Start-up procedures and analysis of heavy metals inhibition on methanogenic activity in EGSB reactor

The effectiveness of operating an industrial UASB reactor, treating wastewater from the beer industry, with flows containing heavy metals was evaluated. A pilot-scale UASB reactor, already used to simulate the industrial reactor, was unsuccessfully employed. An easy start-up was obtained arranging it as an EGSB reactor. Considerations about this modification are reported. The effects of Cu(II), Ni(II) and Cr(III) ions on the anaerobic activity were analyzed by measurements of methane production rate and COD removal. The employed biomass was the sludge of the industrial UASB reactor, while a solution of ethanol and sodium acetate with COD of 3000 mg/L and a heavy metal concentration of 50 mg/L were continuously fed. Experimental results proved higher biomass sensitivity for copper and much slighter for nickel and chromium. Moreover, copper inhibition has been demonstrated to be less significant if a metal-free feed was provided to the system before copper addition.     

Sensitivity of thermophilic methanogenic bacteria to heavy metals

The effects of Cd, Cu, and Ni on pure cultures of thermophilic methanogenic bacteria were studied. The bacteria used wereMethanobacterium thermoautotrophicum and TAM, a thermophilic, acetate-decarboxylating, methanogenic bacterium. Much lower concentrations of heavy metals were needed to cause initial inhibition of TAM (1 mg/liter Cu and Cd; 5 mg/liter Ni) compared withM. thermoautotrophicum (10 mg/liter Cu and Cd; and 100 mg/liter Ni). No growth of TAM occurred at 5 mg/liter Cu and 25 mg/liter Ni, while the corresponding values forM. thermoautotrophicum were 50 mg/liter Cu and 200 mg/liter Ni. Cd (50 mg/liter) was totally inhibitory toM. thermoautotrophicum but allowed minimal growth of TAM. Ni stimulated both organisms at an optimal concentration of 5 mg/liter forM. thermoautotrophicum and 1 mg/liter for TAM. The toxicity of Cd and Cu was found to depend upon the presence of Ni in the medium.     

The influence of substrate transport limitation on porosity and methanogenic activity of anaerobic sludge granules

The relationship between porosity, diameter and methanogenic activity of anaerobic granules has been investigated. Experiments with different granular sludges revealed that substrate transport limitations increase with the diameter of the granules. As a consequence, autolysis can occur in the core of the granule, producing hallow granules. The porosity measurements revealed that the hollow centre is not available for substrate transport. Possibly as an effect of bacterial lysis, the porosity decreases in the more interior layers of the granules. This results in a inactive inner part of the large granules, which is not involved in the treatment process; the specific methanogenic activity decreases with granule size. No marked difference in substrate affinity is observed between granules of different sizes, which probably indicates that for large granules only the exterior is biological active. Correspondence to: G. Lettinga     

Effect of heavy metals on marine phytoplankton

Phytoplankton community responses were used in a heavy metals (HM) marine pollution monitoring biological system. A multifactorial analysis was used in in situ experiments in the White Sea to study HM toxicity to a planktonik algae population in their copresence. It was ascertained that algae with a high rate of increase in population size, producing metabolites, restricting development of phytoplankton community associates, gain advantages in isolation conditions. The algae responded differently to addition of individual metals and their combinations in the environment. Change in the number of dominants resulted in disturbance of the phytoplankton community structure. It has been shown that there are cardinal points in phytoplankton development, determining the growth of individual algae populations and planktonic community on the whole, against a background of competition for biogenic elements and space in conditions of TM environment pollution.     

Metabolic properties and kinetics of methanogenic granules

Two types of mesophilic methanogenic granules (R- and F-granules) were developed on different synthetic feeds containing acetate, propionate and butyrate as major carbon sources and their metabolic properties were characterized. The metabolic activities of granules on acetate, formate and H₂-CO₂ were related to the feed composition used for their development. These granules performed a reversible reaction between H₂ production from formate and formate synthesis from H₂ plus bicarbonate. Both types of granules exhibited high activity on normal and branched volatile fatty acids with three to five carbons and low activity on ethanol and glucose. The granules performed a reversible isomerization between isobutyrate and butyrate during butyrate or isobutyrate degradation. Valerate and 2-methylbutyrate were produced and consumed during propionate-butyrate degradation. The respective apparent K _m (mm) for various substrates in disrupted R- and F-granules was: acetate, 0.43 and 0.41; propionate, 0.056 and 0.038; butyrate, 0.15 and 0.19; isobutyrate, 0.12 and 0.19; valerate, 0.15 and 0.098. Both granules had an optimum temperature range from 40 to 50° C for H₂-CO₂ and formate utilization and 40° C for acetate, propionate and butyrate utilization and a similar optimum pH. Correspondence to: J. G. Zeikus     

Effect of heavy metals on root growth and peroxidase activity in barley root tip

In the present work, we investigated the alteration of oxidative and peroxidative activities of peroxidases (PODs) along the longitudinal root axis of barley seedlings during heavy metal (HM; e.g., Cd, Cu, Hg, Ni, Pb) treatment. Analysis of the individual root segments revealed that all of the analyzed HMs caused an increase of guaiacol-POD activity, however to a different extent and spatial distribution. Cd-induced ferulic acid POD activity was observed along the whole root tip (RT), while Cu and Hg caused its increase in the meristematic zone and Ni mainly at the end of the differentiation zone of RT. The activation of coniferyl alcohol POD by HMs was detected along the whole RT. HM-induced hydrogen peroxide-generating POD activity was localized mainly to the elongation zone of RT. Elevated chlorogenic acid POD activity was observed in the meristematic zone and at the end of the differentiation zone of RTs. The activation of several PODs is probably associated with enhanced H₂O₂ production and lignification as a defense response of roots to several HM, to prevent their uncontrolled flux. On the other hand, this defense response is accompanied by root growth inhibition, due to the enhanced rigidification of cell wall and accelerated differentiation of RTs.     

Effect of heavy metals on isoperoxidases of Wheat

The influence of increasing concentrations of copper, zinc, lead, nickel, chromium and cadmium on 14-day-old seedlings of wheat (Triticum aestivum L. cv. Vergina) was studied. Plants were grown in 1/10 strength Rorison’s nutrient solution with increasing concentrations of each of the metals added separately. The toxicity of metals depressed shoot growth but the most evident symptoms were on roots. The concentration of each metal which caused inhibition of root growth was chosen to study the influence of metals on isoperoxidases of wheat shoots. The concentrations employed did not alter the number of peroxidase bands but almost in all cases enhanced the intensities of bands of pH 4.0-4.2 and 5.0-5.4, while they decreased the intensities of bands of pH 4.2-4.6 and 5.4-6.5. The similar effects of the different heavy metals employed may suggest similarity in metal action on wheat isoperoxidases. The increased intensities of peroxidase bands may be considered as an indication of enhanced senescence caused by the heavy metal treatments. Generally, our results suggest that the heavy metals employed have caused complex changes on the multiple forms of peroxidases.     

Effect of heavy metals on peppermint and cornmint

Heavy metal pollution of agricultural soils and air is one of the most severe ecological problems on a world scale and in Bulgaria in particular. The biggest sources of pollution in Bulgaria are some non-ferrous metals smelters, such as the Non-Ferrous Metals Combine (NFMC) near Plovdiv, situated on very fertile soils. Vegetable, arable and animal production in this area results in contaminated produce with excessive amounts of Cd, Pb, Cu, Mn and Zn.In order to discover some crops which could be grown on these areas without contamination of the end product, we conducted (in 1991–1993) field experiments in the vicinities of NFMC near Plovdiv. As experimental material we used Mentha piperita L. (cv Tundza and Clone No 1) and Mentha arvensis var piperascens Malinv. (cv Mentolna-14). Plants have been grown on three Plots: Plot No 1-at a distance of 400 m from the source of pollution; Plot No 2-at 3 km from the source of pollution and on a control Plot-in the experimental gardens of University of Agriculture in Plovdiv, at 10 km from the source of pollution. It was established that heavy metal pollution of soil and air at a distance of 400 m from the source of pollution decreased the yields of fresh herbage by 9–16% and the yield of essential oil by up to 14% compared to the control, but did not negatively affect the essential oil content and its quality.Oils obtained from Plot 1 at a distance of 400 m from the source of pollution have not been contaminated with heavy metals.Cultivar response to heavy metal pollution was established. A positive correlation between Pb concentration in leaves and in essential oil was found.Heavy metal concentration in the plant parts was found to be in order: for Cd roots > leaves > rhizomes > stems; Pb roots = leaves > rhizomes = stems; Cu roots > rhizomes = stems = leaves; Mn roots > leaves > stems = rhizomes; Zn leaves > roots > stems = rhizomes.The tested cultivars of peppermint and cornmint could be successfully grown in highly heavy metal polluted areas, as in the area around NFMC near Plovdiv, without contamination of the end product-the essential oils.Despite of the yield reduction (up to 14%), due to heavy metal contamination, mint still remained a very profitable crop and it could be used as substitute for the other highly contaminated crops.     

Effect of molybdate on methanogenic and sulfidogenic activity of biomass

The effect of molybdate, a sulfate analog, on the total methanogenic activity (TMA) and total sulfidogenic activity (TSA) of biomass metabolizing synthetic sucrose based substrate containing sulfate was investigated in batch assays. In Phase I of the study, TMA and TSA were assessed twice for four feed changes at a chemical oxygen demand to sulfate (COD/SO(4)(2-)) ratio of 3.5. In Phase II, long-term experiments were conducted for 10-13 feed changes with varying chemical oxygen demand (COD) concentration, sulfate concentration, COD/SO(4)(2-) ratio, molybdate dose and biomass with different growth histories. Assays with 3mM molybdate showed TSA inhibition over 85%. Dose dependency was observed for sulfate concentration, COD/SO(4)(2-) ratio, and biomass history. The minimum concentration that gave over 93% TSA inhibition was 0.25 mM. However, intermediate concentrations of molybdate inhibited methane producing bacteria (MPB) activity. TMA stimulation was observed at 0.75-2.0 mM molybdate.     

Effect of four heavy metals on the biology of Nostoc muscorum

Summary This study presents the effects of Cr, Pb, Ni and Ag on growth, pigments, protein, DNA, RNA, heterocyst frequency, uptake of NH₄ ⁺ and N0₃ ^–, loss of electrolytes (Na⁺ and K⁺), nitrate reductase and glutamine synthetase activities ofNostoc muscorum. The statistical tests revealed a direct positive correlation between the metal concentration and inhibition of different processes. Ni was found to be more toxic against growth, pigments and heterocyst differentiation compared to the other metals. Inhibition of pigment showed the following trend: chlorophyll > phycocyanin > carotenoid. No generalized trend for inhibition of macromolecules was observed. The loss of K⁺ and Na⁺ as affected by Cr, Ni and Pb was similar but more pronounced for K⁺ than Na⁺. The inhibition of physiological variables depicted the following trend: Na⁺ loss > K⁺ loss > glutamine synthetase > NH₄ uptake > growth > N0₃ ^– uptake > nitrate reductase > heterocyst frequency. This study therefore suggests that loss of electrolytes can be used as a first signal of metal toxicity in cyanobacteria. However, further study is needed to confirm whether the abnormality induced by nickel (branch formation) is a physiological or genetic phenomenon.     

Effect of heavy metals on the growth of selected wood-rotting basidiomycetes

Mercury, cadmium and cobalt were found to be the most toxic heavy metals, inducing strong growth inhibition of the tested basidiomycetes. The studied species differed significantly in their sensitivity to cadmium. The most sensitive fungus,Inonotus obliquus, did not grow at Cd concentrations higher than 0.1 mmol/L, whereasStereum hirsutum grew at more than 2 mmol Cd/L. Changes in mycelial morphology were observed inS. hirsutum andTrametes versicolor cultivated in the presence of cadmium and mercury. The toxicity of heavy metals was lower in rich, complex media. Presented at the 4th Mini-Symposium on Biosorption and Microbial Degradation, Prague, Czech Republic, November 26–29, 1996.     

Effect of chlorinated aliphatic hydrocarbons on the acetoclastic methanogenic activity of granular sludge

The toxicity of chlorinated aliphatic hydrocarbons on acetoclastic methanogens in anaerobic granular sludge was determined using a standardized anaerobic bioassay method. Most of the chloroaliphatics tested were strong inhibitors of methanogenesis. Tri- and tetrachloride derivatives of methane and ethane were the most highly toxic compounds tested, with concentrations of less than 18 mg/l resulting in 50% inhibition (IC₅₀) of the methanogenic activity. Dichlorinated compounds were less toxic, with IC₅₀ values ranging from 40 mg/l to 100 mg/l. On the other hand, perchlorinated derivatives of ethane and ethene were scarcely inhibitory at concentrations near their maximum water solubility. The toxicity caused by chlorinated aliphatic hydrocarbons was reversible. The comparison of structurally related compounds indicated that unsaturated chloroaliphatics were less toxic than their saturated counterparts. A reverse correlation between the electric dipole moment of these compounds and their methanogenic toxicity is discussed. Received: 9 July 1996 / Received revision: 11 October 1996 / Accepted: 18 October 1996     

重金属离子含量对利川莼菜生长的影响

莼菜原产于湖北省利川市,因其富含果胶质而具有极高的营养价值,是中国传统药食两用植物,也是国家一级珍稀濒危水生植物。为更好地保护莼菜这一珍稀植物资源,本研究以利川市高、中、低产莼菜田为研究对象,初步分析田中水和土壤的重金属离子含量对莼菜生长的影响,并了解其生长所需要的部分环境条件。结果显示:三类田的水质都达到了一类水质标准,其中锌离子含量只在高-低产田间表现出显著差异,在高、中产田间,中、低产田间未见显著差异;土壤中重金属离子含量总体处于三级水平,说明累积量较少,土质尚好。同时三类田中水为中性而土壤为偏酸性,且未表现出显著性差异。相关性分析表明水土中重金属离子并未对莼菜生长和产量产生实质影响,研究结果为下一步深入分析重金属离子对莼菜生长的影响机制以及制定资源保护策略奠定了基础。     

Effect of ammonia on the methanogenic activity of methylaminotrophic methane producing Archaea enriched biofilm

Ammonia is a metabolic product in the decomposition of protein wastes, and has a recognized inhibitory effect on methanogenesis; this effect has been slightly quantified on methanogenic biofilms and particularly those populated by methanogenic Archaea which produce ammonia as a catabolic product from methylated amines. This paper presents studies on the effect of ammonia on maximum methanogenic activity of anaerobic biofilms enriched by methylaminotrophic methane producing Archaea (mMPA). The effect of unionized free ammonia on the specific maximum methanogenic activity of a mMPA enriched biofilm was studied, using 250 mL flasks containing ceramic rings colonized by 30 day-old experimental biofilm and adding 48.8 (control system), 73.8, 98.8, 148.8, 248.8, 448.8 and 848.8 mg NH(3)-N/L. The systems were maintained for ten days at a pH of 7.5 and temperature of 37 degrees C. The results showed that at 848.8 mg NH(3)-N/L, biofilm methane production required 36 h adaptation period, prior to entering into maximum production phase. The highest maximum methanogenic activity reached a value of 2.337+/-0.213 g COD methane/g VSS *day when 48.8 mg NH(3)-N/L was added, and inhibition was clearly observed in those systems above 148.8 mg NH(3)-N/L, producing under 1.658+/-0.185 g COD methane/g VSS *day. The lowest methanogenic activity reached was 0.639+/-0.162 g COD methane/g VSS *day at the system added with 848.8 mg NH(3)-N/L. When applying the Luong and non-competitive inhibition models, the best fit was obtained with the non-competitive model, which predicted 50% inhibition of methanogenic activity at 365.288 mg NH(3)-N/L.     

Effect of heavy metals and temperature on the oxalate oxidase activity and lignification of metaxylem vessels in barley roots

The effect of Cd on oxalate oxidase (OxO) activity and its localisation were analysed in barley root. In Cd-treated roots OxO activity was strongly induced in the region 2–4 mm behind the root tip and in the area toward the root base. In situ analyses showed that Cd-induced OxO activity was localised to the cell wall (CW) of early metaxylem vascular bundles and surrounding parenchyma cells and was accompanied by lignification of metaxylem vessels. OxO activation was also observed during treatment with other heavy metals (HMs), salt treatment and at elevated non-optimal temperature. In contrast to HM activation of OxO and lignification, high temperature and NaCl indeed activated OxO but did not induce lignification of metaxylem vessels. These results suggest that oxalate oxidase as an H₂O₂-generating enzyme is activated in response to several stresses, however the ectopic lignification of metaxylem vessels is activated specifically by HMs. This HM-induced premature root xylogenesis due to ectopic lignification of metaxylem vessels probably causes shortening of the root elongation zone and therefore a reduction in root growth.     

Effect of heavy metals and temperature on the oxalate oxidase activity and lignification of metaxylem vessels in barley roots

The effect of Cd on oxalate oxidase (OxO) activity and its localisation were analysed in barley root. In Cd-treated roots OxO activity was strongly induced in the region 2–4 mm behind the root tip and in the area toward the root base. In situ analyses showed that Cd-induced OxO activity was localised to the cell wall (CW) of early metaxylem vascular bundles and surrounding parenchyma cells and was accompanied by lignification of metaxylem vessels. OxO activation was also observed during treatment with other heavy metals (HMs), salt treatment and at elevated non-optimal temperature. In contrast to HM activation of OxO and lignification, high temperature and NaCl indeed activated OxO but did not induce lignification of metaxylem vessels. These results suggest that oxalate oxidase as an H₂O₂-generating enzyme is activated in response to several stresses, however the ectopic lignification of metaxylem vessels is activated specifically by HMs. This HM-induced premature root xylogenesis due to ectopic lignification of metaxylem vessels probably causes shortening of the root elongation zone and therefore a reduction in root growth.     

Effect of medium composition on amylase production by some starch-degrading yeasts

Abstract The production of extracellular amylase activity by a number of recently described amyloytic yeast species, viz. Candida homilentoma, C. silvanorum, C. tsukubaensis, Cryptococcus flavus, Leucosporidium capsuligenum, Filobasidium capsuligenum and Trichosporon pullulans , was investigated. The effects on amylase secretion of pH, different carbon sources (glucose, maltose, dextrin, soluble starch) and of various nitrogen sources [yeast nitrogen base, yeast extract, corn steep liquor (CSL)] were compared for these yeasts.     

Effects of heavy metals on microbial activity of water and sediment communities

The effects of Cd²⁺, Cr³⁺ and Zn²⁺ on the microbial activity of water and sediment samples from a contaminated stream were studied. The maximum [¹⁴C]glucose uptake (V_max) and the mineralization (¹⁴CO₂) rates were determined. A 10% reduction in V_max was obtained at lower metal concentrations in water samples than in sediment ones. Moreover, a 10% decrease in ¹⁴CO₂ was observed at significantly minor metal levels, so ¹⁴CO₂ was more sensitive to evaluated heavy metal pollution. On the basis of MICs obtained for both communities, they were more sensitive to Cd²⁺ than to Cr³⁺ and Zn²⁺. Zinc was less inhibitory to V_max and ¹⁴CO₂ rates; Cr³⁺ showed an intermediate toxicity, and Cd²⁺ was 10–100 times more inhibitory than the other metals.     

The impact of heavy metals on the activity of some enzymes along the barley root

Barley seedlings 48 h after the onset of germination on filter paper treated for 24 h by 1 mM cadmium (Cd), 3 mM nickel (Ni) or 0.5 mM mercury (Hg) showed similar approximately 45% root growth inhibition. Although root growth inhibition was similar, loss of cell viability evaluated, as Evans blue uptake was distinct among Cd, Ni and Hg treated roots. While Cd and Hg caused cell death along the whole barley root (0–8 mm), Ni induced significant loss of cell viability only in root cells 6–8 mm distance from the root tip. Our results suggest that different metabolic processes are activated in different parts of barley root in relation to distance from the root tip during heavy metal (HM) treatment. Some of them are characteristic for several HMs such as inhibition of ascorbic acid oxidase or glutathione-S-transferase stimulation, while others are specific for individual HMs, e.g. activation of acid phosphatase and lipoxygenase by Cd and Hg, or inhibition of ascorbate peroxidase by Ni and Hg treatment.