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  • Author: Miroslav Ondrejovič x
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Abstract

The lignocellulolytic enzymes are routinely produced by submerged fermentation using lignocellulosic material, but for more effective production, it would be suitable to precede the production phase on the lignocellulose by propagation phase in the nutrition medium suitable for growth of the fungi. Therefore, the aim of this study was to increase the laccase production by the white-rot fungus Pleurotus ostreatus by two-step cultivation strategy. In the first step, propagation medium was optimized for the maximal biomass growth, the second step included the laccase production by produced fungal biomass in media with the selected lignocellulosic material (pine sawdust, alfalfa steam and corn straw). From our experiments, parameters such as glucose concentration, yeast extract concentration and pH of propagation medium were selected as key factors affecting growth of P. ostreatus. The optimal conditions of propagation medium for maximal fungal growth determined by response surface methodology were: glucose concentration 102.68 g/L, yeast extract concentration 43.65 g/L and pH of propagation medium 7.24. These values were experimentally verified and used statistical model of biomass production prediction was appropriate adjusted. Thus prepared fungal biomass produced in the media with lignocellulose approximately 9-16 times higher concentrations of the laccase in 3 times shorter time than the fungal biomass without propagation phase in optimized propagation medium.

Abstract

Eleutherococcus senticosus is known as adaptogen with benefits in general health promotion. The aim of this study was to investigate the effect of major extraction parameters on extraction yield of antioxidants measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity. Secondly, content of total polyphenols was evaluated. Optimal conditions of the extraction were processed by response surface methodology. The independent variables of extraction were proposed as temperature, solid-liquid ratio and solvent composition. For the optimal antioxidant extraction, E. senticosus is suitable to extract by 23 % (v/v) aqueous ethanol at 70 °C in ratio 53 mL of extraction solvent per g of plant material. The optimal conditions calculated for the extraction of total polyphenols were very similar (70 °C, 22 % (v/v) aqueous ethanol) expect solid-liquid ratio which indicates need of increasing of solid-liquid ratio to 91 mL of extraction solvent per g of plant material

Antioxidant Activity of Milling Fractions of Selected Cereals

The aim of this study was to evaluate antioxidant potential of four milling fractions of selected cereals grew in the year 2009 and 2010. Free radical scavenging activity of samples was measured using DPPH assay and reducing power was determined using FRAP assay. Secondary, total phenolic and flavonoid content of cereal extracts was evaluated. We found that flour fractions (break flour and reduction flour) showed the lower proportion of the total antioxidant potential than bran fractions (fine bran and coarse bran), which was balanced in observed years. Extract from barley had the highest values of antioxidant activity and polyphenol content.

Abstract

The aim of this study was to determine the influence of malting on the antioxidant content in cereals such as wheat (PS Sunanka, Zaira, PS 57/11 and Vanda), oat (Dunajec) and barley (Laudis 550) harvested in 2013. Antioxidant and polyphenol contents of these cereals and malts were investigated. Secondary, technological parameters of prepared malts were evaluated and compared with malt from barley Laudis 550 used as reference material. Malting of selected cereals had an impact on antioxidant and polyphenol content and allowed a better extraction of these compounds from cereal matrix, except of barley malt, whose antioxidant and total polyphenol content remained comparable. For other cereal malts, antioxidant contents were 2.0, 1.8, 2.6, 2.9 and 3.2-fold higher and total polyphenol content were 1.8, 1.9, 1.9, 3.1 and 3.4-fold higher than in wheat (PS Sunanka, Zaira, PS 57/11, Vanda) and oat (Dunajec), respectively. From correlation analysis, the results showed that not all polyphenols released by malting have antioxidant activity. Technological parameters (friability, haze of wort, saccharification rate, filtration rate, extract and diastatic power) also indicated that good malt quality had oat Dunajec and wheat PS Sunanka and Zaira in comparison with reference material (barley Laudis 550).

Abstract

The aim of this work was to identify the main microbiota in raw cow milk from dairy farm of Slovakia and to describe the selected microorganisms responsible for thermostable protease and lipase production which can affected the quality of dairy products. The main bacterial classes identifying by MALDI-TOF MS were Gammaproteobacteria (62 %), Actinobacteria (19 %) and Bacilli (12 %). The dominant microbial genus of raw cow milk was Pseudomonas. From milk bacteria, the strain Lactococcus lactis and from the family Enterobacteriaceae, namely Enterococcus faecalis, Hafnia alvei, Citrobacter braakii and Raoultella ornithinolytica were observed in raw milk. The spoilage of milk products is caused by thermostable enzymes with lipolytic and proteolytic activity. Qualitative proteolytic and lipolytic activities were performed on skin milk agar and olive oil, respectively. From 16 identified microorganisms, only 8 strains (P. fragii, P. gessardii, P. lundesis, H. alvei, C. braakii, R. ornithinolytica, Kocuria rhizophila and Candida inconspicua) showed protease activity. Quantitative protease and lipase activities were determined by casein and olive oil, respectively. The highest both activities were measured for the genus Pseudomonas. While lipases produced by all isolated microbial species lose enzymatic activity at 77 °C for 30 – 40 min, almost proteases showed comparable activities during whole pasteurization experiment at selected experimental conditions (70 °C, 40 min).

Solid-Phase Extraction for Photometric Determination of Rosmarinic Acid in Lemon Balm (Melissa Officinalis) Extracts

The aim of this study was evaluation of the solid-phase extraction for elimination of interference compounds from lemon balm extracts aimed for photometric determination of rosmarinic acid. In experiments, evaluated conditions were as follows: composition and volume of mobile phase, ratio between volume of sample and mass of stationary phase and flow rate of mobile phase during separation. The results indicated that interfered compounds were eliminated. The lemon balm extracts should be pretreated by adsorption on normal stationary phase (silica gel) in ratio sample volume to silica gel weight 1:1 (v/w) elution by mobile phase - diethyl ether: acetic acid (9:1; v/v) - volume - 40 times of crude extract volume - with flow rate 5 ml/min. After selection of SPE conditions, the method was validated with comparison to HPLC analysis. The results suggest that this method may be useable for determination of rosmarinic acid by photometric measurement based on the complexation of Fe2+ ions with rosmarinic acid.

Abstract

The aim of this study was to set parameters of repeated-batch cultivation of Ceriporiopsis subvermispora for laccase production and evaluate the efficiency of this type of cultivation for production of selected enzyme. The suitable conditions for repeated-batch cultivation were designed on the base of study of batch cultivation of white-rot fungus C. subvermispora. C. subvermispora was cultivated in media with different concentration of casein hydrolysate as nitrogen source and glucose as carbon source. A suitable concentration of casein hydrolysate to stimulate the laccase production was 1.5 and 2.5 g/L. Laccase production was started at certain critical concentration of glucose (5 g/L). In order to improve laccase production by repeated-batch cultivation of C. subvermispora, glucose was tested in concentration 10 g/L and casein hydrolysate in concentration 1.5 g/L. During a repeated-batch cultivation was measured increase laccase activities from 177.8 to 266 U/L. It was also observed, the cultivation time needed to reach maximum laccase production was shortened to 10 days.

Abstract

Laccases provide a promising future as a tool to be used in the field of biodegradation of synthetic dyes with different chemical structures. These enzymes are able to oxidize a wide range of phenolic substrates without the presence of additional co-factors. Laccases have been confirmed for their potential of synthetic dye degradation from wastewater and degradation products of these enzymatic reactions become less toxic than selected dyes. This study discusses the potential of laccase enzymes as agents for laccase-catalyzed degradation in terms of biodegradation efficiency of synthetic dyes, specifically: azo dyes, triphenylmethane, indigo and anthraquinone dyes. Review also summarizes the laccase-catalyzed degradation mechanisms of the selected synthetic dyes, as well as the degradation products and the toxicity of the dyes and their degradation products.

Abstract

The aim of the present study was to investigate the dye decolorization ability of laccase from Trametes versicolor. Five azonaphthalene dyes (Acid Violet 7, Acid Red 1, Allura Red AC, Orange G and Sunset Yellow FCF) were used to evaluate dye decolorization. Laccase from T. versicolor is capable of decolorizing dyes, namely Acid Violet 7 (53.7±2.3 %) and Orange G (46.0±2.2 %). The less effective ability of laccase was observed at the decolorization of other selected dyes (6.9 - 18.6 %). The presence of redox mediator (1-hydroxybenzotriazole) increased decolorization percentage for all tested dyes (≥ 90.5 %). Toxic effect of azo dyes and their degradation products after laccase treatment was observed on the growth of selected bacteria (Micrococcus luteus, Bacillus subtilis, Pseudomonas syringae and Escherichia coli), yeasts (Candida parapsilosis and Saccharomyces cerevisiae) and algae (Chlorella vulgaris and Microcystis aeruginosa). It was confirmed that degradation products showed lower inhibition effect compared to initial dyes. These findings suggest that laccase from T. versicolor are able to decolorize and detoxify selected azonaphthalene dyes.

Abstract

The aim of this study was investigate the influence of different metal ions on laccase activity and triphenylmethane dye decolorization by laccase from white-rot fungus Trametes versicolor. Laccase activity was inhibited by monovalent ions (Li+, Na+, K+ and Ag+) but the presence of divalent ions increased laccase activity at the concentration of 10 mmol/l. The effect of metal ions on decolorization of triphenylmethane dyes with different structures namely Bromochlorophenol Blue, Bromophenol Blue, Bromocresol Blue and Phenol Red was tested. The presence of metal ions (Na+, K+, Mg2+, Ca2+, Ba2+, Mn2+, Zn2+) slightly decreased triphenylmethane dye decolorization by laccase from T. versicolor except Na+ and Mg2+, which caused the increase of decolorization for all tested dyes. Decolorization of selected dyes showed that the presence of low-molecular-weight compounds is necessary for effective decolorization. Hydroxybenzotriazole (HBT) is the most frequently used. Although HBT belongs to most frequently used redox mediator and generally increase decolorization efficiency, so its presence decreased decolorization percentage of Bromophenol Blue and Bromochlorophenol Blue, the influence of metal ions to dye decolorization by laccase has the similar course with or without presence of redox mediator HBT.