Simultaneous saccharification and fermentation of kraft pulp by recombinant Escherichia coli for phenyllactic acid production

Simultaneous saccharification and fermentation (SSF) of renewable cellulose for the production of 3-phenyllactic acid (PhLA) by recombinant Escherichia coli was investigated. Kraft pulp recovered from biomass fractionation processes was used as a model cellulosic feedstock and was hydrolyzed using 10–50 filter paper unit (FPU) g⁻¹ kraft pulp of a commercial cellulase mixture, which increased the glucose yield from 21% to 72% in an enzyme dose-dependent manner. PhLA fermentation of the hydrolyzed kraft pulp by a recombinant E. coli strain expressing phenylpyruvate reductase from Wickerhamia fluorescens TK1 produced 1.9 mM PhLA. The PhLA yield obtained using separate hydrolysis and fermentation was enhanced from 5.8% to 42% by process integration into SSF of kraft pulp (20 g L⁻¹) in a complex medium (pH 7.0) at 37 °C. The PhLA yield was negatively correlated with the initial glucose concentration, with a five-fold higher PhLA yield observed in culture medium containing 10 g L⁻¹ glucose compared to 100 g L⁻¹. Taken together, these results suggest that the PhLA yield from cellulose in kraft pulp can be improved by SSF under glucose-limited conditions.     

Effect of water restriction on productive performance and blood parameters in comisana sheep reared under intensive condition

The effect of water restriction on milk yield and composition, feed intake, body weight and blood parameters was evaluated in Comisana sheep reared under intensive condition. The experiment, lasted 40 days, was performed on 26 lactating ewes subdivided into three treatment groups; the control T group received water ad libitum (W-100) and Group 1 (W-80) and Group 2 (W-60) were watered, respectively, with 80 and 60% of the water consumed by the control T group. Water was supplied in the morning once a day while feed twice. Milk quality analysis was performed every 10 days for pH, fat, total protein, lactose and somatic cell content. Serum samples, performed at days 0, 13, 26 and 40, were analyzed for glucose, cholesterol, triglycerides, creatinine, total proteins, albumin, sodium, potassium, calcium and chloride. Compared to W-100, W-60 was significantly different (P < 0.05) for body weight and serum potassium levels and showed an increase (P < 0.01) in serum concentrations of triglycerides, albumin, total proteins and cholesterol (P < 0.05). Total proteins, triglycerides and sodium levels increased (P < 0.05) in W-80. Body weight showed a significant difference (P < 0.05) only in W-60 if compared to W-100. No significant differences were observed in milk yield, milk composition and feed intake across the treatment groups.     

Phytotoxic activity in Flourensia campestris and isolation of (−)-hamanasic acid A as its active principle compound

An aqueous extract from Flourensia campestris (Asteraceae) dry aerial parts showed strong inhibition on the germination and growth of Lactuca sativa. Based on bio-guided chromatographic fractionation of aq. extracts from dry and fresh leaves and spectroscopic means, (-)-hamanasic acid A (7-carboxy-8-hydroxy-1(2), 12(13)-dien-bisabolene (1)) was isolated as the most inhibitory active principle on germination (ECg₅₀ = 2.9 mM) and on root (ECr₅₀ = 1.5 mM)/shoot (ECs₅₀ = 2.0 mM) growth. As measured by GC, and correlated with a simple designed 2D-TLC, compound 1 was distributed throughout the plant, with a remarkably high concentration (1.6%) in the leaves and the inflorescences. At least a quarter of the amount of 1 was found in aqueous extracts suggesting that leaching would be a key route for its release into the environment. By contrast, leaf essential oils (HD) between 0.5 and 1.5 μl ml⁻¹ did not show herbicidal effects and 1 was not found in them (TLC) nor among volatiles (HS-SPME). Volatile compositions were assessed by GC-FID and GC–MS and led to the identification of 23 compounds (4 monoterpenes and 19 sesquiterpenes) with a wide seasonal (spring–summer%) variation, represented principally by bicyclo-germacrene (37–6%), spathulenol (4–32%), globulol (20–0%), beta-caryophyllene (15–6%), caryophyllene oxide (1–13%) and bicycloelemene (10–1%), respectively. The high amount of 1 in F. campestris together with its feasibility of being extracted with water suggest that (−)-hamanasic acid A is an allelochemical in this species. Species-specific studies must be carried out to evaluate the potential of 1 as a natural herbicidal compound.     

Oxidation of regenerated cellulose with NaClO2 catalyzed by TEMPO and NaClO under acid-neutral conditions

A new TEMPO-mediated oxidation with catalytic amounts of TEMPO and NaClO, and NaClO₂ as the primary oxidant under aqueous conditions at pH 3.5–6.8 was used to prepare water-soluble β-(1 → 4)-linked polyglucuronic acid Na salts (cellouronic acids, CUAs) with high molecular weight in good yield. When regenerated cellulose with original degree of polymerization (DP) of 680 was oxidized by the 4-acetamide-TEMPO/NaClO/NaClO₂ system at pH 5.8 and 40 °C for 3 days, CUA with weight average DP (DPw) of 490 was obtained quantitatively. No peaks other than six signals from β-(1 → 4)-linked anhydroglucuronic acid units of CUA were detected in the solution-state ¹³C NMR spectra of the oxidized products. Although the oxidized product prepared under the above conditions contained about 20% unoxidized cellulose particles, the non-CUA fraction was separable from CUAs by filtration or salt precipitation. The DPw values and yields of CUAs after the filtration or salt precipitation treatment were 250–380 and 45–71%, respectively.     

Large-scale separation of clavine alkaloids from Ipomoea muricata by pH-zone-refining centrifugal partition chromatography

Centrifugal partition chromatography in the pH-zone-refining mode was successfully applied to the separation of alkaloids, directly from a crude extract of Ipomoea muricata. The experiment was performed with a two-phase solvent system composed of methyl tert-butyl ether (MtBE)–acetonitrile–water (4:1:5, v/v) where triethylamine (10 mM) was added to the upper organic stationary phase as a retainer and trifluoroacetic acid (10 mM) to the aqueous mobile phase as an eluter. From 4 g of crude extract, 210 mg lysergol and 182 mg chanoclavine were obtained in 97% and 79.6% purities. Total yield recovery was >95%. Isolated alkaloids were characterized on the basis of their ¹H, ¹³C NMR and ESI-MS data.     

Bioreactor leaching of uranium from a low grade Indian silicate ore

Bio-leaching studies were carried out in a 2 L bioreactor- BIOSTAT-B^® equipped with a PLC based controller at 20–40% (w/v) pulp density using enriched culture of A.ferrooxidans for Turamdih uranium ore (Jharkhand, India). With the enriched culture of A.ferrooxidans adapted on Fe(II) at pH 2.0, 35 °C and 20% (w/v) pulp density, a 98.3% uranium recovery was recorded in 14 days. The leaching of uranium in the bioreactor improved the dissolution rate by reducing the time from 40 days in shake flask as per our earlier studies to 14 days. While investigating the importance of biogenic Fe(III) in the bio-leaching process a maximum recovery of 84.7% U₃O₈ was observed at pH 2.0 and 20% (w/v) pulp density in 10 h as compared to the uranium leaching of 38.3% in the control experiments. On raising the pulp density to 30%, uranium bio-recovery increased to 87.6% in 10 h at pH 2.0 with <76 μm size material. This showed a distinct advantage because of better mixing of slurry in the bioreactor with auto-controlled conditions that improved the kinetics.     

Action spectra of photosystems II and I and quantum yield of photosynthesis in leaves in State 1

The spectral global quantum yield (Y_II, electrons/photons absorbed) of photosystem II (PSII) was measured in sunflower leaves in State 1 using monochromatic light. The global quantum yield of PSI (Y_I) was measured using low-intensity monochromatic light flashes and the associated transmittance change at 810 nm. The 810-nm signal change was calibrated based on the number of electrons generated by PSII during the flash (4 · O₂ evolution) which arrived at the PSI donor side after a delay of 2 ms. The intrinsic quantum yield of PSI (y_I, electrons per photon absorbed by PSI) was measured at 712 nm, where photon absorption by PSII was small. The results were used to resolve the individual spectra of the excitation partitioning coefficients between PSI (a_I) and PSII (a_II) in leaves. For comparison, pigment–protein complexes for PSII and PSI were isolated, separated by sucrose density ultracentrifugation, and their optical density was measured. A good correlation was obtained for the spectral excitation partitioning coefficients measured by these different methods. The intrinsic yield of PSI was high (y_I = 0.88), but it absorbed only about 1/3 of quanta; consequently, about 2/3 of quanta were absorbed by PSII, but processed with the low intrinsic yield y_II = 0.63. In PSII, the quantum yield of charge separation was 0.89 as detected by variable fluorescence F_v/F_m, but 29% of separated charges recombined (Laisk A, Eichelmann H and Oja V, Photosynth. Res. 113, 145–155). At wavelengths less than 580 nm about 30% of excitation is absorbed by pigments poorly connected to either photosystem, most likely carotenoids bound in pigment–protein complexes.     

Chemical modifications by ionic liquid-inspired cations improve the activity and the stability of formate dehydrogenase in [MMIm][Me2PO4]

The formate dehydrogenase (FDH, EC: 1.2. 1.2) from Candida boidinii was found to be inactivated and unstable in the presence of high concentration (>50%) of the water soluble dimethylimidazolium dimethyl phosphate ([MMIm][Me₂PO₄]) ionic liquid. In order to circumvent this problem, the enzyme was chemically modified by cations usually present in ionic liquids: cholinium (1), hydroxyethyl-methylimidazolium (2) and hydroxypropyl-methylimidazolium (3) cations were activated with carbonyldiimidazole before being reacted with the FDH leading to a heterogeneous population of 6–7 biocatalysts. FDH modified by (1) or (3) led to 3–9 modifications while FDH modified by (2) led to 6 proteins presenting 7–12 grafted cations. Specific activity of the modified enzymes was decreased by a 2.5–3-fold factor (0.10–0.15 μmol min⁻¹ mg⁻¹) compared to the non-modified FDH (0.33 μmol min⁻¹ mg⁻¹) when assayed in carbonate buffer (pH 9.7, 25 mM). After modification, the FDH still present 0.06 μmol min⁻¹ mg⁻¹ in 70% [MMIm][Me₂PO₄] (v:v) (30–45% of their activity in aqueous buffer) while the native enzyme is inactive at this ionic liquid concentration, proving the efficiency of this strategy. The half-life of the modified enzyme is also increased by a 5-fold factor after modification by (1) (t_1/2 of 9 days) and by a 3-fold factor after modification by (2) or (3) (t_1/2 of 6 and 5 days respectively) in aqueous solution. When stored in 37.5% [MMIm][Me₂PO₄] (v:v), both modified and unmodified FDH have an increased half-life (t_1/2 of 6–9 days). This grafting strategy is found to be good methods to mimic and study the stabilizing effect of ionic liquids on enzymes.     

Lentinula edodes (shiitake mushroom): An assessment of in vitro anti-atherosclerotic bio-functionality

Mushrooms have been highly regarded as possessing enormous nutritive and medicinal values. In the present study, we evaluated the anti-oxidative and anti-atherosclerotic potential of shiitake mushroom (Lentinula edodes) using its solvent–solvent partitioned fractions that consisted of methanol:dichloromethane (M:DCM), hexane (HEX), dichloromethane (DCM), ethyl acetate (EA) and aqueous residue (AQ). The hexane fraction (1 mg/mL) mostly scavenged (67.38%, IC₅₀ 0.55 mg/mL) the 2,2-diphenyl-1-picryl hydrazyl (DPPH) free radical, contained the highest reducing capacity (60.16 mg gallic acid equivalents/g fraction), and most potently inhibited lipid peroxidation (67.07%), low density lipo-protein oxidation and the activity of 3-hydroxy 3-methyl glutaryl co-enzyme A reductase (HMGR). GC–MS analyses of the hexane fraction identified α-tocopherol (vitamin E), oleic acid, linoleic acid, ergosterol and butyric acid as the bio-functional components present in L. edodes. Our findings suggest that L. edodes possesses anti-atherosclerotic bio-functionality that can be applied as functional food-based therapeutics against cardiovascular diseases.     

Extraction and purification of a lectin from small black kidney bean (Phaseolus vulgaris) using a reversed micellar system

Lectin from crude extract of small black kidney bean (Phaseolus vulgaris) was successfully extracted using the reversed micellar extraction (RME). The effects of water content of organic phase (W_o), ionic strength, pH, Aerosol-OT (AOT) concentration and extraction time on the forward extraction and the pH and ionic strength in the backward extraction were studied to optimize the extraction efficiency and purification factor. Forward extraction of lectin was found to be maximum after 15 min of contact using 50 mM AOT in organic phase with W_o 27 and 10 mM citrate-phosphate buffer at pH 5.5 containing 100 mM NaCl in the aqueous phase. Lectin was backward extracted into a fresh aqueous phase using sodium-phosphate buffer (10 mM, pH 7.0) containing 500 mM KCl. The overall yield of the process was 53.28% for protein recovery and 8.2-fold for purification factor. The efficiency of the process was confirmed by gel electrophoresis analysis.     

Development of a recombinant Escherichia coli-based biocatalyst to enable high styrene epoxidation activity with high product yield on energy source

A highly active recombinant whole-cell biocatalyst, Escherichia coli pETAB2/pG-KJE1, was developed for the efficient production of (S)-styrene oxide from styrene. The recombinant E. coli overexpressed styAB the genes of styrene monooxygenase of Pseudomonas putida SN1 and coexpressed the genes encoding chaperones (i.e., GroEL–GroES and DnaK–DnaJ–GrpE). The styrene monooxygenases were produced to ca. 40% of the total soluble proteins, enabling the whole-cell activity of the recombinant of 180 U/g CDW. The high StyAB activity in turn appeared to direct cofactors and molecular oxygen to styrene epoxidation. The product yield on energy source (i.e., glucose) reached ca. 40%. In addition, biotransformation in an organic/aqueous two-liquid phase system allowed the product to accumulate to 400 mM in the organic phase within 6 h, resulting in an average specific and volumetric productivity of 6.4 mmol/g dry cells/h (106 U/g dry cells) and 67 mM/h (1110 U/L_aq), respectively, under mild reaction conditions. These results indicated that the high productivity and the high product yield on energy source were driven by the high enzyme activity. Therefore, it was concluded that oxygenase activity of whole-cell biocatalysts is one of the critical factors to determine their catalytic performance.     

Production of (R)-mandelic acid by immobilized cells of Saccharomyces cerevisiae on chitosan carrier

The asymmetric microbial reduction of phenylglyoxylic acid (PGA) to (R)-mandelic acid ((R)-MA) with immobilized Saccharomyces cerevisiae cells on globular chitosan was studied. The immobilization conditions and characterization of the immobilized cells were carried out. Chitosan–acetic acid solution was injected into a mixture of 20% NaOH and 30% CH₃OH aqueous solution to obtain globular chitosan, and then the globular chitosan was treated with 1% solution of glutaraldehyde to immobilize yeast cells, which were used to synthesize (R)-MA. The optimum conditions were identified as the substrate concentration of 10 mmol L⁻¹, pH of 6.5 and reaction temperature of 30 °C with the yield of 62% for (R)-MA and the enantiomeric excess (e.e.) of 98% for (R)-MA. The immobilized cells showed good operation and storage stability.     

Effects of temperature on purification of eutrophic water by floating eco-island system

The effects of temperature on pollutant removal of two plant species (Oenanthe javanica D.C. and Nasturtium officinale) were evaluated using simulated microcosms of the floating eco-island system (FEIS). Both the planted FEIS (P-FEIS) and the non-planted FEIS (NP-FEIS) dramatically decreased NH₄–N concentration in the hypereutrophic water at low (10 °C), medium (22 °C), and high (35 °C) temperatures, and to a greater extent for the P-FEIS and at medium temperature. The NO₂–N concentration was effectively decreased from 0.23 to 0.01 mg/L after 4 d treatment with the P-FEIS at all the three temperatures, but was slightly increased in the NP-FEIS at low temperature. The P-FEIS could decrease NO₃–N concentration in the eutrophic water over 1–3 times depending on temperature, with greater decrease at high temperature. The remove of total P (TP) reached 78%, on average, with the FEIS treatment for 4 d at all temperatures, which was over three times greater than those with the NP-FEIS at low temperature. The removal rates of Chla, COD_Mn, and BOD₅ by the P-FEIS from the hypereutrophic water were, on average, 70%, 85%, 83% at 22 °C and 35 °C, respectively, while over 1–2 times smaller at 10 °C. More effective removals of Chla, COD_Mn, and BOD₅ (over 1–2 times) were noted with the P-FEIS than those with the NP-FEIS. N. officinale showed more efficiency in removing ammonium and TN at low temperature, and BOD₅ at medium and high temperatures, as compared to O. javanica. Whereas O. javanica could more effectively decrease Chla at 22 °C and 35 °C and COD_Mn at 10 °C than N. officinale after 4 d treatment. Higher dissolved oxygen concentration and pH was found in the FEIS with N. officinale than that with O. javanica D.C. The results imply that plant eco-island system had remarkable purification ability to remove pollutants from hypereutrophic water, and mixed planting of O. javanica D.C. with N. officinale on the FEIS may enhance nutrient removal and water quality improvement of eutrophic water bodies, especially at low temperature season.     

SEC determination of cross-link efficiency in hyaluronan fillers

The cross-link efficiency in hyaluronan fillers was determined by means of triple detector (RI, LALS-RALS and a Differential Viscometer) GPC/SEC in aqueous buffer. The low water solubility of HA cross-linked with BDDE (HBC) was overcome with an alkaline hydrolysis step. The kinetics of linear HA hydrolysis was investigated at different NaOH concentrations (0.25–0.5–1 M), initial polymer Mws (200–700–1000–1200–1600 kDa) and polymer concentrations (0.1–0.3–0.5 mg/ml). As expected for first-order kinetics, the apparent hydrolysis constant (k_h) was independent of polymer concentration and initial Mws. The k_h was found to be linearly dependent on the NaOH concentration, suggesting a random polymer degradation. A similar behavior was observed for HBC polymers, synthesized with 5–7.5–10–14–18% mol/mol of BDDE for HA repeat unit. The degree of crosslinking was obtained using the Zimm–Stockmayer equation for random, tri-functional polydisperse polymers. The contraction factor (g) was determined after an accurate experimental measurement of the structure factor (?). Comparative studies were performed by ¹H NMR spectroscopy and rheological measurements. Interestingly, the number of effective cross-links found is very low compared to the total BDDE linked; i.e. in a HBC sample only 0.04% of total BDDE linked (equal to 4.6% by ¹H NMR analysis) gives an effective cross-link.     

Cytotoxic effects of stem bark extracts and pure compounds from Margaritaria discoidea on human ovarian cancer cell lines

Margaritaria discoidea (Baill.) G. L. Webster (Euphorbiaceae) is a well-known medicinal plant in Africa used for the treatment of various diseases. So far, no cytotoxic effects of plant extracts on cancer cell lines have been reported.Aim of the studyTo evaluate the cytotoxicity against human ovarian cancer cells of extracts of M. discoidea and characterize the major bioactive compounds.MethodsBoth organic and aqueous extracts of this plant were obtained by maceration. The sulforhodamine B cell proliferation assay was used for evaluation of their cytotoxic activities and the potential bioactive compounds were characterized by gas chromatography–mass spectrometry.ResultsThe organic extract of M. discoidea showed stronger cytotoxicity than the aqueous extract with IC₅₀ values of 14.4 ± 3.0, 14.2 ± 1.2 and 34.7 ± 0.5 µg/ml on OVCAR-8, A2780 and cisplatin-resistant A2780cis ovarian cancer cells, respectively. The organic extract was further subjected to bioassay-guided fractionation by partitioning with n-hexane, ethyl acetate, and n-butanol in water. The ethyl acetate fraction was the most potent on the three ovarian cancer cell lines. A GC–MS analysis of trimethylsilyl derivatives of this fraction indicated the presence of phenolic compounds such as gallic acid and the alkaloid securinine. The IC₅₀ values of these two compounds were determined to be in the range of 3–16 µM, which indicated that they could contribute to the cytotoxic activity of the extract of M. discoidea.ConclusionsThis study has evaluated the cytotoxicity of stem bark extracts of M. discoidea against ovarian cancer cells and provided a basis of further development of this plant for the treatment of ovarian cancer.     

Kinetic models and process parameters for ultrasound-assisted extraction of water-soluble components and polysaccharides from a medicinal fungus

This study was on the kinetics and process parameters for ultrasound-assisted extraction (UAE) of water-soluble components and polysaccharides (PS) from the dry mycelium of a medicinal fungus, Cordyceps sinensis Cs-HK1. Four process variables (factors) were evaluated at different levels, ultrasound intensity (2.44–44.1 W/cm²), temperature (40–70 °C), solid particle size (156.5–750 μm), and solid-to-liquid ratio (1/30–1/70 g/mL). The experimental data of yields versus time in most cases were fitted closely to two empirical kinetic models for solid–liquid extraction, parabolic diffusion equation (y = y_o + y₁t^1/2) and power law (y = βtⁿ) with high correlation coefficients (R²) of 0.95–0.99 for total extract yield, and 0.90–0.96 for PS yield. The PS yield was increased more significantly than the total extract yield with the ultrasound intensity. Reducing the particle size and increasing the extraction temperature led to a higher yield and extraction rate; increasing the solid-to-liquid ratio (or decreasing the liquid volume) increased the PS yield and extraction rate but had little influence on the total extract. Significant correlations were found between extraction rate (dy/dt) and ultrasound power density (P/V), and between extract yield (y) and energy density (Pt/V). The kinetic and process parameters are useful for rational design and efficient operation of UAE processes.     

5CN05 partitioning in an aqueous two-phase system: A new approach to the solubilization of hydrophobic drugs

Liquid–liquid extraction for the purification of molecules has been central to many advances in the pharmaceutical industry. These processes were developed based on the property that some polymer and/or micellar solutions present to separate into a concentrated phase and a diluted phase. Based on the differences in the physical and chemical environments of the two coexisting phases, and since both phases contain approximately 60–90% of water, liquid–liquid extraction provides a powerful alternative to both extract and solubilize a molecule. This paper examines the partition behavior of the synthetic drug, 2-[(3,4-dichlorine-benzylidene)-amino]-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (5CN05), in an aqueous two-phase polymer system (ATPPS) and also in an aqueous two-phase micellar system (ATPMS). The results showed that both systems are favorable for extraction the 5CN05 drug high partition coefficient values (K_5CN05 > 200) and yield (Y_5CN05 > 99.48%) in the concentrated phase were achieved with the systems. However, the ATPPS generated a partition coefficient (K_5CN05) higher than the one obtained with ATPMS. The results suggest that both processes may be used for the extraction and concentration of molecules with hydrophobic characteristics, such as 5CN05. They also provide an optimal environment for the solubilization of such molecules, allowing for greater efficiency when purifying many classes of drugs.     

Separation,purification and preliminary characterization of sulfated polysaccharides from Sargassum plagiophyllum and its in vitro anticancer and antioxidant activity

Sulfated polysaccharides (SPs) were identified in different portions of the thallus of Sargassum plagiophyllum C. Agardh, with TBO staining. SPs were extracted using a blade and purified by Q sepharose fast flow anion-exchange chromatography, resulting in SP fractions F1, F2 and F3, with molecular weights of 30, 35 and 20 kDa, respectively. An SP yield of 43.1% was obtained in F3, while F2 yielded a sulfate content of 21.9%. Furthermore, the in vitro anticancer and antioxidant activities of the polysaccharide fractions were evaluated. The F2 fraction showed higher anticancer activity against HepG2 and A549 cells than the other two fractions, with IC₅₀ values of 600 μg/mL and 700 μg/mL, respectively. The normal breast epithelial cell line (HBL-100) exhibited IC₅₀ concentrations of 1200 and 1400 μg/mL for crude sulfated polysaccharides (CSPs) and all SP fractions (F1–F3). These results indicated that the anticancer activity of F2 could be related to its sulfate content. However, the antioxidant activities of F1–F3 were low at their tested concentrations.     

Straighthead disease of rice (Oryza sativa L.) induced by arsenic toxicity

Straighthead disease is a physiological disorder of rice (Oryza sativa L.) characterized by sterility of the florates/spikelets leading to reduced grain yield. Though the exact cause of straighthead is unknown, a glass house experiment was conducted to investigate the effect of inorganic arsenic on straighthead disease in rice (Oryza sativa L.). BRRI dhan 29, a popular Bangladeshi rice strain, was grown in soils spiked with arsenic (prepared from sodium arsenate, Na₂HAsO₄·7H₂O) at the rate of 10, 20, 30, 40, 50, 60, 70, 80 and 90 mg of As kg^?1 and one control treatment was also run to compare the results. Although there may be some other soil physico-chemical factors involved, arsenic concentration was found to be closely associated with straighthead of rice. With the increase of soil arsenic concentration, the severity of straighthead increased significantly. Up to the 50 mg of As kg^?1 soil treatments, the severity of straighthead incidences were not prevalent. Straighthead resulted in sterile florets with distorted lemma and palea, reduced plant height, tillering, panicle length and grain yield. Straighthead caused approximately 17–100% sterile florates/spikelets formation and about 16–100% loss of grain yield. Straighthead also causes the reduction of panicle formation and panicle length significantly (p < 0.01). In the present study, panicle formation was found to be reduced by 21–95% by straighthead.     

Solvent free biocatalytic synthesis of isoniazid from isonicotinamide using whole cell of Bacillus smithii strain IITR6b2

A biocatalytic route for the synthesis of isoniazid, an important first-line antitubercular drug, in aqueous system is presented. The reported bioprocess is a greener method, does not involve any hazardous reagent and takes place under mild reaction conditions. Whole cell amidase of Bacillus smithii strain IITR6b2 having acyltransferase activity was utilized for its ability to transfer acyl group of isonicotinamide to hydrazine–2HCl in aqueous medium. B. smithii strain IITR6b2 possessed 3 folds higher acyltransferase activity as compared to amide hydrolase activity and this ratio was further improved to 4.5 by optimizing concentration of co-substrate hydrazine–2HCl. Various key parameters were optimized and under the optimum reaction conditions of pH (7, phosphate buffer 100 mM), temperature (30 °C), substrate/co-substrate concentration (100/1000 mM) and resting cells concentration (2.0 mg_dcw/ml), 90.4% conversion of isonicotinamide to isoniazid was achieved in 60 min. Under these conditions, a fed batch process for production of isoniazid was developed and resulted in the accumulation of 439 mM of isoniazid with 87.8% molar conversion yield and productivity of 6.0 g/h/g_dcw. These results demonstrated that enzymatic synthesis of isoniazid using whole cells of B. smithii strain IITR6b2 might present an efficient alternative route to the chemical synthesis procedures without the involvement of organic solvent.