Plant growth promoting microorganisms (PGPM) are an important group of microbial inoculants, which exist in rhizosphere and have the ability to inhabit the root of the plants and improve their development. Their positive influence is achieved through solubilization of phosphorus, nitrogen fixation, production of plant nutrients and phytohormones, protection from pathogens and recovery from stressful environmental conditions. This is the main reason for the increasing usage of many PGPMs which formulations are commonly known as microbial fertilizers. Microbial fertilizers represent an attractive replacement for chemical fertilizers that are polluting the environment. They are used to increase the crop yield in an eco-friendly way while relying on sustainable agriculture principles. The biggest problem nowadays is the very poor quality of such products, which results in the lack of confidence and makes commercialization much more difficult. In order to increase production and hence the commercialization of microbial fertilizers, desired quality and stability should be achieved. For this reason, many researches are done in this particular field. In order to develop an optimal product, it is important to know and understand the process, including the physiology of bacteria and plants, mass multiplication technological processes as well as the existing formulation and the specific effect on the desired plant. For this purpose, the aim of this review is to indicate the significance of microbial fertilizers and their beneficial effects on the plants, as well as to give a brief survey of the different aspects of production processes with a special emphasis on mass multiplication.

The homogeneous base-catalyzed methanolysis of waste cooking oil (WCO) was investigated at a methanol:WCO molar ratio of 6:1, the initial KOH amount of 1% (based on the oil weight) and moderate temperatures (30 o C to 60 o C) with the aim to model the methanolysis reaction kinetics. It was observed that the methanolysis reaction occurred via a pseudo-homogeneous regime where the chemical reaction controls the overall process kinetics and with no mass transfer limitation. It was shown that irreversible pseudo-first and-second order reactions were reliable for describing the methanolysis reaction. However, a better fitting of experimental data was observed by using the irreversible pseudo-second order kinetic model. The reaction rate constant increased with increasing the reaction temperature and at 60 o C the WCO conversion of 97% was achieved in 3 minutes. The final products satisfied the EN 14214 biodiesel standard specifications.

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Apple pomace is a solid waste derived from the apple processing industry. To foster sustainability, the apple processing industry must implement the circular economy model of biorefinery and treat apple pomace as a valuable source of apple seed oil. The first time, this study dealt with the design, economic, and potential environmental impact assessment of biodiesel production using apple pomace as a source of apple seed oil. An Aspen Plus? and WAR? software were used to evaluate the designed biodiesel production. Supercritical CO2 extraction and methanolysis of apple seed oil, methanol recovery, and biodiesel separation were the main production steps. The production facility was assumed to process 24 tons of apple seeds daily. The total capital and production costs were 1.26 US$ million and 2.82 US$ million, respectively. If revenues from selling apple seed meal as cattle feed were included, a biodiesel price could be 0.39 US$/kg. The process was environmentally friendly when apple seed meal was not treated as waste.

Food contamination is one of the major problems in food distribution. Microorganisms and their metabolites are the most common food contaminants. This review consolidates the reported food contamination cases in the Republic of Serbia. Mycotoxins were stated as the most common contaminants in various foods. Among them mycotoxins like zearalenone, aflatoxins, fumonisins, and deoxynivalenol were the most frequently detected. Also, the contamination caused by the presence of various microorganisms like L. monocytogenes, E. coli, Salmonella spp. and S. aureus was reported in high frequency. The microbial contamination was usually detected in meat and dairy products. Although heavy metals were detected in some products, in most cases their concentrations were in accordance with the legislation. A higher level of Pb and Hg was stated only in a few samples of tea, milk and fish. The constant analysis, control and prevention are needed at all levels of the production in order to compile the safety requirements and international legislation.

2 Prirodno-matematički fakultet, Odsek Biologija i Ekologija, Univerzitet u Nišu, Niš, Srbija Ulje semena korovske biljke magareći trn (Onopordum acanthium L.) je korišćeno za sintezu metil estara masnih kiselina. Zbog većeg kiselinskog broja ulja, primenjen je dvostepeni proces koji uključuje esterifikaciju slobodnih masnih kiselina u ulju katalizovanu H2SO4 i metanolizu esterifikovanog ulja katalizovanu KOH. Kinetika reakcije metanolize esterifikovanog ulja je modelovana primenom nepovratne reakcije pseudo-prvog reda i pseudo-drugog reda. Izračunate su konstante brzine reakcije metanolize i energije aktivacije. Adekvatnost modela procenjivana je na osnovu vrednosti R 2 linearnih zavisnosti i srednjeg relativnog procentnog odstupanja eksperimentalnih i izračunatih vrednosti stepena konverzije triacilglicerola. Iako su oba kinetička modela pogodna za fitovanje eksperimentalnih podataka, veća tačnost je ostvarena primenom modela nepovratne reakcije pseudo-drugog reda. Karakteristike dobijenog biodizela su, generalno, u okviru vrednosti propisanih standardom kvaliteta bodizela EN14214. Zbog toga, seme O. acanthium L. može biti korišćeno kao jeftina sirovina za sintezu biodizela.Ključne reči: dvostepeni process; biodizel; kinetika; magareći trn; metanoliza; Onopordum acanthium L. UvodDemografska ekspanzija i razvoj industrije uslovljavaju kontinualno povećanje potreba za energijom, zbog čega su mnogobrojna istraživanja usmerena ka pronalaženju novih, alternativnih izvora energije: iskorišćenju energije biomase, sunca, vetra, talasa i plime i oseke. U sektoru transporta najčešću primenu imaju goriva dobijena iz biomase, među kojima značajno mesto zauzima biodizel. Biodizel predstavlja ekološki "čisto" gorivo, biorazgradivo i manje toksično u odnosu na dizel fosilnog porekla, koje se dobija iz obnovljivih sirovina i pogodno je za primenu u dizel motorima. Dobija se postupkom alkoholize biljnih ulja ili životinjskih masti sa nižim alifatičnim alkoholima. Najčešće korišćeni alkoholi u sintezi biodizela su metanol, a u poslednje vreme i etanol [1]. Za dobijanje biodizela trenutno se najčešće koriste jestiva biljna ulja, kao što su: ulje uljane repice, soje, suncokreta ili palme [2]. Međutim, korišćenje jestivih ulja u procesima dobijanja biodizela ograničavaju njihova primarna primena u ljudskoj ishrani i visoka cena. S obzirom da u ukupnoj ceni proizvodnje biodizela uljne sirovine imaju najveći udeo [3,4], poslednjih godina pažnju istraživača privlači ispitivanje mogućnosti primene novih i jeftinijih ulja kao što su ulja dobijena iz semena različitih korovskih biljaka:Magareći trn ili čkalj (Onopordum acanthium L.) je korovska biljka koja pripada familiji Asteraceae. Ova familija biljaka predstavlja najobimniju familiju dikotiledonih skrivenosemenica. Njihova primena je široka, kako u narodnoj medicini za lečenje povišenog krvnog pritiska [10], tako i u hemijskoj industriji za proizvodnju biogoriva pirolizom [11] ili likvefakcijom [12] biomase. U dosadašnjim istraživanjima ulje semena Onopordum acanthium L. nije ispit...

A heterogeneous reaction process using propylene glycol (PEG), ethyl acetate and diethyl ether as cosolvents for the transesterification of sunflower oil with ethanol in the presence of calcium oxide as a catalyst has been developed. Significant results were obtained with propylene glycol as a cosolvent. Under determined reaction conditions (Cao concentration, based on the oil weight 1.3736 mol•dm-3 ; temperature 70 °C; and ethanol-to-oil molar ratio 12:1), the conversion of sunflower oil to fatty acid ethyl esters (FAEE) exceeded 98% after 120 min, which was 2 times faster than transesterification of sunflower oil without a cosolvent. After initially enhanced ethanolysis, after 180 min ethyl acetate and diethyl ether negatively influenced the reaction rate and the FAEE yield.