Publications

@conference{nokey,

title = {New possibilities for the valorisation of waste aqueous fractions from the essential oil industry using nanofiltration.},

author = {Dimitar Peshev and Borislava Dimitrova and Petko Penchev and Chavdar Chilev},

url = {http://www.nanoessential.eu/wp-content/uploads/Poster_Peshev-1.pdf},

year  = {2021},

date = {2021-12-02},

booktitle = {Abstract book Euromembrane},

organization = { Euromembrane 2021},

abstract = {The possibility to fractionate hydrosols and extracts (residual waters) from the steam and hydrodistillation of essential

oil plants using nanofiltration was investigated. The separation performance of five commercial nanofiltration

membranes with respect to key biologically active components of the studied waste aqueous fractions was predicted

based on regression models [1,2]. Membranes of different MWCO, structure and composition were analysed.

Descriptors in the models for the membrane rejection were the membrane MWCO and zeta potential as well as

solute’s molecular weight, octanol-water partition coefficient (log P) and charge at pH of the solution (or pKa). For

consistency of the results, log P and pKa of all studied components were calculated according to the COSMO-RS

method, which has the quantum-chemical basis of the Conductor-like Screening Model (COSMO). The calculations

were performed using the BIOVIA COSMOsuite software package package (Dassault Systèmes SE). The theoretical

assessment was subjected to experimental verification by nanofiltration of hydrosols and extracts collected from

industrial facilities using commercial polyethersulfone and composite polyamide membranes. The results showed that

independently of the membrane material, the polymeric membranes exhibit high retention capability against charged

solutes such as the contained in the residual waters phenolic acids. Since the pKa of the phenolic compounds,

representatives of the flavonoid family is within the range of pH of the aqueous extracts, their retention or permeation

could be controlled by slight variations of the pH. The dissolved in the aqueous fractions essential oil components

would be easily permeating through the membranes. These results clearly demonstrated the viability of nanofiltration

for isolation of refined polyphenolic fractions from the extracts effluents and for recovery of phenethyl alcohol and

eugenol from hydrosols of Rosa damascena and cloves respectively.

Reference 1:

K. Boussu, C. Vandecasteele, B. Van der Bruggen, J. Mem. Sci., 310, 51 (2008)

Reference 2:

D. Peshev, Bul. Chem. Commun., 52, 4, 532 (2020)



Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {Utilization of the waste lavender residue from the essential oil industry via extraction and membrane filtration},

author = {Chavdar Chilev and Dimitar Peshev},

url = {http://www.nanoessential.eu/wp-content/uploads/Poster_Chilev.pdf},

year  = {2021},

date = {2021-12-02},

urldate = {2021-12-02},

booktitle = {Abstract book Euromembrane},

organization = {Euromembrane 2021},

abstract = {The possibility for utilization of WLR from the essential oil industry by combination of extraction and membrane

filtration were studied. The WLR from the essential oil industry is Lavandula angustifolia from which the lavender oil is

extracted by steam distillation. Thus, the residue contains KBAC -rosmarinic acid, caffeic acid, quercetin and luteolin.

Extraction of KBAC from WLR by extraction under different conditions was investigated. By studying the equilibrium

and kinetics, the parameters of the extraction process (solid-liquid ratio, time, type of solvent) were experimentally

optimized. The time intervals to extract the KBAC from 600 to 10800s were studied. The results showed that

equilibrium was reached at approximately 7000s after the start of the experiment. Thus, a time of 7200s for performing

the extraction is selected. Two liquid-solid ratios, respectively: 0.01 and 0.03 , were tested. A faster kinetics and more

complete extraction of KBAC at solid-liquid ratio 0.01 are observed. To determine the optimal solvent, four solvents

were tested, respectively: pure water, 99.99% Ethanol and mixtures between them - 40% and 60% Ethanol. Maximum

amounts of KBAC in 40% Ethanol were found. Thus, the optimal conditions under which the experiments were

performed were determined: temperature - 40℃, solid-liquid ratio - and the solvent - 40% Ethanol.

The extracts are aqueous-alcoholic solutions containing both hydrophobic and hydrophilic compounds. A range of

commercial NF (DL, SUEZ (GE); NP030, NADIR, Puramem 200, Evonik MET) and RO (X201, TriSep) membranes were

tested for their capability to fractionate or concentrate the KBAC in the obtained extracts. The use of membranes with

different structure and composition of the selective layer, and with different hydrophobicity respectively, allowed for

qualitative conclusions on the effects from the KBAC components interactions with the membranes. The adverse depot

effect due to the adsorption of solutes in the membranes during batch filtration was evaluated. The membrane

materials included modified polyimide (Duramem 200), polyethersulfone (NP030), polyamide (DL) and polyamide-urea

(X201).

Keywords: essential oil, nanofiltration, membrane, fractionation, extraction.

Abbreviations:

WLR - Waste Lavender Residue

KBAC - Key Biologically Active Components

RO - Reverse Osmosis

NF - Nanofiltration

Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {Extraction of essential oil from cloves using steam and hydro distillation},

author = {Ch. Chilev and D.Peshev and N. Lazarova},

url = {http://www.nanoessential.eu/wp-content/uploads/Poster_1-1.pdf},

year  = {2021},

date = {2021-10-23},

urldate = {2021-10-23},

booktitle = {Book of abstracts of the 67th Scientific Conference with International Participation "Food Science, Engineering and Technology - 2020"},

publisher = {University of Food Technology - Plovdiv },

organization = {UFT, Plovdiv, Bulgaria},

abstract = {Essential  oils  are  used  in  a  wide  variety  of  consumer  goods  such  as  detergents,    toilet  products,  cosmetics,  pharmaceuticals,  confectionery  food  products,  soft  drinks,  distilled   alcoholic   beverages   and   insecticides. The extracts of cloves have a pleasant smell, and direct practical applications as a flavoring agent, antioxidant, antifungal agent, local anesthetic, and nutraceutical. The goal of this study is to isolate the natural product, essential oil, from cloves using the steam and water distillation. Both techniques are often used in industry to essential oils manufacturing. The experiments and detailed procedures of water and steam distillation are developed and presented. The optimal clove-to-distillate ratio [g(cloves)/ml(obtained distillate)] with respect to total oil production were determined. The ratio was varied between 0.125 g/mL and 0.0625g/mL. It was found that the optimal ratio of clove-to-distillate was 0.0833 g/mL. The antibacterial activity of the essential oils obtained by two present techniques was determined by the disk diffusion method against Escherichia coli K12 and Bacillus subtilis 3562. The antioxidant activity of the samples was also analysed by the DPPH free radical method where a gallic acid was used as a reference solution.



This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {Study of the biological activity of essential oil-water mixtures},

author = {Nevena Lazarova-Zdravkova and D. Tsanova and Y. Stoyanova and Ch. Chilev and N. Georgieva and Dimitar Peshev},

url = {http://www.nanoessential.eu/wp-content/uploads/Poster_2-1.pdf},

year  = {2021},

date = {2021-10-23},

booktitle = {Book of abstracts of the 67th Scientific Conference with International Participation "Food Science, Engineering and Technology - 2020"},

publisher = {UFT, Plovdiv, Bulgaria},

organization = {University of Food Technology - Plovdiv},

abstract = {This study aimed to investigate the biological activity of aqueous mixtures of two essential oils. The mixtures were prepared by mixing certain amounts of lavender and clove oils with distilled water at room temperature. In the case of lavender oil, a relatively clear saturated aqueous phase was obtained after mixing with excess of the essential oil. The clove oil formed stable oil-in-water emulsions. The antibacterial activity of lavender oil and its aqueous solution were tested against two model bacterial strains. The growth of Escherichia coli K12 and Bacillus subtilis 3562 in the presence of the analysed samples was determined in 96-well microplates and also by a disk diffusion test (Kirby–Bauer test). The results showed that the lavender aqueous solution did not exhibit antibacterial activity against both – the Gram-negative and Gram-positive strains but the oil itself indicated inhibition zones of around 11.7 mm during the tests against B. subtilis 3562. The DPPH free radical method showed no antioxidant activity for the lavender aqueous solution of lavender oil. At the same time the pure lavender oil exhibit low activity compared to the gallic acid (used as a reference) and the clove essential oil. The inhibitory effect of the lavender samples were further compared with the essential oil from clove and its oil-in-water emulsion.



Keywords:  antibacterial activity, antioxidant activity, essential oils



Abbreviations:

DPPH – 2,2-diphenyl-1-picryl-hydrazyl-hydrate



Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)wledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {Theoretical assessment of the possibility for fractionation of waste aqueous fractions from the essential oil industry using nanofiltration.},

author = {Dimitar Peshev and Nevena Lazarova-Zdravkova and Chavdar Chilev},

url = {http://www.nanoessential.eu/wp-content/uploads/Poster_3-1.pdf},

year  = {2021},

date = {2021-10-23},

booktitle = {Book of abstracts of the 67th Scientific Conference with International Participation "Food Science, Engineering and Technology - 2020"},

publisher = {UFT, Plovdiv, Bulgaria},

organization = {University of Food Technology - Plovdiv},

abstract = {The possibility to fractionate hydrosols and extracts (residual waters) from the distillation of essential oil plants using nanofiltration was investigated. The rejections of five commercial nanofiltration membranes with respect to key bioactive components were predicted based on regression models. Membranes of different MWCO, structure and composition were analysed. Descriptors in the models were the membrane MWCO and zeta potential as well as the molecular weight, log P and pKa of the solute. For consistency, log P and pKa of all studied components were calculated according to the COSMO-RS method, which has the quantum-chemical basis of the Conductor-like Screening Model (COSMO). The calculations were performed using the BIOVIA COSMOsuite software package. The results showed that independently on the membrane material, the polymeric membranes exhibit high retention capability against charged solutes such as the contained in the residual waters phenolic acids. Since the pKa of the phenolic compounds, representatives of the flavonoid family is within the range of pH of the aqueous extracts, their retention or permeation could be controlled by slight variations of the pH. The dissolved in the aqueous fractions essential oil components would be easily permeating through the membranes.



Keywords:  essential oil, nanofiltration, membrane, fractionation, hydrosol, residual water, phenolic compounds, COSMO-RS



Abbreviations:

MWCO – Molecular Weight Cut-Off



Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {BIOLOGICAL ACTIVITY OF CLOVE OIL},

author = {Y. Stoyanova and N. Georgieva and N. Lazarova-Zdravkova and D. Tsanova and D. Peshev

},

url = {http://www.nanoessential.eu/wp-content/uploads/3FHSI_STOYANOVA_D_Y_Poster_2021.pdf},

year  = {2021},

date = {2021-06-25},

urldate = {2021-06-25},

booktitle = {XVIII НАУЧНА ПОСТЕРНА СЕСИЯ ЗА МЛАДИ УЧЕНИ, ДОКТОРАНТИ И СТУДЕНТИ НА ХТМУ},

organization = {UCTM},

abstract = {The clove essential oil isolated from the buds of the species Eugenia caryophyllata (Myrtaceae) also found in the literature as Syzygium aromaticum is widely used and widely known for its healing properties. Clove oil has a number of benefits, ranging from anti-inflammatory for oral infections to treating toothache and acne. Due to its widespread use in the pharmaceutical, flavoring and food industries, demand for clove oil is expected to increase to 6000 tonnes by 2022. 

The aim of this work is to study the antibacterial and antioxidant activity of clove oil. Gram-negative Escherichia coli K12 407 and Gram-positive Bacillus subtilis 3562 bacterial strains were used to study the inhibitory ability of the clove oil. The agar-diffusion method was used to test the susceptibility of the bacteria when treated with the clove oil. Antioxidant activity was determined spectrophotometrically using the DPPH method.



Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14).},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {Antibacterial activity of aqueous solutions of essential oils as an indicator for their content},

author = {N. Georgieva and N. Lazarova-Zdravkova and Y. Todorova and D. Tsanova and D. Peshev },

url = {http://www.nanoessential.eu/wp-content/uploads/Praga-Poster_Abstract-p579.pdf

http://www.nanoessential.eu/wp-content/uploads/poster-Praga-PDF.pdf},

doi = {10.1080/13102818.2020.1871545},

year  = {2021},

date = {2021-02-26},

urldate = {2021-02-26},

booktitle = {Poster Abstracts, Biotechnology & Biotechnological Equipment},

volume = {35},

number = {S1},

pages = {579},

publisher = {Informa UK Limited, trading as Taylor & Francis Group.},

organization = {European Biotechnology Congress 2020},

series = {S62-S128},

abstract = {According to market forecasts, annual consumption of essential oils on the world market is growing steadily, reaching 403 thousand tonnes in 2025. The steam distillation of the plant materials to produce essential oils generates vast amounts of aqueous fractions as by-products. Certain amounts of essential oils remain dissolved in these fractions, predetermining their biological activity. If discarded into the environment they have a negative impact on the ecological balance. At the same time, these aqueous fractions are an attractive source of high value-added substances if subjected to valorization. A preliminary appraisal of their quality is required prior to both disposal and valorization. In the present work, antibacterial activity is suggested as an indicator of the content of essential oils in the analyzed products, as far as they are known for their bactericidal potential. To prove the concept, antibacterial activity of pure essential oils dissolved in water in different concentrations was determined using Gram-negative Escherichia coli K12 and Gram-positive Bacillus subtilis 356 bacterial strains. The minimum inhibitory concentrations of essential oils and antibacterial activity using the agardiffusion method were determined.



Funding: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14).},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {Antibacterial and antioxidant activity of waste fractions from the essential oil industry},

author = {Y. Stoyanova and N. Georgieva and N. Lazarova-Zdravkova and D. Tsanova and D. Peshev},

url = {http://www.nanoessential.eu/wp-content/uploads/Yoana-Stoyanova-PP-044.pdf},

year  = {2021},

date = {2021-00-00},

urldate = {2021-00-00},

organization = {European Biotechnology Congress 2021},

abstract = {Tens of millions of tonnes of waste plant mass are generated every year, which in the areas with traditions in the production of essential oils becomes an environmental problem. Due to the presence of volatile organic components and polyphenolic compounds in the waste products, they are expected to exhibit antimicrobial and antioxidant activity and their uncontrolled disposal has an adverse effect on the ecological balance due to pollution of surface and groundwater. Moreover, valuable substances with biological activity are lost.

The aim of the present work is to study the antibacterial and antioxidant activity of waste materials from the production of essential oils. The accurate determination of the wastes biological activity enables their valorisation. Gram-negative Escherichia coli K12 407 and Gram-positive Bacillus subtilis 3562 bacterial strains were used to study the inhibitory ability of the studied samples. The method of micro-dilution in broth was used to test the susceptibility of the bacteria against the waste fractions. Antioxidant activity was determined spectrophotometrically using the DPPH method.



Keywords: antibacterial, antioxidant, waste product, essential oil.



Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {Conference},

pubstate = {forthcoming},

tppubtype = {conference}

}

@conference{nokey,

title = {IDENTIFICATION OF BIOACTIVE COMPAUNDS IN HYDROSOL AND RESIDUAL WATER AFTER STEAM DESTILATION OF ESSENTIAL OIL CULTURES},

author = {Y. Todorova and D. Tsanova and N. Lazarova-Zdravkova and C. Chilev and D. Peshev and N. Georgieva

},

url = {http://www.nanoessential.eu/wp-content/uploads/3FHSI_TODOROVA_D_Y_Poster_2020.pdf},

year  = {2020},

date = {2020-06-26},

urldate = {2020-06-26},

booktitle = {XVII НАУЧНА ПОСТЕРНА СЕСИЯ ЗА МЛАДИ УЧЕНИ, ДОКТОРАНТИ И СТУДЕНТИ НА ХТМУ},

organization = {UCTM},

abstract = {Steam distillation is a common technological process, which guarantees high and sustainable quality of the extracted oils. As a result of the distillation, in addition to the essential oil and the distilled biomass, there are also two another liquid fractions - hydrosol and residual water. Due to the presence of volatile organic components in the hydrosol and polyphenolic compounds in the residual water they are likely to exhibit antimicrobial and antioxidant activity and their uncontrolled disposal could lead to pollution of surface and groundwater and disturb the ecological balance.

The aim of this study is to identify the main components with biological activity in the hydrosol and the residual water of selected four plants – Rosa Damascena, Lavender, Lemon balm and Clove. HPLC and GC chromatographic methods will be used to identify and quantify these components. Determination of antioxidant and antibacterial activity will also be performed. 



Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14).},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}

@conference{nokey,

title = {APPLICATION OF NANOMEMBRANE SEPARATION FOR UTILIZATION OF WASTE PRODUCTS FROM THE ESSENTIAL OIL PRODUCTION},

author = {D. Tsanova and N. Lazarova-Zdravkova and D. Peshev and N. Georgieva and Ch. Chilev and Y. Todorova and V. Yonkova},

url = {http://www.nanoessential.eu/wp-content/uploads/3FHSI_TSANOVA_G_D.pdf},

year  = {2020},

date = {2020-06-26},

urldate = {2020-06-26},

booktitle = {XVII НАУЧНА ПОСТЕРНА СЕСИЯ ЗА МЛАДИ УЧЕНИ, ДОКТОРАНТИ И СТУДЕНТИ НА ХТМУ},

organization = {UCTM},

abstract = {Steam distillation is a widely used process for essential oil extraction. Besides the final product a vast amount of other fractions are obtained – hydrosol, distilled biomass and residual water. Depending on the characteristics of the oil-bearing plants a secondary distillation – cohobation could be carried out in order to recover additional amount of the essential oil. Very often cohobation is unfeasible and as a result hydrosols are disposed in the environmental. Residual water fraction represents hot water extracts from the plant material.. They are rich of components with antibacterial and antioxidant activity. In the practice they are often neglected and disposed in the environment. Usually distilled biomass is treated as a waste. However it contains various biologically active components that could be extractable with organic solvents such as ethanol.

In this work nanofiltration is regarded as a useful technology for valorization of these waste fractions.





Acknowledgements: This work was supported by the Bulgarian National Science Fund (contract KP-06-H37/14)},

keywords = {Conference},

pubstate = {published},

tppubtype = {conference}

}