H2S degradation is reflected by both the activity and composition of the microbial community in a compost biofilter

In this study, 16S rRNA- and rDNA-based denaturing gradient gel electrophoresis (DGGE) were used to study the temporal and spatial evolution of the microbial communities in a compost biofilter removing H₂S and in a control biofilter without H₂S loading. During the first 81 days of the experiment, the H₂S removal efficiencies always exceeded 93% at loading rates between 4.1 and 30 g m⁻³ h⁻¹. Afterwards, the H₂S removal efficiency decreased to values between 44 and 71%. RNA-based DGGE analysis showed that H₂S loading to the biofilter increased the stability of the active microbial community but decreased the activity-based diversity and evenness. The most intense band in both the RNA- and DNA-based DGGE patterns of the H₂S-degrading biofilter represented the sulfur oxidizing bacterium Thiobacillus thioparus. This suggested that T. thioparus constituted a major part of the bacterial community and was an important primary degrader in the H₂S-degrading biofilter. The decreasing H₂S removal efficiencies near the end of the experiment were not accompanied by a substantial change of the DGGE patterns. Therefore, the decreased H₂S removal was probably not caused by a failing microbiology but rather by a decrease of the mass transfer of substrates after agglutination of the compost particles.     

Ethylene Removal by a Biofilter with Immobilized Bacteria

A biofilter which eliminated ethylene (C₂H₄) from the high parts-per-million range to levels near the limit for plant hormonal activity (0.01 to 0.1 ppm) was developed. Isolated ethylene-oxidizing bacteria were immobilized on peat-soil in a biofilter (687 cm³) and subjected to an atmospheric gas flow (73.3 ml min⁻¹) with 2 or 117 ppm of C₂H₄. Ethylene was eliminated to a minimum level of 0.017 ppm after operation with 2.05 ppm of C₂H₄ for 16 days. Also, the inlet C₂H₄ concentration of 117 ppm was reduced to <0.04 ppm. During operation with 2 and 117 ppm of C₂H₄, an increase in the C₂H₄ removal rate was observed, which was attributed to proliferation of the immobilized bacteria, notably in the first 0- to 5-cm segment of the biofilter. The maximal C₂H₄ elimination capacity of the biofilter was 21 g of C₂H₄ m⁻³ day⁻¹ during operation with 117 ppm of C₂H₄ in the inlet gas. However, for the first 0- to 5-cm segment of the biofilter, an elimination capacity of 146 g of C₂H₄ m⁻³ day⁻¹ was calculated. Transition of the biofilter temperature from 21 to 10°C caused a 1.6-fold reduction in the C₂H₄ removal rate, which was reversed during operation for 18 days. Batch experiments with inoculated peat-soil demonstrated that C₂H₄ removal still occurred after storage at 2, 8, and 20°C for 2, 3, and 4 weeks. However, the C₂H₄ removal rate decreased with increasing storage time and was reduced by ca. 50% after storage for 2 weeks at all three temperatures. The biofilter could be a suitable tool for C₂H₄ removal in, e.g., horticultural storage facilities, since it (i) removed C₂H₄ to 0.017 ppm, (ii) had a good operational stability, and (iii) operated efficiently at 10°C.     

Biological removal of H2S from the livestock manure using a biofilter

In this paper, the biological removal of H₂S from air had been investigated using a self-made biofilter with efficient bioceramics and a polyhedral hollow ball. The biological removal efficiency of H₂S had been analyzed at different experimental conditions, such as inlet H₂S concentration, residence time, initial pH value, and reaction temperature etc. The results showed that the initial pH value had a slight effect on H₂S removal efficiency from pH 3 to 9. The optimal initial pH value was 5.5, while the H₂S removal efficiency was 100%. The H₂S removal efficiency increased with increases in the nutrient solution spraying rate. The appropriate temperature was 25°C in the temperature range from 15 to 30°C. The H₂S removal efficiency dropped with the increase of air input and inlet H₂S concentration. After being isolated and screened, six strains of heterotrophic sulfide oxidizing bacteria and one strain autotrophic sulfide oxidizing bacteria were determined to be involved in the removal of H₂S within the biofilter. The reaction kinetics of H₂S was in accordance with first order reaction kinetics.     

Treatment of H2S using a horizontal biotrickling filter based on biological activated carbon: reactor setup and performance evaluation

Biological treatment is an emerging and prevalent technology for treating off-gases from wastewater treatment plants. The most commonly reported odorous compound in off-gases is hydrogen sulfide (H₂S), which has a very low odor threshold. A self-designed, bench-scale, cross-flow horizontal biotrickling filter (HBF) operated with bacteria immobilized activated carbon (termed biological activated carbon—BAC), was applied for the treatment of H₂S. A mixed culture of sulfide-oxidizing bacteria dominated by Acidithiobacillus thiooxidans acclimated from activated sludge was used as bacterial seed and the biofilm was developed by culturing the bacteria in the presence of carbon pellets in mineral medium. HBF performance was evaluated systematically over 120 days, depending on a series of changing factors including inlet H₂S concentration, gas retention time (GRT), pH of recirculation solution, upset and recovery, sulfate accumulation, pressure drop, gas-liquid ratio, and shock loading. The biotrickling filter system can operate at high efficiency from the first day of operation. At a volumetric loading of 900 m³ m^–3 h^–1 (at 92 ppmv H₂S inlet concentration), the BAC exhibited maximum elimination capacity (113 g H₂S/m^–3 h^–1) and a removal efficiency of 96% was observed. If the inlet concentration was kept at around 20 ppmv, high H₂S removal (over 98%) was achieved at a GRT of 4 s, a value comparable with those currently reported for biotrickling filters. The bacterial population in the acidic biofilter demonstrated capacity for removal of H₂S over a broad pH range (pH 1–7). A preliminary investigation into the different effects of bacterial biodegradation and carbon adsorption on system performance was also conducted. This study shows the HBF to be a feasible and economic alternative to physical and chemical treatments for the removal of H₂S.     

Petrochemical wastewater odor treatment by biofiltration

The treatment of odorous pollutants by microorganisms on packed waste straw and cortex was investigated at the wastewater treatment plant of the Shanghai petrochemical factory. The removal efficiency of H₂S, NH₃ and VOCs (volatile organic compounds) reached 98%, 91% and 90%, respectively after operation for one month at an empty bed retention time (EBRT) of 120 s. The heterotrophic bacteria were found to be the dominant microorganism in the biofilter, while fungi and actinomycetes were also present. The bacteria were mostly identified as the members of the genus Bacillus (62.5% of cultured bacteria). The single strand conformation polymorphism (SSCP) results revealed that the genus Bacillus and Pseudomonas were the predominant bacteria. The microbial diversity gradually increased as the treatment progressed, which indicated that the microbial community in the biofilter became more stable upon pollutant removal. The scanning electron microscopy (SEM) was performed to evaluate the microorganism growth on the media. It was found that the waste straw and cortex were suitable for microorganism attachment and growth, and may have potential application in odor treatment.     

Characteristics of H2S oxidizing bacteria inhabiting a peat biofilter

Bacteria associated with H₂S oxidization were isolated from a peat biofilter to which various concentrations of H₂S gas were supplied. After acclimation of the peat, a facultative autotrophic bacterium, Thiobacillus itnermedius, was primarily responsible for H₂S oxidation. The cell number isolates increased at above pH 3, but decreased when pH fell below 3, in which range breakthrough of H₂S was finally observed. When pH was controlled at around 3, constant removal of H₂S continued without a decline of the cell number. The specific H₂S uptake rate of the autotrophic bacterium was determined as 1.4 × 10⁻¹³ g-H₂S-S/h/cells. The cell number of the bacteria during steady state H₂S removal was proportional to the inlet H₂S concentration, verifying the kinetic equation derived previously.     

Ethylene Removal at Low Temperatures under Biofilter and Batch Conditions

Removal of the plant hormone ethylene (C₂H₄) is often required by horticultural storage facilities, which are operated at temperatures below 10°C. The aim of this study was to demonstrate an efficient, biological C₂H₄ removal under such low-temperature conditions. Peat-soil, acclimated to degradation of C₂H₄, was packed in a biofilter (687 cm³) and subjected to an airflow (~73 ml min⁻¹) with 2 ppm (μl liter⁻¹) C₂H₄. The C₂H₄ removal efficiencies achieved at 20, 10, and 5°C, respectively, were 99.0, 98.8, and 98.4%. This corresponded to C₂H₄ levels of 0.022 to 0.032 ppm in the biofilter outlet air. At 2°C, the average C₂H₄ removal efficiency dropped to 83%. The detailed temperature response of C₂H₄ removal was tested under batch conditions by incubation of 1-g soil samples in a temperature gradient ranging from 0 to 29°C with increments of 1°C. The C₂H₄ removal rate was highest at 26°C (0.85 μg of C₂H₄ g [dry weight]⁻¹ h⁻¹), but remained at levels of 0.14 to 0.28 μg of C₂H₄ g (dry weight)⁻¹ h⁻¹ at 0 to 10°C. At 35 to 40°C, the C₂H₄ removal rate was negligible (0.02 to 0.06 μg of C₂H₄ g [dry weight]⁻¹ h⁻¹). The Q₁₀ (i.e., the ratio of rates 10°C apart) for C₂H₄ removal was 1.9 for the interval 0 to 10°C. In conclusion, the present results demonstrated microbial C₂H₄ removal, which proceeded at 0 to 2°C and produced a moderately psychrophilic temperature response.     

Quantification of Nitrosomonas oligotropha-Like Ammonia-Oxidizing Bacteria and Nitrospira spp. from Full-Scale Wastewater Treatment Plants by Competitive PCR

Utilizing the principle of competitive PCR, we developed two assays to enumerate Nitrosomonas oligotropha-like ammonia-oxidizing bacteria and nitrite-oxidizing bacteria belonging to the genus Nitrospira. The specificities of two primer sets, which were designed for two target regions, the amoA gene and Nitrospira 16S ribosomal DNA (rDNA), were verified by DNA sequencing. Both assays were optimized and applied to full-scale, activated sludge wastewater treatment plant (WWTP) samples. If it was assumed that there was an average of 3.6 copies of 16S rDNA per cell in the total population and two copies of the amoA gene per ammonia-oxidizing bacterial cell, the ammonia oxidizers examined represented 0.0033% ± 0.0022% of the total bacterial population in a municipal WWTP. N. oligotropha-like ammonia-oxidizing bacteria were not detected in an industrial WWTP. If it was assumed that there was one copy of the 16S rDNA gene per nitrite-oxidizing bacterial cell, Nitrospira spp. represented 0.39% ± 0.28% of the biosludge population in the municipal WWTP and 0.37% ± 0.23% of the population in the industrial WWTP. The number of Nitrospira sp. cells in the municipal WWTP was more than 62 times greater than the number of N. oligotropha-like cells, based on a competitive PCR analysis. The results of this study extended our knowledge of the comparative compositions of nitrifying bacterial populations in wastewater treatment systems. Importantly, they also demonstrated that we were able to quantify these populations, which ultimately will be required for accurate prediction of process performance and stability for cost-effective design and operation of WWTPs.     

Chemolithotrophic acetogenic H2/CO2 utilization in Italian rice field soil

Acetate oxidation in Italian rice field at 50 °C is achieved by uncultured syntrophic acetate oxidizers. As these bacteria are closely related to acetogens, they may potentially also be able to synthesize acetate chemolithoautotrophically. Labeling studies using exogenous H₂ (80%) and ¹³CO₂ (20%), indeed demonstrated production of acetate as almost exclusive primary product not only at 50 °C but also at 15 °C. Small amounts of formate, propionate and butyrate were also produced from ¹³CO₂. At 50 °C, acetate was first produced but later on consumed with formation of CH₄. Acetate was also produced in the absence of exogenous H₂ albeit to lower concentrations. The acetogenic bacteria and methanogenic archaea were targeted by stable isotope probing of ribosomal RNA (rRNA). Using quantitative PCR, ¹³C-labeled bacterial rRNA was detected after 20 days of incubation with ¹³CO₂. In the heavy fractions at 15 °C, terminal restriction fragment length polymorphism, cloning and sequencing of 16S rRNA showed that Clostridium cluster I and uncultured Peptococcaceae assimilated ¹³CO₂ in the presence and absence of exogenous H₂, respectively. A similar experiment showed that Thermoanaerobacteriaceae and Acidobacteriaceae were dominant in the ¹³C treatment at 50 °C. Assimilation of ¹³CO₂ into archaeal rRNA was detected at 15 °C and 50 °C, mostly into Methanocellales, Methanobacteriales and rice cluster III. Acetoclastic methanogenic archaea were not detected. The above results showed the potential for acetogenesis in the presence and absence of exogenous H₂ at both 15 °C and 50 °C. However, syntrophic acetate oxidizers seemed to be only active at 50 °C, while other bacterial groups were active at 15 °C.     

兼性厌氧细菌硫化氢的产生机理及其生理功能

硫化氢(H_2S)是继一氧化氮(NO)和一氧化碳(CO)后发现的第3种气态信号分子,但其细菌生理学研究才刚刚起步。本文根据作者对奥内达希瓦氏菌的研究,结合新近文献,就细菌的H_2S产生机理及其生理功能作了较为全面的阐述。细菌的H_2S产生途径主要有2条,一是通过降解半胱氨酸产生,二是通过厌氧呼吸产生。产生的H_2S除可为互生性微生物提供能源、供氢体和无机矿质营养外,还具有抑制竞争性微生物的生长,有效占领生态位的作用。H_2S在氧化应答中也起着重要的作用,一方面可抑制过氧化氢酶活性,增加过氧化氢对细菌的杀灭效果;另一方面可作为信号分子激活细菌的氧化应答,诱导拮抗系统的表达,保护细胞免受氧化损伤。这两种看似"矛盾"的作用与H_2S的处理时间有关:短时间处理以抑制为主,而延长处理时间则以保护为主。细菌H_2S产生机理及生理功能的阐明可为硫元素生物地球化学循环规律的揭示和感染性病原细菌的控制提供有益的参考。     

In vitro medicinal potentials of Bryum capillare,a moss sample,from Turkey

In this study was conducted the in vitro antimicrobial, antibiofilm, antioxidant, antigenotoxic and anticancer activities investigations on the moss Bryum capillare Hedw (BC). Antimicrobial and antibiofilm activity were tested by MIC and microplate biofilm methods on antibiotic resistant bacteria. While the antioxidant activity of the extract was evaluated by DPPH, metal chelating, plasma lipid peroxidation and total phenolic content, the antigenotoxicity and cytotoxicity were established by Comet test and the WST-1 Cell proliferation assay kit respectively. The MIC values were found to be ≥ 125 µg.mL⁻¹ and a biofilm inhibition of 3–5% against only S. epidermidis was observed. Total phenolic compounds were determined as 23.26 mg/g. The results of DPPH assay, chelating and plasma lipid peroxidation activity were found to be 15%, 3% and 4% respectively. The extract was observed to decrease the affect of H₂O₂ that cause DNA damage. The BC was also determined 60 ± 5% anticancer activity against SKBR 3 and 76 ± 5% anticancer activity against HeLa cells, where this concentration had only 18 ± 5% cytotoxicity against MCF-12A cells. Also, these results have indicated the potential of Bryum capillare for the first time in novel natural compounds search.     

Neural networks as a tool for control and management of a biological reactor for treating hydrogen sulphide

Based on an experimental database consisting of 194 daily cases, artificial neural networks were used to model the removal efficiency of a biofilter for treating hydrogen sulphide (H₂S). In this work, the removal efficiency of the reactor was considered as a function of the changes in the air flow and concentration of H₂S entering the biofilter. In order to obtain true representative values, the removal efficiencies (outputs) were measured 24 h after each input was changed. A MLP (multilayer perceptron 2-2-1) model with two input variables (unit flow and concentration of the contaminant fed into the biofilter) rendered good prediction values with a determination coefficient of 0.92 for the removal efficiency within the range studied. This means that the MLP model can explain 92% of the overall variability detected in the biofilter corresponding to a wide range of operating conditions.     

Enhanced removal efficiency of malodorous gases in a pilot-scale peat biofilter inoculated with Thiobacillus thioparus DW44

A newly isolated autotrophic bacterium, Thiobacillus thioparus DW44, which is capable of degrading sulfur-containing gases, was inoculated into a pilot-scale peat biofilter to treat the exhaust gas from a night soil treatment plant. Hydrogen sulfide (H₂S), methanethiol (MT), dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the exhaust gas were efficiently removed for six months. Average removal ratios were 99.8% for H₂S, 99.0% for MT, 89.5% for DMS and 98.1% for DMDS at a space velocity of 46 h⁻¹ during the period of operation. No acclimation period was needed to reach such a high efficiency in the removal of the gases, indicating that the ability of this bacterium to remove these gases was occurred immediately after its inoculation to the peat. Ammonia (NH₃) in the exhaust gas was neutralized with SO₄²⁻, which is the final product of the oxidation of H₂S, MT, DMS and DMDS by the bacterium. No remarkable decline of pH, which often causes a deterioration in bacterial activity, was observed, mainly because of the reaction of SO₄²⁻ with NH₃. This study is the first report on the application of an isolated microorganism to a practical deodorizing system. The inoculation of T. thioparus DW44 into the pilot-scale peat biofilter could overcome such disadvantages of the conventional peat biofilter as a long acclimation period to reach a constant gas removability and the low removability of DMS, and resulted in enhanced removal efficiency of malodorous gases.     

Synthesis and cytotoxic activity of organotin(IV) diallyldithiocarbamate compounds as anticancer agent towards colon adenocarcinoma cells (HT-29)

ContextDiphenyltin(IV) diallyldithiocarbamate compound (Compound 1) and triphenyltin(IV) diallyldithiocarbamate compound (Compound 2) are two newly synthesised compounds of organotin(IV) with diallyldithiocarbamate ligands.ObjectiveTo assess the cytotoxic effects of two synthesised compounds against HT-29 human colon adenocarcinoma cells and human CCD-18Co normal colon cells.Materials and methodsTwo successfully synthesised compounds were characterised using elemental (carbon, hydrogen, nitrogen, and sulphur) analysis, Fourier-Transform Infrared (FTIR), and ¹H, ¹³C ¹¹⁹Sn Nucleus Magnetic Resonance (NMR) spectroscopies. The single-crystal structure of both compounds was determined by X-ray single-crystal analysis. The cytotoxicity of the compounds was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazholium bromide (MTT) assay upon 24 h of treatment. While the mode of cell death was determined based on the externalisation of phosphatidylserine using a flow cytometer.ResultsThe elemental analysis data of the two compounds showed an agreement with the suggested formula of (C₆H₅)₂Sn[S₂CN(C₃H₅)₂]₂ for Compound 1 and (C₆H₅)₃Sn[S₂CN(C₃H₅)₂] for Compound 2. The two major peaks of infrared absorbance, i.e., ν(C = N) and ν(C = S) were detected at the range of 1475–1479 cm⁻¹ and 972–977 cm⁻¹, respectively. The chemical shift of carbon in NCS₂ group for Compound 1 and 2 were found at 200.82 and 197.79 ppm. The crystal structure of Compound 1 showed that it is six coordinated and crystallised in monoclinic, P2₁/c space group. While the crystal structure of Compound 2 is five coordinated and crystallised in monoclinic, P2₁/c space group. The cytotoxicity (IC₅₀) of the two compounds against HT-29 cell were 2.36 μM and 0.39 μM. Meanwhile, the percentage of cell death modes between 60% and 75% for compound 1 and compound 2 were mainly due to apoptosis, suggesting that both compounds induced growth arrest.ConclusionOur study concluded that the synthesised compounds showed potent cytotoxicity towards HT-29 cell, with the triphenyltin(IV) compound showing the highest effect compared to diphenyltin(IV).     

Performance of three pilot-scale immobilized-cell biotrickling filters for removal of hydrogen sulfide from a contaminated air steam

Hydrogen sulfide (H₂S) is a major malodorous compound emitted from wastewater treatment plants. In this study, the performance of three pilot-scale immobilized-cell biotrickling filters (BTFs) spacked with combinations of bamboo charcoal and ceramsite in different ratios was investigated in terms of H₂S removal. Extensive tests were performed to determine the removal characteristics, pressure drops, metabolic products, and removal kinetics of the BTFs. The BTFs were operated in continuous mode at low loading rates varying from 0.59 to 5.00 g H₂S m⁻³ h⁻¹ with an empty bed retention time (EBRT) of 25 s. The removal efficiency (RE) for each BTF was >99% in the steady-state period, and high standards were met for the exhaust gas. It was found that a multilayer BTF had a slight advantage over a perfectly mixed BTF for the removal of H₂S. Furthermore, an impressive amount >97% of the H₂S was eliminated by 10% of packing materials near the inlet of the BTF. The modified Michaelis–Menten equation was adopted to describe the characteristics of the BTF, and K_s and V_m values for the BTF with pure bamboo charcoal packing material were 3.68 ppmv and 4.26 g H₂S m⁻³ h⁻¹, respectively. Both bamboo charcoal and ceramsite demonstrated good performance as packing materials in BTFs for the removal of H₂S, and the results of this study could serve as a guide for further design and operation of industrial-scale systems.     

In Vitro-Controlled Release Delivery System for Hydrogen Sulfide Donor

Hydrogen sulfide (H₂S) is having many potential pharmacological and physiological actions which reported that therapeutically useful concentration is low (100–160 μM) and a higher concentration could be toxic. Most of its donors produce it on coming into contact with water. All of these problems could be solved by a controlled-release delivery system which does not utilize water in any of its development steps. Therefore, 12 sustained release formulations were prepared by dissolving sodium hydrogen sulfide (NaHS)—a model H₂S donor—in polymer solutions, prepared by dissolving polymers (consisted of either polylactide (PLA) or polylactide co-glycolide (PLGA), containing free carboxylic acid or capped allyl ester end group) in a mixture of benzyl benzoate (BB) and benzyl alcohol (BA). The formulation was injected in simulated tear fluid (STF) from which samples were withdrawn at specified times and assayed for NaHS content. We found decrease in burst and overall release with increase in polymer concentration from 10 to 20% w/v. The formulations containing free end group showed significant (p < 0.05) reduction of burst release (11% vs 21%). However, the overall release or the average amount released per hour was found to be significantly (p < 0.05) increased for formulations containing polymers with free end group than those with capped end group. A sustained level of H₂S was found to be maintained for 72 h which should be further increased to a month to make it a viable H₂S donor delivery system in addition to investigating toxicity profile specifically for the purpose of subconjunctival ocular delivery.KEY WORDS: controlled release, hydrogen sulfide, hydrogen sulfide donor, in situ gel forming, phase sensitive, smart polymer     

Solubility and permeation of hydrogen sulfide in lipid membranes

Hydrogen sulfide (H₂S) is mainly known for its toxicity but has recently been shown to be produced endogenously in mammalian tissues and to be associated with physiological regulatory functions. To better understand the role of biomembranes in modulating its biological distribution and effects; we measured the partition coefficient of H₂S in models of biological membranes. The partition coefficients were found to be 2.1±0.2, 1.9±0.5 and 2.0±0.6 in n-octanol, hexane and dilauroylphosphatidylcholine liposome membranes relative to water, respectively (25°C). This two-fold higher concentration of H₂S in the membrane translates into a rapid membrane permeability, P_m = 3 cm s⁻¹. We used a mathematical model in three dimensions to gain insight into the diffusion of total sulfide in tissues. This model shows that the sphere of action of sulfide produced by a single cell expands to involve more than 200 neighboring cells, and that the resistance imposed by lipid membranes has a significant effect on the diffusional spread of sulfide at pH 7.4, increasing local concentrations. These results support the role of hydrogen sulfide as a paracrine signaling molecule and reveal advantageous pharmacokinetic properties for its therapeutic applications.     

Isolation and Characterization of Antidermatophytic Bioactive Molecules from Piper longum L. Leaves

Piper longum L. (Piperaceae) commonly known as “long pepper” is a well known medicinal plant in ayurveda. Different parts of this plant, such as root, seed, fruit, whole plant etc. are used traditionally in various ailments. Here we have investigated the antidermatophytic activity of sequentially extracted petroleum ether, chloroform, methanol and water extracts from P. longum leaf against Trichophytonmentagrophytes, T. rubrum, T. tonsurans, Microsporum fulvum and M. gypseum. Better activity of chloroform and methanol extracts was observed. The chloroform extract was selected for further study and the MIC value was recorded as 5.0 mg ml⁻¹ against the test organisms. In the chloroform extract, tannins and phenolic compounds were detected. Further activity-guided fractionation of chloroform extract by silica gel column chromatography yielded nine major fractions. Among these, fraction-1, 4, 5 and 7 showed higher antidermatophytic activity. Fraction-4 on further purification by repeated column chromatography yielded a potential antidermatophytic fraction showing MIC value of 0.625 mg ml⁻¹ against T. mentagrophytes and T. rubrum as determined by broth microdilution method. The major compounds were identified as 1,2-benzenedicarboxylic acid, bis(2-ethylhexyl) ester (C₂₄H₃₈O₄] (41.45 %), 2,2-dimethoxybutane (C₆H₁₄O₂] (13.6 %) and β-myrcene (C₁₀H₁₆) (6.75 %) based on GC–MS data.     

Production,purification, characterization,antioxidant and antiproliferative activities of extracellular L-asparaginase produced by Fusarium equiseti AHMF4

L-Asparaginase is an antileukemic agent that depletes L-asparagine “an important nutrient for cancer cells” through the hydrolysis of L-asparagine into L-aspartic acid and ammonia leading to leukemia cell starvation and apoptosis in susceptible leukemic cell populations. Moreover currently, bacterial L-asparaginase has been limited by problems of lower productivity, stability, selectivity and a number of toxicities along with the resistance towards bacterial L-asparaginase. Then the current work aimed to provide pure L-asparaginase with in-vitro efficacy against various human carcinomas without adverse effects related to current L-asparaginase formulations. Submerged fermentation (SMF) bioprocess was applied and improved to maximize L-asparaginase production from Fusarium equiseti AHMF4 as alternative sources of bacteria. The enzyme production in SMF was maximized to reach 40.78 U mL⁻¹ at the 7th day of fermentation with initial pH 7.0, incubation temperature 30 °C, 1.0% glucose as carbon source, 0.2% asparagine as nitrogen source, 0.1% alanine as amino acid supplement and 0.1% KH₂PO₄. The purification of AHMF4 L-asparaginase yielded 2.67-fold purification and 48% recovery with final specific activity of 488.1 U mg⁻¹ of protein. Purified L-asparaginase was characterized as serine protease enzyme with molecular weight of 45.7 kDa beside stability at neutral pH and between 20 and 40 °C. Interestingly, purified L-asparaginase showed promising DPPH radical scavenging activity (IC₅₀ 69.12 μg mL⁻¹) and anti-proliferative activity against cervical epitheloid carcinoma (Hela), epidermoid larynx carcinoma (Hep-2), hepatocellular carcinoma (HepG-2), Colorectal carcinoma (HCT-116), and breast adenocarcinoma (MCF-7) with IC₅₀ equal to 2.0, 5.0, 12.40, 8.26 and 22.8 μg mL⁻¹, respectively. The enzyme showed higher activity, selectivity and anti-proliferative activity against cancerous cells along with tiny cytotoxicity toward normal cells (WI-38) which indicates that it has selective toxicity and it could be applied as a less toxic alternative to the current formulations.     

Reduction of ammonia and volatile organic compounds from food waste-composting facilities using a novel anti-clogging biofilter system

The performance of a pilot-scale anti-clogging biofilter system (ABS) was evaluated over a period of 125 days for treating ammonia and volatile organic compounds emitted from a full-scale food waste-composting facility. The pilot-scale ABS was designed to intermittently and automatically remove excess biomass using an agitator. When the pressure drop in the polyurethane filter bed was increased to a set point (50 mm H₂O m⁻¹), due to excess biomass acclimation, the agitator automatically worked by the differential pressure switch, without biofilter shutdown. A high removal efficiency (97-99%) was stably maintained for the 125 days after an acclimation period of 1 week, even thought the inlet gas concentrations fluctuated from 0.16 to 0.55 g m⁻³. Due the intermittent automatic agitation of the filter bed, the biomass concentration and pressure drop in the biofilter were maintained within the ranges of 1.1-2.0 g-DCW g PU⁻¹ and below 50 mm H₂O m⁻¹, respectively.