Independent behavior of bacterial laccases to inducers and metal ions during production and activity

Laccase, a blue copper oxidase, is an enzyme that is involved in the oxidation of aromatic compounds which prove otherwise difficult to degrade in the environment. The substrates of laccase are xenobiotics and synthetic dyes. The isolation of bacterial strains was investigated for laccase production and its activity. The medium for production was a high nitrogen medium containing aromatic compounds as inducers, for instance, guaiacol, phenol red and black liquor (from pulp and paper industry) gave higher production. The enzymes of isolated bacteria had the optimum pH and temperature in the range of 3 to 5 and 32 to 37°C, respectively. Furthermore, metal ions had an effect on the laccase enzyme; MnSO4 and CuSO4 showed a significant increase in laccase activity. However, the effects of metal ions on either laccase production or laccase activity were not clear. The laccase production and activity were dependent on species of bacterial strains. The laccase bacteria were identified as Rhodococcus sp., Enterobacter sp., Staphylococcus saprophyticus and Delftia tsuruhatensis. The synthetic dyes were determined in the reduction of color using the G32 strain; this strain gave 20 to 65% of dye reduction within three days.Key words: Bacterial laccases, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), inducers, metal ions, dye reduction

Properties of Barium Ferrite Nanoparticles and Bacterial Cellulose-Barium Ferrite Nanocomposites Synthesized by a Hydrothermal Method

Barium ferrite (BFO) is a class of hard magnetic materials which is technologically important for many applications. Likewise, bacterial cellulose (BC) is a natural cellulose with a unique nanostructure and properties. Particularly, magnetic BC membrane, produced by incorporation of magnetic nanoparticles (NPs) in the BC structure, has recently been a research focus of many research groups. In this work, BFO NPs and BC/BFO nanocomposites were fabricated by hydrothermal synthesis. The BFO NPs could be fabricated only when the synthesis temperature reached 290 °C, with the faceted plate-like shape. Increasing the synthesis temperature gradually changed the magnetic properties from paramagnetic to superparamagnetic and ferromagnetic. Maximum Ms, Mr and Hc of 43 emu/g, 21 emu/g, and 1.6 kOe, respectively, were found. For BC/BFO nanocomposites, the hydrothermal synthesis conditions were limited by the stability of BC, i.e., 150 – 210 °C (for 1 h), or 1 – 7 h (at 190 °C). Using the higher temperature or time resulted in disintegration or decomposition of BC. It was found that very small NPs were coated on the BC nanofibers but the BFO phase was not observed by XRD. However, the magnetic measurement showed the hysteresis loops for the nanocomposites synthesized at 190 °C for 3 – 7 h. The observation of the hysteresis loops could be attributed to a small fraction of BFO in the nanocomposite that cannot be detected by XRD. The BC/BFO nanocomposite membranes were demonstrated for their magnetic attraction, flexibility, and lightness, which make them potential uses for flexible information storage or lightweight magnets

Compost Seed of Trichoderma harzianum UD12-102 in Controlling Collar and Stem Rot of Tomato Caused by Sclerotium rolfsii

Antagonistic fungus, Trichoderma harzianum UD12-102, exhibited 90% inhibition against Sclerotium rolfsii in vitro and 80% survival of tomatoes infected by S. rolfsii in vivo. Moreover, the antagonistic fungi increased the effectiveness of a commercial fungicide (vitavax) in controlling S. rolfsii in tomatoes. In field experiments, composts were used as carriers for T. harzianum UD12-102 inoculum preparation. Following S. rolfsii inoculation, the survival percentages of tomato plants were not significantly different with all treatments receiving T. harzianum UD12-102 antagonist. However, the inoculum prepared with compost B (inoculated the antagonist at beginning of composting) resulted in a high survival percentage (more than 60%) with 4 weeks of infection, while the survival percentage of control plants dramatically decreased on week 2 (8.35%), and the plants died after 3 weeks due to S. rolfsii. The compost was a good alternative carrier for antagonistic fungi inoculation and was friendly with soil environments

Screening and potential for biological control of anthracnose disease (Colletotrichum capsici) on chili fruits by yeast isolates

Abstract-Antagonistic yeasts to Colletotrichum capsici were isolated from rhizosphere soil, fruits and leaves of chili plants. The majority of yeast isolates (60 isolates; 31.09%) were isolated from rhizosphere soil. In dual culture tests, five of the isolates screened (HS6, SS11, SLD5, SS10 and PLN13) were found to inhibit C. capsici growth with biocontrol efficacies as 43.12%, 42.50%, 41.87, 41.25 and 40.62%, respectively. Morphological characteristics of them were examined by observing cell and colony patterns. They produced septate pseudohyphae, holoblastic budding and ascospore with two-layers. The colony of each antagonistic yeast was globose, mucoid, white, glistering, raised and smooth. Based on statistical analysis, these antagonistic yeasts (HS6, SS11, SLD5, SS10 and PLN13) could significantly control disease incidence in chili fruits when compared control. The most effective antagonistic isolate was PLN13, the percentage of survival in chili fruits being 60.00 %

Co2P2O7 Microplate/Bacterial Cellulose–Derived Carbon Nanofiber Composites with Enhanced Electrochemical Performance

Nanocrystalline Co2P2O7 and carbon nanofiber (Co2P2O7/CNFs) composites with enhanced electrochemical performance were obtained by calcination after a hydrothermal process with NH4CoPO4∙H2O/bacterial cellulose precursors under an argon atmosphere. SEM images showed that the CNFs were highly dispersed on the surfaces of Co2P2O7 microplates. The diagonal size of the Co2P2O7 plates ranged from 5 to 25 µm with thicknesses on a nanometer scale. Notably, with the optimal calcining temperature, the Co2P2O7/CNFs@600 material has higher specific micropore and mesopore surface areas than other samples, and a maximal specific capacitance of 209.9 F g−1, at a current density of 0.5 A g−1. Interestingly, CNF composite electrodes can enhance electrochemical properties, and contribute to better electrical conductivity and electron transfer. EIS measurements showed that the charge–transfer resistance (Rct) of the CNF composite electrodes decreased with increasing calcination temperature. Furthermore, the Co2P2O7/CNF electrodes exhibited higher energy and power densities than Co2P2O7 electrodes

Interaction between Phosphate Solubilizing Bacteria and Arbuscular Mycorrhizal Fungi on Growth Promotion and Tuber Inulin Content of Helianthus tuberosus L

Arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing bacteria (PSB) could interact synergistically because PSB solubilize sparingly available phosphorous compounds into orthophosphate that AMF can absorb and transport to the host plant. Little is known about the interactions between these two groups in terms of promoting Jerusalem artichoke, Helianthus tuberosus L., which is widely planted by farmers because of its high inulin content. Production depends mainly on synthetic fertilizers as source of plant nutrients. This study aimed to isolate and characterize PSB and investigate the effects of co-inoculation of AMF and PSB on plant performance and inulin accumulation. Isolate UDJA102x89-9, identified as Klebsiella variicola (KV), showed phosphate-solubilizing ability and produced high amounts of several organic acids in vitro and of indole-3-acetic acid (IAA). The experiment combined KV and two AMF species (Glomus multisubtensum (GM) and Rhizophagus intraradices (RI)). Co-inoculation of KV with RI, in combination with rock phosphate, showed the largest increases in plant growth and tuber inulin content, compared both to an unfertilized and fertilized control. This result would reveal whether the phosphate solubilization and IAA property of the PSB in vitro played a significant role in changing plant growth and production, and the available P was subsequently taken up and transported to plant roots by AMF. The high combined effect may have the potential for use by farmers in the future as a biofertilizer for inulin production by Helianthus tuberosus L.</p