Investigating the synthesis parameters of durian skin-based activated carbon and the effects of silver nanocatalysts on its recyclability in methylene blue removal

Activated carbon (AC) is the most common and economically viable adsorbent for eliminating toxic organic pollutants, particularly dyes, from wastewater. Its widespread adoption is due to the simplicity and affordable production of AC, wherein low-cost agricultural wastes, such as durian skin can be used. Converting durian skin into AC presents a promising solution for its solid waste management. However, inherent drawbacks such as its non-selectivity, relatively short lifespan and laborious replacement and recovery processes diminish the overall efficacy of AC as an adsorbent. To address these challenges, the immobilisation of metal nanocatalysts such as silver nanoparticles (AgNPs) is one of the emerging solutions. AgNPs can facilitate the regeneration of the adsorption sites of AC by catalysing the conversion of the adsorbed dyes into harmless and simpler molecules. Nevertheless, the immobilisation of AgNPs on AC surface can be challenging as the pore size formation of AC is hard to control and the nanomaterials can easily leach out from the AC surface. Hence, in this study, we synthesised AC from durian skin (DS) and immobilised AgNPs on the AC-DS surface. Then, we used methylene blue (MB) removal for studying the adsorption capability and recyclability of the AC-DS. In the synthesis of AC-DS, the influences of reaction temperature, activating agent, and acid-washing to its capability in adsorptive removal of  MB in solution were first determined. It was found that 400 °C, KOH activating agent, and the presence of acid-washing (50% of HNO3) resulted in AC-DS with the highest percentage of MB removal (91.49 ± 2.86%). Then, the overall results from three recyclability experiments demonstrate that AC-DS with immobilised AgNPs exhibited higher MB removal after several cycles (up to 6 cycles) as compared to AC-DS alone, proving the benefit of AgNPs for the recyclability of AC-DS. We also found that AgNPs/Citrate@AC-DS exhibited better adsorption capability and recyclability as compared to AgNPs/PVP@AC-DS indicating significant influences of type of stabilisers in this study. This study also demonstrates that the presence of more oxygen-containing functional groups (i.e., carboxyl and hydroxyl functional groups) after acid-washing on AC-DS and in citrate molecules, has greater influence to the performance of AC-DS and AgNPs/Citrate@AC-DS in the removal of MB as compared to the influences of their BET surface area and pore structure. The findings in this study have the potential to promote and serve as a guideline for harnessing the advantages of nanomaterials, such as AgNPs, to enhance the properties of AC for environmental applications.

Analysis of DNA methylation at birth and in childhood reveals changes associated with season of birth and latitude

BACKGROUND

Seasonal variations in environmental exposures at birth or during gestation are associated with numerous adult traits and health outcomes later in life. Whether DNA methylation (DNAm) plays a role in the molecular mechanisms underlying the associations between birth season and lifelong phenotypes remains unclear.

METHODS

We carried out epigenome-wide meta-analyses within the Pregnancy And Childhood Epigenetic Consortium to identify associations of DNAm with birth season, both at differentially methylated probes (DMPs) and regions (DMRs). Associations were examined at two time points: at birth (21 cohorts, N = 9358) and in children aged 1-11 years (12 cohorts, N = 3610). We conducted meta-analyses to assess the impact of latitude on birth season-specific associations at both time points.

RESULTS

We identified associations between birth season and DNAm (False Discovery Rate-adjusted p values < 0.05) at two CpGs at birth (winter-born) and four in the childhood (summer-born) analyses when compared to children born in autumn. Furthermore, we identified twenty-six differentially methylated regions (DMR) at birth (winter-born: 8, spring-born: 15, summer-born: 3) and thirty-two in childhood (winter-born: 12, spring and summer: 10 each) meta-analyses with few overlapping DMRs between the birth seasons or the two time points. The DMRs were associated with genes of known functions in tumorigenesis, psychiatric/neurological disorders, inflammation, or immunity, amongst others. Latitude-stratified meta-analyses [higher (≥ 50°N), lower (< 50°N, northern hemisphere only)] revealed differences in associations between birth season and DNAm by birth latitude. DMR analysis implicated genes with previously reported links to schizophrenia (LAX1), skin disorders (PSORS1C, LTB4R), and airway inflammation including asthma (LTB4R), present only at birth in the higher latitudes (≥ 50°N).

CONCLUSIONS

In this large epigenome-wide meta-analysis study, we provide evidence for (i) associations between DNAm and season of birth that are unique for the seasons of the year (temporal effect) and (ii) latitude-dependent variations in the seasonal associations (spatial effect). DNAm could play a role in the molecular mechanisms underlying the effect of birth season on adult health outcomes.

First report of bacterial panicle blight (BPB) in Rice caused by Burkholderia gladioli in Bangladesh

Bacterial panicle blight (BPB) has become one of the most destructive diseases of rice worldwide and Burkholderia gladioli and B. glumae are two major pathogens causing BPB (1). This disease causes several types of damage, most importantly grain spotting, rot, and panicle blight, which can result in yield losses of 75% or more (1,3). In recent years, symptoms including sheath rot, grain spotting, grain rot, and panicle blight have been observed in both inbred and hybrid rice varieties. These symptoms resemble those of BPB and cause cultivar-dependent yield losses. (3) also reported the same symptoms for BPB. To confirm the cause of the disease, 21 rice panicles (Haridhan, a local variety) with typical BPB symptoms were collected from a farmer's field in the region of Mymensingh, Bangladesh during the rainy season in mid-October, 2021. Due to the severity of the outbreak, the panicles became dark brown and produced chaffy grains; nearly 100% of the rice panicles in that field were severely infected. To identify the causal pathogen(s), 1g of rice grains from 20 plants with typical BPB symptoms were surface-sterilized by immersing them in 70% ethanol for a few seconds followed by sodium hypochlorite solution (3%) for 1min. The grains were then rinsed with sterilized distilled water three times. Surface-sterilized grains were then ground with a mortar and pestle; 5mL of sterile distilled water was added during grinding. The extracted suspension (20µL) was then either streaked or spread onto the selective medium (S-PG) (2). Bacterial colonies showing purple color on the S-PG medium were selected and purified as candidate pathogens. For molecular characterization, species specific primers targeting gyrB gene were used to perform PCR and resulted in 479bp as reported by (4). To verify further, the PCR products of 16SF & 16SR were amplified and sequenced partially producing around 1400bp (1) and five 16SF partial sequences were deposited into NCBI GenBank (OP108276 to OP108280). 16S rDNA and gyrB revealed almost 99% homology with Burkholderia gladioli (KU851248.1, MZ425424.1) and B. gladioli (AB220893, CP033430) respectively using BLAST analysis. These purified bacterial isolates produced a diffusible light-yellow pigment on King's B medium indicating toxoflavin production (3). The candidate five bacterial isolates were then confirmed by inoculating 10ml suspension 10⁸CFU/mL into the panicles and sheaths of BRRIdhan28 in net house condition as described previously (1). All of the bacterial isolates obtained from the spotted rice grains produced light brown lesions on the inoculated leaf sheath as well as spotting on the grain. To fulfill Koch's postulates, the bacteria were re-isolated from the symptomatic panicles and were confirmed as B. gladioli by analyzing the sequences of gyrB and 16s rDNA genes. Taken together, these results confirmed that B. gladioli is responsible for causing BPB in the rice grain samples that we collected. To our knowledge, this is the first report of BPB caused by B. gladioli in Bangladesh and further research is necessary to develop an effective disease management technique, or else the production of rice will be severely hampered.

Native Trichoderma Induced the Defense-Related Enzymes and Genes in Rice against Xanthomonas oryzae pv. oryzae (Xoo)

The application of Trichoderma is a form of biological control that has been effective in combating Xanthomonas oryzae pv. oryzae, the causative agent of the devastating disease known as bacterial blight of rice. In this present study, four strains of Trichoderma, viz., T. paraviridescens (BDISOF67), T. erinaceum (BDISOF91), T. asperellum (BDISOF08), and T. asperellum (BDISOF09), were collected from the rice rhizosphere and used to test their potentiality in reducing bacterial blight. The expression patterns of several core defense-related enzymes and genes related to SA and JA pathways were studied to explore the mechanism of induced resistance by those Trichoderma strains. The results primarily indicated that all Trichoderma were significantly efficient in reducing the lesion length of the leaf over rice check variety (IR24) through enhancing the expression of core defense-related enzymes, such as PAL, PPO, CAT, and POD activities by 4.27, 1.77, 3.53, and 1.57-fold, respectively, over control. Moreover, the results of qRT-PCR exhibited an upregulation of genes OsPR1, OsPR10, OsWRKY45, OsWRKY62, OsWRKY71, OsHI-LOX, and OsACS2 after 24 h of inoculation with all tested Trichoderma strains. However, in the case of RT-PCR, no major changes in OsPR1 and OsPR10 expression were observed in plants treated with different Trichoderma strains during different courses of time. Collectively, Trichoderma induced resistance in rice against X. oryzae pv. oryzae by triggering these core defense-related enzymes and genes associated with SA and JA pathways.

Rep-PCR Analyses Reveal Genetic Variation of Ralstonia solanacearum Causing Wilt of Solanaceaous Vegetables in Bangladesh

Ralstonia solanacearum, a soil-borne and seed-borne plant pathogenic bacterium, causes bacterial wilt to several important crop plants causing substantial economic losses. To provide population information on this pathogen for developing effective control strategies, Rep-PCR was used to analyze the genetic variation of 18 representative isolates of R. solanacearum collected in Bangladesh. Phenotypic analyses revealed that all eighteen isolates belong to biotype 3 with wide diversity in aggressiveness on eggplant, tomato, and chili. Rep-PCR studies utilizing the REP, ERIC, and BOXIR primers showed a wide variation at the genetic level among the R. solanacearum isolates used in this study. Dendrogram constructed using REP, ERIC, and BOXIR primers based on banding patterns implied that R. solanacearum isolates were genetically diversified and distributed in four clusters at 83%, 80%, and 63% similarity index, respectively. The genetic relationship assayed by rep-PCR highlighted a wide range of genetic variation but no relation among geographical origin, aggressiveness, and phylogenetic groups of R. solanacearum isolates. These results conceded that other molecular markers related to virulence gene(s) might reveal the complex relationship among geographical origin, aggressiveness, and phylogenetic groups.

Health risk assessment for heavy metal accumulation in leafy vegetables grown on tannery effluent contaminated soil

Accumulation of metals (Cr, Zn, Ni, Cd, and Cu) in leafy vegetables cultivated on tannery effluent contaminated soil and agricultural land soil were determined with an Atomic Absorption Spectrophotometer (AAS). The values of risk factors for the human population were studied, where metals were transferred from tannery effluent to plants via effluent contaminated soil and finally, transmitted to human body through the consumption of these metal accumulated leafy vegetables. Leafy vegetables, namely Stem amaranths (Amaranthus lividus), Spinach (Spinacia oleracea), Red amaranths (Amaranthus gangeticus), Jute mallows (Corchorus capsularis), Water spinach (Ipomoea aquatica), and Malabar spinach (Basella alba) were cultivated on the soils collected from downstream of Hazaribagh tannery area and Keraniganj agricultural land. The study revealed that the metal contents in contaminated soil exceeded the permissible limits recommended by WHO/DoE. Tannery effluent contaminated soil was found more polluted than the agricultural land soil. Metal contents in leafy vegetables cultivated on contaminated soil were higher than that of agricultural soil and exceeded the permissible limit, particularly in the case of Cr (125.50–168.99 mg/kg Dw) and Cd (0.19–0.83 mg/kg Dw). Metal content order was found as Cr>Zn>Ni>Cu>Cd for contaminated soil and Zn>Cr>Cu>Ni>Cd for agricultural land soil. The metal accumulation and translocation were found in vegetables in the order of Spinach>Water spinach>Malabar spinach>Jute mallows>Red amaranths>Stem amaranths. The analyses also revealed that the metal translocation rate in the plants of contaminated soil was higher than that of non-contaminated agricultural soil. The values of each risk index exceeded 1 in case of vegetables cultivated in contaminated soil. Therefore, the possible threat of chronic and carcinogenic diseases emerged if those polluted vegetables would be consuming as daily diet.

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Evaluation of translocation of metals from soil to edible parts in plants.

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Assessment of possible health risk due to consumption of heavy metal accumulated vegetables.

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Higher concentration of heavy metals in soil samples yields to a higher translocation of metals into plants from soil.

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Possibilities of potential health risk may arise upon consuming the leafy vegetables grown in contaminated soil.

Novel Myco-Coagulant Produced by Lentinus squarrosulus for Removal of Water Turbidity: Fungal Identification and Flocculant Characterization

Several river water fungal strains (RWF-1 to RWF-6) were isolated to investigate the potential of having coagulant properties from the metabolites produced by the fungus. The myco-coagulant produced from the liquid-state process was characterized and tested for flocculation of kaolin water. Molecular identification of the fungal strain isolated from river water and characterization of the myco-coagulant produced by the strain are presented in this paper. The genomic DNA of the fungal 18S ribosomal ribonucleic-acid (rRNA) and 28S rRNA genes were used and the species was identified as Lentinus squarrosulus strain 7-4-2 RWF-5. The characterization of myco-coagulant by Fourier-transform infrared spectroscopy (FTIR) showed that hydroxyl, carbonyl, amide and amine groups as principal functional groups were present in the new myco-coagulant. The mean zeta potential value of the myco-coagulant was −7.0 mV while the kaolin solution was −25.2 mV. Chemical analyses of the extracellular myco-coagulant revealed that it contained total sugar (5.17 g/L), total carbohydrate (237 mg/L), protein (295.4 mg/L), glucosamine (1.152 mg/L); and exhibited cellulase activity (20 units/L) and laccase activity (6.22 units/L). Elemental analyses of C, H, O, N and S showed that the weight fractions of each element in the myco-coagulant was 40.9, 6.0, 49.8, 1.7 and 1.4%, respectively. The myco-coagulant showed 97% flocculation activity at a dose of 1.8 mg/L, indicating good flocculation performance compared to that of polyaluminum chloride (PAC). The present work revealed that the fungal strain, L. squarrosulus 7-4-2 RWF-5 is able to produce cationic bio-coagulant. The flocculation mechanism of the novel myco-coagulant was a combination of polymer bridging and charge neutralization.

Directional excitation of surface plasmon using multi-mode interference in an aperture

Plasmonics is a promising technology that can find many applications in nanophotonics and biosensing. Local excitation of surface plasmons with high directionality is required for many of these applications. We demonstrate that by controlling the interference of light in a metal slot with the adjustment of the angle of incidence, it is possible to achieve highly directional surface plasmon excitation. Our numerical analysis of the structure showing a strong directionality of excited surface plasmon is confirmed by near field scanning measurements. The proposed structure can be useful for many applications including excitation of plasmonic waveguides, nanolithography, and optical sensing. To illustrate its usefulness, we experimentally demonstrate that it can be used for highly directional excitation of a dielectric loaded plasmonic waveguide. We also propose a simple structure for surface plasmon interference lithography capable of providing high image contrast using this scheme.

Comparative evaluation of rapid Salmonella Typhi IgM/IgG and Widal test for the diagnosis of enteric fever

Background: Accurate and early diagnosis of enteric fever is a diagnostic challenge where facility for blood culture is not available. As a result, Widal test is still used widely in resource limited settings. Recently, user-friendly rapid immunochromatographic tests (ICT) have been introduced for quick diagnosis of enteric fever. So, we evaluated sensitivity and specificity of an immunochromatography based Salmonella Typhi IgM/IgG test kit and Widal test compared to blood culture for the diagnosis of enteric fever. Method: The study was conducted in the Department of Microbiology, Ibrahim Medical College (IMC) and Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders (BIRDEM) from June 2017 to September 2017. Clinically suspected enteric fever cases were included. Blood culture, Widal and Salmonella Typhi IgM/IgG detecting ICT were employed for the diagnosis of enteric fever. Results: Out of 71 suspected cases of enteric fever, blood culture was positive in 36 cases (50.7%) while 42 (59.15%) and 35 (49.29%) cases were positive by Widal test and ICT respectively. Widal and ICT had sensitivity and specificity of 100% and 89.9% and 82.9% & 91.4% respectively. Conclusion: Findings of the study suggest that both Widal and immunochromatographic tests can be used interchangeably for rapid diagnosis of enteric fever. Ibrahim Med. Coll. J. 2020; 14(1): 18-25

Active Fractions of Methanol Crude Obtained from Acacia seyal gum: Antioxidant Capacity, using FTIR Analysis

The present study is on Acacia seyal gum (ASG), which is an exudate from Talha tree. It provides a rich source of polyphenolics compounds that are used traditionally in folk medicine. The study aims to determine the antioxidant capacity (AC) and functional groups of ASG and Prebio-T-commercial (PTC) samples. The methanol crude extracts of both ASG and PTC have fractioned into chloroform (CHF), hexane (HF), acetone (AF) and methanol (MF) using solvent-solvent portion. Both ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC) assays for each fraction examined. Crude methanol extracts (CME) and its active compositions also analysed carefully using Fourier Transform Infrared Spectroscopy (FTIR) technique. The findings presented a wide variety of functional groups provided by the FTIR spectra (eights bands approximately. Regarding cupric reducing antioxidant capacity (CUPRAC), the methanol crude extracts values are 888.6�4.57 mg TE/100g extract, for PTC as compared to 474.3� 2.23 mg TE/100g of extract for ASG. However, both methanol and acetone fractions revealed significantly (p = 0.05) high FRAP values ranged between 599.8�7.5 and 741.8�5.8 mg TE/100g fraction; for PTC and ASG, respectively. While CUPRAC showed insignificant (p = 0.05) same values 356.1�2.62 mg TE/100g of fraction; for MF of both PTC and ASG respectively. Therefore, in this study, methanolic fractions (MFs) are found to be more effective than acetone fractions (AFs), except for CHF and HF. Finally, the antioxidant activity of the active fraction has provided some evidence regarding its functional groups which may have used in traditional medicine.

Jasmonate-Induced Defense Mechanisms in the Belowground Antagonistic Interaction Between Pythium arrhenomanes and Meloidogyne graminicola in Rice

Next to their essential roles in plant growth and development, phytohormones play a central role in plant immunity against pathogens. In this study we studied the previously reported antagonism between the plant-pathogenic oomycete Pythium arrhenomanes and the root-knot nematode Meloidogyne graminicola, two root pathogens that co-occur in aerobic rice fields. In this manuscript, we investigated if the antagonism is related to imbalances in plant hormone levels, which could be involved in activation of plant defense. Hormone measurements and gene expression analyses showed that the jasmonate (JA) pathway is induced early upon P. arrhenomanes infection. Exogenous application of methyl-jasmonate (MeJA) on the plant confirmed that JA is needed for basal defense against both P. arrhenomanes and M. graminicola in rice. Whereas M. graminicola suppresses root JA levels to increase host susceptibility, Pythium inoculation boosts JA in a manner that prohibits JA repression by the nematode in double-inoculated plants. Exogenous MeJA supply phenocopied the defense-inducing capacity of Pythium against the root-knot nematode, whereas the antagonism was weakened in JA-insensitive mutants. Transcriptome analysis confirmed upregulation of JA biosynthesis and signaling genes upon P. arrhenomanes infection, and additionally revealed induction of genes involved in biosynthesis of diterpenoid phytoalexins, consistent with strong activation of the gene encoding the JA-inducible transcriptional regulator DITERPENOID PHYTOALEXIN FACTOR. Altogether, the here-reported data indicate an important role for JA-induced defense mechanisms in this antagonistic interaction. Next to that, our results provide evidence for induced expression of genes encoding ERF83, and related PR proteins, as well as auxin depletion in P. arrhenomanes infected rice roots, which potentially further contribute to the reduced nematode susceptibility seen in double-infected plants.

Protein improvement of banana peel through sequential solid state fermentation using mixed-culture of Phanerochaete chrysosporium and Candida utilis

Banana peel (BP) is a major waste produced by fruit processing industries. Pre-treatment of BP at different temperatures led to 40% reduction in saponin at 100 °C (from 9.5 to 5.7 mg/g). Sequential mixed culture of Phanerochaete chrysosporium (P. chrysosporium) and Candida utilis (C. utilis) gave highest protein enrichment (88.93 mg/g). There is 26% increase in protein synthesis (from 88.93 to 111.78 mg/g) after media screening. Inclusion of KH₂PO₄, FeSO₄·7H₂O, wheat flour and sucrose in the media contributed positively to protein synthesis, while elevated concentration of urea, peptone, K₂HPO₄, KCl, NH₄H₂PO_4, and MgSO₄.7H₂O are required to reach optimum protein synthesis. Total soluble sugar (TSS), total reducing sugar (TRS) and total carbohydrate (CHO) consumption varied with respect to protein synthesis in all experimental runs. Optimum protein synthesis required 6 days and inclusion of 5% sucrose, 0.6% NH₄H₂PO₄, 0.4% KCl, and 0.5% MgSO₄·7H₂O as concentration media constituents to reach 140.95 mg/g protein synthesis equivalent to 300% increase over the raw banana peel protein content (35.0 mg/g).

Growth, substrate consumption, and product formation kinetics of Phanerochaete chrysosporium and Schizophyllum commune mixed culture under solid-state fermentation of fruit peels

Kinetic analysis of solid-state fermentation (SSF) of fruit peels with Phanerochaete chrysosporium and Schizophyllum commune mixed culture was studied in flask and 7 kg capacity reactor. Modified Monod kinetic model suggested by Haldane sufficiently described microbial growth with co-efficient of determination (R ²) reaching 0.908 at increased substrate concentration than the classical Monod model (R ² = 0.932). Leudeking-Piret model adequately described product synthesis in non-growth-dependent manner (R ² = 0.989), while substrate consumption by P. chrysosporium and S. commune fungal mixed culture was growth-dependent (R ² = 0.938). Hanes-Woolf model sufficiently represented α-amylase and cellulase enzymes synthesis (R ² = 0.911 and 0.988); α-amylase had enzyme maximum velocity (V _max) of 25.19 IU/gds/day and rate constant (K _m) of 11.55 IU/gds/day, while cellulase enzyme had V _max of 3.05 IU/gds/day and K _m of 57.47 IU/gds/day. Product yield in the reactor increased to 32.65 mg/g/day compared with 28.15 mg/g/day in shake flask. 2.5 cm media thickness was adequate for product formation within a 6 day SSF in the tray reactor.

Chemical and structural changes of pretreated empty fruit bunch (EFB) in ionic liquid-cellulase compatible system for fermentability to bioethanol

The pretreatment of empty fruit bunch (EFB) was conducted using an integrated system of IL and cellulases (IL-E), with simultaneous fermentation in one vessel. The cellulase mixture (PKC-Cel) was derived from Trichoderma reesei by solid-state fermentation. Choline acetate [Cho]OAc was utilized for the pretreatment due to its biocompatibility and biodegradability. The treated EFB and its hydrolysate were characterized by the Fourier transform infrared spectroscopy, scanning electron microscopy, and chemical analysis. The results showed that there were significant structural changes in EFB after the treatment in IL-E system. The sugar yield after enzymatic hydrolysis by the PKC-Cel was increased from 0.058 g/g of EFB in the crude sample (untreated) to 0.283 and 0.62 ± 06 g/g in IL-E system after 24 and 48 h of treatment, respectively. The EFB hydrolysate showed the eligibility for ethanol production without any supplements where ethanol yield was 0.275 g ethanol/g EFB in the presence of the IL, while lower yield obtained without IL-pretreatment. Moreover, it was demonstrated that furfural and phenolic compounds were not at the level of suppressing the fermentation process.

Effectiveness of Some IPM Packages Consisting of Chemical and Non Chemical Components for Suppressing Pod Borer and Aphid in Summer Country Bean

An experiment was conducted in the experimental farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU), Gazipur to evaluate the efficacy of IPM packages for suppressing aphid and pod borer of summer country bean BARI Seem-3. In case of aphid, among the different IPM packages, P4 [comprising mechanical control (hand picking) and 4 sprays of admire 50 SP (imidacloprid) @ 1ml l-1 of water at 7 days interval] had minimum inflorescence infestation (4.99), whereas untreated control plot P7 totally overturned. In case of pod borer, among the IPM packages, P5 [comprising mechanical control, hand picking with 4 sprays of ripcord 10 EC (cypermethrin) @ 1 ml l-1 of water at 7 days interval] ensured minimum inflorescence and pod infestation (by number and weight) and pod diameter with the lowest pest incidence (4.59 %). In consideration of the economic analysis of the different management packages for controlling pod borer of country bean, the highest BCR ratio (4.28) was recorded in the P5 [comprising mechanical control, hand picking with 4 sprays of ripcord 10 EC (cypermethrin) @ 1 ml l-1 of water at 7 days interval] followed by 3.76 in P6. However, based on marketable pod yield and BCR, hand picking with 4 sprays of ripcord 10 EC (cypermethrin) @ 1 ml l-1 of water at 7 days interval may be considered as the most effective option.J. Environ. Sci. & Natural Resources, 10(1): 109-115 2017

Vertically integrated spot-size converter in AlGaAs-GaAs

We report on the demonstration of a spot size converter (SSC) for monolithic photonic integration at a wavelength of 850 nm on a GaAs substrate. We designed and fabricated a dual-waveguide AlGaAs chip. The design consists of a lower waveguide layer for efficient end-fire coupling to a single-mode fiber, an upper waveguide layer for high refractive index contrast waveguides, and a vertical SSC to connect the two waveguide layers. We measured a SSC conversion efficiency of 91% (or -0.4  dB) between the upper and lower waveguide layers for the TE mode at a wavelength of 850 nm.

Optimization of thermostable organic solvent-tolerant lipase production by thermotolerant Rhizopus sp. using solid-state fermentation of palm kernel cake

This study enhanced the production of thermostable organic solvent-tolerant (TS-OST) lipase by locally isolated thermotolerant Rhizopus sp. strain using solid-state fermentation (SSF) of palm kernel cake (PKC). The optimum conditions were achieved using a series of statistical approaches. The cultivation parameters, which include fermentation time, moisture content, temperature, pH, inoculum size, various carbon and nitrogen sources, as well as other supplements, were initially screened by the definitive screening design, and one-factor-at-a-time using PKC as the basal medium. Three significant factors (olive oil concentration, pH, and inoculum size) were further optimized using face-centred central composite design. The results indicated a successful and significant improvement of lipase activity by almost two-fold compared to the initial screening production. The findings showed that the optimal conditions were 2% (v/w) inoculum size, 2% (v/w) olive oil, 0.6% (w/w) peptone, 2% (v/w) ethanol, 70% moisture content at initial pH 10.0 and 45 °C within 72 h of fermentation. Process optimization resulted in maximum lipase activity of 58.63 U/gram dry solids (gds). The analysis of variance showed that the statistical model was significant (p value <0.0001) and reliable with a high value of R² (0.98) and adjusted R² (0.96). This indicates a better correlation between the actual and predicted responses of lipase production. By considering this study, the low-cost PKC through SSF appears to be promising in the utilization of agro-industrial waste for TS-OST lipase production. This is because satisfactory enzyme activity could be attained that promises industrial applications.

Evaluation of several ionic liquids for in situ hydrolysis of empty fruit bunches by locally-produced cellulase

Lignocellulosic biomasses, exhibit resistance to enzymatic hydrolysis due to the presence of lignin and hemicellulose. Ionic liquids proved their applicability in lignin degradation, however, ionic liquid removal has to be performed to proceed to hydrolysis. Therefore, this study reports an in situ hydrolysis of empty fruit bunches (EFB) that combined an ionic liquid (IL) pretreatment and enzymatic hydrolysis. For enzyme production, palm kernel cake (PKC) was used as the primary media for microbial cellulase (PKC-Cel) from Trichoderma reesei (RUTC30). The obtained enzyme exhibited a promising stability in several ionic liquids. Among few, in choline acetate [Cho]OAc, PKC-Cel retained 63.16 % of the initial activity after 6 h and lost only 10 % of its activity in 10 % IL/buffer mixture. Upon the confirmation of the PKC-Cel stability, EFB was subjected to IL-pretreatment followed by hydrolysis in a single step without further removal of the IL. The findings revealed that choline acetate [Cho]OAc and choline butyrate [Cho]Bu were among the best ILs used in the study since 0.332 ± 0.05 g glucose/g and 0.565 ± 0.08 g total reducing sugar/g EFB were obtained after 24 h of enzymatic hydrolysis. Compared to the untreated EFB, the amount of reducing sugar obtained after enzymatic hydrolysis increased by three-fold in the case of [Cho]OAc and [Cho]Bu, two-fold with [EMIM]OAc and phosphate-based ILs whereas the lowest concentration was obtained in [TBPH]OAc. Pretreatment of EFB with [Cho]OAc and [Cho]Bu showed significant differences in the morphology of EFB samples when observed with SEM. Analysis of the lignin, hemicellulose and hemicellulose showed that the total lignin content from the raw EFB was reduced from 37.8 ± 0.6 to 25.81 ± 0.35 % (w/w) upon employment of [Cho]OAc in the compatible system. The PKC-Cel from T. reesei (RUTC30) exhibited promising characteristics that need to be investigated further towards a single-step process for bioethanol production.

Polarization rotator based on augmented low-index-guiding waveguide on silicon nitride/silicon-on-insulator platform

Using a newly proposed augmented low-index-guiding scheme with silicon nitride/silicon dual-core waveguide, we have designed, fabricated, and characterized a transverse electric (TE) to transverse magnetic (TM) and TM-to-TE compact polarization rotator. The polarization rotation is realized in an asymmetric directional coupler. The measured peak conversion efficiencies for the TE-to-TM and TM-to-TE rotations are approximately 97%. The measured polarization extinction ratio for the TE-to-TM rotation is greater than 20 dB over 50-nm bandwidth, while for the TM-to-TE rotation it is greater than 15 dB over the C-band.

Effect of storage duration on the stored pupae of parasitoid Bracon hebetor (Say) and its impact on parasitoid quality

The ecto-endo larval parasitoid, Bracon hebetor (Say) is an important biocontrol agent. Effective storage methods for B. hebetor are essential for raising its success as a commercial bio-control agent against lepidopteran pests. The study was undertaken to determine the effect of storage duration on the pupae of Bracon hebetor in terms of pupal survival, adult emergence, percent parasitism, female and male longevity, female fecundity and sex ratio. Three to four days old pupae were stored for 0, 1, 2, 3, 4, 5, 6, 7 and 8 weeks at 4 ± 1oC. The ranges of time for adult emergence from stored pupae, production of total adult, survivability of pupae, parasitism of host larvae by the parasitoid, longevity of adult female and male and fecundity were 63.0 -7.5 days, 6.8-43.8/50 host larvae, 13.0-99.5%, 0.0 -97.5%, 0.00-20.75 days, 0.00-17.25 days and 0.00- 73.00/50 female, respectively. The time of adult emergence and mortality of pupae increased but total number of adult emergence, survivability of pupae, longevity of adult female and male decreased gradually with the progress of storage period of B. hebetor pupae. The prevalence of male was always higher than that of female. Therefore, short-term storage of B. hebetor pupae could be stored for up to 4 weeks without disturbing the functioning of the parasitoid. It is important for sustaining and accumulating large numbers of parasitoids in mass rearing programs and subsequent use of field application.Bangladesh J. Agril. Res. 41(2): 297-310, June 2016

Prospects for flavonoid and related phytochemicals as nature-inspired treatments for Clostridium difficile infection

AIMS

There is a need for novel treatments for Clostridium difficile infection(CDI). Antibacterial flavonoids are part of a large family of polyphenol phytochemicals with a long history of use in ethnomedicine, but are unexamined against Cl. difficile. We explored their anti-difficile properties.

METHODS AND RESULTS

Anti-difficile activities were determined for several naturally occurring flavonoids, olympicin A and synthetic 4-chromanone and chalcone analogues. With the exception of olympicin A, most naturally occurring phytochemicals tested were poorly active. Diversified synthetic flavonoids resembling olympicin A retained anti-difficile activity, suggesting olympicin A could act as a pharmacophore to obtain novel agents. They also demonstrated concentration-dependent killing of logarithmic and stationary phase cultures and reduced sporulation and toxin production. Olympicin A and some synthetic flavonoids dissipated the bacterial transmembrane potential. Interestingly, mutants could only be selected with the analogue 207 at a frequency of 10(-9).

CONCLUSIONS

Based on the potent anti-difficile properties of olympicin A and modified flavonoids, further exploration of this class of phytochemicals is warranted.

SIGNIFICANCE AND IMPACT OF THE STUDY

Clostridium difficile infection is a major problem in developed countries. These studies point to there being an avenue for optimizing plant-derived flavonoids, and related antibacterial phytochemicals, as nature-inspired approaches to treat CDI.

Prevalence, antibiotic susceptibility profiles and ESBL production in Klebsiella pneumoniae and Klebsiella oxytoca among hospitalized patients

Background and Purpose: Klebsiella pneumoniae and Klebsiella oxytoca are the two most common pathogens causing nosocomial infections in humans and are of great concern for developing multidrug resistance. In the present study, K. pneumoniae and K. oxytoca from clinical samples were evaluated for their antibiotic sensitivity patterns against commonly used antibiotics and production of extended-spectrum beta-lactamase (ESBL). Materials and Methods: The isolates were obtained from tracheal swabs, sputum, wound swabs, pus, blood and urine samples of hospitalized patients. Klebsiella pneumoniae and Klebsiella oxytoca were identified by cultural and biochemical methods. Antibiotic sensitivity test was performed by modified Kirby-Bauer disc diffusion technique. ESBL production in Klebsiella spp. was confirmed by double disc synergy test.Results and Conclusion: Out of 500 clinical isolates, 120 were found positive for Klebsiella among which 108 were K. pneumoniae and 12 were K. oxytoca based on indole test. Prevalence rate of Klebsiella was found more prominent in males aged over 50 years, mostly in urine samples. Overall resistance pattern of Klebsiella isolates to Ampicillin, Amoxicillin, Ceftriaxone, Ciprofloxacin, Co-trimoxazole, Gentamicin, Nalidixic acid, Tetracycline was 100%, 90%, 45%, 40%, 45%, 25%, 50%, 35% respectively. Multidrug resistance was found more common in K. pneumoniae (56%) than in K. oxytoca (50%). Prevalence rate of ESBL producing Klebsiella was found 45% among which K. pneumoniae (50%) were found more prominent than K. oxytoca (25%). All the ESBL producing Klebsiella isolates were found to be multidrug resistant, showing 100% resistance to Ampicillin, Amoxicillin, Ceftriaxone and Ciprofloxacin. Keywords: Multi-drug resistant, Klebsiella, extended-spectrum beta-lactamase.

Compact and broadband polarization beam splitter based on a silicon nitride augmented low-index guiding structure

We propose a compact polarization beam splitter (PBS) based on a silicon nitride enhanced silicon-on-insulator platform using an augmented low-index guiding (ALIG) waveguide structure. In the ALIG structure, the TM mode is mostly confined in the low-index silicon nitride, while the TE mode is confined in the high-index silicon. Since the two modes are confined in two separate layers, their properties can be controlled independently. The PBS is formed using an asymmetric multimode interference (MMI) section. The TM mode is directed to an output port by the ALIG waveguide, while the TE mode is coupled to the other output port via the multimode interferometer. Such a PBS has a very small footprint, low insertion loss, high polarization extinction ratio, and broadband response.

Genetic improvement of purslane (Portulaca oleracea L.) and its future prospects

Common purslane (Portulaca oleracea), also known as pigweed, fatweed, pusle, and little hogweed, is an annual succulent herb in the family Portulacaceae that is found in most corners of the globe. From the ancient ages purslane has been treated as a major weed of vegetables as well as other crops. However, worldwide researchers and nutritionists have studied this plant as a potential vegetable crop for humans as well as animals. Purslane is a nutritious vegetable with high antioxidant properties and recently has been recognized as the richest source of α-linolenic acid, essential omega-3 and 6 fatty acids, ascorbic acid, glutathione, α-tocopherol and β-carotene. The lack of vegetable sources of ω-3 fatty acids has resulted in a growing level of attention to introduce purslane as a new cultivated vegetable. In the rapid-revolutionizing worldwide atmosphere, the ability to produce improved planting material appropriate to diverse and varying rising conditions is a supreme precedence. Though various published reports on morphological, physiological, nutritional and medicinal aspects of purslane are available, research on the genetic improvement of this promising vegetable crop are scant. Now it is necessary to conduct research for the genetic improvement of this plant. Genetic improvement of purslane is also a real scientific challenge. Scientific modernization of conventional breeding with the advent of advance biotechnological and molecular approaches such as tissue culture, protoplast fusion, genetic transformation, somatic hybridization, marker-assisted selection, qualitative trait locus mapping, genomics, informatics and various statistical representation have opened up new opportunities of revising the relationship between genetic diversity, agronomic performance and response to breeding for varietal improvement. This review is an attempt to amalgamate the assorted scientific information on purslane propagation, cultivation, varietal improvement, nutrient analyses, medicinal uses and to describe prospective research especially for genetic improvement of this crop.

Isolation and selection of new biosurfactant producing bacteria from degraded palm kernel cake under liquid state fermentation

Biosurfactants are surface-active compounds produced by different microorganisms. The aim of this study was to introduce palm kernel cake (PKC) as a novel substrate for biosurfactant production using a potent bacterial strain under liquid state fermentation. This study was primarily based on the isolation and identification of biosurfactant-producing bacteria that could utilize palm kernel cake as a new major substrate. Potential bacterial strains were isolated from degraded PKC and screened for biosurfactant production with the help of the drop collapse assay and by analyzing the surface tension activity. From the screened isolates, a new strain, SM03, showed the best and most consistent results, and was therefore selected as the most potent biosurfactant-producing bacterial strain. The new strain was identified as Providencia alcalifaciens SM03 using the Gen III MicroPlate Biolog Microbial Identification System. The yield of the produced biosurfactant was 8.3 g/L.

Evaluation of solvent system for the enzymatic synthesis of ethanol-based biodiesel from sludge palm oil (SPO)

A green technology of biodiesel production focuses on the use of enzymes as the catalyst. In enzymatic biodiesel synthesis, suitable solvent system is very essential to reduce the inhibition effects of the solvent to the enzymes. This study produced ethanol-based biodiesel from a low-cost sludge palm oil (SPO) using locally-produced Candida cylindracea lipase from fermentation of palm oil mill effluent (POME) based medium. The optimum levels of ethanol-to-SPO molar ratio and enzyme loading were found to be 4:1 and 10 U/25 g of SPO respectively with 54.4% w/w SPO yield of biodiesel and 21.7% conversion of free fatty acid (FFA) into biodiesel. Addition of tert-butanol at 2:1 tert-butanol-to-SPO molar ratio into the ethanol-solvent system increased the yield of biodiesel to 71.6% w/w SPO and conversion of FFA into biodiesel to 28.8%. The SPO and ethanol have promising potential for the production of renewable biodiesel using enzymatic-catalyzed esterification and transesterification.

Laparoscopic assisted appendicectomy in District Hospital, Joypurhat, Bangladesh

"Laparoscopic assisted appendicectomy" refers to visualization of abdominal cavity, identification of appendix, drawing the appendix out through the port wound and appendicectomy. The objective of this study is to evaluate the outcome of the procedure of laparoscopic assisted appendicectomy. In this prospective study patients with appendicitis were randomly selected for laparoscopic assisted appendicectomy from August 2007 to February 2009 in the Department of Surgery, Modernized District Hospital, Joypurhat, Bangladesh. Out of 73 patients Laparoscopic assisted appendicectomy was performed successfully in 95.89% cases and conversion rate was 4.11%. Male to female ratio was almost 1:2 with mean±SD age 18.62±9.16 years. The wound infection rate was 8.2% and urinary retention 2.7%. Early postoperative feeding was started within 24 hours in 86.3% cases and mean duration of hospital stay was 2 days in 76.71% patients. More than 82% returned to their home and started social activities within 5 days. Duration of surgery was almost similar in emergency and interval appendicectomy group (19.35±10.13 vs. 23.66±9.43) minutes. Postoperative morbidity in emergency appendicectomy group showed significantly higher morbidity than interval appendicectomy group (p=0.003). This study indicates that the laparoscopic assisted appendicectomy is feasible for the majority of the patients with appendicitis in both emergency and interval settings. It reduces the operative time, shortens hospital stay and helps in early resumption of normal activities with good cosmetic outcome and patients' satisfaction.

Regional metastasis in supraglottic and glottic carcinoma of larynx

This cross sectional study was conducted in Sir Salimullah Medical College Hospital, Mitford and Dhaka Medical College Hospital, Dhaka, Bangladesh from January 2009 to December 2009 by purposive sampling method. Among the 50 cases, involvement of supraglottic (72%) region is significantly higher than glottic (28%) region. Affected peoples are mainly male and mean age was 58.1±10.4 years. Frequency of regional metastasis of supraglottic carcinoma (47.22%) was higher than glottic carcinoma (7.14%). Most of the lymphnode involvement was at level-II to IV. Most of the patients presented at stage-I & stage-II.

Compact low loss and broadband hybrid plasmonic directional coupler

We propose a novel broadband coupler for silicon photonics using a hybrid plasmonic waveguide section. The hybrid plasmonic waveguide is used to create an asymmetric section in the middle of a silicon nanowire waveguide coupler to introduce a phase delay to allow for a 3-dB power coupling ratio over a 150 nm bandwidth around 1.55 µm. The device is very compact (<8.5 µm) and has a low insertion loss (<0.15 dB).

Pd-based integrated optical hydrogen sensor on a silicon-on-insulator platform

We have experimentally demonstrated a compact, integrated optical hydrogen sensor on a silicon-on-insulator platform. The sensor consists of silicon waveguide coated with a thin palladium film. The sensitivity and response time of the sensor was tested for volumetric hydrogen concentrations ranging from 0% to 4%. The proposed hydrogen sensor shows great potential as a building block for an optical nose capable of simultaneous detection of multiple gases as well as environmental effects such as temperature and humidity.

Effect of seasonal variations on jackfruit trunk borer (Batocera rufomaculata De Geer) infestation

The study of seasonal influence on incidence of trunk borer infestation was undertaken during 2010 at Kapasia upazila under district of Gazipur, Bangladesh. The borer was found in orchard from June to September with a peak emergence in mid July. The larval population of Jackfruit trunk borer is the destructive pest stage, which evokes concern in jackfruit growing areas of Bangladesh. The highest percentage of infestation was in July (7.33%) followed by June and August (6.00%). The cumulative infestation over the year in the study area was 35.33% in October. The lowest infestation was observed in February (0.67%) whereas no activity was found during November to January. The incidence of infestation of trunk borer was influenced by temperature, rainfall and relative humidity due to seasonal variations and their contribution of the regression (R2) were 63, 65 and 31%, respectively. Five independent weather factors in stepwise regression equation pooled responsible for 67.4% of the total variance. Stepwise regression showed that maximum temperature was the most important to influence 35.3% and the influence was lowest (2.1%) in case of average rainfall.

Biodegradation potential and ligninolytic enzyme activity of two locally isolated Panus tigrinus strains on selected agro-industrial wastes

The degradation potential and ligninolytic enzyme production of two isolated Panus tigrinus strains (M609RQY and M109RQY) were evaluated in this study. These strains were grown on three selected abundant agro-industrial wastes (rice straw; rice husk and cassava peel) under solid-state fermentation conditions. Degradation potential was determined by analyzing the chemical composition of the selected substrates before and after fermentation along with ligninolytic enzyme production. The strain M609RQY led to the highest lignin degradation of 40.81% on cassava peel, 11.25% on rice husk and 67.96% on rice straw. Both strains significantly increased the protein content of cassava peel. Rice husk stimulated maximum laccase (2556 U/L) and lignin peroxidase (24 U/L) production by the strains M109RQY and M609RQY, respectively. Furthermore, cassava peel stimulated maximum manganese-dependent peroxidase (141 U/L) production by the strain M109RQY. The de-lignified rice straw and the nutritionally-improved cassava peel could serve as potential animal feed supplements.

Compact hybrid plasmonic polarization rotator

We propose a novel ultracompact (5 μm) hybrid plasmonic polarization rotator operating at telecommunication wavelength for integrated silicon photonic circuits. The polarization mode of a silicon waveguide is rotated with >14 dB polarization extinction ratio and low total insertion losses of 2.1 dB.

Identification of the causative agent of cutaneous leishmaniasis in Chichaoua province, Morocco

Cutaneous leishmaniasis (CL) in Morocco is caused by three species, Leishmania major, L. tropica and L. infantum. CL has been known in Chichaoua province since 2000. Using DNA extracted from microscopic slides and parasite cultures, collected in the years 2006 and 2009, we identified for the first time L. tropica as the causative agent of CL in this region. Species identification was achieved by performing the ITS1-PCR-RFLP approach. By using this method it was possible to identify parasites in Giemsa stained slides containing less than five parasites per oil-immersion field even they were conserved for up to four months.

Polarization-independent hybrid plasmonic coupler for a silicon on insulator platform

Hybrid plasmonic waveguides consisting of a high-index slab separated from a metal plane by a low-index spacer provide an optimal compromise between the loss and confinement for surface plasmon waves in passive medium. In such hybrid structures, because power for the TE and TM modes are concentrated in two different regions of the guide, the characteristics of the two modes can be controlled independently by changing the waveguide dimensions. We propose to use this property to implement a hybrid plasmonic polarization-independent directional coupler for a silicon on insulator platform. We also investigate the effects of variations of wavelength and device dimensions on the performance of the proposed device.

Compact and silicon-on-insulator-compatible hybrid plasmonic TE-pass polarizer

Hybrid plasmonic waveguides consisting of a metal plane separated from a high-index medium by a low-index spacer have recently attracted much interest. Here we show that, by suitably choosing the dimensions and material properties of the hybrid waveguide, a very compact and broadband TE-pass polarizer can be implemented. Finite-difference time-domain simulation indicates that the proposed device can provide large extinction ratio with low insertion loss for the TE mode.

Utilization of sludge palm oil as a novel substrate for biosurfactant production

This paper introduces sludge palm oil (SPO) as a novel substrate for biosurfactant production by liquid state fermentation. Potential strains of microorganism were isolated from various hydrocarbon-based sources at palm oil mill and screened for biosurfactant production with the help of drop collapse method and surface tension activity. Out of 22 isolates of microorganism, the strain S02 showed the highest bacterial growth with a surface tension of 36.2 mN/m and was therefore, selected as a potential biosurfactant producing microorganism. Plackett-Burman experimental design was employed to determine the important nutritional requirement for biosurfactant production by the selected strain under controlled conditions. Six out of 11 factors of the production medium were found to significantly affect the biosurfactant production. K(2)HPO(4) had a direct proportional correlation with the biosurfactant production while sucrose, glucose, FeSO(4), MgSO(4), and NaNO(3) showed inversely proportional relationship with biosurfactant production in the selected experimental range.

Sludge palm oil as a renewable raw material for biodiesel production by two-step processes

In this study, biodiesel was produced from sludge palm oil (SPO) using tolune-4-sulfonic monohydrate acid (PTSA) as an acid catalyst in different dosages in the presence of methanol to convert free fatty acid (FFA) to fatty acid methyl ester (FAME), followed by a transesterification process using an alkaline catalyst. In the first step, acid catalyzed esterification reduced the high FFA content of SPO to less than 2% with the different dosages of PTSA. The optimum conditions for pretreatment process by esterification were 0.75% (w/w) dosage of PTSA to SPO, 10:1 M ratio, 60 °C temperature, 60 min reaction time and 400 rpm stirrer speed. The highest yield of biodiesel after transesterification and purification processes was 76.62% with 0.07% FFA and 96% ester content. The biodiesel produced was favorable as compared to EN 14214 and ASTM 6751 standard. This study shows a potential exploitation of SPO as a new feedstock for the production of biodiesel.

Propagation characteristics of hybrid modes supported by metal-low-high index waveguides and bends

Hybrid-mode waveguides consisting of a metal surface separated from a high index medium by a low index spacer have attracted much interest recently. Power is concentrated in the low index spacer region for this waveguide. Here we investigate the properties of the hybrid mode in detail and numerically demonstrate the possibility of realizing compact waveguide bends using this wave guiding scheme.

Solid State Bioconversion of Oil Palm Biomass for Ligninase Enzyme Production

A laboratory-scale study of bioconversion of local lignocellulosic material, oil palm biomass (OPB) was conducted by evaluating the enzyme production through microbial treatment in solid state bioconversion (SSB). OPB in the form of empty fruit bunches (EFB) was used as a solid substrate and treated with the white-rot fungus, Phanerochaete chrysosporium, to produce ligninase. The results showed that the highest ligninase activity of 400.27 U/liter was obtained at day 12 of fermentation. While the optimum study indicated the enzyme production of 1472.8 U/liter with moisture content of 50%, 578.7 U/liter with 10% v/w of inoculum size, and 721.8 U/liter with co-substrate concentration of 1% (w/w) at days 9, 9 and 12 of fungal treatment, respectively. The parameters glucosamine and reducing sugar were observed to evaluate the growth and substrate utilization in the experiment.

Improvement of production of citric acid from oil palm empty fruit bunches: optimization of media by statistical experimental designs

A sequential optimization based on statistical design and one-factor-at-a-time (OFAT) method was employed to optimize the media constituents for the improvement of citric acid production from oil palm empty fruit bunches (EFB) through solid state bioconversion using Aspergillus niger IBO-103MNB. The results obtained from the Plackett-Burman design indicated that the co-substrate (sucrose), stimulator (methanol) and minerals (Zn, Cu, Mn and Mg) were found to be the major factors for further optimization. Based on the OFAT method, the selected medium constituents and inoculum concentration were optimized by the central composite design (CCD) under the response surface methodology (RSM). The statistical analysis showed that the optimum media containing 6.4% (w/w) of sucrose, 9% (v/w) of minerals and 15.5% (v/w) of inoculum gave the maximum production of citric acid (337.94 g/kg of dry EFB). The analysis showed that sucrose (p<0.0011) and mineral solution (p<0.0061) were more significant compared to inoculum concentration (p<0.0127) for the citric acid production.

Optimization of decolorization of methylene blue by lignin peroxidase enzyme produced from sewage sludge with Phanerocheate chrysosporium

Optimization of decolorization of methylene blue (MB) dye by lignin peroxidase (LiP) enzyme produced by white-rot fungus Phanerochaete chrysosporium using sewage treatment plant (STP) sludge as a major substrate was carried out in the laboratory. Optimization by the one-factor-at-a-time (OFAT) and statistical approach was carried out to determine the process conditions on optimum decolorization of MB dye using LiP enzyme in static mode. The OFAT method indicated that the optimum conditions for decolorization of MB dye (removal: 14-40%) was at temperature 55 degrees C, pH 5.0 with hydrogen peroxide (H(2)O(2)) concentration 4.0mM, MB dye concentration 20mg/L and LiP activity 0.487U/ml. The addition of veratryl alcohol to the reaction mixtures did not contribute any further increases in decolorization. The initial concentration of MB and the activity of LiP enzyme were further optimized using response surface methodology (RSM). The contour and surface plots suggested that the optimum initial concentration of MB and LiP activity predicted were 15mg/L and 0.687U/ml, respectively for the removal of 65%. The validation of the model showed that the decolorization process gave the higher removal of 90% in agitation mode compared to the static mode with 65% for 60min of incubation time by LiP enzyme.

Statistical optimization of process conditions for cellulase production by liquid state bioconversion of domestic wastewater sludge

A two-level fractional factorial design (FFD) was used to determine the effects of six factors, i.e. substrate (domestic wastewater sludge - DWS) and co-substrate concentration (wheat flour - WF), temperature, initial pH, inoculum size and agitation rate on the production of cellulase enzyme by Trichoderma harzianum in liquid state bioconversion. On statistical analysis of the results from the experimental studies, optimum process conditions were found to be temperature 32.5 degrees C, substrate concentration (DWS) 0.75% (w/w), co-substrate (WF) concentration 2% (w/w), initial pH 5, inoculum size 2% (v/w) and agitation 175 rpm. Analysis of variance (ANOVA) showed a high coefficient of determination (R2) of 0.975. Cellulase activity reached 10.2 FPU/ml at day 3 during the fermentation process which indicated about 1.5-fold increase in production compared to the cellulase activity obtained from the results of design of experiment (6.9 FPU/ml). Biodegradation of DWS was also evaluated to verify the efficiency of the bioconversion process as a waste management method.