Effect of gaseous ozone treatment on the microbial and physicochemical properties of buckwheat-based composite flour and shelf-life extension of fresh noodles

In recent years, the application of gaseous or aqueous ozone in the processing of flour and noodles has been reported. However, little information is available about buckwheat-based (buckwheat-wheat-gluten) composite flour treated with gaseous ozone and fresh noodles made from the flour. This study investigated the microbial count, and physicochemical properties of buckwheat-based composite flour treated with gaseous ozone at 2.4 g h⁻¹ for 0, 2.5, 7.5 and 15 min and the shelf-life of fresh buckwheat noodles made from ozone-treated buckwheat-based composite flour (OTBF). Gaseous ozone significantly (p < 0.05) reduced the microbial total plate count and increased the CIE L* value, water absorption, development time, and stability time of the OTBF. The peak viscosity, final viscosity, setback, swelling capacity and solubility of the flour were also enhanced by ozone treatment. Scanning electron microscopy showed that ozone treatment facilitated the formation of more clumps and exposure of starch granules in the composite flour. In addition, gaseous ozone treatment at 2.4 g h⁻¹ for 15 min significantly suppressed microbial growth and reduction of L* value, maintained the overall sensory acceptability during the whole storage period, and the shelf-life of fresh noodles prepared from ozone-treated flour was extended to 96 h.     

Bacillus megaterium A6 suppresses Sclerotinia sclerotiorum on oilseed rape in the field and promotes oilseed rape growth

Sclerotinia sclerotiorum causes serious yield losses in oilseed rape and other crops worldwide. Field trials were conducted at two locations to evaluate two formulations of oilseed rape seed containing the plant-growth promoting bacterium Bacillus megaterium A6 for suppression of this pathogen. Treatments containing strain A6 in pellet and in wrap formulations resulted in oilseed rape seed yields that were similar to the chemical control and significantly greater than the untreated seed control at both locations. Treatments containing A6 in pellet and wrap formulations also resulted in an incidence of disease caused by S. sclerotiorum that was similar to the chemical control. Both of these treatments significantly decreased disease incidence relative to the untreated seed control and to the respective formulated seed controls (that did not contain strain A6) at both locations. Strain A6 applied to oilseed rape seed in these two formulations promoted growth in greenhouse pot studies conducted with autoclaved soil. In two experiments, these treatments resulted in significant increases in mean shoot dry weight per pot and mean % total N per plant relative to their respective controls containing formulated oilseed rape seed without strain A6 and to the untreated seed control. Both formulations provided stable B. megaterium A6 (≥10⁶ CFU) and seed germination (>85%) over a six month period at room temperature. Experiments reported here indicate the commercial potential of these formulations of B. megaterium A6 for suppression of S. sclerotiorum on oilseed rape.     

Glycemic index and firming kinetics of partially baked frozen gluten-free bread with sourdough

Gluten-free bread often has low nutritive value, high glycemic index (GI) and short shelf-life. The aim of this research was to investigate the influence of sourdough addition on GI, quality parameters and firming kinetics of gluten-free bread produced by partially baked frozen technology. Sourdough was fermented with a commercial starter of Lactobacillus fermentum and added to bread batter at four levels (7.5; 15; 22.5 or 30%). We determined biochemical characteristics of the sourdough and bread chemical composition, glycemic index in vivo, physical properties and firming kinetics after final rebaking. All breads were enriched with inulin and were high in fiber (>6 g/100 g). Control bread that was prepared without sourdough had medium GI (68). Sourdough addition decreased bread GI. However, only breads with 15 and 22.5% of sourdough had low GI. Moreover, addition of 15 and 22.5% of sourdough had positively affected the quality parameters of partially baked frozen bread: specific volume increased, crumb firmness decreased and firming was delayed. In conclusion, the combined application of sourdough and partially baked frozen technology can decrease glycemic index, improve quality and shelf-life of gluten-free bread. Such breads can be recommended as a part of well balanced gluten-free diet.     

Impact of guar and xanthan gums on proofing and calorimetric parameters of frozen bread dough

The influence of guar and xanthan gum and their combined use on dough proofing rate and its calorimetric properties was investigated. Fusion enthalpy, which is related to the amount of frozen water, was influenced by frozen dough formulation and storage time; specifically gum addition reduced the fusion enthalpy in comparison to control formulation, 76.9 J/g for formulation with both gums and 81.2 J/g for control, at 28th day. Other calorimetric parameters, such as T_g and freezable water amount, were also influenced by frozen storage time. For all formulations, proofing rate of dough after freezing, frozen storage time and thawing, decreased in comparison to non-frozen dough, indicating that the freezing process itself was more detrimental to the proofing rate than storage time. For all formulations, the mean value of proofing rate was 2.97 ± 0.24 cm³ min⁻¹ per 100 g of non-frozen dough and 2.22 ± 0.12 cm³ min⁻¹ per 100 g of frozen dough. Also the proofing rate of non-frozen dough with xanthan gum decreased significantly in relation to dough without gums and dough with only guar gum. Optical microscopy analyses showed that the gas cell production after frozen storage period was reduced, which is in agreement with the proofing rate results.     

Effect of high pressure processing and addition of glycerol and salt on the properties of water in corn tortillas

The effects of high pressure processing (HPP) at 500 and 800 MPa for 1 and 10 min, and the addition of glycerol (4% w/w) and salt (1% w/w) on the properties of water in corn tortillas were investigated. Moisture content and water activity were not affected by either HPP or addition of glycerol/salt. Thermal analysis techniques (such as differential scanning calorimetry and thermogravimetric analysis) and nuclear magnetic resonance spectroscopy (¹H cross-relaxation and ¹H T₁ and T₂ relaxation times) were used to characterize these samples at a structural and molecular level, respectively. Addition of glycerol and salt significantly decreased the ‘freezable’ water content of the tortillas while HPP had little effect on the measured structural properties. The proton mobility was significantly decreased by HPP but not affected by addition of glycerol and salt. These results show that both composition and HPP may alter the structural and molecular properties of water in corn tortillas.     

Impact of guar and xanthan gums on proofing and calorimetric parameters of frozen bread dough

The influence of guar and xanthan gum and their combined use on dough proofing rate and its calorimetric properties was investigated. Fusion enthalpy, which is related to the amount of frozen water, was influenced by frozen dough formulation and storage time; specifically gum addition reduced the fusion enthalpy in comparison to control formulation, 76.9 J/g for formulation with both gums and 81.2 J/g for control, at 28th day. Other calorimetric parameters, such as T_g and freezable water amount, were also influenced by frozen storage time. For all formulations, proofing rate of dough after freezing, frozen storage time and thawing, decreased in comparison to non-frozen dough, indicating that the freezing process itself was more detrimental to the proofing rate than storage time. For all formulations, the mean value of proofing rate was 2.97 ± 0.24 cm³ min⁻¹ per 100 g of non-frozen dough and 2.22 ± 0.12 cm³ min⁻¹ per 100 g of frozen dough. Also the proofing rate of non-frozen dough with xanthan gum decreased significantly in relation to dough without gums and dough with only guar gum. Optical microscopy analyses showed that the gas cell production after frozen storage period was reduced, which is in agreement with the proofing rate results.     

Effect of arabinoxylans and laccase on batter rheology and quality of yeast-leavened gluten-free breads

The supplementation effects of maize fiber arabinoxylans (MFAX, 0%–6%), laccase (0–2 U/g flour) and water absorption level (90%–100%) on gluten-free (GF) batter rheology and bread quality were analyzed. From viscoamylograph analysis, lower starch amount in GF flour due to MFAX addition decreased peak viscosity and retrogradation. Surface response plots showed that laccase did not have significant effect on GF batter rheology and bread quality, whilst water was the most important variable. Higher levels of water absorption benefited bread texture. Higher water level (>100 mL/100 g flour) was needed in the experimental design to evaluate correctly the effect of 6% MFAX replacement on GF bread quality. Further analyses were carried in order to adjust water absorption of batters according to their consistency index (K ≈ 100 Pa sⁿ), resulting an optimal water absorptions of 95%, 100% and 105% for control flour and flours supplemented with 3% or 6% MFAX, respectively. Thus, MFAX addition enhanced water-binding capacity of flour and yielded GF breads with higher specific volume and softer crumb texture. These quality parameters were best rated with 6% MFAX addition to flours. This research demonstrated the potential of MFAX to develop GF breads with improved quality, when optimal water level is used.     

Bacillus subtilis SPB1 biosurfactant: Production optimization and insecticidal activity against the carob moth Ectomyelois ceratoniae

Bacillus subtilis SPB1 was shown to produce a lipopeptide biosurfactant. The insecticidal activity of this biosurfactant was evaluated against Ectomyelois ceratoniae Zeller, a moth pest of stored dates in Tunisia. The LC₅₀ and LC₉₀ values after six days of contact were 152 μg/g and 641 μg/g, respectively. To promote an economical production of this highly effective bioinsecticide, statistical experimental designs and response surface methodology were employed to optimize the concentrations of agro-industrial residues and humidity, for lipopeptide biosurfactant production by B. subtilis SPB1 under solid state fermentation. The optimal medium leading to a production yield near to 28 mg of crude lipopeptide preparation per g of wet solid material was composed of a mixture of 4.34 g of tuna fish flour and 5.66 g of potato waste flour with a moisture content of 76%.     

Effects of applying Lactobacillus plantarum and Chinese gallnut tannin on the dynamics of protein degradation and proteases activity in alfalfa silage

The effects of Lactobacillus plantarum (LP) and Chinese gallnut (Rhus chinensis Mill) tannin on the fermentation quality, nitrogen distribution, protein fractions and proteases activity of alfalfa (Medicago sativa) silage were studied. Additives added to alfalfa forage (approximately 40% DM) were LP (1 × 10⁶ cfu/g FW) plus sucrose (4 g/kg FW) (LP + S), LP (1 × 10⁶ cfu/g FW) plus commercial cellulase (0.1 g/kg FW) (LP + C) and Chinese gallnut tannin at two levels (20 and 50 g/kg DM) (TA 2% and TA 5%). The control was sprayed with the same volume of distilled water. Silage was sampled and analysed on days 1, 3, 5, 7, 14, 21, 28 and 35. The results showed that the degradation of protein to nonprotein nitrogen took place mainly during the first 3 days, while the degradation of peptides and free amino acids occurred throughout the ensiling process. All additives lowered nonprotein nitrogen and free amino acids nitrogen proportion during the ensiling. Additive TA 5% was the most effective to inhibit proteolysis among the four additives, followed by LP + S. They inhibited the activities of all three plant proteases and decreased production of nonprotein nitrogen, free amino acids and ammonia nitrogen during the ensiling process.     

Effects of water regime,nitrogen fertilization,and rice plant density on growth and reproduction of lowland weed Echinochloa crus-galli

Direct-seeded rice systems are increasing in Asia as farmers respond to the high labor cost and shortage of water. Echinochloa crus-galli is one of the most problematic and competitive weeds in direct-seeded rice systems. Because of concerns about excessive herbicide use, there is an interest in developing cultural weed management strategies. However, the design of such strategies requires a better understanding of the weed response to crop density, nutrition, and water regime. A study was therefore conducted in pots to determine the effect of water (flooded and aerobic), nitrogen (N) fertilization (0, 100, and 200 kg N ha⁻¹), and rice density [0, 4 rice plants (≈20 kg seed ha⁻¹), and 16 rice plants (≈80 kg seed ha⁻¹)] on the growth and reproduction of E. crus-galli. When grown alone, the growth and seed production of E. crus-galli were higher in flooded conditions than in aerobic conditions. However, no such differences were observed when E. crus-galli was grown with rice interference. E. crus-galli growth and seed production increased with increases in N rate. Irrespective of water regime and N rate, the growth and seed production of E. crus-galli declined with increases in rice density. At 100 kg N ha⁻¹, for example, E. crus-galli shoot biomass and seed production decreased by 84–86% and 82–87%, respectively, when grown with 16 rice plants compared with its growth without rice interference. The results suggest that growth and seed production of E. crus-galli can be greatly reduced by increasing rice seeding rate. However, there is a need to involve other weed management strategies to achieve complete control of E. crus-galli and other weed species.     

Effectiveness of imidacloprid in combination with a root nitrogen fertilizer applied to tomato seedlings against Bemisia tabaci (Hemiptera: Aleyrodidae)

The whitefly Bemisia tabaci (biotype B) is a worldwide pest of vegetables and field crops. We tested the efficacy of imidacloprid (IM) with a root fertilizer ‘Root Feed (RF)’ (9% N, 7% Ca, 1.5% Mg and 0.1% B) sub-irrigated in the growing medium against the whitefly on tomato. Tomato seedlings (3–4 true leaves) were treated with 0, 3, 6 or 12 mg active ingredient (a.i.) seedling⁻¹ of IM and with RF (0, 0.02, 0.04 or 0.08 ml seedling⁻¹). The efficacy of 12 mg IM seedling⁻¹ was further evaluated in the greenhouse for 60 days. The survival of B. tabaci adults, nymphs, and egg production were negatively affected by the treatments in a dosage-dependent manner. Treatment of 12 mg IM seedling⁻¹ caused >60% adult and nymph mortality 50 days after treatment (DAT). The active ingredient of IM in tomato leaves also increased with the increase of IM dosage. The RF exhibited a limited effect on B. tabaci. However, the mortality of whitefly adults and nymphs treated with RF (0.02 or 0.04 ml seedling⁻¹) positively interacted with IM, and was greater than IM alone. In the greenhouse, 12 mg IM seedling⁻¹ greatly reduced the number of whitefly adults and increased the dry weight of the tomato plants at 30 DAT. In conclusion, application of 12 mg IM seedling⁻¹ on tomato seedlings before transplanting effectively controled B. tabaci for up to 50 days, and the efficacy of IM combined with 0.02 ml RF seedling⁻¹ performed even better. This could be a cost-effective method for managing B. tabaci on tomato and other vegetables.     

Comparison of the impact of dextran and reuteran on the quality of wheat sourdough bread

This study investigates the influence of in situ exopolysaccharides (EPS) and organic acids on dough rheology and wheat bread quality. Dextran forming Weissella cibaria MG1 was compared to reuteran forming Lactobacillus reuteri VIP. For in situ production of EPS, sourdoughs were supplemented with 15% sucrose. Control sourdoughs were prepared with the same strain but without sucrose. W. cibaria MG1 and L. reuteri VIP formed 5.1 and 5.8 g kg⁻¹ dextran and reuteran, respectively. Formation of EPS from sucrose led to production of high amounts of acetate by L. reuteri VIP, but only small amounts were detected in W. cibaria MG1 sourdough. EPS containing sourdough or control sourdough was incorporated at 10% and 20% in wheat dough. EPS significantly influenced the rheological properties of the dough, with dextran exhibiting the strongest impact. The addition of dextran enriched W. cibaria MG1 sourdough significantly increased CO₂ production, whereas increased acidity in reuteran containing dough reduced gas production. The quality of wheat bread was enhanced when 10% of L. reuteri-sucrose sourdough was added. The positive effect of reuteran was masked by increased acidification after 20% sourdough addition. Incorporation of dextran enriched sourdough (10% and 20%) provided mildly acidic wheat bread with improved bread quality.     

Optimization of cultivation medium for enhanced production of antifungal metabolites by Streptomyces hygroscopicus

Antifungal potential of Streptomyces hygroscopicus metabolites was tested against the isolates of Colletotrichum spp., obtained from rotten apple fruits. Experimental factorial design and response surface methodology were employed to optimize medium composition and enhance antifungal components productivity by S. hygroscopicus. Results of optimization suggest that the optimal medium composition is (g/L): glycerol (13.92), yeast extract (5.00), phosphates (0.63), CaCO₃, (3.0), NaCl, (3.0), MgSO₄, (0.5). Further research was performed to validate the obtained results and confirm their applicability in planta on artificially inoculated apple fruits. The obtained efficacy after 14 days of incubation was 99.3% against Colletotrichum acutatum and 99.8% against Colletotrichum gloeosporioides. Application of supernatant of S. hygroscopicus cultivation medium, produced under defined conditions, in biological control of apple rot could offer safe and healthy apple fruits on the market, while simultaneously helping to solve the problem of waste glycerol disposal in the biodiesel industry.     

Evaluation of Fusarium oxysporum as an enzyme factory for the hydrolysis of brewer's spent grain with improved biodegradability for ethanol production

Brewer's spent grain (BG), the most abundant brewing by-product, is used in the present study as a low-cost feedstock for the production of ethanol by the mesophilic fungus Fusarium oxysporum using a consolidated bioconversion process. The production of required cellulolytic and hemicellulolytic enzymes was optimized under solid-state cultivation (SSC) concerning carbon source and initial moisture. The optimal medium contains BG and corn cobs (CC) in a ratio 7:3 while the optimal initial moisture is 66% (w/w). SSC in a laboratory horizontal bioreactor using the optimized medium allowed the large-scale production of a multienzymic system including endoglucanase, cellobiohydrolase, β-d-glucosidase, xylanase, feruloyl esterase, acetyl esterase, β-d-xylosidase and α-l-arabinofuranosidase. Chromogenic (fluorogenic) 4-methylumbelliferyl substrates were used to partially characterize the extracellular proteome of the microbe after the separation by isolectric focusing (IEF) electrophoresis. Alkali pretreatment of brewer's spent grain and different aeration levels were studied for the optimization of the ethanol production by F. oxysporum in a consecutive submerged fermentation. A yield about 65 g ethanol kg⁻¹ of dry BG was obtained with alkali pretreated BG under microaerobic conditions (0.01 vvm) corresponding to 30% of the theoretical yield based on total glucose and xylose composition of BG.     

Effect of sodium selenite addition and sponge dough fermentation on selenomethionine generation during production of yeast-leavened breads

The effect of sodium selenite addition and fermentation times on production of selenomethionine (SeM) during sponge bread production was evaluated. Doughs were supplemented with sodium selenite (Na₂SeO₃) and fermented with yeast, avoiding addition of sulfur salts. The effect of Na₂SeO₃ on yeast activity was evaluated using a pressurometer. Results showed that there were not statistical differences (p < 0.05) in CO₂ production and dough pH at all the sodium selenite concentrations tested. HPLC-fluorescence data showed that SeM production was higher with the increase of fermentation times, while less significant effects were observed due to changes in Na₂SeO₃ concentration. Two slices of Se-enriched bread can provide about 200 μg SeM, the dose recommended to prevent cancer and oxidative stress. The physical features (water absorption, bread weight, bread volume, color, density, oven spring, etc.) and organoleptic evaluations for the enriched loaves were evaluated. In all these parameters, the experimental enriched breads had practically identical attributes compared to the control. The breads rich in SeM have potential to be used as functional foods because this amino acid is synthesized into higher quantities of glutathione peroxidase, an enzyme considered as one of the most protective mechanisms against oxidative stress and preventive of cancer and chronic diseases.     

Potential of two entomopathogenic fungi,Beauveria bassiana and Metarhizium anisopliae (Coleoptera: Scarabaeidae), as biological control agents against the June beetle

The aim of this study was to evaluate the effectiveness of the entomopathogenic fungi (EPF), Beauveria bassiana (Bals.) Vuill. (Deuteromycotina: Hyphomycetes) strain PPRI 5339 [BroadBand, an emulsifiable spore concentrate (EC) formulation] and Metarhizium anisopliae (Metsch.) Sorokin (Hypocreales: Clavicipitaceae) strain F52 [Met52, both EC and granular (GR) formulations] against the larvae of Polyphylla fullo (L.) (Coleoptera: Scarabaeidae). Larvicidal bioassays were performed in foam boxes (100 by 75 by 50 cm; length by width by height), containing moist soil medium with some humus and potato tubers as food. Although the B. bassiana product (min. 4 × 10⁹ conidia/ml) was applied at 100, 150, and 200 ml/100 l water; M. anisopliae strain F52 was applied at 500, 1,000, and 1,500 g/m³ of moist soil medium for GR (9 × 10⁸ cfu/g) and 75, 100, and 125 ml/100 l water for EC (5.5 × 10⁹ conidia/ml) formulation. Both fungi were pathogenic to larvae of the pest; however, young larvae (1st and 2nd instars) were more susceptible to infection than older ones (3rd instar). Mortality rates of young and older larvae varied with conidial concentration of both fungi and elapsed time after application. The B. bassiana product was more effective than both of the formulations of the M. anisopliae product, causing mortalities up to 79.8 and 71.6% in young and older larvae, respectively. The highest mortality rates of young and older larvae caused by the M. anisopliae product were 74.1 and 67.6% for the GR formulation, 70.2 and 61.8% for the EC formulation, respectively. These results may suggest that both fungi have potential to be used for management of P. fullo.     

Effect of nanoclay incorporation method on mechanical and water vapor barrier properties of starch-based films

The objective of this study was to investigate the influence of nanoclay incorporation procedure on the mechanical and water vapor barrier properties of starch/nanoclay composite films. Cassava starch films were prepared with (nanocomposite) and without nanoclay (control) in two steps: firstly the production of extruded pellets and secondly thermo-pressing. The nanocomposite films were prepared via two different methods: in D samples the nanoclay was dispersed in glycerol and subsequently incorporated into the starch; and in ND samples all ingredients were added in a single step before the extrusion. All the composite-films were prepared with cassava starch using 0.25 g of glycerol/g of starch and 0.03 g of nanoclay/g of starch. Control samples showed V_A-type crystallinity induced by the manufacturing process and the nanocomposites presented a semicrystalline and intercalated structure. The nanoclay improved the water vapor barrier properties of the starch film and this effect was more pronounced in D samples, where the water vapor permeability (K^w) was 60% lower than that of the control samples. The K^w reduction was associated with decreases in the effective diffusion coefficient (approximately 61%) and in the coefficient of solubility (approximately 22-32%). On the other hand, the incorporation of nanoclay increased the tensile strength and the rigidity of the films and this effect was more significant when the nanoclay was dispersed in glycerol. Thus, the incorporation of nanoclay into starch-based films is a promising way to manufacture films with better mechanical and water vapor barrier properties.     

Microtuberization of Potato (Solanum tuberosum L.) as Influenced by Supplementary Nutrients, Plant Growth Regulators, and In Vitro Culture Conditions

Five experiments with in vitro-grown plantlets of potato cvs ‘Superior,’ ‘Early Valley,’ ‘Golden Valley,’ and ‘Winter Valley’ were carried out to investigate in a stepwise approach the potential for enhancing microtuber production of (1) adding supplementary nutrients (SN) including KNO₃, NH₄H₂PO₄, Ca(NO₃)₂.4H₂O, and MgSO₄ in full- or half-strength Murashige and Skoog (MS) medium, (2) adding a pretested combination of plant growth regulators (PGRs), i.e., 10 mg l⁻¹ 6-benzyl aminopurine plus 200 mg l⁻¹ succinic acid 2,2-dimethylhydrazide, (3) varying the timing of the supplemental applications, and (4) varying the replenishment of the medium. Plantlets of ‘Superior’ for microtuberization were grown from two-node explants for 75 days under environmental conditions consisting of 22 ± 2 °C and a 16-h photoperiod on a solid basal medium consisting of half-strength MS (1/2 MS) medium containing 6 % sucrose and a moderate concentration of supplementary nutrients, SN-2 (KNO₃, 1.22 g l⁻¹; NH₄H₂PO₄, 1.41 g l⁻¹; Ca(NO₃)₂4H₂O, 0.23 g l⁻¹; and MgSO₄, 0.74 g l⁻¹). Thereafter, plantlets were grown for 60 days under dark conditions. Liquid media containing different combinations of MS, SN, and PGR levels plus 8 % sucrose were added as a supplement and were evaluated for their ability to increase tuberization compared to the control composition of the supplement (MS with 8 % sucrose). In the first experiment, addition of 1/2 MS liquid medium containing 8 % sucrose and SN-2 before dark incubation induced the highest total number of microtubers (on average 1.4 per plantlet), a significantly higher weight and size than the control, and the highest percentage (50 %) of large-sized (>500 mg) microtubers. In the second experiment, addition of 1/2 MS liquid medium containing 8 % sucrose, SN-2, and PGRs produced the highest number (on average 1.5 per plantlet) and total yield (on average 971 mg per plantlet) of microtubers, and significantly the highest percentage (66 %) of large-sized (>500 mg) microtubers. The size of the microtubers was higher than for the treatment without growth regulators. The optimum time for addition of supplemental medium containing 8 % sucrose, SN-2, and PGRs was shown in experiment 3 to be latest 1 week before dark incubation. This timing resulted in both the highest microtuber number (on average 1.6 per plantlet) and yield (on average 1208 mg per plantlet), and the highest percentage (64 %) of large-sized microtubers. Finally, it was found that a second supplemental treatment consisting of 50 % replacement of the liquid medium (by volume) 2 weeks after transfer to dark conditions gave rise to the highest number (on average 1.9 per plantlet), yield (on average 1346 mg per plant), and also significantly the highest percentage (25 %) of large-sized microtubers (>1000 mg) as compared to replacement of a greater or smaller proportion of the medium. Four potato cultivars, ‘Superior,’ ‘Early Valley,’ ‘Golden Valley,’ and ‘Winter Valley’ produced acceptable numbers and yield of microtubers of relatively large-sized tubers using a process that included supplemental liquid medium with 1/2 MS, 8 % sucrose, moderate concentration (SN-2) of SNs and PGRs, followed by a 50 % replacement of the same medium.     

Control of tobacco mosaic virus by Pseudomonas fluorescens CZ powder in greenhouses and the field

Pseudomonas fluorescens strain CZ has been reported to inhibit tobacco mosaic virus (TMV) by producing an antibiotic protein. In this study the effects of CZ powder on TMV infection were investigated on tobacco grown in greenhouses and in the field. CZ stocks were cultured in a mixture medium (5 g wheat bran, 1 g soybean flour, 1 g corn flour, 1 g peanut flour), and then mixed with silica white at a ratio of 6 ml:1 g to make CZ powder. The effective cell concentration in a 100-fold dilution of CZ powder was 49.8 × 10¹⁰ cfu ml⁻¹. In greenhouse experiments where Nicotiana tabacum cv. Samsun NN plants were challenged by mechanical inoculation with a mixture of the 100-fold diluted CZ powder and TMV, the in vitro suppression of the TMV infection was 88.3% compared to the controls in which a mixture of water and TMV was used as inoculum. Similarly when N. tabacum cv. NC89 plants were inoculated by cutting the leaves with virus-contaminated scissors, dipping the scissors in a 100-fold dilution of CZ powder before cutting showed a disinfection effect of 96.3% compared with water dipping controls. Drenching and spraying a 100-fold dilution of CZ promoted growth and inhibited virus infection by 59.2% on N. tabacum cv. NC89 plants in the greenhouse. In field trials, 100-fold dilution of CZ suppressed TMV infection by 58.2% and 47.6% in 2010 and 2011, respectively, which was similar to the effect of Ningnanmycin (antibiotic purified from Streptomyces noursei var. xichangensis), a registered antiviral agent in tobacco. All these results indicated that CZ has a potential to be used as a hand tool disinfector and an antiviral agent against TMV.     

Synthesis of withanolide A depends on carbon source and medium pH in hairy root cultures of Withania somnifera

Withania somnifera (L.) Dunal. (Indian ginseng) is an important medicinal plant which yields pharmaceutically active compounds called withanolides. The present work deals with optimization of parameters of hairy root culture of W. somnifera for the production of biomass and withanolide A. We also investigated the effects of carbon source [sucrose, glucose, fructose, maltose, glucose + fructose (1:1), fructose + sucrose (1:1) and sucrose + glucose (1:1)], sucrose concentration (1%, 2%, 3%, 4%, 6% and 8%) and the initial medium pH (4.0, 4.5, 5.0, 5.5, 5.8, 6.0 and 6.5) on growth and production of withanolide A in hairy root cultures of W. somnifera. We found that biomass accumulation and production of withanolide A was highest when sucrose was used as the carbon source (11.92 g l⁻¹ DW and 11.96 mg g⁻¹ DW of withanolide A). Further 3% sucrose concentration was found to be optimal for biomass accumulation (11.92 g l⁻¹ DW) and 4% sucrose favoured the production of withanolide A (13.28 mg g⁻¹ DW) in the tested range of concentrations (1-8%). The biomass of hairy roots was optimal when the initial medium pH was 5.8 (12.1 g l⁻¹ DW) and the withanolide A production was highest in the medium pH set at 6.0 (13.84 mg g⁻¹ DW).