Maria Gerginova

Bio: Maria Gerginova is an academic researcher from Bulgarian Academy of Sciences. The author has contributed to research in topics: Phenol & Energy source. The author has an hindex of 9, co-authored 23 publications receiving 344 citations.

Phenol and cresol mixture degradation by the yeast Trichosporon cutaneum

Abstract: Most industrial wastes contain different organic mixtures, making important the investigation on the microbial destruction of composite substrates. The capability of microbes to remove harmful chemicals from polluted environments strongly depends on the presence of other carbon and energy substrates. The effect of mixtures of phenol- and methyl-substituted phenols (o-, m-, p-cresol) on the growth behaviour and degradation capacity of Trichosporon cutaneum strain was investigated. The cell-free supernatants were analysed by HPLC. It was established that the presence of o-, m- and p- cresol has not prevented complete phenol assimilation but had significant delaying effect on the phenol degradation dynamics. The mutual influence of phenol and p-cresol was investigated. We developed the kinetic model on the basis of Haldane kinetics, which used model parameters from single-substrate experiments to predict the outcome of the two-substrate mixture experiment. The interaction coefficients indicating the degree to which phenol affects the biodegradation of p-cresol and vice versa were estimated. Quantitative estimation of interaction parameters is essential to facilitate the application of single or mixed cultures to the bio-treatment of hazardous compounds.

Growth of Trametes versicolor on phenol.

Abstract: Trametes versicolor 1 was shown to grow on phenol as its sole carbon and energy source. The culture growth and degradation ability dependence on culture medium pH value was observed. The optimal pH value of a liquid Czapek salt medium was 6.5. The investigated strain utilized completely 0.5 g/l phenol in 6 days. The dynamics of the phenol degradation process was investigated. The process was characterized by specific growth rate μmax 0.33 h−1, metabolic coefficient k = 4.4, yield coefficient Y x/s = 0.23 and rate of degradation Q = 0.506 h−1. The intracellular activities of phenol hydroxylase (0.333 U/mg protein) and cis,cis-muconate lactonizing enzyme (0.41 U/mg protein) were demonstrated for the first time in this fungus. In an attempt to estimate the occurrence of gene sequences in T. versicolor 1 related to phenol degradation pathway a dot blot analysis with total DNA isolated from this strain was performed. Two synthetic oligonucleotides were used as hybridizing probes. One of the probes was homologous to the 5′end of phyA gene coding for phenol hydroxylase in Trichosporon cutaneum ATCC 46490. The other probe was created on the basis of cis,cis-muconate lactonizing enzyme coding gene in T. cutaneum ATCC 58094. The results of these investigations showed that T. versicolor 1 may carry genes similar to those of Trichosporon cutaneum capable to degrade phenol.

Charcoal Volatile Matter Content Influences Plant Growth and Soil Nitrogen Transformations

Abstract: A series of short-term greenhouse experiments and laboratory incubations were conducted to evaluate the effect of macadamia (Macadamia integrifolia Maiden & Betche) nut shell (MNS) charcoal with varying volatile matter (VM) content on soil properties and plant growth in two tropical soils. Lettuce (Lactuca sativa L.) and corn (Zea mays L.) were planted in an Andisol amended with four rates of MNS charcoal (0, 5,10, and 20% w/w) containing relatively high VM content (225 g kg -1 ) with andwithout N fertilizer. Increasing rates ofcharcoalwithout N caused a significant decline in both lettuce and corn growth. Corn growth declined significantly with or without N at the two highest charcoal rates. In a third experiment, corn growth also declined significantly in an Ultisol amended with the MNS charcoal (5% w/w) with and without fertilizers. In a fourth experiment, charcoals with high VM (225 g kg -1 ) showed negative effects on plant growth while the low-VM (63.0 g kg -1 ) charcoal supplemented with fertilizer showed a significant positive effect on corn growth. Results from the 2-wk incubation experiments showed that high-VM charcoal caused a significant decline in soil NH 4 + -N and a significant increase in soil respiration compared with the soil amended with low-VM charcoal and the soil alone. We propose that phenolic compounds and other products in the high-VM charcoal stimulated microbial growth and immobilization of plant-available N. Our results demonstrate that VM content appears to be an important property of charcoal that has short-term effects on soil N transformations and plant growth. Longer incubation experiments and field trials are needed to further elucidate the role of charcoal VM content on soil processes and plant growth.