional fermentation is a technology that utilizes fungi to ferment medicinal edible substrates, with synergistic and complementary advantages. In this work, a fermentation strategy was established to produce a high yield of γ-aminobutyric acid (GABA) and Monascus pigments (MPs) using Monascus and mulberry leaves (MLs). Firstly, the basic fermentation parameters were determined using single-factor experiments, followed by Plackett-Burman (PB) experimental design to identify MLs, glucose, peptone, and temperature as significant influencing factors. The fermentation parameters were optimized using an artificial neural network (ANN). Finally, the effects of bidirectional fermentation of MLs and Monascus were investigated by bioactivity analysis, microstructure observation, and RT-qPCR. The outcomes showed that the bidirectional fermentation significantly increased the bioactive content and promoted the secondary metabolism of Monascus. The established fermentation conditions were 44.2 g/L of MLs, 57 g/L of glucose, 15 g/L of peptone, 1 g/L of MgSO4, 2 g/L of KH2PO4, 8% (v/v) of inoculum, 180 rpm, initial pH 6, 32 °C and 8 days. The content of GABA reached 13.95 g/L and the color value of MPs reached 408.07 U/mL. This study demonstrated the feasibility of bidirectional fermentation of MLs and Monascus, providing a new idea for the application of MLs and Monascus.

Transfer of Enterococcus faecium and Salmonella enterica during simulated postharvest handling of yellow onions (Allium cepa).

Bacterial transfer during postharvest handling of fresh produce provides a mechanism for spreading pathogens, but risk factors in dry environments are poorly understood. The aim of the study was to investigate factors influencing bacterial transfer between yellow onions (Allium cepa) and polyurethane (PU) or stainless steel (SS) under dry conditions. Rifampin-resistant Enterococcus faecium NRRL B-2354 or a five-strain cocktail of Salmonella was inoculated onto onion skin or PU surfaces at high or moderate levels using peptone, onion extract, or soil water as inoculum carriers. Transfer from inoculated to uninoculated surfaces was conducted using a texture analyzer to control force, time, and number of contacts. Transfer rates (ratio of recipient surface to donor surface populations) of E. faecium (4-5%) were significantly higher than those of Salmonella (0.5-0.6%) at the high (7 log CFU/cm2) but not moderate (5 log CFU/cm2) inoculum levels. Significantly higher populations of E. faecium transferred from onion to PU than from PU to onion. The transfer rates of E. faecium were impacted by inoculum carrier (61% [onion extract], 1.6% [peptone], and 0.31% [soil]) but not by inoculation level or recipient surface (PU versus SS). Bacterial transfer during dry onion handling is significantly dependent on bacterial species, inoculation levels, inoculum carrier, and transfer direction.

Unraveling the potential and constraints associated with corn steep liquor as a nutrient source for industrial fermentations.

Costly complex media components such as yeast extract and peptone are still widely used in industrial bioprocesses, despite their ill-defined composition. Side stream products such as corn steep liquor (CSL) present a compelling economical alternative that contains valuable nutrients required for microbial growth, that is, nitrogen and amino acids, but also vitamins, trace elements, and other minerals. However, as a side stream product, CSL may be subject to batch-to-batch variations and compositional heterogeneity. In this study, the Respiration Activity MOnitoring System designed for shake flasks (RAMOS) and 96-well microtiter plates (µTOM) were applied to investigate the potential and constraints of CSL utilization for two model microorganisms: E. coli and B. subtilis. Considering the dry substance content of complex nutrients involved, CSL-based media are more efficient in biomass production than the common lysogeny broth (LB) medium, containing 5 g/L yeast extract, 10 g/L peptone, and 5 g/L NaCl. At a glucose to CSL (glucose/CSL, g/g) ratio of 1/1 (g/g) and 2/1 (g/g), a secondary substrate limitation occurred in E. coli and B. subtilis cultivations, respectively. The study sheds light on differences in the metabolic activity of the two applied model organisms between varying CSL batches, which relate to CSL origin and production process, as well as the effect of targeted nutrient supplementation. Through a targeted nutrient supplementation, the most limiting component of the CSL-glucose medium used for these applied model microorganisms was identified to be ammonium nitrogen. This study proves the suitability of CSL as an alternative nutrient source for E. coli and B. subtilis. The RAMOS and µTOM technique detected differences between CSL batches, allowing easy and early identification of varying batches. A consistent performance of the CSL batches in E. coli and B. subtilis cultivations was demonstrated.

Utilization of wild Cressa cretica biomass for pectinase production from a halo-thermotolerant bacterium.

Halophytes are the native inhabitants of saline environment. Their biomass can be considered as a potential substrate for the production of microbial enzymes. This study was intended at feasible utilization of a halophytic biomass, Cressia cretica, for pectinase production using a halo- and thermo-tolerant bacterium, Bacillus vallismortis MH 10. The data from fractionation of the C. cretica biomass revealed presence of 17% pectin in this wild biomass. Seven different factors (temperature, agitation, pH, inoculum size, peptone concentration, substrate concentration, and incubation time) affecting pectinase production using C. cretica were assessed through a statistical tool, Plackett-Burman design. Consequently, two significant factors (incubation time and peptone concentration) were optimized using the central composite design. The strain produced 20 IU mL-1 of pectinase after 24 h under optimized conditions. The enzyme production kinetics data also confirmed that 24 h is the most suitable cultivation period for pectinase production. Fourier transform infrared spectroscopy and scanning electron microscopy of C. cretica biomass ascertained utilization of pectin and structural changes after fermentation. The purification of pectinase by using DEAE column yielded specific activity and purification fold of 88.26 IU mg-1 and 3.2, respectively. The purified pectinase had a molecular weight of >65 kDa. This study offers prospects of large-scale production of pectinase by halotolerant strain in the presence of economical and locally grown substrate that makes the enzyme valuable for various industrial operations.

Meat extract casein peptone agar - A novel culture medium for the enumeration of Bacillus endospores in commercial products.

Here we propose a novel culture medium, Meat Extract Casein Peptone (MECP) agar, to support the enumeration of Bacillus endospores in commercial products. The formulation is the result of screening eight different veterinary, pharmaceutical, and industrial grade peptones for the ability to support the formation of small, well-defined Bacillus colonies on solid culture medium. The impact of agar purity, agar formulation rate, and metal cation additives were examined in prototype medium batches prepared from preferred peptone inputs. A customized plate counting assay based on the resultant MECP agar formulation was compared with standardized pour-plate and spread-plate assays (ISO 4833) and flow cytometry for the ability to accurately enumerate five Bacillus-based biostimulants and biofertilizers. Estimations of Bacillus endospore concentration generated by the customized spread-plate assay were significantly higher than those produced by ISO 4833 pour-plate and spread-plate assays for four out of the five tested products and were in better agreement with flow cytometry values; however, flow cytometry values were numerically higher than values returned by both plating methods. Both flow cytometry and plating assays based on MECP or similar culture media represent potential candidates for standardization and validation through organizations such as ISO and AOAC International for the enumeration of Bacillus-based products.

Three semi-selective media for Pseudomonas syringae pv. maculicola and P. cannabina pv. alisalensis.

Three semi-selective media, DTarTA, SPbc, and SPamt, were developed and tested to isolate Pseudomonas syringae pv. maculicola (Psm) and P. cannabina pv. alisalensis (Pca) from Raphanus sativus seeds. DTarTA contained D-tartaric acid as a carbon source and potassium tellurite, ampicillin sodium, and methyl violet as antibiotics. DTarTA suppressed growth in 19 of the 24 pathovars from the P. syringae complex, whereas Psm and Pca grew and formed gray to black colonies. SPamt contained sucrose and peptone as nutrient sources and was supplemented with bromothymol blue and the same antibiotics present in DTarTA and Psm and Pca formed yellowish to dark brown colonies on the SPamt medium. SPbc contained sucrose and peptone and was supplemented with cephalexin and boric acid as antibiotics and Psm and Pca formed semi-translucent to white colonies on the SPbc medium. SPamt and SPbc suppressed the growth of several plant-associated bacteria (except the P. syringae complex). The growth of saprophytic bacteria in seeds on the different media was compared with that on King's B medium, using five types of commercially available Raphanus sativus seeds. The suppression rate of DTarTA was 85-99% and was lower for seeds with more saprophytic bacteria. The suppression rates of SPamt and SPbc were 90-99%. In detection tests using 10,000 seed samples mixed with Pca or Psm-contaminated seeds, it was possible to selectively isolate Psm and Pca using SPamt and SPbc, even when the colony numbers of the target bacterium constituted less than 10% of the total colonies. KEY POINTS: • Bacterial leaf spot and blight pathogens were selectively isolated from seeds. • DTarTA medium distinguishes these pathogens from P. syringae complex pathovars. • SPamp and SPbc media have different selectivity for plant-associated bacteria.

Statistical optimization of media components for production of extracellular lipase from edible mushroom Cantharellus cibarius.

Cantharellus cibarius is a wild edible mushrooms and considered as a plethora of compounds with potential biotechnological applications. This study highlighted the utilization of C. cibarius mushroom in the production of extracellular lipase under submerged fermentation, representing the first report on lipase production by this mushroom. Various physicochemical factors were optimized via one-factor-at-a time (OFAT) method. Maximum enzyme production was recorded when the mushroom mycelium was grown at 30 °C on pH 6.0 for 96 h in the medium supplemented with 1% [(v/v)] olive oil. Productivity of enzyme was affected by variation in the nitrogen sources, carbon sources, metal ions and NaCl salt. Glucose and peptone significantly enhanced enzyme production as carbon and nitrogen sources, respectively. Stimulatory and inhibitory effects were found by Ca2+ and Zn2+ ions, respectively. Furthermore, Box-Behnken Design (BBD) of Response Surface Methodology (RSM) was employed to optimize the interactive effects of specific media components like glucose, olive oil and CaCl2. The regression model was significant with a coefficient of determination (R2) value of 0.9483. Statistically optimized design (RSM) resulted approximately two-fold increase (23.5-42.283 UmL-1) of lipase production than classical optimization method (OFAT), confirmed the validation of model. The kinetic parameters for p-nitrophenyl palmitate hydrolysis, Km and Vmax were 5.24 mM and 0.768 mmol/min/mg respectively, established a high affinity for the substrate.

Lactic acid production from food waste hydrolysate by Lactobacillus pentosus: Focus on nitrogen supplementation, initial sugar concentration, pH, and fed-batch fermentation.

Lactic acid production from food waste via fermentation is environmentally sustainable. However, the characteristics of food waste fermentation to produce lactic acid are not well understood due to the complexity of food waste. This study aims to understand the effects of key variables on the characteristics of food waste fermentation to maximize lactic acid production. Food waste was enzymatically hydrolyzed and fermented by Lactobacillus pentosus. Key fermentation variables, including nitrogenous nutrient supplementation, initial sugar concentration, and pH, were investigated in batch fermentation to unveil their effects on fermentation titer, yield, and productivity. The results showed that supplementation of 0.25% (w/v%) yeast extract and peptone to the food waste fermentation media significantly improved fermentation titer and productivity, but further increase in the supplementation level did not improve fermentation. Increasing the initial sugar concentration from 40 g/L to 100 g/L increased the fermentation titer from 41.0 g/L to 93.0 g/L and productivity from 0.34 g/L/h to 0.76 g/L/h. pH 6.0 was the optimal pH for the fermentation. At the optimal conditions, food waste fermentation resulted in the highest fermentation titer, yield, and productivity of 106.7 g/L, 1.12 g/g, and 3.09 g/L/h, respectively. The high fermentation yield of 1.12 g/g might be explained by the extra lactic acid production from unidentified compounds in food waste hydrolysates. By applying fed-batch fermentation, the lactic acid concentration reached 157.0 g/L with a yield and overall productivity of 0.92 g/g and 2.0 g/L/h, respectively. Based on the mass balance, a total of 251 kg lactic acid was produced from 1000 kg food waste. PRACTICAL APPLICATION: Food waste is one of the largest municipal solid wastes in the US, and most food waste ends up in landfills, causing significant economic losses and environmental concerns. In this study, we developed a fermentation process to convert food waste into biorenewable lactic acid and demonstrated that food waste is a superior feedstock for fermentation due to its embedded nutrients. Moreover, due to the embedded nutrients in food waste, the supplementation of yeast extract and peptone to fermentation can be reduced by over 50%, which can reduce the operating cost of lactic acid fermentation on an industrial scale.

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.

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.

The effect of carbon, nitrogen and iron ions on mono-rhamnolipid production and rhamnolipid synthesis gene expression by Pseudomonas aeruginosa ATCC 15442.

Pseudomonas spp. are the main producers of rhamnolipids. These products have applications in pharmaceuticals, cosmetics, food industry and bioremediation. The biosynthesis of rhamnolipids is influenced by nutrient composition, pH and temperature. In this study, the impact of nutrients on the expression levels of rhamnolipid synthesis genes was evaluated in P. aeruginosa ATCC 15442. Glucose and glycerol were used as carbon sources; while, NaNO3, NH4NO3 and yeast extract/peptone were employed as nitrogen sources. The effect of different concentrations of Fe2+ and Fe3+ on rhamnolipid synthesis genes was also evaluated. Highest biosurfactant production was obtained in minimal medium supplemented with glucose, NaNO3 and Fe2+. Two rhamnolipid synthesis genes, rhlA and rhlB, were amplified with PCR. CapLC ESI-Ion trap-MS/MS detected only mono-rhamnolipid Rha-C10-C10 in the extract. Although similar induction levels were recorded in the presence of 0.05 g/L iron ions, the presence of Fe2+ resulted in higher expression levels than Fe3+ at concentrations equivalent to 0.025 and 0.075 g/L.

Direct transesterification of fatty acids produced by Fusarium solani for biodiesel production: effect of carbon and nitrogen on lipid accumulation in the fungal biomass.

AIMS: The present work aims to explore a new oleaginous Fusarium isolate potential to accumulate lipids in its biomass from inexpensive substrates. In addition, impacts of carbon and nitrogen sources and their ratios on lipid production by the interested fungal isolate were also studied. METHODS AND RESULTS: Lipid was assayed by sulfo-phospho-vanillin colorimetric method. Among 11 Fusarium isolates obtained on potato dextrose agar from rhizosphereic soils, Fusarium RAS18 was selected as the highest producer that accumulates above 20% lipid. It was identified based on phenotypic characterization and the internal transcribed spacer sequence as Fusarium solani, that was recorded in the GenBank database under the accession number MK167372.1. The optimized lipid yield (34·5%) is obtained using glycerol (35 g l-1 ) and peptone (1·5 g l-1 ) as carbon and nitrogen sources respectively. The produced fatty acid methyl esters (biodiesel) is composed of linoleic acid (56·81%), palmitic acid (17·81%), oleic acid (11·81%) and stearic acid (11·12). The unsaturated fatty acids accounted for 69% and this is nearly similar to the plant oils commonly used in biodiesel production. CONCLUSIONS: These findings suggest the applicability of F. solani RAS18 as a promising strain to accumulate lipids from glycerol as a feedstock for biodiesel production. SIGNIFICANCE AND IMPACT OF THE STUDY: Fusarium solani RAS18 is a new oleaginous fungal isolate that is able to produce lipid (34·5%, g g-1 ) from glycerol. Glycerol is a cheap substrate and is formed as a byproduct from transesterification process and others industries. Thus, recyclation of glycerol for lipid production by micro-organisms is an important point of economic view. Direct transesterification of the produced fatty acids indicated its similarity to the plant oil composition used in biodiesel production. So, F. solani RAS18 might be a potential lipid source as a feedstock for biodiesel production.

Levan production from sucrose using chicken feather peptone as a low cost supplemental nutrient source.

Chicken feather peptone (CFP) derived from poultry waste is a rich source of essential minerals and amino acids. This, along with suitable carbon source, can be used as a low cost complex supplemental nutrient source for microbial fermentation. In the present work, CFP blended with sucrose was evaluated for the production of levan using Bacillus subtilis MTCC 441. Amount of CFP added to the medium significantly influenced levan production and it was found that at a concentration 2 g/L, maximum levan yield of 0.26 ±â€¯0.04 g/g sucrose was obtained. The levan yield obtained with CFP as a low cost supplemental nutrient source was comparable with that obtained from commercial medium (0.31 ±â€¯0.02 g/g sucrose). Levan produced using CFP was tested on primary cell lines at various concentrations (100-1000 µM) and found to be non-toxic and bio-compatible in nature. This indicates that CFP could be used as low cost nutrient source for levan production.

Effects of Culture Media On Naegleria fowleri Growth At Different Temperatures.

Nelson medium and modified PYNFH medium were used for the axenic culture of the Naegleria fowleri clinical strain LDL to compare the effects of different temperatures on the organism's growth. In addition, Nelson medium supplemented with 1% peptone (N + pep) and modified PYNFH medium without peptone (PYNFH - pep), without yeast extract (PYNFH - yext), without folic acid (PYNFH - folac), and without yeast nucleic acid (PYNFH - yna) were used in order to compare the various effects of these medium components. In general, N. fowleri grew best at 37 C. The highest trophozoite densities per 10,000 µm2 were observed when N + pep and PYNFH - yext were used. At 25, 37, and 43 C, the growth density profile values were 50.5 ± 6.36 vs. 58 ± 1.41; 2,550 ± 494.97 vs. 2,100 ± 141.42; and 1,735 ± 21.21 vs. 1,800 ± 14.14, respectively. On the other hand, PYNFH - pep gave the lowest growth with its highest cell densities being 9 ± 1.41 at 25 C, 108 ± 7.07 at 37 C, and 169 ± 15.55 at 43 C. When the various medium components were compared, supplementation with peptone promoted parasite growth. Besides, yeast extract had an inhibitory effect and was able to swamp the growth promoting effect of peptone. Thus N + pep and PYNFH - yext are recommended as the best media for in vitro culture of N. fowleri.

Characterization and Antioxidant Activity of an Exopolysaccharide Produced by Rigidoporus microporus (Agaricomycetes).

In this investigation we developed an optimal fermentation medium to produce an exopolysaccharide (EPS) with antioxidant activity from Rigidoporus microporus. Lactose and tryptone were chosen as the optimal carbon and nitrogen sources, respectively, for EPS production, with a 6-day cultivation cycle. After removing proteins through the use of the Sevag method, one EPS fraction was purified from the culture filtrates by gel filtration chromatography on a Sepharose CL-6B column. The preliminary chemical structure of the EPS fraction was determined by Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance. The results indicated that the main structure of the EPS consisted of ß-glucopyranose and mannopyranose. Furthermore, conformational parameters such as molecular weight (Mw), intrinsic viscosity ([η]), mean-square radii of gyration (Rg), and hydrodynamic radius (Rh) of the EPS were characterized using a size exclusion chromatography-multiangle light scattering-refractive index viscometry method. It showed that the EPS was a kind of water-soluble polysaccharide with a moderate molecular weight (34.1 × 104) and a flexible, linear random coil chain structure. The antioxidant activity tests suggested that the EPS has great potential application as a natural antioxidant material in foods and medicines.

Antioxidant Activity of Water Extract from Fermented Mycelia of Cordyceps sobolifera (Ascomycetes) in Caenorhabditis elegans.

This research aimed to evaluate the potential of Cordyceps sobolifera in mycelial biomass production via liquid culture and to assay the safety and determine the antioxidative and antiaging activities of Caenorhabditis elegans. A C. sobolifera isolate was cultured using the one-factor-at-a-time method to illustrate its carbon and nitrogen requirements. To assess safety, we determined the lethality, locomotion behavior, and reproduction of C. elegans cultured on a mycelial water extract (MWE) containing nematode growth medium (NGM). To investigate antiaging activity, C. elegans treated with MWE was incubated on NGM plates. The lethality was recorded throughout the whole life cycle. To identify antioxidant activity, C. elegans treated with MWE was exposed to paraquat, causing superoxide conditions. The results showed that C. sobolifera was favored by glucose and peptone as carbon and nitrogen sources, respectively. MWE was considered to be safe, as no abnormal behaviors were observed in C. elegans. Compared with nematodes pretreated with no MWE but with water instead, MWE at 1.0 mg/mL significantly prolonged the mean lifespan of C. elegans by 24%. We observed an obvious dose-effect relation between concentration and mean lifespan. The effective antioxidant activity was recorded at the high concentration of MWE. These findings demonstrate the potential antiaging and antioxidant properties of C. sobolifera as functional food and dietary supplement.

Natural Mutagenesis-Enabled Global Proteomic Study of Metabolic and Carbon Source Implications in Mutant Thermoacidophillic Archaeon Sulfolobus solfataricus PBL2025.

The thermoacidophilic crenarchaeon Sulfolobus solfataricus has been widely used as a model organism for archaeal systems biology research. Investigation using its spontaneous mutant PBL2025 provides an effective metabolic baseline to study subsequent mutagenesis-induced functional process shifts as well as changes in feedback inhibitions. Here, an untargeted metabolic investigation using quantitative proteomics and metabolomics was performed to correlate changes in S. solfataricus strains P2 against PBL2025 and under both glucose and tryptone. The study is combined with pathway enrichment analysis to identify prominent proteins with differential stoichiometry. Proteome level quantification reveals that over 20% of the observed overlapping proteome is differentially expressed under these conditions. Metabolic-induced differential expressions are observed along the central carbon metabolism, along with 12 other significantly regulated pathways. Current findings suggest that PBL2025 is able to compensate through the induction of carbon metabolism, as well as other anabolic pathways such as Val, Leu and iso-Leu biosynthesis. Studying protein abundance changes after changes in carbon sources also reveals distinct differences in metabolic strategies employed by both strains, whereby a clear down-regulation of carbohydrate and nucleotide metabolism is observed for P2, while a mixed response through down-regulation of energy formation and up-regulation of glycolysis is observed for PBL2025. This study contributes, to date, the most comprehensive network of changes in carbohydrate and amino acid pathways using the complementary systems biology observations at the protein and metabolite levels. Current findings provide a unique insight into molecular processing changes through natural (spontaneous) metabolic rewiring, as well as a systems biology understanding of the metabolic elasticity of thermoacidophiles to environmental carbon source change, potentially guiding more efficient directed mutagenesis in archaea.

Isolation and identification of a novel bacterium, Lactobacillus sakei subsp. dgh strain 5, and optimization of growth condition for highest antagonistic activity.

In the present study, we isolated Lactobacillus sakei strain DGH5 from raw beef meat. This bacterium plays an inhibitory effect against food-spoiling bacteria and food-borne pathogens, including Listeria monocytogenes, a gram-positive and pathogenic bacterium. Lactobacillus sakei strain DGH5 was identified through both phenotypical and biochemical tests accompanied with 16S rRNA sequence analysis. Among all the sources of carbon, nitrogen and phosphorous forms, we selected the most potent compounds to optimize the condition for the highest antagonistic activity. Among the sugars, polygalacturonic acid demonstrated to improve the antagonistic activity. Ammonium nitrate demonstrated to be suitable nitrogen sources. Amongst phosphorous sources, disodium hydrogen phosphate had the greatest antagonistic effect. According to Taguchi's orthogonal array, temperature, disodium hydrogen phosphate and soy Peptone had significant effect on antagonistic activity. Furthermore, mean comparisons showed that the optimum conditions achieved at pH 6.0, 25 °C temperature, 1.5% (w/v) Na2HPO4 and 0.5% (w/v) peptone.