CO assimilation by autotrophic microbes is an important process in soil carbon cycling, and our understanding of the community composition of autotrophs in natural soils and their role in carbon sequestration of these soils is still limited. Here, we investigated the autotrophic C incorporation in soils from three natural ecosystems, i.e., wetland (WL), grassland (GR), and forest (FO) based on the incorporation of labeled C into the microbial biomass. Microbial assimilation of C (C-MBC) differed among the soils from three ecosystems, accounting for 14.2-20.2% of C-labeled soil organic carbon (C-SOC). We observed a positive correlation between the cbbL (ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large-subunit gene) abundance, C-SOC level, andC-MBC concentration confirming the role of autotrophic bacteria in soil carbon sequestration. Distinct cbbL-bearing bacterial communities were present in each soil type; form IA and form IC RubisCO-bearing bacteria were most abundant in WL, followed by GR soils, with sequences from FO soils exclusively derived from the form IC clade. Phylogenetically, the diversity of CO-fixing autotrophs and CO oxidizers differed significantly with soil type, whereas cbbL-bearing bacterial communities were similar when assessed using coxL. We demonstrate that local edaphic factors such as pH and salinity affect the C-fixation rate as well as cbbL and coxL gene abundance and diversity. Such insights into the effect of soil type on the autotrophic bacterial capacity and subsequent carbon cycling of natural ecosystems will provide information to enhance the sustainable management of these important natural ecosystems.
Introduction: Azomonas agilis, a nitrogen-fixing bacterium, was isolated from rhizospheric soil in central Myanmar.Methods & Materials: The nitrogen-fixing activity of this bacterium was detected by plate screening method using glucose nitrogen free mineral medium and ammonium test-kit Cellulolytic activity was screened by plat assay and detected by Dinitrosalicyclic acid method (DNS).Results & Discussion: The isolated A. agilis grew in media containing 3-12% of NaCl, although the growth became poor when NaCl concentrations increased. Among various carbon sources, sucrose was the best source for ammonium accumulation of this bacterium, whereas arabinose was not the suitable carbon source. Although the nitrogen-fixing activity of A. agilis was highest after one week incubation, cellulase enzyme production was highest after 2-3 days of incubation. It was observed that cellulase enzyme activity of A. agilis for cellulose and sodium carboxymethyl cellulose (CMC) was almost the same. Three agricultural wastes were used to detect the cellulase enzyme activity of A. agilis, cellulase activity was better on filter paper as a substrate when compared to rice-straw and sawdust.Conclusion:So, the isolated A. agilis has high potential as an effective bacterial strain to use in sustainable agriculture and degradation of some agricultural residues.
In this paper, the producing process of using V2O3 as raw material to obtain vanadium nitride was analyzed through the predominance area diagrams. The analysis shows that VN-phase can be accessed in the conversion process of V2O3 by controlling gas phase composition and temperature of the reaction system and the one-step method preparing for vanadium nitride is feasible. Effect of technical parameters on nitrogen content of products is investigated. The temperature of the reaction system has prominent influence on the nitrogen content of products, and the reaction is very sensitive to temperature. The quantities of nitrogen increase first and decrease later with increasing the reactive temperature, and the result researches the optimum at 1673K. The nitrogen content of the products tended to be constant after soaking over 2 hours at 1673K.Experimental observations shows that additives can increase the nitrogen content of VN. However, the effect of various additives on the nitrogen content is different. Among the additives referred in this paper, the effect of the iron powder, compounds of alkaline earths and NH4Cl are superior.
Distillation-crystallization coupling process is a new kind of separation technology based on vapor-liquid equilibrium and solid-liquid equilibrium. The separation of azeotropic systems composed with Acetic acid and N-neptane by distillation-crystallization process (DCC) was studied in this paper. We apply the orthogonal experiment to search for the optimal technique process. The final results demonstrate that the DCC process can purify the heavy and light components over 90 wt% respectively, verifying the advantage of the DCC for the azeotropic systems separation.
In this research work, twenty two xylose-utilizing yeasts were isolated from various sources. Although all isolates could assimilate all tested sugars, they have variations in sugar fermentation pattern. In temperature tolerant activity, almost all yeast isolates could grow well at 40°C. Weak growth of seven yeast isolates (YP3, YP4, YP7, YP8, YP11, YP12 and YP15) was occurred at 45°C. Yeast isolates could grow at pH range (pH3 to pH6) and their optimum growth was occurred at pH3 and pH4. Moreover, isolated yeast strains were tolerant to ethanol concentration of 5%. Some yeast isolates could grow at 7% ethanol concentration. Among all isolates, YP5 and YP14 could produce 1.1% and 1.5% of ethanol concentration respectively at 14 days incubation period and YP17 could produce 0.6% at 3 days incubation period.
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