Effects of cobalt and manganese on biomass and nitrogen fixation yields of a free-living nitrogen fixer - Azotobacter chroococcum

The effects of different concentrations of cobalt and manganese on the biomass and the ability of Azotobacter chroococcum to fix nitrogen were investigated. In vitro trials were conducted in Jensen’s (nitrogen free) broth (half strength) under continuous air flow, incubated at ambient room temperatures for seven days. Results obtained showed that 12.5 mg/l, 25 mg/l, 50 mg/l, 100 mg/l, and 200 mg/l concentrations of cobalt and manganese respectively enhanced microbial growth of Azotobacter chroococcum concomitantly. However, nitrogen fixation was enhanced only at 12.5 mg/l and 25 mg/l concentrations for cobalt, and only at 12.5 mg/l concentration for manganese. Statistical analysis revealed no significant difference in the specific growth rates and nitrogen fixations respectively, between the cobalt and manganese trials. Kinetic modeling revealed that nitrogen fixation was associated with biomass concentration, and not with cell mass growth. DOI: http://dx.doi.org/10.5281/zenodo.115709

Antifungal potencies of ethanol leaf extracts of four plants found around traditional Yan Barns in south eastern Nigeria on five Yam pathogens implicated in postharvest Yam rot

The susceptibilities of five fungi implicated in postharvest rot of yam, namely, Aspergillus niger, Penicillium oxalicum, Mucor circinelloides, Fusarium oxysporum, and Rhizopus nigricans were evaluated using ethanol leaf extracts of four plants commonly found around traditional yam barns in south eastern. The plants screened were Fagara rubescens, Neubouldia laevis, Pterocarpus soyauxii, and Vernonia amygdalina. Antimicrobial susceptibility was measured as an index of turbidity of broth cultures after incubation 72 hours at ambient temperature (29 – 310C). The optical densities (OD650) were measured by spectrophotometry. None of the test isolates showed susceptibility to any of the plant extracts screened irrespective of the concentration employed. This study also revealed that though all the plants contained bioactive secondary metabolites, no antifungal potency was detected for any of the plant extracts on the test organisms

The Expression of Lipoxygenase Isoforms in Response to Wounding in Peas

Peas are an important leguminous crop and, like soybeans, are subject to loss in yields because of infection and abiotic stresses. Lipoxygenases are enzymes that function in many roles in plant development and defense. They exist in multiple forms and have been implicated in the wound response. Veronico’s research group studied the expression of a specific type of LOX called LOXN2 in pea after mechanical wounding. Their data showed an increase in the expression of LOXN2 and this occurred three hours after wounding. Limited studies have been done in pea leaves. In this research study, Little Marvel pea seedlings were grown for 14 days. Then the leaves for one set of plants were wounded and the second set of plants were left untreated. Plants tissues were harvested 0, 4, 8, 12, and 24 hours after wounding and immediately frozen in liquid nitrogen. The messenger RNAs from the plant tissues were purified by using the mirVANA microRNA Isolation Kit. Quality and quantity of the larger RNAs were assessed using a Nanodrop Lite instrument. Total cDNAs were obtained using random hexamers and a High Capacity cDNA RT-PCR Kit. Primers and probes were designed to specifically measure the expression of LOXN2 and LOXN3 as well as elongation factor-1 alpha as the endogenous control. Initial qPCR results gave standard curves with high PCR efficiencies of 99.25% and 99.75% for the LOXN3 target and for EF1- alpha, respectively. It is hypothesized that the expression of LOXN2 and LOXN3 will increase after mechanical wounding

Effects of cobalt and manganese on biomass and nitrogen fixation yields of a free-living nitrogen fixer - Azotobacter chroococcum

The effects of different concentrations of cobalt and manganese on the biomass and the ability of Azotobacter chroococcum to fix nitrogen were investigated. In vitro trials were conducted in Jensen’s (nitrogen free) broth (half strength) under continuous air flow, incubated at ambient room temperatures for seven days. Results obtained showed that 12.5 mg/l, 25 mg/l, 50 mg/l, 100 mg/l, and 200 mg/l concentrations of cobalt and manganese respectively enhanced microbial growth of Azotobacter chroococcum concomitantly. However, nitrogen fixation was enhanced only at 12.5 mg/l and 25 mg/l concentrations for cobalt, and only at 12.5 mg/l concentration for manganese. Statistical analysis revealed no significant difference in the specific growth rates and nitrogen fixations respectively, between the cobalt and manganese trials. Kinetic modeling revealed that nitrogen fixation was associated with biomass concentration, and not with cell mass growth. DOI: http://dx.doi.org/10.5281/zenodo.115709

Impacts of different concentrations of Copper and Zinc on in vitro responses of Azotobacter chroococum in biomass and nitrogen fixing outputs

The responses of Azotobacter chroococum for copper and zinc were surveyed in this study. The impacts of different concentrations of copper and zinc on biomass formation and nitrogen fixation of Azotobacter chroococum were investigated. Batch trials were performed under continuous airflow using Jensen’s nitrogen free broth, at ambient room temperatures for seven days. Maximum biomass yields of 0.068 OD600 units and 0.131 OD600 units were recorded at 25 mg L-1 and 200 mg L-1 for copper and zinc amended trials, respectively. Maximum nitrogen fixations of 1.446 ppm and 1.507 ppm were also recorded for copper and zinc amended trials at 12.5 mg L-1, respectively. Statistical analysis revealed strong significant correlations between metal concentrations and nitrogen fixation for copper and zinc amended trials, respectively. Leudeking-Piret modeling showed that nitrogen fixations of Azotobacter chroococum in both copper and zinc amended trials were associated with biomass density

Optimizing biomethanation of a lignocellulosic biomass using indigenous microbial-cellulases systems

Studies on enhancing biomethanation were performed to ascertain whether amending lignocellulosic biomass waste with indigenous microbial-cellulases systems will improve biomethane output. To evaluate this, gastrointestinal contents of slaughtered beef cattle were treated with inocula derived from the guts of giant African land snail ( Archachatina marginata ) and worker termites ( Coptotermes formosanus ), individually as well as combined. The fed-batch method operating at prevailing ambient room temperatures (30 ± 2EC) for a hydraulic retention time (HRT) of 60 days was adopted. Feedstock slurry without amendment, amended with Archachatina marginata -derived inoculum, amended with Coptotermes formosanus -derived inoculum, and amended with Archachatina marginata : Coptotermes formosanus (50 : 50%) mixed inocula yielded cumulative biomethane of 65.26 ml/g VS, 63.21 ml/g VS, 125.99 ml/g VS, and 97.16 ml/g VS, respectively. Physicochemical analysis of feedstock and digestates revealed increased reductions in lignin, hemicelluloses, and celluloses (lignocelluloses) in trials amended with microbial-cellulases systems. This study revealed that among the experiments assayed, the trial amended with the cellulases system from Coptotermes formosanus yielded the highest cumulative biomethane

Effects of initiating anaerobic digestion of layer-hen poultry dung at sub-atmospheric pressure

This study investigated the effects of initiating anaerobic digestion (AD) of dry layer-hen poultry dung at the sub-atmospheric pressure of -30 cmHg on biodegradation, biogasification, and biomethanation. The setup was performed as a batch process at an average ambient temperature of 29±2 ºC and a retention time of 15 days. Comparisons were made with two other experiments which were both begun at ambient atmospheric pressure; one was inoculated with digestate from a previous layer-hen dung AD, while the other was not inoculated. The bioreactors initiated at sub-atmospheric pressure, ambient atmospheric pressure without inoculum, and ambient atmospheric pressure with inoculum showed the following for biogas and biomethane yields respectively: 16.8 cm³ g-1 VS and 15.46 cm³ g-1 VS, 25.10 cm³ g-1 VS and 12.85 cm³ g-1 VS, 21.44 cm³ g-1 VS and 14.88 cm³ g-1 VS. In the same order, after AD, the following values were recorded for volatile solids and total viable counts (prokaryotes and fungi) in the digestates: 40.33% and 23.22 x 10(6) cfu mL-1, 43.42% and 22.17 x 10(6) cfu mL-1, 41.11% and 13.3 x 10(6) cfu mL-1. The feedstock showed values of 83.93% and 3.98 x 10(6) cfu mL-1 for volatile solids and total viable count respectively. There was a slight difference in the volatile solids of the digestates of the three bioreactors after AD. The pH recorded for the feedstock slurry before AD was 7.9 at 30ºC, while after AD, the digestates from all the three bioreactors showed the same pH of 5.9 at 29 ºC. Statistical analysis using ANOVA showed no significant difference in biogas yields of the feedstock for the three bioreactors (A, B, C). ANOVA showed no significant difference for biomethane yields in the bioreactors initiated at sub-atmospheric pressure and for those initiated at ambient atmospheric pressure with inoculums. However, it showed significant difference in the bioreactor initiated at sub-atmospheric pressure and that initiated at ambient atmospheric pressure without inoculums, and significant difference in the two sets of bioreactors initiated at ambient atmospheric pressure (with and without inoculum). Initiating AD at reduced atmospheric pressure (-30 cmHg) and the addition of inoculum at ambient atmospheric pressure both increased biomethanation, by 20.31% and 15.80% respectively. The AD initiated at sub-atmospheric pressure yielded the least amount of carbon dioxide (a greenhouse gas), and improved biodegradation and biomethanation. The results also suggest that biomethane production is dependent on specific methanogenic growth. Analyzing the populations of methanogens isolated from the different bioreactors in relation to their biomethane yields suggests that Methanosarcina barkeri may have been largely responsible for the differences in biomethane yields

Optimizing biomethanation of a lignocellulosic biomass using indigenous microbial-cellulases systems

Studies on enhancing biomethanation were performed to ascertain whether amending lignocellulosic biomass waste with indigenous microbial-cellulases systems will improve biomethane output. To evaluate this, gastrointestinal contents of slaughtered beef cattle were treated with inocula derived from the guts of giant African land snail ( Archachatina marginata ) and worker termites ( Coptotermes formosanus ), individually as well as combined. The fed-batch method operating at prevailing ambient room temperatures (30 ± 2EC) for a hydraulic retention time (HRT) of 60 days was adopted. Feedstock slurry without amendment, amended with Archachatina marginata -derived inoculum, amended with Coptotermes formosanus -derived inoculum, and amended with Archachatina marginata : Coptotermes formosanus (50 : 50%) mixed inocula yielded cumulative biomethane of 65.26 ml/g VS, 63.21 ml/g VS, 125.99 ml/g VS, and 97.16 ml/g VS, respectively. Physicochemical analysis of feedstock and digestates revealed increased reductions in lignin, hemicelluloses, and celluloses (lignocelluloses) in trials amended with microbial-cellulases systems. This study revealed that among the experiments assayed, the trial amended with the cellulases system from Coptotermes formosanus yielded the highest cumulative biomethane