Nadejda Peneva

Bio: Nadejda Peneva is an academic researcher from Bulgarian Academy of Sciences. The author has contributed to research in topics: Aspergillus fumigatus & Biodegradation. The author has an hindex of 7, co-authored 16 publications receiving 148 citations.

Phenol utilization by filamentous yeast Trichosporon cutaneum

Abstract: The investigated strain Trichosporon cutaneum shows well expressed capability for metabolizing high concentrations of phenol, up to 1 g/l, utilizing it as the sole carbon source for the growth and development of the population. The data reported, prove the good perspectives for its application in protecting the environment from phenol pollution. No data about modelling the process of cultivation of Trichosporon cutaneum in phenol media is available in scientific literature up to now. The mathematical model, reported here, consists of two nonlinear differential equations, describing cell growth and substrate consumption. The unknown parameters are estimated following the method of Hooke and Jeeves. A number of simulation investigations are carried out. They prove the adequacy of the model and its applicability in further studies on the processes of growth and phenol uptake of Trichosporon cutaneum.

Biodegradation of phenol by Antarctic strains of Aspergillus fumigatus.

Abstract: Taxonomic identification of three newly isolated Antarctic fungal strains by their 18S rDNA sequences revealed their affiliation with Aspergillus fumigatus. Phenol (0.5 g/l) as the sole carbon source was completely degraded by all strains within less than two weeks. Intracellular activities of three key enzymes involved in the phenol catabolism were determined. Activities of phenol hydroxylase (EC 1.14.13.7), hydroquinone hydroxylase (EC 1.14.13.x), and catechol 1,2-dioxygenase (EC 1.13.11.1) varied significantly between strains. The rates of phenol degradation in the three strains correlated best with the activity of catechol 1,2-dioxygenase. Six pairs of oligonucleotide primers were designed on the basis of the Aspergillus fumigatus Af293 genome sequence (NCBI Acc. No. XM_743491.1) and used to amplify phenol hydroxylase-related gene sequences. DNA sequences of about 1200 bp were amplified from all three strains and found to have a high degree of sequence identity with the corresponding gene of Aspergillus fumigatus Af293.

Efficiency of microbial fuel cells based on the sulfate reduction by lactate and glucose

Abstract: The influence of lactate and glucose, used as electron donors on the rate of sulfate reduction, electricity generation and microbial communities in anodic chamber of microbial fuel cells, was studied. Effective sulfate and chemical oxygen demand removal was achieved at different hydraulic retention times by the laboratory installations, consisting of anaerobic fixed-bed reactor and microbial fuel cell with air–cathode. The highest maximum power density of 349 mW/m2 was obtained in the lactate-fed microbial fuel cell under hydraulic retention time of 66 h. The type of electron donor had a great impact on the composition of the microbial community. The metagenomic data obtained showed that the most abundant phylum in both bacterial communities was Proteobacteria—67% and 46% when using lactate and glucose as an electron donor, respectively. Euryarchaeota was found in significant quantities (11.57%) in the microbial communities cultivated on lactate, whereas when using glucose, they were 0.01%. The bacterial community at glucose was characterized with the phyla belonging to Verrucomicrobia (15.11%) and Spirochaetes (17.26%). In both microbial communities in anodic chamber were presented sulfate-reducing bacteria that can incompletely oxidize the organic compound usually with acetate as an end product, as the dominant microbial species among sulfate-reducing bacteria was Desulfomicrobium baculatum (3.21%) in the microbial fuel cell at lactate, and Desulfovibrio mexicanus dominated (2.73%) in the microbial fuel cell at glucose.

Kinetic Parameters Determination of the Phenolic Derivatives Assimilation by Trichosporon Cutaneum R57

Abstract: The kinetic parameters characteristic of the growth and degradation capacity of Trichosporon cutaneum R57 strain in relation to o-, m-, p-chlorophenol, o-, m-, p-cresol and o-, m-, p-nitrophenol are presented in this study. The investigated strain degraded up to 0.1 g/l of all mono-chlorophenols. A concentration of 0.2 g/l p- cresol was completely degraded whereas m- cresol was degraded to an extent of 32%. No degradation of o- cresol was observed. O- nitrophenol in concentration of 0.1 g/l was less readily degraded than the same concentration of m-nitrophenol and p- nitrophenol was not degraded. The Haldane equation has frequently been used to describe the biodegradation of toxic substrates but little is known about the kinetic constants for the biodegradation of aromatic compounds. The coefficients obtained confirmed the higher toxicity of the investigated phenol derivatives on Trichosporon cutaneum R57. The yield coefficient (Y) was least of all in the medium supplemented with o- chlorophenol w...

Rhamnolipid-biosurfactant permeabilizing effects on gram-positive and gram-negative bacterial strains.

Abstract: The potential of biosurfactant PS to permeabilize bacterial cells of Pseudomonas aeruginosa, Escherichia coli, and Bacillus subtilis on growing (in vivo) and resting (in vitro) cells was studied. Biosurfactant was shown to have a neutral or detrimental effect on the growth of Gram-positive strains, and this was dependent on the surfactant concentration. The growth of Gram-negative strains was not influenced by the presence of biosurfactant in the media. Cell permeabilization with biosurfactant PS was shown to be more effective with B. subtilis resting cells than with Pseudomonas aeruginosa. Scanning-electron microscopy observations showed that the biosurfactant PS did not exert a disruptive action on resting cells such that it was detrimental to the effect on growing cells of B. subtilis. Low critical micelle concentrations, tender action on nongrowing cells, and neutral effects on the growth of microbial strains at low surfactant concentrations make biosurfactant PS a potential candidate for application in different industrial fields, in environmental bioremediation, and in biomedicine.

Microbial degradation of phenol and phenolic derivatives

Abstract: Phenol and its derivatives are one of the largest groups of environmental pollutants due to their presence in many industrial effluents and broad application as antibacterial and antifungal agents. A number of microbial species possess enzyme systems that are applicable for the decomposition of various aliphatic and aromatic toxic compounds. Intensive efforts to screen species with high-degradation activity are needed to study their capabilities of degrading phenol and phenolic derivatives. Mostofthecurrentresearchhasbeendirectedattheisolationandstudyofmicrobial species of potential ecological significance. In this review, some of the best achievementsindegradingphenoliccompoundsbybacteriaandyeastsarepresented,which draws attention to the high efficiency of strains of Pseudomonas, Candida tropicalis, Trichosporon cutaneum, etc. The unique ability of fungi to maintain their degradation potential under conditions unfavorable for other microorganisms is outstanding. Mathematical models of the microbial biodegradation dynamics of single and mixed aromatic compounds, which direct to the benefit of the processes studied in optimization of modern environmental biotechnology are also presented.