Stefania Frassinetti

Effects of compost-derived humic acids on vegetable biomass production and microbial growth within a plant ( Cichorium intybus)-soil system: a comparative study

The responses of chicory plants to amendments with natural and synthetic surface active substances, represented by either potassium humates from compost stabilised green waste or Tween 80, are reported from a pot trial. Results are evaluated in terms of plant biomass production and behaviour of soil microbial populations following different treatments. Amendments with humic acids stimulated vegetative growth of chicory. They also caused significative variations in the numbers of bacterial heterotrophs and autotrophic nitrifiers in the soil. The study suggests that the mechanism through which humic acids affect both plant and soil microbes may chiefly involve enhancement of cell membrane permeability to nutrients.

Biodegradation of 4-(1-nonyl)phenol by axenic cultures of the yeast Candida aquaetextoris : identification of microbial breakdown products and proposal of a possible metabolic pathway

Candida aquaetextoris, a yeast recently described for its ability to use 4-(1-nonyl)phenol (pNP) as the sole carbon and energy source in aerobic conditions, has been studied in order to determine the degradation products deriving from the growth on such a compound which is of environmental concern because of its proved toxicity to several organisms. Two main metabolites, namely trans-4-hydroxy-cinnamic acid and 4-hydroxy-acetophenone (4-acetylphenol), have been identified through either TLC and NMR spectrometry analyses of liquid substrate from cultures of C. aquaetextoris grown on pNP, with 4-acetylphenol that accumulates without any further degradation. These findings suggest that C. aquaetextoris might metabolise pNP via terminal oxidation of the alkyl chain, followed by a β-oxidation pathway. On the basis of this evidence, a novel metabolic route for the microbial degradation of 4-(1-nonyl)phenol, at least in certain yeasts, is proposed.

Genotoxicity of 4-nonylphenol and nonylphenol ethoxylate mixtures by the use of Saccharomyces cerevisiae D7 mutation assay and use of this text to evaluate the efficiency of biodegradation treatments

Nonylphenol ethoxylates (NPnEOs, where n is the number of ethoxylic units in the molecule) are non-ionic surfactants widely used for domestic and industrial purposes. 4-Nonylphenol (4-NP), the main product of NPnEO biodegradation, is a toxic xenobiotic compound classified as endocrine disrupter. While numerous studies reported the toxicity and oestrogenic activity of nonylphenols, little is known about the mutagenicity of these compounds. In this paper, the genotoxicity of 4-NP and NPnEO mixtures was evaluated by using the D7 strain of Saccharomyces cerevisiae as experimental model. The same genotoxicity tests were applied to effluents deriving from experimental packed-bed bioreactors, developed for the treatment of NPnEO contaminated wastewater, in order to evaluate the residual genotoxic potential with respect to the influent waste. The target compounds fed to the bioreactors were 4-NP and NPnEO mixtures possessing an average of 5 or 1.5 ethoxylic units (Igepal CO-520 and Igepal CO-210, respectively). The results showed that 4-NP induced significant cytotoxic effect on S. cerevisiae cells at 50 mg/L, as well as mutagenic effects at the lowest tested concentrations (12 and 25 mg/L). 4-NP was the most genotoxic compound among those assayed, followed by Igepal CO-210, whereas Igepal CO-520 did not induce genotoxicity at any of the assayed concentrations. The genotoxic effects of 4-NP on yeast cells disappeared after the treatment of 4-NP artificially contaminated water in the bioreactor. This indicates that the biological treatment is capable of removing not only the pollutant, but also the toxicity associated to the compound and its degradation metabolites. This study represents, to the best of our knowledge, the first report that evaluates the genotoxicity of both 4-NP, NPnEOs and their potential aerobic degradation products on an eukaryotic organism. The obtained results suggest that the S. cerevisiae D7 strain is a very effective model microorganism to study the induction of genotoxic damage by the compounds under study. Moreover, this yeast assay has been proved effective to evaluate the detoxification effect deriving from biotreatment processes.

Biodegradation of nonionic surfactants. I. Biotransformation of 4-(1-nonyl)phenol by a Candida maltosa isolate

Results are reported concerning biodegradation of 4-(1-nonyl)phenol by cultures of a Candida maltosa strain isolated from aerobic sludge samples collected at a depuration plant treating wastewaters from a textile industry. The yeast was able to utilize 4-(1-nonyl)phenol as a sole carbon and energy source. Preliminary attempts to draw the actual metabolic pathway evidenced microbial attack on the alkyl chain with the production of 4-acetylphenol. To the best of our knowledge this is the first report describing a microorganism capable of attacking nonylphenol in axenic culture and at the same time allowing for the identification of its degradation products.

Genotoxicity evaluation of effluents from textile industries of the region Fez-Boulmane, Morocco: A case study

In order to investigate the biological hazard of effluents from textile industries of Fez-Boulmane region in Morocco, mutagenicity and phytotoxicity tests were performed on different biological systems. Moreover, the efficiency of a Sequencing Batch Reactor (SBR) system, working by activated sludge on a laboratory scale, was estimated by comparing the ecotoxicity results observed before and after wastewater treatment. Evaluation of the genotoxic potential was investigated by means of classic mutagenicity tests on D7 strain of Saccharomyces cerevisiae and by phytotoxicity tests on Allium sativum L., Vicia faba L. and Lactuca sativa L., estimating micronuclei presence, mitotic index and cytogenetic anomalies. The results obtained by testing untreated wastewater demonstrated major genotoxicity effects in S. cerevisiae and various levels of phytotoxicity in the three plant systems, while after SBR treatment no more ecotoxicological consequences were observed. These data confirm the effectiveness of the SBR system in removing toxic substances from textile wastewaters in Fez-Boulmane region.

Candida aquaetextoris sp. nov., a new species of yeast occurring in sludge from a textile industry wastewater treatment plant in Tuscany, Italy.

We describe Candida aquaetextoris, a new yeast species isolated from sludge that accumulates at the main wastewater treatment facility which processes discharges from textile factories located in the Prato metropolitan district, northern Tuscany, Italy. This yeast degrades 4-(1-nonyl)phenol, a toxic intermediate originating from the microbial attack of nonylphenol polyethoxylates, which are nonionic surfactants largely used in leather and textile industries. In the investigation we employed conventional and molecular taxonomy techniques to compare the new isolate to strains of physiologically similar species, such as Candida maltosa and Candida tropicalis, as well as strains of quite phenotypically different species, such as Candida haemulonii. The results demonstrate that the yeast which we identified represents a separate taxon. The type strain of C. aquaetextoris is strain Lmar1, which has been deposited in the Industrial Yeast Collection of the Division of Applied Microbiology, Department of Plant Biology, University of Perugia, Perugia, Italy, as strain DBVPG 6732.

Nonylphenol polyethoxylate degradation in aqueous waste by the use of batch and continuous biofilm bioreactors

An aerobic bacterial consortium (Consortium A) was recently obtained from textile wastewater and was capable of degrading 4-nonylphenol and nonylphenol polyethoxylates (NPnEOs). In the perspective of developing a biotechnological process for the treatment of effluents from activated sludge plants fed with NPnEO contaminated wastewater, the capability of Consortium A of biodegrading an industrial mixture of NPnEOs in the physiological condition of immobilized cells was investigated. Two identically configured packed bed reactors were developed by immobilizing the consortium on silica beads or granular activated carbon. Both reactors were tested in batch and continuous mode by feeding them with water supplemented with NPnEOs. The two reactors were monitored through chemical, microbiological and molecular integrated methodology. Active biofilms were generated on both immobilization supports. Both reactors displayed comparable NPnEO mineralization under batch and continuous conditions. FISH analyses evidenced that the biofilms evolved with time by changing the reactor operation mode and the organic load. Taken together, the data collected in this study provide a preliminary strong indication on the feasibility of Consortium A-based biofilm technology for the decontamination of NPnEO containing effluents.

Antibacterial and Antioxidant Activity of Essential Oils from Citrus spp.

Abstract The antibacterial and antioxidant activities of essential oils from Bitter orange, Sweet orange, Lemon and Mandarin were investigated. The antimicrobial capability of these oils was determined against ten strains of Gram-negative and Gram-positive bacteria, including some phytopathogenic strains. The antibacterial activity of the oils was expressed as minimum inhibitory concentrations (MICs). All oils showed good antibacterial activity against both Gram-negative and Gram-positive bacteria. The MICs for selected oils ranged 15–250 µg/mL. The lowest MICs were 15 µg/mL and 20 µg/mL against Xanthomonas citri strains, respectively. The antioxidant and antiradical scavenging properties of the selected oils were tested by means of 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. All examined oils exhibited a free radical scavenging activity, ranging 20–70% of DPPH inhibition. Lemon oil showed the most antioxidant capacity, with DPPH inhibition rate of 70%.

Bacterial attack of non-ionic aromatic surfactants: comparison of degradative capabilities of new isolates from nonylphenol polyethoxylate polluted wastewaters

Nonylphenol polyethoxylates (NPEOs) are largely used in many different industrial applications. In 1987 estimated production of NPEOs in Europe was 150,000 tons, with 25,000 tons only produced in Italy (1). They represent a group of compounds which are of environmental concern because of their toxicity to biological systems. Furthermore, NPEOs and their intermediates tend to accumulate in sewage sludge during wastewater depuration or possibly in sediments once treated waters are discharged into rivers and sea. Primary degradation of NPEOs, that also means the loss of surfactant properties, easily occurs in aerobic conditions as a consequence of the progressive loss of ethylene oxide units. On the other hand, complete mineralization appears to proceed very slowly. Anyway scarce information is available about microorganisms which possibly carry out biodegradation of these compounds. The present paper reports results concerning the isolation and characterization of three different Gram negative bacteria from...

Antimutagenic and antioxidant activity of Lisosan G in Saccharomyces cerevisiae.

In the present study the antimutagenic and antioxidant effects of a powder of grain (Lisosan G) in yeast Saccharomyces cerevisiae were studied. Results showed that Lisosan G treatment decreased significantly the intracellular ROS concentration and mutagenesis induced by hydrogen peroxide in S. cerevisiae D7 strain. The effect of Lisosan G was then evaluated by using superoxide dismutase (SOD) proficient and deficient strains of S. cerevisiae. Lisosan G showed protective activity in sod1Δ and sod2Δ mutant strains, indicating an in vivo antioxidant effect. A high radical scavenging activity of Lisosan G was also demonstrated in vitro using the oxygen radical absorbance capacity (ORAC) assay. The obtained results showed a protective effect of Lisosan G in yeast cells, indicating that its antioxidant capacity contributes to its antimutagenic action.