Initial Inoculum Density Research Articles

A Novel Algal–Algal Microbial Fuel Cell for Enhanced Chemical Oxygen Demand Removal

To enhance the removal of COD (Chemical Oxygen Demand) by microalgae, this study constructed a novel microalgae–microalgae microbial fuel cell system (AA-MFC). It investigated the coupling relationship between the COD treatment efficiency at the anode and the production of high-value microalgal products at the cathode, as well as explored the effects of different initial inoculum densities and light–dark cycles. The experiment first measured the operational performance of the newly constructed AA-MFC in open-circuit and closed-circuit modes, demonstrating that this novel AA-MFC could start up rapidly within 32 h and operate stably. The results showed that the AA-MFC enhanced the removal of COD and the growth of microalgae biomass at the anode while maintaining stable power generation. When the initial inoculation density of the anode was 1.2 × 108 cell/cm2 and the light–dark cycle time was 18:6 h, the AA-MFC had the most obvious promoting effect on the COD removal of the anode. Compared with normal culture conditions, the COD removal rate increased by 26.0% to 96.1%. These results indicate that the AA-MFC can not only effectively remove pollutants, but also promote the accumulation of high-value microalgae biomass.

Densidade inicial de inóculo, época de avaliação e reprodução de Meloidogyne enterolobii em goiabeira 'Paluma'

ABSTRACT Guava decline is a complex disease caused by the interaction between Meloidogyne enterolobii and Neocosmospora falciformis (Syn.: Fusarium solani). Thus, selecting M. enterolobii-resistant genotypes within the genus Psidium is essential for controlling this disease, and developing a resistant cultivar of Psidium guajava could significantly impact this issue. Thus, the objective of this study was to assess the response of the guava plants of the cultivar Paluma to different densities of M. enterolobii inoculum. Guava seedlings were inoculated with 500, 1,000, 5,000, 10,000, and 20,000 eggs + second-stage juveniles (J2) of M. enterolobii per plant. Root and shoot fresh weights, shoot dry weight, root length, plant height, and stem base diameter were evaluated at 70 and 135 days after inoculation (DAI). Total number of M. enterolobii eggs + J2 in the root system and nematode reproduction factor nematode were assessed. Nematode multiplication in roots was not proportional to increases in initial inoculum density; thus, the best plant responses to nematode multiplication in the evaluated cultivar were found for the lowest tested densities. The reproduction factor decreased as the inoculum density was increased, at both evaluations (70 and 135 DAI).

Impact of cover crops on population density of the root-knot nematode Meloidogyne chitwoodi

Summary Management strategies applied to reduce Meloidogyne chitwoodi populations below economic damage threshold depend strongly on measures taken during the intercrop period. Therefore, this study evaluated the reproductive potentials of M. chitwoodi on different cultivars of cover crops. Twenty-two different cultivars were evaluated against M. chitwoodi at low and high initial inoculum density in a pot experiment under controlled conditions. Fallow was used as control. Based on the reproductive factor, the cover crops were classified under five different categories: Non-host, Poor host, Maintenance host, Good host and Excellent host. In this study, at both low (10 second-stage juveniles (J2) 100 cm−3 soil) and high (100 J2 100 cm−3 soil) initial inoculum density of M. chitwoodi, fodder radish ‘Maximus’, ‘Contra’, ‘Dacapo’ and ‘Defender’, Italian ryegrass ‘Meroa’, rye ‘Matador’ and bird’s foot trefoil ‘Barguay’, ‘Franco’ and ‘Lotar’ were considered poor hosts reducing the M. chitwoodi population in the pot test based on reproductive factor (RF) values. Field experiments were carried out that confirmed most of our results in the pot experiments. However, the field experiments showed that the rotations in which the cover crops are implemented are influenced by weather conditions, previous crop grown, their growing period and initial population densities. Based on our findings, selected non- and poor-host cover crops could be recommended for integrated management of M. chitwoodi.

Can Beauveria bassiana reduce the root lesion nematode, Pratylenchus thornei, infection on wheat?

BackgroundLimited number of control methods against root-lesion nematodes has increased the search for alternative management strategies. Due to secondary metabolites such as toxins and enzymes secreted by the entomopathogenic fungus, Beauveria bassiana, the number of studies on nematicidal potentials on many plant parasitic nematodes has increased. Almost no work was done on the nematicidal activity of B. bassiana, which is widely used as a bio-insecticide, on the root lesion nematode, Pratylenchus thornei, commonly found on wheat in Turkey. In the present study, it was aimed to determine the pathogenicity of two native B. bassiana isolates (BIM-001 and BY2) obtained from Turkey against P. thornei on wheat under controlled conditions.ResultsSpore suspension of B. bassiana isolates affected P. thornei soil, root, final nematode density and reproduction rate at different degrees according to spore concentration. The soil, root, total nematode density, and reproduction rate in the control on İkizce cv. were 1234.0 adult + larvae/500 g soil, 1105.0 adult + larvae/per pot, 2341.0 (soil + root density) and 5.8 (PF(final nematode density/PI (initial inoculum density)), respectively. It was determined that these parameter values were at the lowest at 108 spore/ml than other concentrations in both isolates of B. bassiana. In 108 spore/ml concentrations of BIM-001 isolate, while P. thornei soil, root, total nematode density, and reproduction rate on İkizce were 641.7 adult + larvae/500 g soil, 930.9 adult + larvae/per pot, 1572.6 (soil + root density) and 3.9 (PF/PI), respectively, these parameter values were found to be 645.2 adult + larvae/500 g soil, 849.0 adult + larvae/per pot, 1492.2 (soil + root density) and 3.6 (PF/PI) at 108 spore/ml concentrations of BY2 isolate. It was observed that the reproduction rate of P. thornei decreased at 108 spore/ml concentration of BIM-001 and BY2 isolates compared to the control.ConclusionNative B. bassiana isolates of BIM-001 and BY2 reduced P. thornei on wheat and the concentration was important for the pathogenicity of B. bassiana. While the reproduction rate of P. thornei at 108 and 107 spores/ml concentrations in both isolates decreased than the control. At 106 spore/ml concentration it was found similar to the control. Even though B. bassiana is known as an effective biocontrol agent against insects and some plant-parasitic nematodes, more detailed studies should be done on its effect on P. thornei.

Bioprocess development for enhancing cell biomass, differential picrosides accumulation, and gene expression profiling at shake flask levels in suspension cultures of Picrorhiza kurroa

Plant cell suspension culture is an alternative and perpetual source for large-scale metabolites production in significantly less time. However, this approach has not yet been executed in Picrorhiza kurroa for their specialized metabolites production. Therefore, the present study aimed to develop the suspension culture process from the rhizome and leaf callus of P. kurroa by optimizing the physical cultivation parameters. Furthermore, the established cultures were subjected to sequential scale-up at 250, 500, 1000, 2000, and 5000 mL shake flask levels to evaluate growth, metabolites accumulation, and gene expression profiling of picrosides biosynthesis. Concurrently, the growth, metabolites content, and gene expression patterns were also assessed at the 4th, 8th, and 12th months of the incubation period. The investigation results revealed that the cell biomass in suspension cultures significantly improved solely by varying the culture parameters. The initial inoculum density (3 g/75 mL), subculture by pouring method, shaking speed (80 rpm), and pH (5.8) were suitable for enhanced production of cell biomass in rhizome and leaf suspension cultures in a 250 mL shake flask. During sequential scale-up, the cell biomass was reached in rhizome suspension (335 g FW; 13.80 g DW) and leaf suspension (263.33 g FW; 10.87 g DW) under optimized parameters at 5000 mL shake flask level. However, a maximum increase in the cell growth index and cell biomass (DW) in g/L of the medium was observed in a 250 mL flask compared to other shake flask volumes. In rhizome and leaf suspension, total picrosides (PI, PII, and PIII) (rhizome: 2.36–2.48 mg/g DW; leaf: 2.50–2.67 mg/g DW) and total precursors (vanillic acid, caffeic acid, cinnamic acid, catalpol, and aucubin) (rhizome: 1.35–1.37 mg/g DW; leaf: 1.20–1.45 mg/g DW) content range was observed during sequential scale-up at 250–5000 mL shake flask levels. Hence, no significant level of variation was observed in picrosides content (PI, PII, and PII in mg/g DW) with respect to different shake flask volumes (250–5000 mL) in rhizome and leaf suspension culture, respectively. Nevertheless, the productivity of metabolites content in mg/L of medium with respect to cell growth in g/L of medium showed a significant level of variation. The 250 mL shake flask volume culture of rhizome and leaf cell suspension accumulated the maximum total picrosides (31.07 and 31.20 mg/L of medium) and total precursors (17.04 and 16.94 mg/L of medium) content with cell biomass (12.53 and 11.69 g/L of medium), respectively. The results also revealed that the shikimate/phenylpropanoid pathway (EPSPS), mevalonate pathway (PMK and GDPS), non-mevalonate pathway (ISPD, DXPS, and ISPE), and iridoid pathway (GS, G10H, UGT, F3D, SQM, and ACT) genes showed upregulated expression in the rhizome and leaf suspension cultures. Analyzing the 1st month cultures with 4th, 8th, and 12th month cultures, the study depicted that growth index, cell viability, metabolites content, productivity in mg/L of the medium, and gene expression pattern were decreased with the age of cultures under one year of incubation. The present investigation delivered a simple yet feasible suspension culture process for metabolites enriched cell biomass production in P. kurroa.

New Angled Twin–layer Porous Substrate Photobioreactors for Cultivation of Nannochloropsis oculata

An angled twin-layer porous substrate photobioreactor (TL-PSBR) using LED light was designed to cultivate Nannochloropsis oculata. Flocculation and sedimentation by modification of pH to 11 were determined as the optimal method for harvesting the N. oculata inoculum. The following optimised parameters were found: tilt angle 15°, Kraft 220gm-2 paper as substrate material, initial inoculum density of 12.5gm-2, 140µmol photons m-2 s-1 light intensity, and a light/dark cycle of 6:6 (h). Test cultivation for 14days was performed under optimised conditions. The total dried biomass standing crop was 75.5gm-2 growth area with an average productivity of 6.3gm-2 d-1, the productivity per volume of used culture medium was 126.2mg/L d-1, total lipid content 21.9% (w/w), and the highest productivity of total lipids was 1.33gm-2 d-1. The dry algal biomass contained 3% eicosapentaenoic acid (w/w), 3.7% palmitoleic acid (w/w), and 513mgkg-1 vitamin E. The optimisation of N. oculata cultivation on an angled TL-PSBR system yielded promising results, and applications for commercial products need to be further explored.

Development of an in vivo bioassay to identify Turkish chickpea genotypes resistance to Ditylenchus dipsaci (Kühn, 1857) (Tylenchida: Anguinidae)

Stem and bulb nematode, Ditylenchus dipsaci (Kühn, 1857) (Tylenchida: Anguinidae) is one of the most damaging plant-parasitic nematodes and damage most legume crops such as chickpea. The aim of the study was to develop a protocol for in-vivo bioassay to investigate D. dipsaci interaction with chickpea. Nine accessions of wild and domesticated Cicer spp. including three Cicer reticulatum Ladiz., three Cicer echinospermum P.H.Davis and three Cicer arietinum L. (Fabales: Fabaceae) were used to evaluate chickpea genotype for resistance to D. dipsaci between 2019 and 2020 at Çukurova University, Nematology laboratory. The incubation time and inoculum density were determined to correlate with the size of the produced nematode population. It was concluded that the highest reproduction of D. dipsaci on carrot discs occurred between 20 and 25°C at 45-60 days and an initial inoculum density were determined 100 nematodes per carrot disc. Also, the initial inoculum density of 300 and the growing time of 16 weeks was the best practice to identify reaction of chickpea genotypes to D. dipsaci . These methods provided that quick screening for resistance studies in chickpea against D. dipsaci to observe information of highest reproduction period of D. dipsaci as time, temperature, inoculum density.

Low temperature combined with high inoculum density improves alpha-linolenic acid production and biochemical characteristics of Chlamydomonas reinhardtii

Chlamydomonas reinhardtii grows fast and is rich in polyunsaturated fatty acids. To explore whether the alpha-linolenic acid (ALA) content can be further enhanced, the cultures were incubated under different culture temperatures, light intensities and inoculum densities. Results showed that temperature exhibited more great impact on ALA synthesis of C. reinhardtii than light intensity and inoculum size. The changes of light intensity and inoculum size displayed non-significant effects on ALA content. The optimal ALA proportion in cells was obtained under the condition of 10 °C, 50 μE/m2/s and 5% inoculum density, which reached ∼ 39%.The augmented initial inoculum density could markedly improve the biomass of C. reinhardtii under 10 °C. The maximum ALA productivity (16.42 mg/L/d) was gained under 10 °C coupled with 25% inoculum size, where higher intracellular sugar and protein yield were observed. These results suggest C. reinhardtii would be an alternative feedstock for the industrial production of ALA.

Effect of Glucose, Agar Supplementation and Bacterial Cell Density on the in vitro Liquid Culture of Steinernema jeffreyense

Entomopathogenic nematodes (EPNs) of the family Steinernematidae are effective biological control agents against important pest insects. The in vitro liquid culture method of mass production is used to produce EPNs of high quantity, quality and with reduced cost by upscaling. The first step in liquid mass production is the use of shake flasks to obtain monoxenic infective juvenile (IJ) inoculum for optimisation purposes, followed by upscaling to a desktop fermenter. This study was undertaken to assess the impact of the addition of agar and glucose to the culture medium, as well as assessing the impact of bacterial cell density inoculum on IJ recovery and yield. Steinernema jeffreyense was cultured in 250 ml Erlenmeyer flasks, with the mutualistic bacterium Xenorhabdus khoisanae. In this study the impact of four different agar and glucose concentrations showed negligible impact on nematode recovery and yield. Different initial bacterial inoculum densities inoculated to the culture medium showed a low inoculum density of 2 % (6 × 106 cells) of the bacteria culture to be the optimal inoculum concentration. A bacterial growth curve for X. khoisanae in tryptic soy broth, showed 40–44 h to be the optimum time for introduction of the initial nematode inoculum into the complex medium.

Optimization of culture conditions for in vitro adventitious roots and selected flavonoids production in Boesenbergia rotunda liquid suspension culture

Boesenbergia rotunda (L.) Mansf. is one of the unique monocotyledonous perennial plant species belonging to the ginger (Zingiberaceae) family. Locally known as ‘Temu Kunci’ in Malaysia and Indonesia, this medicinal plant has been widely used in Asian dishes, particularly as a condiment or as traditional natural medicines. The important medicinal properties of B. rotunda majorly derived from flavonoids which are highly sought as pharmaceuticals. In this study, culture conditions for the growth of adventitious roots in liquid suspension cultures were optimized. The highest adventitious root production was achieved when cultured with initial inoculum density of 1.5 g and pH value at 5.8 after five weeks of culture. HPLC analysis discovered that production of valuable flavonoid compounds (pinostrobin, cardamonin and panduratin A) was significantly higher when the adventitious roots were cultured with initial inoculum density of 1.5 g whereas the initial pH medium did not significantly affect flavonoid production.

Sheath blight development and yield loss on rice in different epidemiological conditions

Rice sheath blight and its causal agent Rhizoctonia solani AG-1 IA are associated with intensive and high input production systems. To our knowledge, resistant varieties have not been introduced for this disease, thus good crop management is expected to be among viable disease control methods. The aims of the present study were to determine the effect of different rates of nitrogen fertilizer, planting spaces and inoculum densities on sheath blight incidence and severity, including grain yield loss. Additionally we aimed to identify those developmental stages that are more susceptible to the disease. Field experiments were conducted over two consecutive years, in 2017 and 2018 in the Guilan province of Iran. Results indicated that higher N rates, denser planting and higher initial inoculum density resulted in greater disease development. Among five different growth stages, inoculation of plants at booting and flowering stages, resulted in maximum disease severity and grain yield loss. Taken together, reasonable use of nitrogen fertilizer, optimum planting space and reduced inoculum density obtained by spraying fungicide at the booting and flowering stages of rice are suggested as the best options to control sheath blight epidemics in rice.

In vitro liquid culture and optimization of Steinernema jeffreyense using shake flasks

Entomopathogenic nematodes (EPNs) of the families Heterorhabditidae and Steinernematidae are efficient biological control agents against important insect pests. In vitro liquid culture production technology is a key factor in the success of implementing EPNs as a biological control agent. One of the first steps of in vitro mass culture is to use shake flasks to obtain nematode inoculum for optimising and upscaling to desktop and industrial fermenters. This study was the first attempt on the in vitro liquid mass culture of a local South African isolate, Steinernema jeffreyense, in 250 ml Erlenmeyer flasks, together with their mutualistic bacteria, Xenorhabdus khoisanae. After the successful in vitro production of S. jeffreyense-inoculum, different parameters for optimizing infective juvenile (IJ) recovery (developmental step when the IJ moult to initiate the life cycle) and yield, were investigated. This includes the effect of the volume of liquid medium in the flasks, two different orbital shakers setups and the initial IJ inoculum density. With 30 ml of liquid medium the mean percentage recovery of IJ after six days was 86%, with a yield of 121,833 IJ ml−1 after 14 days, in comparison to 75% and 99,875 IJs ml−1 respectively when 50 ml of liquid medium was used. No significant difference was found between IJ recovery and yield, using different orbital shakers setups. Among the three inoculum concentrations tested (1000, 2000 and 3000 IJ ml−1), the lowest concentration gave the highest IJ recovery and yield. Pathogenicity of IJs cultured in vitro was higher than those cultured in vivo.

Biodegradation of the endocrine disrupter 4-t-octylphenol by the non-ligninolytic fungus Fusarium falciforme RRK20: Process optimization, estrogenicity assessment, metabolite identification and proposed pathways

4-t-octylphenol (4-t-OP), a well-known endocrine disrupting compound, is frequently found in various environmental compartments at levels that may cause adverse effects to the ecosystem and public health. To date, most of the studies that investigate microbial transformations of 4-t-OP have focused on the process mediated by bacteria, ligninolytic fungi, or microbial consortia. There is no report on the complete degradation mechanism of 4-t-OP by non-ligninolytic fungi. In this study, we conducted laboratory experiments to explore and characterize the non-ligninolytic fungal strain Fusarium falciforme RRK20 to degrade 4-t-OP. Using the response surface methodology, the initial biomass concentration and temperature were the factors identified to be more influential on the efficiency of the biodegradation process as compared with pH. Under the optimized conditions (i.e., 28 °C, pH 6.5 with an initial inoculum density of 0.6 g L−1), 25 mg L−1 4-t-OP served as sole carbon source was completely depleted within a 14-d incubation; addition of low dosage of glucose was shown to significantly accelerate 4-t-OP degradation. The yeast estrogenic screening assay further confirmed the loss of estrogenic activity during the biodegradation process, though a longer incubation period was required for complete removal of estrogenicity. Metabolites identified by LC-MS/MS revealed that strain RRK20 might degrade 4-t-OP as sole energy source via alkyl chain oxidation and aromatic ring hydroxylation pathways. Together, these results not only suggest the potential use of non-ligninolytic fungi like strain RRK20 in remediation of 4-t-OP contaminated environments but may also improve our understanding of the environmental fate of 4-t-OP.

Soil fumigation with mustard essential oil to control bacterial wilt in tomato

In vitro experiments showed that six isolates, belonging to different biovars, were equally susceptible to mustard essential oil (MEO) vapor. The proportion of cell mortality and colony growth inhibition were directly related to the dose of MEO. A 24 h exposure to 1 or 2 μL of AITC per liter of box volume resulted in mortality of 89% and 92% of cells, respectively, and exposure to 10 μL L−1 resulted in 100% cell mortality. The growth of developing colonies was reduced by 89% at 2 or 4 μL L−1 and by 96% at 6 or 10 μL L−1. The leakage of intracellular materials increased with increasing doses of MEO vapor. The decline in soil inoculum density by fumigation was directly related to the MEO dose. The initial inoculum density of approximately 3 × 105 colony-forming units per gram of soil declined by 67, 91 and 96% at fumigation doses of 25, 50 and 75 μL of allyl isothiocyanate (AITC) per liter of soil, respectively. The pathogen was not detected at a fumigation dose of 100 μL L−1. Disease control was also related to the fumigation dose. After 48 days, the bacterial wilt symptoms did not develop on the tomatoes when the soil was fumigated at 100 μL L−1 or higher.

An effective method of utilizing vegetable waste in the form of carriers for Trichoderma strains with phytosanitary properties

It has been assumed that compost from savoy cabbage and rapeseed straw is a good substrate for discrimination of the reproduction potential of Trichoderma strains. This hypothesis was verified based on a two-stage incubation experiment. The prepared mixture was fermented in a bio-reactor for 11 weeks. In the second experiment, the mature compost was inoculated with four strains of Trichoderma and a spore concentration of 104 and 106, and then incubated for four weeks. The biomass of autogenic fungi reached a maximum of 12.5 mg∙g−1 DM in the cooling phase. The variability in temperature during composting significantly affected NH3 emission. The pH of mature compost from cabbage wastes, as a result of the elevated NH3 emission reached the alkaline range. The survival of the Trichoderma fungi introduced into the alkali substrate was a result of strain sensitivity to the high pH of the compost and to the initial inoculum density. The adaptation potential of Trichoderma harzianum to the alkali milieu depended on the pH stabilization of the substrate by this fungi, provided the spore inoculum density was 106. The strains of Trichoderma atroviride responded negatively, regardless of the inoculum density, to the alkaline pH of the substrate and to self-induced changes in the compost pH.

Utilization of unfiltered LPG-burner exhaust-gas emission using microalga Coelastrella sp.

This present study evaluated the potential of an untapped thermo-tolerant microalga, Coelastrella sp. FI69 as a promising candidate for scalability, CO2 bio-sequestration and biomass production. The microalga is preliminarily cultivated in elevated CO2 and finite NO3− growth habitat at outdoor field, and developed from lower to higher volume culture. The scaled up culture is eventually used as seed (in two different initial inoculum density, 0.01 and 0.1 g L−1 DW11Dry weight), in 200 L open rectangular pond (ORP22Open rectangular pond) reactor aerated with LPG combusted exhaust-gas streams (10 vol. % of CO2, 150 ppm of nitrogenous gases at atmospheric pressure and 30–40 °C) for 8–10 days for biomass production. The biomass production rate (BPR33Biomass production rate), maximum specific growth rate (μmax44Maximum specific growth rate), CO2 bio-fixation rate (CBFR55CO2 bio-fixation rate) and maximum biomass density (DB-max66Maximum biomass density) of the microalga culture achieved in the exhaust-gas aeration at 0.01 and 0.1 g L-1 are found as 0.065 ± 0.005 and 0.116 ± 0.011 g DW L-1, 0.467 ± 0.014 and 0.426 ± 0.007 day-1, 0.112 ± 0.008 and 0.202 ± 0.002 g CO2 L-1 day-1, and 0.529 ± 0.037 and 1.047 ± 0.022 g DW L-1, respectively. The harvested biomass had heating values of 20.2–21.7 MJ kg-1, contained 16–20% of lipids, and a theoretical methane potential of 586.2 mL CH4 gVS-1. From the biomass energy potential analysis, the microalga cultivation system, which designed to utilize the combustion-gases for biomass production, could reach a promising higher net energy ratio. This study mostly highlights the significance of using the strain for utilization of CO2-rich gas streams.

Growth, morphology and maturation ability of Pinus pinea embryogenic suspension cultures

Stone pine (Pinus pinea L.) is a Mediterranean forest species used for the commercial harvesting of its edible seeds, known as pine nuts. Plant regeneration by somatic embryogenesis on semi-solid medium has been achieved in stone pine, but suspension culture systems for the large-scale production of somatic embryos need to be developed. Suspension cultures were established from several embryogenic lines. Growth parameters as settled cell volume (SCV) and dry weight (DW) in suspension cultures were influenced by genotype, initial inoculum density, orbiting speed and type of carbohydrate in the culture medium. A higher linear growth (DW) up to week four was obtained using 20 mg mL−1 inoculum. The orbiting speed affected the SCV as well as the morphology of embryogenic cultures. Growth parameters decreased when orbiting speed was increased from 50 rpm to 150 rpm. Cultures at 50 rpm most commonly grew as clusters of embryonal cell masses, whereas at 150 rpm there were large numbers of single cells. Cultures grew slowly in medium with maltose instead of sucrose, but growth was not affected when plant growth regulators (PGRs) concentration was decreased. A sustainable suspension culture could be maintained by transferring 250 mg of filtered cell mass to 25 mL of liquid medium at 3-week intervals. Culture scaling-up in liquid medium resulted in a 23-fold DW increase in 6 weeks, compared with 12 fold increase on semi-solid medium. Cotyledonary embryos were obtained on semi-solid maturation medium from lines proliferated in suspension cultures. Increased somatic embryo production was obtained when proliferation was performed at 100 rpm orbiting speed in liquid medium with low PGRs concentration and sucrose instead of maltose.

Pin Nematode Slow Decline of Anthurium andraeanum, a New Disease Caused by the Pin Nematode Paratylenchus shenzhenensis.

High population densities of the plant-parasitic nematode Paratylenchus shenzhenensis have been observed in association with stunted anthurium in Shenzhen, Guangdong Province, China. P. shenzhenensis is now recognized as a new pathogen that causes severe damage to anthurium. Commercial fields of anthurium infected by P. shenzhenensis present a patchy distribution of plants that are usually stunted and in decline and have yellowing leaves. Roots that are heavily infected by this nematode present brown, dark-brown, or black rot, and the entire root mass is often destroyed. In this study, a method of culturing P. shenzhenensis on carrot disks was established, and the effects of temperature and time on the reproduction rate (Rr = final number of nematodes/initial number of nematodes) of this nematode were assessed. The optimum temperature for culturing P. shenzhenensis on carrot disks is 25°C and, after inoculation with 20 females and 10 males at 25°C for 10 weeks, Rr reached 3,834. At the optimum temperature, a suitable extension culture time or an increase in initial inoculum density will improve the reproductive efficiency of P. shenzhenensis. Koch's postulates were fulfilled by inoculating P. shenzhenensis on the roots of anthurium and demonstrating the pathogenicity of the nematode. Histological analyses showed that P. shenzhenensis feed endoparasitically on the roots of anthurium; whole nematode bodies were observed in the outermost epidermal cells and root hairs, and the cell walls and middle lamellae were partially dissolved because of nematode migration and feeding.

Optimizing light regimes on growth and lipid accumulation in Ankistrodesmus fusiformis H1 for biodiesel production

The aim of this study was to optimize the light regimes including initial inoculum density, photoperiod and light intensity on the growth and lipid (TAG) accumulation in Ankistrodesmus fusiformis H1 for biodiesel production. At last, the strategy of 4.47mM urea with initial OD680-0.5, 18:6h light/dark cycle and 200μmolphotonm−2s−1 regimes were optimized. The lipid productivity of 116.88mgL−1d−1 and 57.58% neutral lipid in total lipid were achieved finally. Moreover, the changes of photosynthetic activity, pigments contents and biochemical compositions revealed that more carbon flow to lipid synthesis. Therefore, A. fusiformis H1 is an ideal candidate for biodiesel production by utilizing light appropriately.

Optimization of Culture Conditions of Talinum paniculatum Gaertn. Adventitious Roots in Balloon Type Bubble Bioreactor Using Aeration Rate and Initial Inoculum Density

Optimization of culture conditions of Talinum paniculatum Gaertn. adventitious roots in the balloon type bubble bioreactor have been done in order to increase its production of adventitious roots and saponin content. Culture conditions were used in this research were combination of aeration rate (0.25, 0.5 and 0.75 vvm) and initial inoculum density (0.5, 1, 2 g/400 mL). Bioreactor with a volume of 1000 mL was filled with 400 mL of liquid MS medium supplemented with IBA 2 mg LG1 were then given sterile air through a microfilter (0.2 µm) with different air flow rates. Into each bioreactor were added of different inoculum density of adventitious roots that had previously been induced from leaf explants of T. paniculatum on solid MS medium supplemented with IBA 2 mg LG1. Cultures were maintained for 14 days and sampling was done for every two days to determine the sugar content, conductivity and pH of the medium. The results showed that the combination of aeration rate of 0.5 vvm and inoculum density of 1 g/400 mL was the best treatment that can increase biomass of adventitious roots, whereas the combination of aeration rate of 0.75 vvm and inoculum density of 2 g/400 mL was the best treatment that can be increased of saponin content.