Authors:M. Takó, Elvira Farkas, Szabina Lung, Judit Krisch, Cs. Vágvölgyi, and T. Papp
Extracellular β-glucosidase activity of 94 strains, representing 24 species of the genera
Gilbertella, Mucor, Rhizomucor
was evaluated in submerged culture and under solid state fermentation on wheat bran.
G1 isolate showed the highest activity (70.9 U ml
) followed by other
(58.6–59.0 U ml
isolates (29.2–42.0 U ml
). Optimum temperature for enzyme production was 25 °C for
, and 30 °C for
strains. Enzymes of
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
chibinensis, R. miehei
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.
Authors:P. Poór, P. Borbély, Judit Kovács, Anita Papp, Ágnes Szepesi, Z. Takács, and Irma Tari
The plant hormone ethylene or the gaseous signalling molecule nitric oxide (NO) may enhance salt stress tolerance by maintaining ion homeostasis, first of all K+/Na+ ratio of tissues. Ethylene and NO accumulation increased in the root apices and suspension culture cells of tomato at sublethal salt stress caused by 100 mM NaCl, however, the induction phase of programmed cell death (PCD) was different at lethal salt concentration. The production of ethylene by root apices and the accumulation of NO in the cells of suspension culture did not increase during the initiation of PCD after 250 mM NaCl treatment. Moreover, cells in suspension culture accumulated higher amount of reactive oxygen species which, along with NO deficiency contributed to cell death induction. The absence of ethylene in the apical root segments and the absence of NO accumulation in the cell suspension resulted in similar ion disequilibrium, namely K+/Na+ ratio of 1.41 ± 0.1 and 1.68 ± 0.3 in intact plant tissues and suspension culture cells, respectively that was not tolerated by tomato.
Authors:Miklós Takó, Alexandra Kotogán, Judit Krisch, Csaba Vágvölgyi, Keshab C. Mondal, and Tamás Papp
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.