DETECCIÓN DE HONGOS TOXIGÉNICOS EN LA CADENA PRODUCTIVA DEL MAÍZ (Zea maíz L.)

Se ha determinado la presencia de hongos toxigénicos en los principales productos de la cadena productiva del maíz que son tierra de cultivo, choclo, maíz, maíz pelado y harina de maíz. Los cuales proceden de tres provincias del Departamento de Junín (Huancayo, Concepción y Chupaca). El objetivo de este trabajo fue cuantificar, aislar e identificar los hongos toxigénicos presentes en esta cadena, para proponer medidas de control y evitar su proliferación. Los hongos identificados fueron Penicillium oxalicum, P. viridicatum y P. digitatum en casi todo el estudio, Fusarium roseum y F. moniliforme especialmente en la tierra de cultivo; Aspergillus niger , Rizophus stolonifer y levaduras, especialmente en la harina de maíz. De ellos, Los hongos toxigénicos identificados fueron: F. moniliforme F. roseum, P. viridicatum y A. Níger, y los hongos que causan podredumbre fueron P. digitatum y P. oxalicum. La incidencia de hongos varió de 10 a 4,5 x 105 ufc/g siendo el promedio 4,2 x 104 ufc/g en toda la cadena. También se ha determinado que el maíz pelado y la harina de maíz presentan alto número de hongos especialmente aquellos procedentes de Huancayo, lo que indica que debe hacer un mejor manejo postcosecha y comercialización, ya que estos productos se expenden a granel con mayor riesgo de contaminación.

Biologically formed silver nanoparticles and in vitro study of their antimicrobial activities on resistant pathogens

Background and Objectives: Silver nanoparticles (AgNPs) have been found to have multiple uses as antibacterial, anti- fungal and anti-biofilm agents because of their biological activities and safety. The present study was aimed to analyze the antimicrobial and anti-biofilm activities as well as the cytotoxic effect of AgNPs against different human pathogens. Materials and Methods: AgNPs were synthesized using cell free supernatants of Escherichia coli (ATCC 25922), En- terococcus faecalis (ATCC 19433), Pseudomonas aeruginosa (ATCC 27856), Enterobacter cloacae (ATCC 13047) and Penicillium oxalicum strain, then were analyzed using UV/Vis Spectral Analysis, Transmission electron microscopy (TEM). Scanning Electron Microscope (SEM) and Energy Dispersive-X-ray Spectroscopy (EDX) analysis. Antimicrobial activities of biosynthesized AgNPs were assessed with selected antimicrobial agents against multidrug resistant bacteria and candida. Anti-biofilm and cytotoxicity assays of these biosynthesized AgNPs were also done. Results: The synthesis of AgNPs were confirmed through observed color change and monitoring UV-Vis spectrum which showed homogeneous (little agglomeration) distribution of silver nanoparticles. TEM and SEM have shown that the parti- cle size ranged from 13 to 34 (nm) with spherical shape and a high signal with EDX analysis. Antibacterial and antifungal efficacy of antibiotics and fluconazole were increased in combination with biosynthesized AgNPs against resistant bacteria and candida. Significant reduction in biofilm formation was found better with Penicillium oxalicum AgNPs against biofilm forming bacteria. Conclusion: Penicillium oxalicum has the best effect towards synthesizing AgNPs, for antimicrobial activities against resis- tant bacteria and candida, in addition to anti-biofilm activities against biofilm forming Staphylococcus aureus and E. coli and the safest cytotoxicity effect on (MRC-5) cell line.

The Effects of Silicon Dioxide Nanoparticles and Zinc Oxide Nanoparticles on Waste Land soil Bacterial and Fungal Isolates

Objective: Different bacterial and fungal isolates were collected from the wasteland municipality site, Tambaram. The antimicrobial activity of two types of nanoparticles ZnO & SiO2 [Zinc oxide and Silicon dioxide] against several types of Gram-negative bacteria and fungi was investigated in this work. Methods: P. aeruginosa, B. subtilis, Penicillium oxalicum and Aspergillus fumigatus were isolated from 5 soil samples taken from three sites of Tambaram Municipality wasteland (Chennai). After collecting the samples, we used culturing and biochemical tests to identify the microbes and then used a chemical approach to make ZnO and SiO2 nanoparticles with altered structure and morphological features. Minimum inhibitory concentration (MIC) was used to assess the antibacterial activity of these nanoparticles against various microorganisms. Results: The best inhibition zone was found in Pseudomonas sps and Bacillus sps growth at concentrations of 10 µg/ml and 5 µg /ml of nano-ZnO, respectively, whereas the lower inhibition zone was found in Penicillium oxalicum and Aspergillus fumigatus at a dosage of 2.5 µg /ml of the same nanoparticle. It was also discovered that no inhibitory zone existed in any of the bacteria and fungi at a concentration of 10 µg /ml nano-SiO2. We found that all of the bacteria and fungi we tested were completely inhibited at a concentration of 1.25 g/ml nano-ZnO (MIC), with no antibacterial activity below this concentration. When compared to data that showed that all tested bacteria were not completely inhibited even at a concentration of 0.625 g/ml of nano-SiO2. Conclusion: In comparison to the two nanoparticles (ZnO and SiO2), nano-ZnO outperformed nano-SiO2 in inhibiting most bacteria and fungi at the quantities tested in wasteland soil.

Two New Penicillium Species Penicillium Dongtaiense Sp. Nov and Penicillium Yanchengense sp. nov., Isolated From a Poplar Plantation in China

Studies on the degradation of plant cell wall polysaccharides by fungal extracellular enzymes have attracted much recent attention. In this study, dozens of fungus species spanning genera were isolated from rotting leaves based on their ability to decompose xylan. Using genetic sequencing (rDNA internal transcribed spacer), strains were identified as members of the genera Aspergillus, Penicillium, Alternaria, Campylocarpon, Pyrenochaeta and Cladosporium. Among these strains, two Penicillium strains can’t be assigned to any reported species. In this study, they are described new species as Penicillium yanchengium sp. novT (AF 2021051) and Penicillium dongtaiense sp. novT (AF 2121001) based on multigene phylogenetic analysis and morphology. Penicillium yanchengense sp. novT belong to Penicillium section Lanata-Divaricata and are phylogenetically closely related to Penicillium oxalicum and Penicillium asturianum. Isolates of Penicillium yanchengense sp. novT have a faster growth on Czapek yeast agar (CYA) at 37 ℃, abundant exudate present on CYA, and a greater ability to produce acid on creatine sucrose agar (CREA). Penicillium dongtaiense sp. novT was placed in section Sclerotiora and it is most closely related to Penicillium exsudans, Penicillium mallochii and Penicillium acidum. It is unique in slower growth on CYA and MEA plates, abundant exudate on MEA, and cerebriform grooves on YES compared to its relatives. In this study, we provide detailed description about two species.

Biogenic Synthesis of Silver Nanoparticles Mediated by the Consortium Comprising the Marine Fungal Filtrates of Penicillium Oxalicum and Fusarium Hainanense Along With Their Antimicrobial, Antioxidant and Larvicidal Potency

The silver nanoparticles were biosynthesized using fungal isolates as well as their mixed cell free filtrate acting as a consortium namely, DS-2 (Penicillium oxalicum), DW-8 (Fusarium hainanense) and DSW-28, respectively. The UV-Visible spectra determined the surface plasmon resonance at 438, 441 and 437 nm for the silver nanoparticles synthesized by DS-2, DW-8 and DSW-28, respectively. The Tauc’s plot analysis disclosed the band gap energy between 2.21 eV to 2.24 eV which depicted their ability to act as a semiconductor. The TEM imaging revealed the spherical shape along with the average particle size of DS-2 as 11.14 ± 2.39 nm and DW-8 as 7.59 ± 1.31 nm whereas that of DSW-28 as 5.73 ± 0.4 nm. Thus, the silver nanoparticles synthesized by DSW-28 were smaller in size than the individual isolates. The XRD pattern of the silver nanoparticles exhibited the crystalline structure corresponding to their peaks. The FTIR spectra indicates the presence of different functional groups on the surface of the synthesized silver nanoparticles. The broad-spectrum antimicrobial activity was exhibited by silver nanoparticles synthesized by DSW-28 against Gram positive, Gram negative bacteria and plant pathogen Fusarium oxysporum than the individual fungal isolates. The DSW-28 synthesized silver nanoparticles also acts as an effective antioxidant by depicting their radical scavenging activity against DPPH. Moreover, the silver nanoparticles synthesized by DSW-28 also inhibited the growth of 4th instar larvae of Aedes aegypti and Culex quinquefasciatus more efficiently than DS-2 and DW-8 in a dose-dependent method. The impressive bioactivity of the silver nanoparticles synthesized by the mixture of cell free filtrate of various fungi acting as a consortium recommends their prospective use in agriculture as well as in biomedical as an antimicrobial, antioxidant and larvicidal agents in future.