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1.
Nat Commun ; 12(1): 1683, 2021 Mar 16.
Article in English | MEDLINE | ID: mdl-33727536

ABSTRACT

The mild activity of basaltic volcanoes is punctuated by violent explosive eruptions that occur without obvious precursors. Modelling the source processes of these sudden blasts is challenging. Here, we use two decades of ground deformation (tilt) records from Stromboli volcano to shed light, with unprecedented detail, on the short-term (minute-scale) conduit processes that drive such violent volcanic eruptions. We find that explosive eruptions, with source parameters spanning seven orders of magnitude, all share a common pre-blast ground inflation trend. We explain this exponential inflation using a model in which pressure build-up is caused by the rapid expansion of volatile-rich magma rising from depth into a shallow (<400 m) resident magma conduit. We show that the duration and amplitude of this inflation trend scales with the eruption magnitude, indicating that the explosive dynamics obey the same (scale-invariant) conduit process. This scale-invariance of pre-explosion ground deformation may usher in a new era of short-term eruption forecasting.

3.
Psychol Med ; 51(1): 30-42, 2021 01.
Article in English | MEDLINE | ID: mdl-31327332

ABSTRACT

BACKGROUND: The present paper provides an updated review of both the large number of new/novel/emerging psychoactive substances (NPS) and their associated psychopathological consequences. Focus was here given on identification of those NPS being commented in specialised online sources and the related short-/long-term psychopathological and medical ill-health effects. METHODS: NPS have been identified through an innovative crawling/navigating software, called the 'NPS.Finder®', created in order to facilitate the process of early recognition of NPS online. A range of information regarding NPS, including chemical and street names; chemical formula; three-dimensional image and anecdotally reported clinical/psychoactive effects, were here made available. RESULTS: Using the 'NPS.Finder®' approach, a few thousand NPS were here preliminarily identified, a number which is about 4-fold higher than those figures suggested by European and international drug agencies. NPS most commonly associated with the onset of psychopathological consequences included here synthetic cannabinoids/cannabimimetics; new synthetic opioids; ketamine-like dissociatives; novel stimulants; novel psychedelics and several prescription and over-the-counter medicines. CONCLUSIONS: The ever-increasing changes in terms of recreational psychotropics' availability represent a relatively new challenge for psychiatry, as the pharmacodynamics and pharmacokinetics of many NPS have not been thoroughly understood. Health/mental health professionals should be informed about the range of NPS; their intake modalities; their psychoactive sought-after effects; the idiosyncratic psychotropics' combinations and finally, their medical and psychopathological risks.


Subject(s)
Illicit Drugs/adverse effects , Illicit Drugs/pharmacology , Psychotropic Drugs/adverse effects , Psychotropic Drugs/pharmacology , Substance-Related Disorders/psychology , Humans , Psychopathology , Recreational Drug Use/psychology
4.
J Hosp Infect ; 104(2): 239-242, 2020 Feb.
Article in English | MEDLINE | ID: mdl-31525449

ABSTRACT

This study describes a combined surveillance of surgical site infection implemented in an Italian region, which relies on integration of the specific surveillance (SIChER) with other sources and the targeted review of a small proportion of cases. Additional information on post-surgical follow-up was obtained from hospital discharge, microbiology laboratory and emergency department databases. Based on these data, 76 patients were reclassified as possible cases and revised by the health trust representatives. Eventually 45 new cases were confirmed, leading to an increase in the infection ratio from 1.13% to 1.45%. The proposed method appears to be accurate and sustainable over time.


Subject(s)
Public Health Surveillance/methods , Surgical Wound Infection/epidemiology , Algorithms , Databases, Factual , Diagnostic Errors/statistics & numerical data , Follow-Up Studies , Humans , Italy/epidemiology , Patient Discharge , Surgical Wound Infection/classification , Surgical Wound Infection/diagnosis
5.
Sci Rep ; 8(1): 9331, 2018 06 19.
Article in English | MEDLINE | ID: mdl-29921881

ABSTRACT

Combination of responsive microgels and photonic resonant nanostructures represents an intriguing technological tool for realizing tunable and reconfigurable platforms, especially useful for biochemical sensing applications. Interaction of light with microgel particles during their swelling/shrinking dynamics is not trivial because of the inverse relationships between their size and refractive index. In this work, we propose a reliable analytical model describing the optical properties of closed-packed assembly of surface-attached microgels, as a function of the external stimulus applied. The relationships between the refractive index and thickness of the equivalent microgel slab are derived from experimental observations based on conventional morphological analysis. The model is first validated in the case of temperature responsive microgels integrated on a plasmonic lab-on-fiber optrode, and also implemented in the same case study for an optical responsivity optimization problem. Overall, our model can be extended to other photonic platforms and different kind of microgels, independently from the nature of the stimulus inducing their swelling.

6.
Sci Rep ; 7(1): 14459, 2017 10 31.
Article in English | MEDLINE | ID: mdl-29089550

ABSTRACT

Precision medicine is continuously demanding for novel point of care systems, potentially exploitable also for in-vivo analysis. Biosensing probes based on Lab-On-Fiber Technology have been recently developed to meet these challenges. However, devices exploiting standard label-free approaches (based on ligand/target molecule interaction) suffer from low sensitivity in all cases where the detection of small molecules at low concentrations is needed. Here we report on a platform developed through the combination of Lab-On-Fiber probes with microgels, which are directly integrated onto the resonant plasmonic nanostructure realized on the fiber tip. In response to binding events, the microgel network concentrates the target molecule and amplifies the optical response, leading to remarkable sensitivity enhancement. Moreover, by acting on the microgel degrees of freedom such as concentration and operating temperature, it is possible to control the limit of detection, tune the working range as well as the response time of the probe. These unique characteristics pave the way for advanced label-free biosensing platforms, suitably reconfigurable depending on the specific application.

7.
J Appl Microbiol ; 122(4): 857-869, 2017 Apr.
Article in English | MEDLINE | ID: mdl-28063197

ABSTRACT

This review outlines the recent advances in the knowledge on aerobic and respiratory growth of lactic acid bacteria, focusing on the features of respiration-competent lactobacilli. The species of the genus Lactobacillus have been traditionally classified as oxygen-tolerant anaerobes, but it has been demonstrated that several strains are able to use oxygen as a substrate in reactions mediated by flavin oxidases and, in some cases, to synthesize a minimal respiratory chain. The occurrence of genes related to aerobic and respiratory metabolism and to oxidative stress response apparently correlates with the taxonomic position of lactobacilli. Members of the ecologically versatile Lactobacillus casei, L. plantarum and L. sakei groups are apparently best equipped to deal with aerobic/respiratory growth. The shift from anaerobic growth to aerobic (oxygen) and/or respiratory promoting (oxygen, exogenous haem and menaquinone) conditions offers physiological advantages and affects the pattern of metabolite production in several species. Even if this does not result in dramatic increases in biomass production and growth rate, cells grown in these conditions have improved tolerance to heat and oxidative stresses. An overview of benefits and of the potential applications of Lactobacillus cultures grown under aerobic or respiratory conditions is also discussed.


Subject(s)
Food Industry , Industrial Microbiology , Lactobacillus/metabolism , Aerobiosis , Lactobacillus/genetics , Oxidative Stress , Oxygen/metabolism
8.
J Appl Microbiol ; 122(3): 759-769, 2017 Mar.
Article in English | MEDLINE | ID: mdl-27981716

ABSTRACT

AIMS: To evaluate the effect of cultivation (anaerobiosis vs respiration) and Tween 80 supplementation on the production of metabolites and on the composition of membrane fatty acids (FAs) in Lactobacillus casei N87. METHODS AND RESULTS: Anaerobic and respiratory growth, with or without Tween 80 supplementation, was carried out in a chemically defined medium. Production of biomass, organic acids, volatile organic compounds (VOCs), consumption of amino acids and changes in membrane FAs were investigated. Respiration altered the central metabolism rerouting pyruvate away from lactate accumulation, while Tween 80 had a minor effect on metabolic pathways. VOCs were mainly affected by growth conditions and significant amounts of diacetyl were produced by respiratory cultures. Respiration increased desaturation of membrane lipids and Tween 80 improved the production of essential polyunsaturated FAs. Palmitic acid decreased in Tween-supplemented aerated cultures. CONCLUSIONS: Combination of Tween 80 and respiratory growth promoted production of biomass and aroma compounds and affected the composition of membrane FAs in Lact. casei N87. SIGNIFICANCE AND IMPACT OF THE STUDY: Respiration might be exploited in Lact. casei as a natural strategy for the enhanced production of aroma compounds.


Subject(s)
Fatty Acids/metabolism , Lacticaseibacillus casei/metabolism , Polysorbates/pharmacology , Aerobiosis , Amino Acids/metabolism , Anaerobiosis , Lactic Acid/metabolism , Lacticaseibacillus casei/growth & development , Metabolic Networks and Pathways/drug effects , Pyruvic Acid/metabolism
9.
Clin Microbiol Infect ; 22(11): 946.e1-946.e8, 2016 Nov.
Article in English | MEDLINE | ID: mdl-27475741

ABSTRACT

The overall rate of hepatitis B virus (HBV) reactivation was evaluated in a population of 373 haematological stem cell transplant (HSCT) patients treated with lamivudine (LMV) if they were anti-HBc-positive/HBV-DNA-negative recipients or if they were HBV-negative recipients with an anti-HBc-positive donor. The incidence of HBV reactivation was calculated in two groups of autologous (auto) or allogeneic (allo) HSCT patients who were stratified according to their HBV serostatus. The former group included 57 cases: 10 auto-HSCT and 27 allo-HSCT anti-HBc-positive recipients, two auto-HSCT and three allo-HSCT inactive carriers, and 15 allo-HSCT recipients with an anti-HBc-positive donor. Forty-seven (82.4%) patients in this group received LMV prophylaxis (the median (interquartile range, IQR) of LMV treatment was 30 (20-38) months). The second group consisted of 320 anti-HBc-negative auto-HSCT and allo-HSCT recipients with anti-HBc-negative donors. None of these patients received any prophylaxis. Two patients in the first group and two in the second group experienced reactivation of HBV infection, with an incidence of 3.5% (95% CI 0.4-12.1%) and 0.6% (95% CI 0.1-2.2%), respectively. Only one out of four reactivated patients was LMV-treated. The cumulative probability of HBV reactivation at 6 years from HSCT was 15.8% (95% CI 15.2-16.4%). Three of four viral isolates obtained from the HBV-reactivated patients harboured mutations in the immune-active HBsAg-region. In a HSCT population carefully evaluated for HBV prophylaxis, a risk of HBV reactivation persisted in the group of patients who were not LMV-treated. Only one LMV-treated patient experienced reactivation of HBV with a resistant HBV isolate.


Subject(s)
Hematologic Neoplasms/therapy , Hematopoietic Stem Cell Transplantation/adverse effects , Hepatitis B virus/physiology , Hepatitis B/epidemiology , Lamivudine/administration & dosage , Adult , Carrier State/immunology , Female , Hepatitis B virus/immunology , Humans , Lamivudine/pharmacology , Male , Middle Aged , Transplantation, Autologous/statistics & numerical data , Transplantation, Homologous/statistics & numerical data , Virus Activation/drug effects
10.
Neurologia ; 31(1): 18-23, 2016.
Article in English, Spanish | MEDLINE | ID: mdl-25261166

ABSTRACT

INTRODUCTION: The 90-day risk of cerebral infarction in patients with transient ischaemic attack (TIA) is estimated at between 8% and 20%. There is little consensus as to which diagnostic strategy is most effective. This study evaluates the benefits of early transthoracic echocardiography (TTE) with carotid and transcranial Doppler ultrasound in patients with TIA. METHODS: Prospective study of patients with TIA in an emergency department setting. Demographic data, vascular risk factors, and ABCD(2) score were analysed. TIA aetiology was classified according to TOAST criteria. All patients underwent early vascular studies (<72hours), including TTE, carotid ultrasound, and transcranial Doppler. Primary endpoints were recurrence of stroke or TIA, myocardial infarction (MI), or vascular death during the first year. RESULTS: We evaluated 92 patients enrolled over 24 months. Mean age was 68.3±13 years and 61% were male. The mean ABCD(2) score was 3 points (≥5 in 30%). The distribution of TIA subtypes was as follows: 12% large-artery atherosclerosis; 30% cardioembolism; 10% small-vessel occlusion; 40% undetermined cause; and 8% rare causes. Findings from the early TTE led to a change in treatment strategy in 6 patients (6.5%) who displayed normal physical examination and ECG findings. At one year of follow-up, 3 patients had experienced stroke (3.2%) and 1 patient experienced MI (1%); no vascular deaths were identified. CONCLUSIONS: In our TIA patients, early vascular study and detecting patients with silent cardiomyopathy may have contributed to the low rate of vascular disease recurrence.


Subject(s)
Ischemic Attack, Transient/diagnosis , Myocardial Infarction/epidemiology , Myocardial Infarction/etiology , Stroke/epidemiology , Stroke/etiology , Vascular Diseases/epidemiology , Vascular Diseases/etiology , Aged , Aged, 80 and over , Early Diagnosis , Echocardiography , Female , Humans , Ischemic Attack, Transient/drug therapy , Ischemic Attack, Transient/mortality , Male , Middle Aged , Myocardial Infarction/diagnostic imaging , Prospective Studies , Stroke/mortality , Ultrasonography, Doppler, Transcranial , Vascular Diseases/diagnostic imaging
11.
Sci Rep ; 5: 15935, 2015 Nov 04.
Article in English | MEDLINE | ID: mdl-26531887

ABSTRACT

We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a 'double-layer' photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology.

12.
J Appl Microbiol ; 119(3): 776-85, 2015 Sep.
Article in English | MEDLINE | ID: mdl-26178377

ABSTRACT

AIMS: Members of the Lactobacillus casei and Lactobacillus plantarum groups are capable of aerobic and respiratory growth. However, they grow poorly in aerobiosis in the currently available chemically defined media, suggesting that aerobic and respiratory growth require further supplementation. METHODS AND RESULTS: The effect of Tween 80, L-alanine, L-asparagine, L-aspartate, L-proline and L-serine on anaerobic and respiratory growth of Lact. casei N87 was investigated using a 2(5) factorial design. The effectiveness of modified CDM (mCDM) was validated on 21 strains of Lact. casei and Lact. plantarum groups. Tween 80 supplementation did not affect anaerobic growth, but improved respiratory growth. L-asparagine, L-proline and L-serine were stimulatory for respiring cells, while the presence of L-aspartate, generally, impaired biomass production. mCDM promoted the growth of Lact. casei and Lact. plantarum, with best results for strains showing a respiratory phenotype. CONCLUSIONS: The nutritional requirements of anaerobic and respiratory cultures of members of the Lact. casei and Lact. plantarum groups differ. Tween 80 and selected amino acids derived from pathways related to TCA cycle, pyruvate conversion and NADH recycling are required for respiration. SIGNIFICANCE AND IMPACT OF THE STUDY: The availability of mCDM will facilitate the study of aerobic metabolism of lactobacilli under controlled conditions.


Subject(s)
Culture Media/metabolism , Lacticaseibacillus casei/growth & development , Lactobacillus plantarum/growth & development , Aerobiosis , Amino Acids/metabolism , Culture Media/chemistry , Lacticaseibacillus casei/genetics , Lacticaseibacillus casei/metabolism , Lactobacillus plantarum/genetics , Lactobacillus plantarum/metabolism
13.
J Dairy Sci ; 98(8): 5133-42, 2015 Aug.
Article in English | MEDLINE | ID: mdl-26074234

ABSTRACT

The occurrence of late blowing defects in cheese produces negative effects on the quality and commercial value of the product. In this work, we verified whether the addition of raw jenny milk to bulk cow milk reduced the late blowing defects in semihard cheeses. During cheesemaking, different aliquots of jenny milk were poured into 2 groups of 4 vats, each containing a fixed amount of cow milk. A group of cheeses was created by deliberately contaminating the 4 vats with approximately 3 log10 cfu/mL milk of Clostridium tyrobutyricum CLST01. The other 4 vats, which were not contaminated, were used for a second group of cheeses. After 120 d of ripening, some physical, chemical, and microbiological parameters were evaluated on the obtained semihard cheeses. Differences in sensory properties among cheeses belonging to the uncontaminated group were evaluated by 80 regular consumers of cheese. Our results showed that the increasing addition of jenny milk to cow milk led to a reduction of pH and total bacterial count in both cheese groups, as well as C. tyrobutyricum spores that either grew naturally or artificially inoculated. We observed a progressive reduction of the occurrence of late blowing defects in cheese as consequence of the increasing addition of jenny milk during cheese making. Moreover, the addition of jenny milk did not affect the acceptability of the product, as consumers found no difference among cheeses concerning sensorial aspects. In conclusion, the important antimicrobial activity of lysozyme contained in jenny milk has been confirmed in the current research. It is recommend for use as a possible and viable alternative to egg lysozyme for controlling late blowing defects in cheese.


Subject(s)
Cheese/analysis , Cheese/microbiology , Milk/chemistry , Animals , Cattle , Equidae , Female , Muramidase/metabolism
14.
J Appl Microbiol ; 119(3): 763-75, 2015 Sep.
Article in English | MEDLINE | ID: mdl-25996113

ABSTRACT

AIMS: This study evaluated the aerobic and respiratory metabolism in Lactobacillus reuteri and Lactobacillus spicheri, two heterofermentative species used in sourdough fermentation. METHODS AND RESULTS: In silico genome analysis, production of metabolites and gene expression of pyruvate oxidase, pyruvate dehydrogenase and cytochrome oxidase were assessed in anaerobic and aerobic cultures of Lact. reuteri and Lact. spicheri. Respiring homofermentative Lactobacillus casei N87 and Lact. rhamnosus N132 were used for comparison. Aerobiosis and respiration increased the biomass production of heterofermentative strains compared to anaerobic cultivation. Respiration led to acetoin production by Lact. rhamnosus and Lact. casei, but not in heterofermentative strains, in which lactate and acetate were the major end-products. Lactobacillus spicheri LP38 showed the highest oxygen uptake. Pyruvate oxidase, respiratory cytochromes, NADH oxidase and NADH peroxidase were present in the genome of Lact. spicheri LP38. Both Lact. spicheri LP38 and Lact. rhamnosus N132 overexpressed pox in aerobic cultures, while cydA was up-regulated only when haeme was supplied; pdh was repressed during aerobic growth. CONCLUSIONS: Aerobic and respiratory growth provided physiological and metabolic advantages also in heterofermentative lactobacilli. SIGNIFICANCE AND IMPACT OF THE STUDY: The exploitation of oxygen-tolerant phenotypes of Lact. spicheri may be useful for the development of improved starter cultures.


Subject(s)
Lactobacillus/metabolism , Limosilactobacillus reuteri/metabolism , Oxygen/metabolism , Aerobiosis , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Fermentation , Lactobacillus/enzymology , Lactobacillus/genetics , Limosilactobacillus reuteri/enzymology , Limosilactobacillus reuteri/genetics , Peroxidases/genetics , Peroxidases/metabolism , Pyruvate Oxidase/genetics , Pyruvate Oxidase/metabolism
15.
J Dairy Sci ; 98(3): 1479-91, 2015 Mar.
Article in English | MEDLINE | ID: mdl-25465632

ABSTRACT

The present study aimed to evaluate the effect of a peptidolytic adjunct (Lactococcus lactis, Lactobacillus helveticus, and Lactobacillus paracasei), as a tool to accelerate ripening, on sensory properties and acceptability of Scamorza cheese obtained using 2 types of milk (Friesian and Friesian+Jersey) and Streptococcus thermophilus as primary starter. A 10-member panel was trained using a specific frame of references and used a specific vocabulary to assess cheese sensory properties through quantitative descriptive analysis (QDA), whereas 87 consumers were used to evaluate product acceptability. Analysis of variance showed that milk type did not markedly alter cheese sensory properties. Conversely, panelists perceived higher intensities of butter, saltiness, and sweetness flavors in cheese without adjunct culture (ST), whereas the addition of the adjunct culture (ST+A) induced higher and sourness flavors, oiliness and grainy textures, and lower adhesiveness, moisture, springiness, and tenderness. Principal component analysis showed positive relationships between pH and tenderness, sweetness and saltiness and a negative correlation between pH and grainy, oiliness, color and structure uniformity, sourness, and milk. Most of the differences observed in QDA and most of the relationships observed in the principal component analysis were linked to the higher microbial activity induced by the adjunct culture. Independently of milk and starter types, consumers perceived Scamorza cheese as characterized by a good eating quality (mean liking scores were all above the neutral point of the hedonic scale). Although ST cheeses showed higher values for overall liking, 2 homogeneous groups of consumers were identified using partial least squares regression analysis. One group preferred ST cheeses with higher levels of tenderness, adhesiveness, springiness, and moisture in terms of texture, butter in terms of flavor, and sweetness in terms of taste, whereas a second group preferred ST+A products characterized by specific attributes of texture (cohesiveness and oiliness), flavor (milk), taste (sourness), and appearance (structure and color uniformity). We conclude that further studies for the development of short-ripened products based on the use of adjunct cultures should be conducted to promote product differentiation and meet the sensory requirements of particular segments of consumers.


Subject(s)
Cheese/analysis , Cheese/microbiology , Consumer Behavior , Food Preferences , Taste , Adult , Color , Female , Food Analysis , Food Microbiology , Humans , Hydrogen-Ion Concentration , Lactobacillus/isolation & purification , Lactobacillus helveticus/isolation & purification , Lactococcus lactis/isolation & purification , Linear Models , Male , Multivariate Analysis , Odorants , Principal Component Analysis
16.
Hematology ; 19(4): 239-43, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24620951

ABSTRACT

A three-decade-long retrospective study of iron status in a cohort of 1250 children aged 8-36 months was carried out at the Pediatric Department at the Second University Naples. Iron status was evaluated with independent variables such as family income, weight for height, introduction of cow's milk (CM), iron supplementation and weaning. Iron deficiency (ID) is prevalent in children with low income, early introduction of CM, delayed weaning, over-weight, and in those not receiving iron supplementation (P < 0.05). The first decade (1980-1990) was marked by low family income, while early introduction of CM characterized the first two decades (1980-1990, 1990-2000) (P < 0.05). ID depends on a variety of social and dietary factors. Hematological tests should be performed early to identify children at risk for ID.


Subject(s)
Anemia, Iron-Deficiency/diagnosis , Anemia, Iron-Deficiency/epidemiology , Iron Deficiencies , Animals , Body Size , Cattle , Child, Preschool , Dietary Supplements , Female , Humans , Income , Infant , Italy/epidemiology , Male , Mass Screening , Milk/physiology , Retrospective Studies , Weaning
17.
Opt Lett ; 39(4): 861-4, 2014 Feb 15.
Article in English | MEDLINE | ID: mdl-24562226

ABSTRACT

In this work, we present a simple fabrication process enabling the integration of a subwavelength amorphous silicon layer inside optical fibers by means of the arc discharge technique. To assess our method, we have fabricated a compact in-line Fabry-Perot interferometer consisting of a thin (<1 µm) a-Si:H layer completely embedded within a standard single-mode optical fiber. The device exhibits low loss (1.3 dB) and high interference fringe visibility (~80%) both in reflection and transmission, due to the high refractive index contrast between silica and a-Si:H. A high linear temperature sensitivity up to 106 pm/°C is demonstrated in the range 120°C-400°C. The proposed interferometer is attractive for point monitoring applications as well as for ultrahigh-temperature sensing in harsh environments.

18.
J Appl Microbiol ; 116(3): 632-43, 2014 Mar.
Article in English | MEDLINE | ID: mdl-24267916

ABSTRACT

AIMS: Lactobacillus plantarum is a lactic acid bacterium involved in the production of many fermented foods. Recently, several studies have demonstrated that aerobic or respiratory metabolism in this species leads to improved technological and stress response properties. METHODS AND RESULTS: We investigated respiratory growth, metabolite production and stress resistance of Lact. plantarum C17 during batch, fed-batch and chemostat cultivations under respiratory conditions. Sixty mutants were selected for their ability to tolerate oxidative stress using H2 O2 and menadione as selective agents and further screened for their capability to growth under anaerobic, respiratory and oxidative stress conditions. Dilution rate clearly affected the physiological state of cells and, generally, slow-growing cultures had improved survival to stresses, catalase production and oxygen uptake. Most mutants were more competitive in terms of biomass production and ROS degradation compared with wild-type strain (wt) C17 and two of these (C17-m19 and C17-m58) were selected for further experiments. CONCLUSIONS: This work confirms that, in Lact. plantarum, respiration and low growth rates confer physiological and metabolic advantages compared with anaerobic cultivation. SIGNIFICANCE AND IMPACT OF THE STUDY: Our strategy of natural selection successfully provides a rapid and inexpensive screening for a large number of strains and represents a food-grade approach of practical relevance in the production of starter and probiotic cultures.


Subject(s)
Lactobacillus plantarum/genetics , Oxidative Stress/genetics , Catalase/metabolism , Lactobacillus plantarum/enzymology , Lactobacillus plantarum/growth & development , Lactobacillus plantarum/metabolism , Mutation , Vitamin K 3/pharmacology
19.
J Appl Microbiol ; 115(3): 848-58, 2013 Sep.
Article in English | MEDLINE | ID: mdl-23782242

ABSTRACT

AIMS: The aim of the study is to gain further insight on the respiratory behaviour of Lactobacillus plantarum and its consequences on stress tolerance. METHODS AND RESULTS: We investigated the effect of temperature and respiration on the growth and stress (heat, oxidative, freezing, freeze-drying) response of Lact. plantarum C17 during batch cultivations. Temperature as well as respiration clearly affected the physiological state of cells, and generally, cultures grown under respiratory conditions exhibited improved tolerance of some stresses (heat, oxidative, freezing) compared to those obtained in anaerobiosis. Our results revealed that the activities in cell-free extracts of the main enzymes related to aerobic metabolism, POX (pyruvate oxidase) and NPR (NADH peroxidase), were significantly affected by temperature. POX was completely inhibited at 37°C, while the activity of NPR slightly increased at 25°C, indicating that in Lact. plantarum, the temperature of growth may be involved in the activation and modulation of aerobic/respiratory metabolism. CONCLUSIONS: We confirmed that respiration confers robustness to Lact. plantarum cells, allowing a greater stress tolerance and advantages in the production of starter and probiotic cultures. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study on respiratory metabolism on a strain other than the model strains WCFS1; novel information on the role of temperature in the modulation of aerobic/respiratory metabolism in Lact. plantarum is presented.


Subject(s)
Lactobacillus plantarum/growth & development , Stress, Physiological , Aerobiosis , Anaerobiosis , Hot Temperature , Lactobacillus plantarum/enzymology , Lactobacillus plantarum/metabolism , Peroxidases/antagonists & inhibitors , Peroxidases/metabolism , Pyruvate Oxidase/metabolism , Temperature
20.
World J Microbiol Biotechnol ; 29(9): 1713-22, 2013 Sep.
Article in English | MEDLINE | ID: mdl-23543191

ABSTRACT

Aerobic metabolism and response to oxidative stress and starvation were studied in 11 Lactobacillus plantarum, L. paraplantarum and L. pentosus strains in order to assess the impact of aerobic metabolism on the growth and on the stress response. The strains were grown in aerobiosis without supplementation (AE), with hemin (AEH) or with hemin and menaquinone (AEHM) supplementation and in anaerobiosis (AN) in a complex buffered substrate. Growth rate, biomass yield, glucose and O2 consumption, production of lactic acid and H2O2, catalase activity, oxidative and starvation stress tolerance were evaluated. Aerobic growth increased biomass yield in late stationary phase. Further increase in yield was obtained with both hemin (H) and menaquinone (M) addition. With few exceptions, the increase in biomass correlated with the decrease of lactic acid which, however, decreased in anaerobic conditions as well in some strains. Addition of H or H + M increased growth rate for some strains but reduced the duration of the lag phase. H2O2 production was found only for aerobic growth with no supplementation due to catalase production when hemin was supplemented. To our knowledge this is the first study in which the advantages of aerobic growth with H or H + M in improving tolerance of oxidative stress and long-term survival is demonstrated on several strains of the L. plantarum group. The results may have significant technological consequences for both starter and probiotic production.


Subject(s)
Lactobacillus plantarum/growth & development , Lactobacillus plantarum/metabolism , Oxidative Stress , Aerobiosis , Anaerobiosis , Biomass , Catalase/metabolism , Culture Media , Fermentation , Hemin , Hydrogen Peroxide/metabolism , Lactic Acid/metabolism , Lactobacillus plantarum/classification , Multivariate Analysis , Oxygen Consumption , Probiotics/metabolism , Vitamin K 2
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