Marine Fungi Aspergillus sydowii and Trichoderma sp. Catalyze the Hydrolysis of Benzyl Glycidyl Ether

Whole cells of the marine fungi Aspergillus sydowii Gc12, Penicillium raistrickii Ce16, P. miczynskii Gc5, and Trichoderma sp. Gc1, isolated from marine sponges of the South Atlantic Ocean (Brazil), have been screened for the enzymatic resolution of (±)-2-(benzyloxymethyl)oxirane (benzyl glycidyl ether; 1). Whole cells of A. sydowii Gc12 catalyzed the enzymatic hydrolysis of (R,S)-1 to yield (R)-1 with an enantiomeric excess (ee) of 24–46% and 3-(benzyloxy)propane-1,2-diol (2) with ee values <10%. In contrast, whole cells of Trichoderma sp. Gc1 afforded (S)-1 with ee values up to 60% and yields up to 39%, together with (R)-2 in 25% yield and an ee of 32%. This is the first published example of the hydrolysis of 1 by whole cells of marine fungi isolated from the South Atlantic Ocean. The hydrolases from the two studied fungi exhibited complementary regioselectivity in opening the epoxide ring of racemic 1, with those of A. sydowii Gc12 showing an (S) preference and those of Trichoderma sp. Gc1 presenting an (R) preference for the substrate.     

Stereoselective Bioreduction of 1-(4-Methoxyphenyl)ethanone by Whole Cells of Marine-Derived Fungi

Nine strains of marine-derived fungi (Aspergillus sydowii Ce15, A. sydowii Ce19, Aspergillus sclerotiorum CBMAI 849, Bionectria sp. Ce5, Beauveria felina CBMAI 738, Cladosporium cladosporioides CBMAI 857, Mucor racemosus CBMAI 847, Penicillium citrinum CBMAI 1186, and Penicillium miczynskii Gc5) were screened, catalyzing the asymmetric bioreduction of 1-(4-methoxyphenyl)ethanone 1 to its corresponding 1-(4-methoxyphenyl)ethanol 2. A. sydowii Ce15 and Bionectria sp. Ce5 produced the enantiopure (R)-alcohol 2 (>99% ee) in accordance with the anti-Prelog rule and, the fungi B. felina CBMAI 738 (>99% ee) and P. citrinum CBMAI 1186 (69% ee) in accordance with the Prelog rule. Stereoselective bioreduction by whole cells of marine-derived fungi described by us is important for the production of new reductases from marine-derived fungi.     

Bioremediation of Fungicides by Spent Mushroom Substrate and Its Associated Microflora

Experiments were conducted both under in vitro and in situ conditions to determine the biodegradation potential of button mushroom spent substrate (SMS) and its dominating microbes (fungi and bacteria) for carbendazim and mancozeb, the commonly used agricultural fungicides. During 6 days of incubation at 30 ± 2°C under broth culture conditions, highest degradation of carbendazim (17.45%) was recorded with B-1 bacterial isolate, while highest degradation of mancozeb (18.05%) was recorded with Trichoderma sp. In fungicide pre-mixed sterilized SMS, highest degradation of carbendazim (100.00–66.50 μg g⁻¹) was recorded with mixed inoculum of Trichoderma sp. and Aspergillus sp., whereas highest degradation of mancozeb (100.00–50.50 μg g⁻¹) was with mixed inoculum of Trichoderma sp., Aspergillus sp. and B–I bacterial isolate in 15 days of incubation at 30 ± 2°C. All these microbes both individually as well as in different combinations grew well and produced extracellular lignolytic enzymes on SMS, which helped in fungicides degradation. Under in situ conditions, among three different proportions of SMS (10, 20 and 30%, w/w) mixed with fungicide pre-mixed soil (100 μg g⁻¹ of soil), the degradation of carbendazim was highest in 30% SMS treatment, while for mancozeb it was in 20% SMS treatment. The residue levels of both fungicides decreased to half of their initial concentration after 1 month of SMS mixing.     

Biodegradation of thiocyanate using co-culture of Klebsiella pneumoniae and Ralstonia sp.

Thiocyanate-degrading microbial co-culture was isolated from thiocyanate-contaminated site and tested for thiocyanate degradation potential and thiocyanate-toxicity tolerance and identified as Klebsiella pneumoniae and Ralstonia sp. by 16S rDNA sequencing. The co-culture was able to degrade thiocyanate with degradation rate of 500 mg L⁻¹d⁻¹ at 2,500 mg L⁻¹ thiocyanate concentration at pH 6.0 and 37oC following thiocyanate hydrolase pathway. The Haldane kinetic model elucidates the growth and thiocyanate biodegradation kinetics of the co-culture with Ki value of 1,876 mg L⁻¹. The thiocyanate biodegradation kinetics was not affected by the additional supply of glucose. The very high activities of thiocyanate hydrolase, cyanide oxygenase, and cytochrome P-450 content during growth on thiocyanate were observed, showing the induction mechanism.     

Bioconversion of Iodoacetophenones by Marine Fungi

Nine marine fungi (Aspergillus sclerotiorum CBMAI 849, Aspergillus sydowii Ce19, Beauveria felina CBMAI 738, Mucor racemosus CBMAI 847, Penicillium citrinum CBMAI 1186, Penicillium miczynskii Ce16, P. miczynskii Gc5, Penicillium oxalicum CBMAI 1185, and Trichoderma sp. Gc1) catalyzed the asymmetric bioconversion of iodoacetophenones 1-3 to corresponding iodophenylethanols 6-8. All the marine fungi produced exclusively (S)-ortho-iodophenylethanol 6 and (S)-meta-iodophenylethanol 7 in accordance to the Prelog rule. B. felina CBMAI 738, P. miczynskii Gc5, P. oxalicum CBMAI 1185, and Trichoderma sp. Gc1 produced (R)-para-iodophenylethanol 8 as product anti-Prelog. The bioconversion of para-iodoacetophenone 3 with whole cells of P. oxalicum CBMAI 1185 showed competitive reduction-oxidation reactions.     

Aerobic heterotrophic bacteria and petroleum-utilizing bacteria from cow dung and poultry manure

In this study, enumeration and identification of total aerobic heterotrophic bacteria and petroleum-utilizing bacteria as well as the degradative potential of petroleum-utilizing bacterial isolates were carried out. The average counts of total aerobic heterotrophic bacteria in cow dung and poultry manure were 74.25 × 10⁵ c.f.u. g⁻¹ and 138.75 × 10⁵ c.f.u. g⁻¹ respectively. Acinetobacter sp, Bacillus sp, Pseudomonas sp, and Serratia spp. occurred as aerobic heterotrophs in both cow dung and poultry manure. However, Alcaligenes spp. occurred only in cow dung while, Flavobacterium sp, Klebsiella sp, Micrococcus sp, and Nocardia spp. occurred only in poultry manure as aerobic heterotrophs. The average counts of petroleum-utilizing bacteria in cow dung and poultry manure were 9.25 × 10⁵ c.f.u. g⁻¹ and 17.25 × 10⁵ c.f.u. g⁻¹ respectively. Pseudomonas spp. occurred as petroleum utilizer in both cow dung and poultry manure. However, Bacillus spp. occurred only in cow dung while Acinetobacter spp. and Micrococcus spp. occurred only in poultry manure as petroleum utilizers. Relative abundance of petroleum utilizers in total aerobic heterotrophs ranged from 6.38% to 20.00% for cow dung and from 9.38% to 17.29% for poultry manure. Introduction of pure cultures of petroleum-utilizing bacteria from cow dung and poultry manure into sterile oil-polluted soil revealed oil degradation in one week period.     

Fungal utilization of organophosphate pesticides and their degradation byAspergillus flavus andA. sydowii in soil

Fungal species were isolated which utilize organophosphate pesticides,viz. phosphorothioic (pirimiphos-methyl and pyrazophos), phosphorodithioic (dimethoate and malathion), phosphonic (lancer) and phosphoric (profenfos) acid derivatives. Pesticide degradation was studiedin vitro andin vivo (soil).Aspergillus flavus, A. fumigatus, A. niger, A. sydowii, A. terreus, Emericella nidulans, Fusarium oxysporum andPenicillium chrysogenum were isolated from pesticide-treated wheat straw. The number ofA. sydowii colonies was significantly promoted by 1 mmol/L pirimiphos-methyl, pyrazophos, lancer, dimethoate and malathion when used as phosphorus sources and by pirimiphos-methyl and pyrazophos when used as carbon sources. The number ofA. flavus colonies increased with 0.5 mmol/L lancer and malathion used as the only carbon sources.A. sydowii, A. niger, A. flavus, E. nidulans andF. oxysporum grew on, and utilized, 5 pesticides as phosphorus source and showed more than 50% mass growth.A. sydowii, A. flavus andF. oxysporum phosphatase hydrolyzed the pesticides suggesting that these species are important pesticide degraders.A. sydowii produced higher amounts of the phosphatase thanA. flavus andF. oxysporum. The enzyme was highly active against pyrazophos, lancer and malathion used as the only sources of organic phosphate.A. flavus andA. sydowii phosphatases efficiently hydrolyzed pesticides at 300 ppm in soil, the degradation at 1000 ppm was lower. Mineralization of 1000 ppm pesticides in soil amended with wheat straw was higher than in nonamended soil. All added pesticides except profenfos were degraded within 3 weeks. Lyophilized adapted biomass ofA. flavus andA. sydowii could thus be used for field biodegradation of these pesticides.     

Biosorption of an Azo Dye by <Emphasis Type="Italic">Aspergillus niger</Emphasis> and <Emphasis Type="Italic">Trichoderma</Emphasis> sp. Fungal Biomasses

Biosorption is an eco-friendly and cost-effective method for treating the dye house effluents. Aspergillus niger and Trichoderma sp. were cultivated in bulk and biomasses used as biosorbents for the biosorption of an azo dye Orange G. Batch biosorption studies were performed for the removal of Orange G from aqueous solutions by varying the parameters like initial aqueous phase pH, biomass dosage, and initial dye concentration. It was found that the maximum biosorption was occurred at pH 2. Experimental data were analyzed by model equations such as Langmuir and Freundlich isotherms, and it was found that both the isotherm models best fitted the adsorption data. The monolayer saturation capacity was 0.48 mg/g for Aspergillus niger and 0.45 mg/g for Trichoderma sp. biomasses. The biosorption kinetic data were tested with pseudo first-order and pseudo second-order rate equations, and it was found that the pseudo second-order model fitted the data well for both the biomasses. The rate constant for the pseudo second-order model was found to be 10–0.8 (g/mg min⁻¹) for Aspergillus niger and 8–0.4 (g/mg min⁻¹) for Trichoderma sp. by varying the initial dye concentrations from 5 to 25 mg/l. It was found that the biomass obtained from Aspergillus niger was a better biosorbent for the biosorption of Orange G dye when compared to Trichoderma sp.     

Exposure to airborne microorganisms,hyphal fragments,and pollen in a field of organically grown strawberries

Many working environments are predisposed for larger than average amounts of fungi and other microorganisms often due to organic material being handled. From 2003 to 2007, the area used for strawberry production in Denmark increased by 62%. The purpose of this study was to determine the levels of exposure to microorganisms, endotoxin, (1→3)-β-d-glucan (β-glucan), and pollen in a field of strawberries. The study was carried out in eastern Denmark from the middle of June to the beginning of August 2008. The strawberries were grown organically, and microbiological pest control agents (MPCAs) were applied during this and former growth seasons. In order to measure exposure to inhalable bioaerosol components, we used stationary filter samplers. Bioaerosol sampling was performed during 4 working days, and a total of 57 samplings were performed. The filters were analysed for contents of fungi, MPCAs, endotoxin, β-glucan, and pollen. The mean exposure was 6,154 CFU Cladosporium sp. m⁻³, 1.0 × 10⁵ fungal spores m⁻³, 4.1 × 10⁴ hyphal fragments m⁻³, 5.8 × 10³ pollen m⁻³, 57.3 ng β-glucan m⁻³, and 8.9 endotoxin units (EU) m⁻³. A significant and positive correlation was found between β-glucan and fungal spores and between CFU of Cladosporium sp. and CFU of fungi. We selected specifically for Metarhizium anisopliae, Beauveria bassiana, and the applied MPCAs Trichoderma harzianum, T. polysporum, and Bacillus thuringiensis but found none of these species. In conclusion, our study shows that berry pickers in this organic strawberry field were potentially subjected to higher levels of fungal spores, Cladosporium sp., hyphal fragments, pollen, and thus also β-glucan than is usually seen in outdoor air. Exposure to MPCAs was not seen. The exposure to endotoxin was only slightly higher than e.g. in a town.     

Biodegradation of phenol by immobilized Aspergillus awamori NRRL 3112 on modified polyacrylonitrile membrane

Covalent immobilization of Aspergillus awamori NRRL 3112 was conducted onto modified polyacrylonitrile membrane with glutaraldehyde as a coupling agent. The polymer carrier was preliminarily modified in an aqueous solution of NaOH and 1,2-diaminoethane. The content of amino groups was determined to be 0.58 mgeq g⁻¹. Two ways of immobilization were used—in the presence of 0.2 g l⁻¹ phenol and without phenol. The capability of two immobilized system to degrade phenol (concentration—0.5 g l⁻¹) as a sole carbon and energy source was investigated in batch experiments. Seven cycles of phenol biodegradation were conducted. Better results were obtained with the immobilized system prepared in the presence of phenol, regarding degradation time and phenol biodegradation rate. Scanning electron micrographs of the polyacrylonitrile membrane/immobilized Aspergillus awamori NRRL at the beginning of repeated batch cultivation and after the 7th cycle were compared. After the 7th cycle of cultivation the observations showed large groups of cells. The results from the batch experiments with immobilized system were compared to the results produced by the free strain. Phenol biodegradation experiments were carried out also in a bioreactor with spirally wound membrane with bound Aspergillus awamori NRRL 3112 in a regime of recirculation. 10 cycles of 0.5 g l⁻¹ phenol biodegradation were run consecutively to determine the degradation time and rate for each cycle. The design of the bioreactor appeared to be quite effective, providing large membrane surface to bind the strain.     

Relevance of bacterioplankton abundance and production in the oligotrophic equatorial Indian Ocean

Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM), southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29, 0.62 ± 0.33 and 0.46 ± 0.19 (× 10⁸ cells l⁻¹), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged ∼0.35 ± 0.14 × 10⁸ cells l⁻¹ in SWM and 0.39 ± 0.16 × 10⁸ cells l⁻¹ in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m⁻² d⁻¹ during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m⁻² d⁻¹) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m⁻²), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further, rapid mineralization by bacteria will make essential nutrients available to autotrophs.     

Optimization of Antifungal Effect of Surfactin and Iturin to <Emphasis Type="Italic">Penicillium notatum</Emphasis> in Syrup of Peach by RSM

In the paper, the sensitivity of Penicillium notatum to surfactin and iturin was determined, and the optimization of the antifungal of surfactin and iturin to Penicillium notatum in syrup of peach by a response surface methodology (RSM) was researched. Results demonstrated that Penicillium notatum was sensitive to them, whose minimal inhibitory concentration (MIC) was 62.5 and 31.25 μg ml⁻¹ respectively. In the optimization experiment, when the temperature was 2.37°C, the action time was 25.21 h, and the concentration (surfactin/iturin weight ratio 1:1) was 40.26 μg ml⁻¹, Penicillium notatum could be sterilized by 5 orders of magnitude. All the results in the experiment indicated surfactin and iturin could kill remarkably Penicillium notatum in syrup of peach.     

Olive mill wastewater disposal in evaporation ponds in Sfax (Tunisia): moisture content effect on microbiological and physical chemical parameters

The study of the isotherms desorption of olive mill wastewater (OMW) was investigated to describe its water activity under different saturated environments. The microbial biodegradation of OMW during its storage in 5 evaporation ponds located in Agareb (Sfax-Tunisia) was carried out during the oil-harvesting year held 105 days in 2004. Gravimetric static method using saturated salt solutions was used and OMW as placed at 30°C and under different water activities ranging from 0.11 to 0.90. Eight models were taken from the literature to describe experimental desorption isotherms. During storage, the evolution of physico-chemical parameters including pH, temperature, evaporation, humidity, total phosphorus, chemical oxygen demand (COD), biological oxygen demand (BOD) and phenols and three microbiological flora (aerobic mesophilic bacteria, yeasts and moulds) were considered. At 30°C, when relative humidity increased in the experimented ponds of 69, 84 and 90%, the evaporation speed decreased from 1.24 × 10⁻⁵ to 5 × 10⁻⁶ cm³ s⁻¹, from 6 × 10⁻⁵ to 7 × 10⁻⁶ cm³ s⁻¹ and from 5 × 10⁻⁶ to 1.1 × 10⁻⁷ cm³ s⁻¹ respectively. The desorption isotherm exhibited a sigmoidal curve corresponding to type II, typical of many organic material. The GAB and Peleg models gave the best fit for describing the relationship between the equilibrium moisture content and water activity in OMW (R ² = 0.998). During the storage period, the analysis showed an increase of all the physico-chemical parameters studied, except phenols and total phosphorus concentrations. The microbiological study showed the predominance of yeasts and moulds and the decrease of bacteria population after 75 days reflecting both effect of recalcitrant compounds and the water activity on microbial growth.     

Cellulase production from agricultural residues by recombinant fusant strain of a fungal endophyte of the marine sponge Latrunculia corticata for production of ethanol

Several fungal endophytes of the Egyptian marine sponge Latrunculia corticata were isolated, including strains Trichoderma sp. Merv6, Penicillium sp. Merv2 and Aspergillus sp. Merv70. These fungi exhibited high cellulase activity using different lignocellulosic substrates in solid state fermentations (SSF). By applying mutagenesis and intergeneric protoplast fusion, we have obtained a recombinant strain (Tahrir-25) that overproduced cellulases (exo-β-1,4-glucanase, endo-β-1,4-glucanase and β-1,4-glucosidase) that facilitated complete cellulolysis of agricultural residues. The process parameters for cellulase production by strain Tahrir-25 were optimized in SSF. The highest cellulase recovery from fermentation slurries was achieved with 0.2% Tween 80 as leaching agent. Enzyme production was optimized under the following conditions: initial moisture content of 60% (v/w), inoculum size of 10⁶ spores ml⁻¹, average substrate particle size of 1.0 mm, mixture of sugarcane bagasse and corncob (2:1) as the carbon source supplemented with carboxymethyl cellulose (CMC) and corn steep solids, fermentation time of 7 days, medium pH of 5.5 at 30°C. These optimized conditions yielded 450, 191, and 225 units/gram dry substrate (U gds⁻¹) of carboxylmethyl cellulase, filter-paperase (FPase), and β-glucosidase, respectively. Subsequent fermentation by the yeast, Saccharomyces cerevisiae NRC2, using lignocellulose hydrolysates obtained from the optimized cellulase process produced the highest amount of ethanol (58 g l⁻¹). This study has revealed the potential of exploiting marine fungi for cost-effective production of cellulases for second generation bioethanol processes.     

Biodegradation kinetics of methyl iso-butyl ketone by acclimated mixed culture

Methyl iso-butyl ketone (MIBK) is a widely used volatile organic compound (VOC) which is highly toxic in nature and has significant adverse effects on human beings. The present study deals with the removal of MIBK using biodegradation by an acclimated mixed culture developed from activated sludge. The biodegradation of MIBK is studied for an initial MIBK concentration ranging from 200–700 mg l⁻¹ in a batch mode of operation. The maximum specific growth rate achieved is 0.128 h⁻¹ at 600 mg l⁻¹of initial MIBK concentration. The kinetic parameters are estimated using five growth kinetic models for biodegradation of organic compounds available in the literature. The experimental data found to fit well with the Luong model (R ² = 0.904) as compared to Haldane model (R ² = 0.702) and Edward model (R ² = 0.786). The coefficient of determination (R ²) obtained for the other two models, Monod and Powell models are 0.497 and 0.533, respectively. The biodegradation rate found to follow the three-half-order kinetics and the resulting kinetic parameters are reported.     

Enantioselective ene‐reduction of E‐2‐cyano‐3‐(furan‐2‐yl) acrylamide by marine and terrestrial fungi and absolute configuration of (R)‐2‐cyano‐3‐(furan‐2‐yl) propanamide determined by calculations of electronic circular dichroism (ECD) spectra

This work reports the green organic chemistry synthesis of E‐2‐cyano‐3(furan‐2‐yl) acrylamide under microwave radiation (55 W), as well as the use of filamentous marine and terrestrial‐derived fungi, in the first ene‐reduction of 2‐cyano‐3‐(furan‐2‐yl) acrylamide to (R)‐2‐cyano‐3‐(furan‐2‐yl)propanamide. The fungal strains screened included Penicillium citrinum CBMAI 1186, Trichoderma sp. CBMAI 932 and Aspergillus sydowii CBMAI 935, and the filamentous terrestrial fungi Aspergillus sp. FPZSP 146 and Aspergillus sp. FPZSP 152. A compound with an uncommon CN‐bearing stereogenic center at the α‐C position was obtained by enantioselective reactions mediated in the presence of the microorganisms yielding the (R)‐2‐cyano‐3‐(furan‐2‐yl) propanamide 3a . Its isolated yield and e.e. ranged from 86% to 98% and 39% to 99%, respectively. The absolute configuration of the biotransformation products was determined by time‐dependent density functional theory (TD‐DFT) calculations of electronic circular dichroism (ECD) spectra. Finally, the tautomerization of 2‐cyano‐3‐(furan‐2‐yl) propanamide 3a to form an achiral ketenimine was observed and investigated in presence of protic solvents.     

Atrazine degradation by a simple consortium of <Emphasis Type="Italic">Klebsiella</Emphasis> sp. A1 and <Emphasis Type="Italic">Comamonas</Emphasis> sp. A2 in nitrogen enriched medium

A simple consortium consisted of two members of Klebsiella sp. A1 and Comamonas sp. A2 was isolated from the sewage of a pesticide mill in China. One member of Klebsiella sp. A1 is a novel strain that could use atrazine as the sole carbon and nitrogen source. The consortium showed high atrazine-mineralizing efficiency and about 83.3% of 5 g l⁻¹ atrazine could be mineralized after 24 h degradation. Contrary to many other reported microorganisms, the consortium was insensitive to some nitrogenous fertilizers commonly used, not only in presence of 200 mg l⁻¹ atrazine but also in 5 g l⁻¹ atrazine mediums. After 24 h incubation, 200 mg l⁻¹ atrazine was completely mineralized despite of the presence of urea, (NH₄)₂CO₃ and (NH₄)₂HPO₄ in the medium. Very minor influence was observed when NH₄Cl was added as additional nitrogen source. Advantages of the simple consortium, high mineralizing efficiency and insensitivity to most of exogenous nitrogen sources, all suggested application potential of the consortium for the bioremediation of atrazine-contaminated soils and waters.     

Biological breakdown of denitrifying sulfide removal process in high-rate expanded granular bed reactor

This work conducted a denitrifying sulfide removal (DSR) test in an expanded granular sludge bed (EGSB) reactor at sustainable loadings of 6.09 kg m⁻³ day⁻¹ for sulfide, 3.11 kg m⁻³ day⁻¹ for nitrate–nitrogen, and 3.27 kg m⁻¹ day⁻¹ for acetate–carbon with >93% efficiency, which is significantly higher than those reported in literature. Strains Pseudomonas sp., Nitrincola sp., and Azoarcus sp. very likely yield heterotrophs. Strains Thermothrix sp. and Sulfurovum sp. are the autotrophs required for the proposed high-rate EGSB-DSR system. The EGSB-DSR reactor experienced two biological breakdowns, one at loadings of 4.87, 2.13, and 1.82 kg m⁻³ day⁻¹; reactor function was restored by increasing nitrate and acetate loadings. Another breakdown occurred at loadings of up to 8.00, 4.08, and 4.50 kg m⁻¹ day⁻¹; the heterotrophic denitrification pathway declined faster than the autotrophic pathway. The mechanism of DSR breakdown is as follows. High sulfide concentration inhibits heterotrophic denitrifiers, and the system therefore accumulates nitrite. Autotrophic denitrifiers are then inhibited by the accumulated nitrite, thereby leading to breakdown of the DSR process.     

Biodegradation of lindane pesticide by non white- rots soil fungus <Emphasis Type="Italic">Fusarium</Emphasis> sp.

Lindane or γ- hexachlorocyclohexane (γ-HCH) is a chlorinated pesticide and its toxic effects on biota necessitate its removal. Microbial degradation is an important process for pesticide bioremediation and the role of soil fungi in recycling of organic matter prompted us to study the biodegradation of lindane using fungi. This study aims at enrichment, isolation and screening of soil fungi capable of metabolizing lindane. Two Fusarium species (F. poae and F. solani) isolated from the pesticide contaminated soil showed better growth on the plates supplemented with lindane as a sole carbon source, when compared with the growth performance of other fungal isolates from the same contaminated soil. However, ANOVA revealed a significant difference in fungal biomass production in both F. poae (F = 22.02; N = 15; P < 0.001) and F. solani (F = 268.75; N = 15; P < 0.001) across different lindane concentrations (0–600 μg ml⁻¹). Growth of both Fusarium sp. was maximum at a lindane concentration of 100 μg ml⁻¹, while minimum at 600 μg ml⁻¹ concentrations. Results on the time dependent release of chlorine by the Fusarium strains in the presence of various concentration of lindane showed the highest mineralization of the pesticide on 10th day of incubation. Time dependent variations in the release of chlorine from 1st to 10th day by both the selected fungal strains were found to be statistically significant. A significant positive relationship exists between fungal biomass increase and chlorine release existed for both F. solani (R2 = 0.960) and F. poae (R2 = 0.628). The results of gas chromatograph analysis of γ- HCH confirmed the biodegradation and utilization of γ- HCH by F. poae and F. solani. The data on lindane degradation by the two fungal strains demonstrated that the biodegradation of lindane by F. solani (59.4%) was slightly higher than that by the F. poae (56.7%).     

The morphological and physiological evolution of <Emphasis Type="Italic">Aspergillus terreus</Emphasis> mycelium in the submerged culture and its relation to the formation of secondary metabolites

The influence of the morphology and differentiation of Aspergillus terreus hyphae on the formation of mevinolinic acid (lovastatin) and (+)-geodin was tested. Lovastatin titre was the highest (above 60 mg l⁻¹) in the system with smaller pellets (diameter below 1.5 mm) and high biomass concentration (above 10 g l⁻¹ in the idiophase). These biomass features were induced by the higher initial number of spores in the preculture (above 2 × 10¹⁰ l⁻¹). At the initial number of spores below 2 × 10⁹ l⁻¹ (+)-geodin biosynthesis was the most efficient but it was rather connected with the elevated C/N ratio than with the pellet size. In order to quantify the hyphal differentiation in fungal pellets a special approach was used. The sectioning of the stained pellets together with the image analysis and calculation procedures were applied. The analysis of hyphal differentiation indicated that lovastatin formation was correlated with the fraction of the active, growing hyphae.