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Cereal Research Communications
Authors: Csaba Vágvölgyi, László Manczinger, Judit Krisch, Miklós Takó, and Tamás Papp
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Acta Biologica Hungarica
Authors: Györgyi Horváth, Julianna Török Jenei, Csaba Vágvölgyi, Andrea Böszörményi, and Judit Krisch

Essential oils (EOs) can be used as alternative or complementary antifungal agents against human pathogenic moulds and yeasts. To reduce the effective dose of antimicrobial agents, EOs are combined which can lead to synergistic or additive effect. In this study the anti-yeast and anti-mould activities of selected EOs were investigated, alone and in combinations, against clinical isolates of Candida albicans, C. parapsilosis, Aspergillus fumigatus, A. terreus, Rhizopus microsporus, Fusarium solani and Lichtheimia corymbifera. Minimum inhibitory concentrations (MICs) were determined for the EOs of cinnamon, citronella, clove, spearmint and thyme. To investigate the combination effect of the EOs, fractional inhibitory concentrations (FICs) were defined by the checkerboard method and the type of interaction was determined by the FIC index (FICI). FIC index below 0.5 was considered as synergism and between 0.5 and 1 as additive effect. Strongest antifungal activity was showed by thyme EO with MIC values below 1.0 mg/ml. Combination of EOs resulted in additive or indifferent effect, with occasional “borderline synergism”. The best combination was cinnamon with clove leading to additive effect in all cases.

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Extracellular β-glucosidase activity of 94 strains, representing 24 species of the genera Gilbertella, Mucor, Rhizomucor , and Rhizopus was evaluated in submerged culture and under solid state fermentation on wheat bran. Gilbertella persicaria G1 isolate showed the highest activity (70.9 U ml −1 ) followed by other Gilbertella (58.6–59.0 U ml −1 ) and Rhizomucor miehei isolates (29.2–42.0 U ml −1 ). Optimum temperature for enzyme production was 25 °C for Gilbertella and Mucor , and 30 °C for Rhizomucor and Rhizopus strains. Enzymes of R. miehei strains proved to be thermotolerant preserving up to 92.8% residual activity after heating to 75 °C in the presence of cellobiose substrate. Enzymes of Mucor racemosus f. chibinensis, R. miehei and Rhizopus microsporus var. oligosporus strains were activated at acidic condition (pH 4). Glucose was a strong inhibitor for each fungal β-glucosidase tested but some of them showed ethanol tolerance up to 20% (v/v). Ethanol also activated the enzyme in these strains suggesting glycosyl transferase activity.

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Cellulolytic, lipolytic and proteolytic enzyme production of zygomycetes Mucor corticolus, Rhizomucor miehei, Gilbertella persicaria and Rhizopus niveus were investigated using agro-industrial wastes as substrates. Solid-state cultures were carried out on untreated corn residues (stalk and leaf) as single substrate (SSF1) or corn residues and wheat bran in mixed fermentation (SSF2). Rapid production of endoglucanase (CMCase) was observed with maximal activity reaching after about 48-h fermentation, while cellobiohydrolase (CBH) and β-glucosidase enzymes generally had their peak after 72-h incubation. Highest filter paper degrading (FPase), CMCase, CBH and β-glucosidase activities obtained were (U g−1 dss) 17.3, 74.1, 12.2 and 158.3, for R. miehei, G. persicaria, M. corticolus and Rh. niveus, respectively. M. corticolus proved to be the best lipolytic enzyme producer in SSF1 presenting 447.6 U g−1 dss yield, while R. miehei showed 517.7 U g−1 dss activity in SSF2. Rh. niveus exhibited significantly greater protease production than the other strains. Suc-AAPF-pNA hydrolyzing activities of this strain were 1.1 and 1.96 U g−1 dss in SSF1 and SSF2, respectively. We conclude that the used corn stalk and leaf residues could potentially be applicable as strong inducers for cellulase and lipase production by Mucoromycotina fungi.

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Acta Biologica Hungarica
Authors: Erika-Beáta Kerekes, Anita Vidács, Julianna Jenei Török, Csilla Gömöri, Tamás Petkovits, Muthusamy Chandrasekaran, Shine Kadaikunnan, Naiyf S. Alharbi, Csaba Vágvölgyi, and Judit Krisch

The anti-listerial effect of marjoram, thyme essential oils (EOs) and thymol on Listeria monocytogenes inoculated chicken breast fillets was investigated. Before inoculation the fillets were pretreated by washing or not under running tap water. Inoculated samples were kept at 6 °C for 24 h to allow the growth of L. monocytogenes. After this, the fillets were put in marinating solutions containing salt (5%) and EOs or thymol in MIC/2 concentration established in vitro. Total germ count (TGC) and L. monocytogenes count was monitored on the meat surface and in the marinating solutions following 24 and 48 h storage at 6 °C. Thyme and thymol reduced significantly Listeria cell count (1–3 log CFU) in both samples. They also gave good flavour to the fried meat. The doses of EOs used were optimal for antimicrobial efficiency and had a pleasant flavour effect. Washing was not efficient in reducing total germ count.

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