Papers by Spyridon Ntougias
Microorganisms, 2022
An increasing human population necessitates more food production, yet current techniques in agric... more An increasing human population necessitates more food production, yet current techniques in agriculture, such as chemical pesticide use, have negative impacts on the ecosystems and strong public opposition. Alternatives to synthetic pesticides should be safe for humans, the environment, and be sustainable. Extremely diverse ecological niches and millions of years of competition have shaped the genomes of algae to produce a myriad of substances that may serve humans in various biotechnological areas. Among the thousands of described algal species, only a small number have been investigated for valuable metabolites, yet these revealed the potential of algal metabolites as bio-pesticides. This review focuses on macroalgae and microalgae (including cyanobacteria) and their extracts or purified compounds, that have proven to be effective antibacterial, antiviral, antifungal, nematocides, insecticides, herbicides, and plant growth stimulants. Moreover, the mechanisms of action of the majo...
Bioresource technology, Jan 10, 2017
A membrane bioreactor (MBR), accomplishing high nitrogen removal efficiencies, was evaluated unde... more A membrane bioreactor (MBR), accomplishing high nitrogen removal efficiencies, was evaluated under various landfill leachate concentrations (50, 75 and 100% v/v). Proteinous and carbohydrate extracellular polymeric substances (EPS) and soluble microbial product (SMP) were strongly correlated (p<0.01) with organic load, salinity and NH4(+)-N. Exceptionally high β-glucosidase activities (6700-10,100Ug(-1)) were determined during MBR operation with 50% v/v leachate, as a result of the low organic carbon availability that extendedly induced β-glucosidases to breakdown the least biodegradable organic fraction. Illumina sequencing revealed that candidate Saccharibacteria were dominant, independently of the leachate concentration applied, whereas other microbiota (21.2% of total reads) disappeared when undiluted leachate was used. Fungal taxa shifted from a Saccharomyces- to a newly-described Cryptomycota-based community with increasing leachate concentration. Indeed, this is the first ...
Bioresource Technology, 2016
The effects of external carbon source addition on the nitrification and denitrification process w... more The effects of external carbon source addition on the nitrification and denitrification process were investigated in an intermittently aerated and fed membrane bioreactor treating landfill leachate by recording system performance, and amoA and nirS diversity dynamics using pyrosequencing. By adding 950mg/L glycerol, denitrification was optimized, resulting in total nitrogen removal efficiency of 81.0±2.4%. Under these conditions, amoA diversity was dominated by genotypes related to Nitrosomonas europaea, while increase in leachate&amp;amp;#39;s content and in glycerol addition by 50% led to irreversible inhibition of nitrification and enhanced ammonia accumulation, causing a severe suppression of Nitrosomonas and an increase in the relative abundance of Nitrosospira. However, this increase not only affected ammonia oxidizers, but also caused a massive shift in denitrifying community structure, resulting in the suppression of Arenimonas metalli-, Candidatus Accumulibacter- and Sulfuritalea hydrogenivorans-nirS related genotypes and the predominance of nirS-associated with Acidovorax and Thaurea sp.
Bioresource technology, Jan 3, 2015
Forty-nine white-rot strains belonging to 38 species of Basidiomycota were evaluated for olive-mi... more Forty-nine white-rot strains belonging to 38 species of Basidiomycota were evaluated for olive-mill wastewater (OMW) degradation. Almost all fungi caused high total phenolics (>60%) and color (⩽70%) reduction, while COD and phytotoxicity decreased to a lesser extent. Culture extracts from selected Agrocybe cylindracea, Inonotus andersonii, Pleurotus ostreatus and Trametes versicolor strains showed non-altered physicochemical and enzymatic activity profiles when applied to raw OMW in the presence or absence of commercial catalase, indicating no interaction of the latter with fungal enzymes and no competition for H2O2. Hydrogen peroxide's addition resulted in drastic OMW's decolorization, with no effect on phenolic content, suggesting that oxidation affects colored components, but not necessarily phenolics. When fungal extracts were heat-treated, no phenolics decrease was observed demonstrating thus their enzymatic rather than physicochemical oxidation. Laccases added to OM...
Environmental science and pollution research international, Jan 25, 2015
A 4-year proactive environmental surveillance of Legionella spp. in the water distribution and co... more A 4-year proactive environmental surveillance of Legionella spp. in the water distribution and cooling systems of five health-care facilities was carried out as part of the strategy for the prevention of hospital-acquired Legionnaires' disease in Northeastern Greece. Legionella spp. were detected in 71 out of 458 collected samples. The majority of strains belonged to Legionella pneumophila serogroups 2-15 (75.0 %), while all L. pneumophila serogroup 1 strains (23.6 %) were isolated from a single hospital. The highest percentage of positive samples was found in distal sites (19.4 %), while no Legionella strains were detected in cooling systems. Each hospital was colonized at least once with L. pneumophila, while remedial actions resulted in significant reduction of Legionella concentration. The molecular epidemiology of environmental L. pneumophila strains was also investigated using random amplified polymorphic DNA (RAPD) and multi-gene sequence-based analysis. Based on RAPD pat...
BioMed research international, 2013
Olive mill wastes (OMWs) are high-strength organic effluents, which upon disposal can degrade soi... more Olive mill wastes (OMWs) are high-strength organic effluents, which upon disposal can degrade soil and water quality, negatively affecting aquatic and terrestrial ecosystems. The main purpose of this review paper is to provide an up-to-date knowledge concerning the microbial communities identified over the past 20 years in olive mill wastes using both culture-dependent and independent approaches. A database survey of 16S rRNA gene sequences (585 records in total) obtained from olive mill waste environments revealed the dominance of members of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Actinobacteria. Independent studies confirmed that OMW microbial communities' structure is cultivar dependent. On the other hand, the detection of fecal bacteria and other potential human pathogens in OMWs is of major concern and deserves further examination. Despite the fact that the degradation and detoxification of the olive mill wastes have been mostly investi...
Fungal biology
The Pleurotus eryngii species-complex comprises choice edible mushrooms growing on roots and lowe... more The Pleurotus eryngii species-complex comprises choice edible mushrooms growing on roots and lower stem residues of Apiaceae (umbellifers) plants. Material deriving from extensive sampling was studied by mating compatibility, morphological and ecological criteria, and through analysis of ITS1-5.8S-ITS2 and IGS1 rRNA sequences. Results revealed that P. eryngii sensu stricto forms a diverse and widely distributed aggregate composed of varieties elaeoselini, eryngii, ferulae, thapsiae, and tingitanus. Pleurotuseryngii subsp. tuoliensis comb. nov. is a phylogenetically sister group to the former growing only on various Ferula species in Asia. The existence of Pleurotusnebrodensis outside of Sicily (i.e., in Greece) is reported for the first time on the basis of molecular data, while P. nebrodensis subsp. fossulatus comb. nov. is a related Asiatic taxon associated with the same plant (Prangos ferulacea). Last, Pleurotusferulaginis sp. nov. grows on Ferulago campestris in northeast Italy,...
Microfauna community structure was examined in the mixed liquor of a bench-scale bioreactor equip... more Microfauna community structure was examined in the mixed liquor of a bench-scale bioreactor equipped with an intermittent aeration and feeding system. The reactor was operated under an intermittent aeration of 25 min in every 1 h and varying feeding conditions (0.264, 0.403 and 0.773 kg BOD 5 /m 3 d). A total of 14 protozoan and metazoan taxa were identified by microscopic examination. Sessile ciliates, followed by crawling ciliates, were the major protozoan groups under 0.403 kg BOD 5 /m 3 d organic loading conditions, while sessile ciliate population was remarkably increased under an organic loading of 0.773 kg BOD 5 /m 3 d. Principal Component Analysis and Pearson correlation coefficient tests were performed in order to reveal relationships between microfauna community and operational parameters. Ciliophora specific-18S rRNA gene clone library was constructed to identify ciliate diversity under 0.773 kg BOD 5 /m 3 d organic loading conditions. Ciliophora diversity consisted of members of Aspidiscidae, Epistylidae, Opisthonectidae and Vorticellidae, with the majority of the clones being associated with the species Vorticella fusca. At least one novel phylogenetic linkage among Ciliophora was identified. Comparisons made after molecular characterization and microscopic examination of Ciliophora community showed that the estimation of broad ciliate groups is useful for ecological considerations and evaluation of the operational conditions in wastewater treatment plants.
Journal of Chemical Technology & Biotechnology, 2013
ABSTRACT BACKGROUND The need to monitor and optimize biological nitrogen removal (BNR) processes ... more ABSTRACT BACKGROUND The need to monitor and optimize biological nitrogen removal (BNR) processes has led to the use of on-line instrumentation. In situ located sensors can monitor in a real-time mode the dynamics of microbial processes, providing the opportunity to understand and optimize process performance. RESULTSA nitrification–denitrification process was monitored on-line for the first time in an intermittently aerated and pulse fed activated sludge system using in situ located sensors for ammonia and nitrate. Pulse feeding created a reduced C/N ratio gradient across the anoxic phase, resulting in complete denitrification within a period of 20 min. Two denitrification rates were determined, corresponding to nitrate reduction during utilization of the readily biodegradable (0.110–0.246 g g-1 d-1) and the slowly (particulate) biodegradable (0.032–0.041 g g-1 d-1) COD, respectively. Despite the fact that the initial C/N ratio at both Food/Microorganism ratio (F/M) 0.20 and 0.28 was decreased from 4.8 to 1.8 at the end of the anoxic phase, the C/N ratio decrease was twice as fast at the higher F/M ratio. CONCLUSION Pulse-feeding resulted in higher C/N ratios at the beginning of the anoxic phase, creating a reduced C/N ratio gradient during the denitrification period. Organic load was mostly consumed during the anoxic phase, resulting in high nitrification efficiency, low oxygen requirement and saving energy. © 2013 Society of Chemical Industry
Folia Microbiologica, 2006
Three hydroxyl-radical producing biomimetic systems, composed of Cu II , hydrogen peroxide and py... more Three hydroxyl-radical producing biomimetic systems, composed of Cu II , hydrogen peroxide and pyridine, glucaric or succinic acid, were able to perform decolorization of olive mill wastewaters (OMW) >85 % within 3 d combined with a significant removal of total phenols (>75 %). The systems consisting of 50 mmol/L succinic acid, 5-10 mmol/L CuSO 4 and 100 mmol/L H 2 O 2 were the most effective at OMW treatment, and led to the reduction of phenol contents to <1 % along with high decolorization (>88 %) and acceptable values of chemical oxygen demand.
Chemosphere, 2012
Thirty-nine white-rot fungi belonging to nine species of Agaricomycotina (Basidiomycota) were ini... more Thirty-nine white-rot fungi belonging to nine species of Agaricomycotina (Basidiomycota) were initially screened for their ability to decrease olive-mill wastewater (OMW) phenolics. Four strains of Ganoderma australe, Ganoderma carnosum, Pleurotus eryngii and Pleurotus ostreatus, were selected and further examined for key-aspects of the OMW biodegradation process. Fungal growth in OMW-containing batch cultures resulted in significant decolorization (by 40-46% and 60-65% for Ganoderma and Pleurotus spp. respectively) and reduction of phenolics (by 64-67% and 74-81% for Ganoderma and Pleurotus spp. respectively). COD decrease was less pronounced (12-29%). Cress-seeds germination increased by 30-40% when OMW was treated by Pleurotus strains. Toxicity expressed as inhibition of Aliivibrio fischeri luminescence was reduced in fungal-treated OMW samples by approximately 5-15 times compared to the control. As regards the pertinent enzyme activities, laccase and Mn-independent peroxidase were detected for Ganoderma spp. during the entire incubation period. In contrast, Pleurotus spp. did not exhibit any enzyme activities at early growth stages; instead, high laccase (five times greater than those of Ganoderma spp.) and Mn peroxidases activities were determined at the end of treatment. OMW decolorization by Ganoderma strains was strongly correlated to the reduction of phenolics, whereas P. eryngii laccase activity was correlated with the effluent's decolorization.
Bioresource Technology, 2011
Despite the numerous compost stability and maturity tests, no universally accepted compost stabil... more Despite the numerous compost stability and maturity tests, no universally accepted compost stability or maturity index exists. The fluorescein di-acetate (FDA) enzymatic assay, originating from soil studies, is examined here as a potential new compost stability test, and is compared to microbial respiration and phytotoxicity indices. Thirteen composts were used in the study from different source materials. Static microbial respiration activity indices calculated were the cumulative O 2 consumptions, O 2 consumption rates, total C-CO 2 production, the respiratory quotient and the bio C/N ratio. Compost phytotoxicity was quantified via a 7-day tomato seed germination assay. Results showed that the net fluorescein release rates correlated with all stability indices. The germination index marginally correlated with the fluorescein release rates, but not with any of the other stability indices. New limits to classify composts regarding their stability were proposed.
Physiological and Molecular Plant Pathology, 2005
A transgenic GUS-expressing strain of the root-infecting fungal pathogen Fusarium oxysporum f.sp.... more A transgenic GUS-expressing strain of the root-infecting fungal pathogen Fusarium oxysporum f.sp. radicis-lycopersici was used to inoculate the roots of tomato plants (Lycopersicon esculentum Mill.) grown on a compost mix made from grape marc wastes and extracted olive press cake (GM-EPC). Plants exhibited an enhanced defensive capacity against the pathogen as compared with control plants grown on peat. Pathogen viability and growth in the potting mixes, as determined by GUS activity measurements and by colony forming unit enumeration, was not affected. Interestingly, the pathogen was not able to penetrate and colonize the root tissue. Moreover, the sterilized compost extract was also able to protect the plants. Induction of systemic resistance by the compost was assessed using the foliar pathogen Septoria lycopersici and by PR gene expression analysis carried out in leaves of tomato plants grown on the GM-EPC compost. Our data strongly indicate that induction of plant defence response is the main mechanism of biological control mediated by the GM-EPC compost. q
New biotechnology, Jan 25, 2017
In this study, the deterioration of the typical EBPR (Enhanced Biological Phosphorus Removal) pro... more In this study, the deterioration of the typical EBPR (Enhanced Biological Phosphorus Removal) process due to the simultaneous presence of electron donor (external substrate) and electron acceptor (oxygen or nitrate) was investigated by using a PAOs (Polyphosphate Accumulating Organisms)-enriched biomass grown in a modified DEPHANOX system. Intracellular and extracellular constituents were monitored in batch tests under different electron donor and acceptor conditions and specific oxygen and nitrogen uptake rates were evaluated. Results showed that phosphorus uptake was inhibited during the simultaneous presence of electron donor (acetate) and acceptor (O2/NO3(-)) in the mixed liquor. In the presence of acetate, PHAs and glycogen were produced under both aerobic and anoxic conditions irrespectively to the PHAs amount already stored intracellularly. The Krebs cycle reactions and oxidative phosphorylation provided the reduced coenzymes and energy required for PHAs synthesis when biomas...
Journal of Environmental Science and Health, Part A, 2016
Mature landfill leachate is a heavily-polluted wastewater due to its recalcitrant nature of organ... more Mature landfill leachate is a heavily-polluted wastewater due to its recalcitrant nature of organic matter, and high ammonia and salt content. Despite the moderate saline and alkaline nature of this habitat, no attention has been paid to the isolation and functional role of extremophiles in such environment. In this work, a total of 73 and 29 bacterial strains were isolated by using alkaline and saline media, respectively, while bacteria from mature landfill leachate growing in these media were enumerated as 1.5 ± 0.1 (×10(8)) and 5.8 ± 0.9 (×10(8)) cfu/L. Based on their pH and salt ranges and optima for growth, all bacterial isolates were halotolerant alkaliphiles (either facultative or obligate), with the majority of them being extremely halotolerant bacteria. These halotolerant alkaliphiles were classified into 14 operational taxonomic units (OTUs). Of these, 12 are placed within known halophilic and alkaliphilic species of the genera Dietzia, Glycocaulis, Halomonas, Marinobacter, Piscibacillus and Rhodobacter, while the remaining OTUs represented two novel phylogenetic linkages among the families Cyclobacteriaceae and Rhodobacteraceae. Examination of their hydrolytic ability through the performance of lipase, protease and β-glucosidase assays using landfill leachate as the growth substrate revealed that all halotolerant alkaliphiles isolated exhibited extremely high lipolytic activities (up to 78,800 U g(-1) protein), indicating a key involvement of extremophilic microbiota at the late landfill maturation stage. The wide extremely lipolytic halotolerant alkaliphilic community identified also makes mature landfill leachate an ideal microbial pool for the isolation of novel extremophiles of biotechnological interest.
Microbes and environments, 2016
Two thirds of Svalbard archipelago islands in the High Arctic are permanently covered with glacia... more Two thirds of Svalbard archipelago islands in the High Arctic are permanently covered with glacial ice and snow. Polar bacterial communities in the southern part of Svalbard were characterized using an amplicon sequencing approach. A total of 52,928 pyrosequencing reads were analyzed in order to reveal bacterial community structures in stream and lake surface water samples from the Fuglebekken and Revvatnet basins of southern Svalbard. Depending on the samples examined, bacterial communities at a higher taxonomic level mainly consisted either of Bacteroidetes, Betaproteobacteria, and Microgenomates (OP11) or Planctomycetes, Betaproteobacteria, and Bacteroidetes members, whereas a population of Microgenomates was prominent in 2 samples. At the lower taxonomic level, bacterial communities mostly comprised Microgenomates, Comamonadaceae, Flavobacteriaceae, Legionellales, SM2F11, Parcubacteria (OD1), and TM7 members at different proportions in each sample. The abundance of OTUs shared in common among samples was greater than 70%, with the exception of samples in which the proliferation of Planctomycetaceae, Phycisphaeraceae, and Candidatus Methylacidiphilum spp. lowered their relative abundance. A multi-variable analysis indicated that As, Pb, and Sb were the main environmental factors influencing bacterial profiles. We concluded that the bacterial communities in the polar aquatic ecosystems examined mainly consisted of freshwater and marine microorganisms involved in detritus mineralization, with a high proportion of zooplankton-associated taxa also being identified.
Plant and Soil, Mar 9, 2010
Rhizospheric and root-associated/endophytic (RAE) bacteria were isolated from tomato plants grown... more Rhizospheric and root-associated/endophytic (RAE) bacteria were isolated from tomato plants grown in three suppressive compost-based plant growth media derived from the olive mill, winery and Agaricus bisporus production agro-industries. Forty-four (35 rhizospheric and 9 RAE) out of 329 bacterial strains showed in vitro antagonistic activity against at least one of the soil-borne fungal pathogens, Fusarium oxysporum f.sp. radicis-lycopersici (FORL), F. oxysporum f.sp. raphani, Phytophthora cinnamomi, P. nicotianae and Rhizoctonia solani. The high percentage of total isolates showing antagonistic properties Plant Soil (2010) 333:233-247
Environmental Technology, 2016
A membrane bioreactor was operated under intermittent aeration and various organic loading rates ... more A membrane bioreactor was operated under intermittent aeration and various organic loading rates (OLR: 0.070, 0.159 and 0.291 g COD L(-1) d(-1)) to remove carbon and nitrogen from mature landfill leachate, where external carbon source (glycerol) addition resulted in effective nitrate removal. A relative increase in soluble microbial product (SMP) over extracellular polymeric substances (EPS) was observed at the highest OLR and glycerol addition, whereas no membrane biofouling occurred. SMP (proteins and carbohydrates) and carbohydrate EPS correlated positively and negatively, respectively, with suspended solids and transmembrane pressure (TMP). Moreover, proteinous SMP significantly correlated with carbon and nitrogen load. Principal component analysis also revealed the influence of leachate organic and nitrogen content on biomass production, TMP and sessile ciliate densities. Although filamentous index (FI) was sustained at high levels (3-4), with Haliscomenobacter hydrossis being the main filamentous bacterium identified, no bulking phenomena occurred. High glycerol addition resulted in a rapid increase in sessile ciliate population. Increased Epistylis and Vorticella microstoma population was detected by microscopic examination during high glycerol addition, while a remarkable Rhogostoma population (supergroup Rhizaria) was identified by molecular techniques. The contribution of Rhizaria in nitrogen processes may lead to the dominance of Rhogostoma during landfill leachate treatment.
World Journal of Microbiology Biotechnology, 2011
Bacterial and b-proteobacterial diversity in Olea europaea var. mastoidis-and O. europaea var. ko... more Bacterial and b-proteobacterial diversity in Olea europaea var. mastoidis-and O. europaea var. koroneiki-generated olive mill wastewaters: influence of cultivation and harvesting practice on bacterial community structure Nektarios Kavroulakis • Spyridon Ntougias Abstract Despite the fact that several approaches have been applied for the bioremediation of olive mill wastewaters, little information is available on bacteria inhabiting these agro-industrial effluents. In the present study, 16S rRNA gene clone libraries were constructed to identify bacterial diversity in olive-oil mill wastewaters generated by two olive varieties, Olea europaea var. mastoidis and O. europaea var. koroneiki. Due to chloroplast excess in wastewater produced from the processing of O. europaea var. koroneiki, a clone library using specific PCR primers for b-Proteobacteria was further constructed. The bacterial diversity in O. europaea var. mastoidis-generated olive mill wastewaters consisted mainly of members of Acetobacteriaceae, Prevotellaceae and Lactobacillaceae, while the majority of b-proteobacteria identified in O. europaea var. koroneiki-generated olive mill wastewaters were placed within the families Comamonadaceae, Oxalobacteraceae, Hydrogenophilaceae and Rhodocyclaceae. At least 17 novel phylogenetic linkages among Bacteria were identified. Olive-oil mill wastewaters microbiota appears to have originated from soil and freshwater environments, while the cultivation and harvesting practice highly influenced the bacterial community structure in olive mill wastewaters. The presence of fecal bacteria in O. europaea var. mastoidis-generated olive mill wastewaters, due to the long harvesting period, should be of concern.
A novel enhanced biological phosphorus removal (EBPR) system, which combined the intermittent fee... more A novel enhanced biological phosphorus removal (EBPR) system, which combined the intermittent feeding design with an anaerobic selector, was examined using on-line oxidation reduction potential (ORP), nitrate and ammonium probes. Two experimental periods were investigated: the aerobic and anoxic phases were set at 40 and 20 minutes respectively for period I, and set at 30 and 30 minutes for period II. Chemical oxygen demand (COD), biochemical oxygen demand (BOD5) and P removal were measured as high as 87%, 96% and 93% respectively, while total Kjeldahl nitrogen (TKN) and NH4(+) removal averaged 85% and 91%. Two specific denitrification rates (SDNRs), which corresponded to the consumption of the readily biodegradable and slowly biodegradable COD, were determined. SDNR-1 and SDNR-2 during period I were 0.235 and 0.059 g N g(-1) volatile suspended solids (VSS) d(-1) respectively, while the respective rates during period II were 0.105 and 0.042 g N g(-1) VSS d(-1). The specific nitrate formation and ammonium oxidizing rates were 0.076 and 0.064 g N g(-1) VSS d(-1) for period I and 0.065 and 0.081 g N g(-1) VSS d(-1) for period II respectively. The specific P release rates were 2.79 and 4.02 mg P g(-1) VSS h(-1) during period I and II, while the respective anoxic/aerobic uptake rates were 0.42 and 0.55 mg P g(-1) VSS h(-1). This is the first report on an EBPR scheme using the intermittent feeding strategy.
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Papers by Spyridon Ntougias