getpdf  NLM-PubMed-Logo  https://doi.org/10.17113/ftb.56.03.18.5618 

Electrochemical Study and Determination of All-trans-Retinol at Carbon Paste Electrode Modified by a Surfactant

 

Simona Žabčíkováorcid tiny, Tomáš Mikysekorcid tiny, Libor Červenkaorcid tiny and Milan Sýs*orcid tiny

 

 


Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-53210 Pardubice, Czech Republic

 

 


Article history:
Received: 22 November 2017
Accepted: 9 May 2018 
cc

 


Key words:
modified carbon paste electrode, differential pulse voltammetry, glassy carbon electrode, all-trans-retinol, surfactant

 

 


Summary:
The oxidation mechanism of all-trans-retinol (vitamin A1) and its several esters in non-aqueous, aqueous organic mixture, and pure aqueous media was investigated by cyclic voltammetry. The oxidation occurred in several irreversible steps. The calculated highest density of electrons in retinoid molecules which are delocalized over carbon atoms of the five conjugated double bonds (C5-C14) was found in the part of the molecule involved in oxidation processes. The most sensitive oxidation peak (at +0.8 V vs Ag/AgCl) was used for development of new direct voltammetric method based on differential pulse voltammetry for the determination of retinol at carbon paste electrode modified with surfactant sodium dodecyl sulfate (CPE/SDS). The results show that 30 % (by mass) of modifier SDS exhibited optimal sensitivity and shape of voltammograms. Compared to commonly used glassy carbon electrode (GCE), the CPE/SDS showed significant progress in the retinol electroanalysis. The linear ranges for retinol determination were 1.5·10−6–1.8·10−4 M for CPE/SDS and 4.4·10−6–7.0·10−4 M for GCE with the detection limits of 1.3·10−6 and 4.6·10−7 M, respectively.

 

 


*Corresponding author: tel2 +420466037068
                                           fax2 +420466037279
                                           email3  milan.sys@upce.cz

getpdf  NLM-PubMed-Logo  https://doi.org/10.17113/ftb.56.03.18.5726 

Development of a New Colorimetric Chemosensor for Selective Determination of Urinary and Vegetable Oxalate Concentration Through an Indicator Displacement Assay (IDA) in Aqueous Media

 


Hossein Tavallali*orcid tiny, Gohar Deilamy-Radorcid tiny and Narges Mosallanejadorcid tiny

 

 

 

Department of Chemistry, Payame Noor University, P.O. Box 19395-3697, Tehran, Iran

 

 


Article history:
Received: 14 February 2018
Accepted: 8 May 2018 
cc 

 


Key words:
colorimetric chemosensor, indicator displacement assay, copper complex, oxalate, urine

 

 


Summary:
The paper proposes a method that exhibits operational simplicity for the indirect spectrophotometric determination of oxalate ion. We developed Reactive Blue 4 (RB4) as a sensor by complexation with copper ion as a simple, inexpensive yet selective colorimetric chemosensing ensemble for the recognition of oxalate over other available competitive analytes via indicator displacement assay (IDA) in both solution (aqueous medium) and solid state (paper-based experiment). The addition of oxalate to RB4-Cu2+ complex changed the colour from sky blue to dark blue due to the regeneration of RB4 by the chelation of oxalate as the competitive analyte with Cu2+. The absorbance band increase is linear with oxalate concentration from 1.76 to 49.4 µmol/L with a detection limit of 0.62 µmol/L. This measurement mode did not show any influence of interferences (available anions and ascorbic acid). This approach eliminated the need for the separation stages, enzymatic multiple-step reactions, sample preparation, organic solvent mixture, chemical modifications and equipment developed to a high degree of complexity. The oxalate determination gave results in different real samples such as urine, mushroom and spinach, which demonstrated the applicability of the existing method. Furthermore, this colorimetric system can serve as IMPLICATION molecular logic gate using Cu2+ and oxalate (C2O2–) as inputs and UV-Vis absorbance signal as the output with potential monitoring applications.

 

 


*Corresponding author: tel3 +989173153520
                                          fax2 +987136222249
                                          email3  Tavallali@pnu.ac.ir

getpdf  NLM-PubMed-Logo  https://doi.org/10.17113/ftb.56.03.18.5546 

Bioethanol Production from Renewable Raw Materials and Its Separation and Purification: A Review


Arijana Bušić1orcid tiny, Nenad Marđetko1orcid tinySemjon Kundas2orcid tiny,  Galina Morzak3orcid tiny,  Halina Belskaya3orcid tiny,  Mirela Ivančić Šantek1orcid tinyDraženka Komes1orcid tiny, Srđan Novakand  Božidar Šantek1*orcid tiny

 

1University of Zagreb, Faculty of Food Technology and Biotechnology, Pierottijeva 6, HR-10000 Zagreb, Croatia
2Belarussian National Technical University, Power Plant Construction and Engineering Services Faculty, Nezavisimosti Ave. 150, BY-220013 Minsk, Belarus
3Belarussian National Technical University, Mining Engineering and Engineering Ecology Faculty, Nezavisimosti Ave. 65, BY-220013 Minsk, Belarus

 

 

Article history:
Received: 22 October 2017
Accepted: 21 May 2018 
cc

 

Key words:
bioethanol, renewable feedstocks, raw material pretreatment, bioprocess operational modes, bioethanol separation and purification

 

 

Summary:
Production of biofuels from renewable feedstocks has captured considerable scientific attention since they could be used to supply energy and alternative fuels. Bioethanol is one of the most interesting biofuels due to its positive impact on the environment. Currently, it is mostly produced from sugar- and starch-containing raw materials. However, various available types of lignocellulosic biomass such as agricultural and forestry residues, and herbaceous energy crops could serve as feedstocks for the production of bioethanol, energy, heat and value-added chemicals. Lignocellulose is a complex mixture of carbohydrates that needs an efficient pretreatment to make accessible pathways to enzymes for the production of fermentable sugars, which after hydrolysis are fermented into ethanol. Despite technical and economic difficulties, renewable lignocellulosic raw materials represent low-cost feedstocks that do not compete with the food and feed chain, thereby stimulating the sustainability. Different bioprocess operational modes were developed for bioethanol production from renewable raw materials. Furthermore, alternative bioethanol separation and purification processes have also been intensively developed. This paper deals with recent trends in the bioethanol production as a fuel from different renewable raw materials as well as with its separation and purification processes.

 

 

*Corresponding author: tel3 +38514605290
                                          fax2 +38514836424  
                                          email3 
bsantek@pbf.hr

getpdf  NLM-PubMed-Logo  https://doi.org/10.17113/ftb.56.03.18.5658 

Microbial Keratinases: Enzymes with Promising Biotechnological Applications

 

Beti Vidmarorcid tiny and Maša Vodovnik*orcid tiny

 


Chair of Microbiology and Microbial Biotechnology, Department of Animal Science, Biotechnical Faculty, University of Ljubljana, Groblje 3, SI-1230 Domžale, Slovenia

 

 


Article history:
Received: 3 January 2018
Accepted: 31 May 2018 
cc

 


Key words:
keratin, keratinase, waste degradation, keratinolytic microorganisms, biotechnological applications

 

 


Summary:
Keratin is a complex and structurally stable protein found in human and animal hard tissues, such as feathers, wool, hair, hoof and nails. Some of these, like feathers and wool, represent one of the main sources of protein-rich waste with significant potential to be transformed into value-added products such as feed, fertilizers or bioenergy. A major limitation impeding valorization of keratinous substrates is their recalcitrant structure and resistance to hydrolysis by common proteases. However, specialized keratinolytic enzymes produced by some microorganisms can efficiently degrade these substrates. Keratinases have already found a purpose in pharmaceutical, textile and leather industries. However, their wider implementation in other processes, such as cost-effective (pre)treatment of poultry waste, still requires optimization of production and performance of the available enzymes. Here we present a comprehensive review covering molecular properties and characteristics of keratinases, their classification, traditional and novel approaches in discovery of novel enzymes, production, characterization, improvement and biotechnological applications.

 

 


*Corresponding author: tel3 +38613203955
                                          fax2 +38617241005
                                          email3 masa.vodovnik@bf.uni-lj.si

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