Assessment of Antifungal Activity of Lactic Acid Bacteria Strains Against Bread Spoilage Fungus Aspergillus ochraceus

Lactic acid bacteria (LAB) are generally recognized as safe and can be used against fungi that contaminate various food commodities. The aim of the research was to select LAB strains with high antifungal activity for the biocontrol of Aspergillus ochraceus. The antifungal activity of eight strains of lactic acid bacteria has been evaluated by overlay assay method against the spoilage fungus, Aspergillus ochraceus isolated from white bread. The antifungal effect was assessed by co-cultivation of lactic acid bacteria strains and Aspergillus ochraceus in liquid media and mycelium growth inhibition was monitored for over 14 days. The LAB strains Lpl, LAB 43 and LAB 13 presented intense antifungal activity with large inhibition zones of fungal growth and sporulation, but smaller for Lpa and LAB 15 strains. Total inhibition of mycelia growth was induced by the strains LAB 43, LAB 13 and Lpa. The strains LAB 15 and LAB 35 had a moderate inhibition activity on the mycelia growth. The results of this study demonstrated the antifungal activity of several LAB strains by overlay assay and by co-cultivation method. Therefore, it was confirmed the inhibitory effect of the strains LAB 43 and LAB 13 against Aspergillus ochraceus. The experiment revealed that these LAB strains could be further used as biocontrol agents

MICROBIAL INOCULANTS APPLIED AS SEED TREATMENTS AND THEIR EFFECT ON COMMON WHEAT Triticum aestivum L.

Wheat is considered the most wide spread culture in the world regarding the area harvested. In Romania, it is grown on approximately 25% of the arable land and 40% of the cereal grains. Improving wheat productivity and yield quality is a continuous concern. Therefore, plant growth promoting microorganisms with biocontrol potential are of great interest for the farmers. In the present, five beneficial microorganisms, bacteria and fungi, were analysed as agro-inoculants. Their effect on wheat germination and growth initiation was evaluated in vitro. According to the biometric analysis best results were obtained when using Azospirillum brassilense and Bacillus amyloliquefaciens strains, although Trichoderma pseudokoningii and Bacillus endophyticus also improved wheat vigour indexes, compared to the untreated control. However, B. endophyticus 1T2 strain delayed the germination process. The dual culture assay performed against Fusarium graminearum, revealed that three strains B.amyloliquefaciens OS17, BW, and T.pseudokoningii Td85, have also biocontrol potential

Comparative Antifungal Effect of Lactic Acid Bacteria Strains on Penicillium digitatum

Lactic acid bacteria (LAB) are natural alternative to chemical preservatives for fruits. The aim of the research was to select LAB strains with high antifungal activity against Penicillium digitatum for the biopreservation of fruits. The antifungal activity of eight lactic acid bacteria strains has been evaluated against Penicilliuum digitatum isolated from orange, by overlay assay method and by optical microscope examination. The reversion of inhibition zone after 96 h was recorded as a fungistatic effect while those with inhibition zone for at least 7 days were recorded as fungicidal. The antifungal effect of efficient LAB strains was assessed by comparing inhibition of fungal biofilm formation in liquid media. The strains Lpl, Lpa, LAB 13, LAB 15, LAB 43 and LAB 58 presented intense antifungal activity with clear inhibition zones diameter over 20 mm. The microscopy evidenced atypical hyphae and delaying of conidial chain formation. The strains Lpa, LAB 13, LAB 15 fully inhibited the mycelia growth, strains LAB 43 and LAB 58 partly with delaying of biofilm formation on the surface of culture medium. The results of comparative antifungal activity of LAB strains evidenced the highest inhibition of fungal biofilm formation and structural damages of hyphae and spores caused by the strains Lpa, LAB 13 and LAB 15. These strains could be efficient biocontrol agents of Penicillium digitatum in fruits

Microorganisme benefice plantelor cu efect de solubilizare a siliciului

Silicon is the second abundant element on Earth. Commonly, it is found as silica and silicates, or in biology as mineral constituent of microorganisms, protozoa and plants. Although silicon it is not considered an essential nutrient for plants, it has been noticed that available silicon positively influences plants’ growth, mechanical strength, and resistance to several biotic and abiotic unfavorable conditions, such as fungal phytopathogens, herbivores and adverse chemicals. Our study presents several microbial strains able to solubilize silicon from different biological and mineral substrates. Some of these microorganisms were isolated from plant material with high content of mineral silicon like horsetail, wheat straw, rosemary and nettle. Moreover, microbial supernatant obtainedon horsetail broth increased hypocotyl and roots length of cowpea Vignaunguiculata (L.) Walp

Biosynthesis of silver nanoparticles mediated by culture filtrate of lactic acid bacteria, characterization and antifungal activity

Silver nanoparticles (AgNPs) are nanomaterials obtained by nanotechnology and due to their antimicrobial properties have a major importance in the control of various species of bacteria, fungi and viruses, with applications in medicine, cosmetics or food industry. The goal of the paper was to present the results of the research carried out on rapid extracellular biosynthesis of silver nanoparticles mediated by culture filtrate of lactic acid bacteria Lactobacillus sp. strain LCM5 and to assess the antimicrobial activity. Analysis of transmission electron microscopy (TEM) micrographs evidenced that the size of AgNPs synthesized using culture filtrates of lactic acid bacteria strain LCM5 ranged between 3 and 35 nm diameter, with an average particle size of 13.84±4.56 nm. AgNPs presented a good dispersion, approximately spherical shape, with parallel stripes certifying crystal structure. Frequency distribution revealed that preponderant dimensions of biosynthesized AgNPs were below 20 nm (94%). Antimicrobial activity of AgNPs was variable depending on both species and group of test microorganisms (bacteria or fungi) involved. Diameter of growth inhibition zone of Aspergillus flavus and Aspergillus ochraceus caused by silver nanoparticles synthesized by lactic acid bacteria strain LCM5 were similar (12.39 ± 0.61mm and 12.86 ± 0.78 mm) but significant stronger inhibition was registered against Penicillium expansum (15.87 ± 1.01mm). The effectiveness of biosynthesized silver nanoparticles was more pronounced against Gram-negative bacteria Chromobacterium violaceum with larger zone of inhibition (18 ± 0.69 mm diameter) when compared to those from fungi. Results recommend the silver nanoparticles biosynthesized using culture filtrate of the lactic acid bacteria Lactobacillus sp. strain LCM5 for biotechnological purposes, as promising antimicrobial agents

Molecular Methods for Assessement the Bacterial Communities from Different Type of Soils in Romania

Rhizobia are soil bacteria that are capable to form nitrogen-fixing symbiosis with leguminous plants. This ability, as well as the diversity of microbial populations in the soil, and in the rhizosphere of host plants and non-host plants is influenced by several factors, including crop management. The aim of this work was the examination of the influence of some factors on indigenous populations of rhizobia in soils under different crop managements. The genetic diversity of rhizobial strains isolated directly from soil (free-living state) or from root nodules of three herbaceous perennial legumes was examined. The study was conducted in the experimental fields located in Moara Domnească area (South of Romania) and in the Braşov County. The characteristics of brown reddish soil were determined (nitrogen content, organic carbon content and pH). Counting of the rhizobia populations was done by most probable number estimation and by viable plate counts. Bacterial strains were isolated directly from soil samples or from root nodules of different plant species (Trifolium repens, T. pratense and Lotus corniculatus). The characterization of rhizobia was performed by DNA fingerprinting (ERIC PCR and BOX PCR) and the bacterial diversity of soils was examined by DGGE technique. The results revealed that the rhizobial diversity was significantly lower in soils under increased fertilization with N. A reduced intraspecific polymorphism was observed in the strains recovered from the same plant species (Trifolium spp.), whatever the origin of the plant (Moara Domnească or Braşov) but clear differences appeared to be related to the origin of nodules (red or white clover) as revealed by DNA fingerprints. However, various amplicon profiles were observed by DGGE when total DNA isolated from soils was examined, the differences being associated with the fertilization level.<br /

Genetic Polymorphism at 15 Codons of the Prion Protein Gene in 156 Goats from Romania

Background: The variability of prion protein gene (PRNP) codons and the frequency of alleles (K222, D146, and S146) that appear to confer genetic resistance to classical scrapie are still unknown in several goat populations/breeds prevalent in Romania. This work aims to assess the genetic polymorphism at 15 PRNP codons in Romanian goat populations to inform the development of goat breeding programs for scrapie resistance. Methods: Whole blood and hair follicles from Carpathian (50), French Alpine (53), and Banat&rsquo;s White (53) breed goats were sampled to extract genomic DNA for genetic analyses and Sanger sequencing. In the targeted goat groups, one classical scrapie-positive Banat&rsquo;s White goat was included. Results: The codons without polymorphisms were G37G, W102W, N146N, R151R, S173S, and I218I. The following non-synonymous polymorphisms of PRNP were recorded: P110P, P110S, P110T, T110T, G127G, G127S, I142I, I142M, T142I, H143H, P143P, R143R, R154R, H154R, P168P, Q168Q, Q211Q, Q211R, Q222Q, H222Q, K222K, S240S, P240P, P240S, and S240P. Conclusions: PRNP polymorphism was recorded in 60% (9/15) of codons. The scrapie-positive Banat&rsquo;s White goat had G37G, W102W, T110T, G127G, I142I, H143H, N146N, R151R, R154R, P168P, S173S, R211R, I218I, Q222Q, and S240S. The K222 allele had a frequency of 6% (3/50) in Carpathian, 9.43% (5/53) in Banat&rsquo;s White, and 15.09% (8/53) in French Alpine. Therefore, the polymorphisms detected in this sample of Romanian goat breeds are too rare to design a breeding program at the current time

Comparative Analysis of the Composition and Active Property Evaluation of Certain Essential Oils to Assess their Potential Applications in Active Food Packaging

The antifungal, antibacterial, and antioxidant activity of four commercial essential oils (EOs) (thyme, clove, rosemary, and tea tree) from Romanian production were studied in order to assess them as bioactive compounds for active food packaging applications. The chemical composition of the oils was determined with the Folin–Ciocâlteu method and gas chromatography coupled with mass spectrometry and flame ionization detectors, and it was found that they respect the AFNOR/ISO standard limits. The EOs were tested against three food spoilage fungi—Fusarium graminearum, Penicillium corylophilum, and Aspergillus brasiliensis—and three potential pathogenic food bacteria—Staphylococcus aureus, Escherichia coli, and Listeria monocytogenes—using the disc diffusion method. It was found that the EOs of thyme, clove, and tea tree can be used as antimicrobial agents against the tested fungi and bacteria, thyme having the highest inhibitory effect. Concerning antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis 3-ethylbenzthiazoline-6-sulfonic acid (ABTS) methods, it has been established that the clove oil exhibits the highest activity because of its high phenolic content. Promising results were obtained by their incorporation into chitosan emulsions and films, which show potential for food packaging. Therefore, these essential oils could be suitable alternatives to chemical additives, satisfying the consumer demand for naturally preserved food products ensuring its safety