Journal of Chemical Technology and Metallurgy, 55, 1, 2020 40 ANTIBACTERIAL ACTIVITY OF MICROENCAPSULATED VIA SPOUTED-BED HYDRO-ALCOHOLIC ROSEMARY EXTRACTS Nevena Lazarova-Zdravkova 1 , Teodora Terzieva 1 , Dimitar Peshev 2 , Nelly Georgieva 1 ABSTRACT In this study the antibacterial activity of microencapsulated rosemary hydro-alcoholic extracts against Escheri- chia coli K12 was observed. The tested microcapsules were previously produced in fve batches varying the type of the inert core and shell material as well as the content of fresh or concentrated rosemary extract. Batch 1 and batch 3 contained equal amount of non-concentrated rosemary extract where batch 2 and batch 4 consisted of the same amount of concentrated rosemary extract. Microcapsules from the last batch 5 were impregnated with three times higher quantity of the non-concentrated rosemary extract than the previous four batches. All fve types of microcapsules were tested by the agar difusion method and showed inhibitory efect against the bacterial strain. The highest antibacte- rial activity was obtained for batch 5 followed by the samples with concentrated extract (batch 2 and batch 4) and the least inhibitory efect was observed by the microcapsules with non-concentrated extract (batch 1 and batch 3). Keywords: antibacterial activity, Rosmarinus ofcinalis, E. coli K12, hydro-alcoholic extracts, agar difusion method. Received 09 May 2019 Accepted 31 July 2019 Journal of Chemical Technology and Metallurgy, 55, 1, 2020, 40-44 1 Department of Biotechnology, University of Chemical Technology and Metallurgy 8 Kl. Ohridski, 1756, Sofa, Bulgaria 2 Department of Chemical Engineering, University of Chemical Technology and Metallurgy 8 Kl. Ohridski, 1756, Sofa, Bulgaria E-mail: n.a.lazarova@gmail.com INTRODUCTION In the last decades the food industry together with the health authorities are focusing on producing safe food products for consumers. Synthetic additives have been widely used and the trend is to decrease their use. Search for natural additives, especially of plant origin has notably increased in recent years. Therefore, the development and application of natural products with both antioxidant and antibacterial activities may be necessary and useful to prolong their storage shelf life and potential for preventing food diseases [1, 2]. Rosmarinus ofcinalis is an aromatic evergreen plant belonging to the family Lamiaceae and is the only repre- sentative of this species that is wild in the Mediterranean regions [3, 4]. Rosemary has а broad range of applica- tions, from culinary to medical, because of its aromatic properties and benefts to human health [5]. It is well known that the biological properties of this species are mainly due to phenolic compounds [6]. The numerous biological activities of rosemary include antioxidant, an- timicrobial, antidiabetic and antidepressant, anti-cancer and anti-infammatory action. Essential oils or extracts of rosemary are used in the food industry, cosmetics, aromatherapy and medicine [7, 8]. Studies show that the inhibitory efect of rosemary is a result of the action of rosmarinic acid, rosmaridiphenol, carnosol, epirosmanol, carnosic acid, rosmanol and isorosmanol [6]. Moreover, according to the experimental data by Romano et al. 2009, the antibacterial activity of the rosemary extract is signifcantly higher than the one of additives used in the food industry such as butylated hydroxytoluene (BHT)