Coffee grounds are one of the very valuable lignocellulosic wastes that have been able to be processed and used for isolated phenolic substances. Many phenolic substances isolated from lignocellulosic wastes have antimicrobial properties. Aim of this thesis is isolation phenolic substances from spent coffee grounds extract and their available antimicrobial properties. Two isolation ways were applied to receive phenolic substances from spent coffee grounds: 1) solvent extraction (hexane, 75% ethanol, 70% acetone, diethyl ether, and ethyl acetate) and 2) release of active substances by alcoholic fermentation. All isolated materials were characterized by the viewpoint of concentration of reducing sugars, polyphenols and flavonoids. Subsequently, their antimicrobial activity was determined by using agar diffusion and broth dilution methods. Two gram-positive bacteria (Bacillus subtilis and Micrococcus luteus), one gram-negative bacteria (Serratia marcescens) and two yeasts (Candida glabrata and Saccharomyces cerevisiae) were used for antimicrobial testing. High-performance liquid chromatography (HPLC) was used to identify phenolic substances in the extracts. First, the results showed that the isolated sample with the highest antimicrobial activity was 70% acetone extract. This extract contained chlorogenic acid, gallic acid, caffeic acid and coumaric acid according to HPLC. The ethyl acetate extract showed the lowest antimicrobial activity. Second, after lyophilization, the isolated materials also revealed high antimicrobial activity. The highest antimicrobial activity displayed the materials obtained by the extraction with 70% ethanol. This sample contained chlorogenic acid, gallic acid and caffeic acids. Next, samples with phenolic compounds were obtained by the alcoholic fermentation of spent coffee grounds. These samples showed similarly to the previous solution extracts significant antimicrobial activity. Interestingly, the unfiltered samples received directly after alcoholic fermentation also showed antifungal properties. The characterization of phenolic compounds by HPLC showed similarly as in previous examples that chlorogenic, caffeic and gallic acids were present in these samples.
| Identifer | oai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:433498 |
| Date | January 2020 |
| Creators | Kurzová, Pavlína |
| Contributors | Veselá, Mária, Kovalčík, Adriána |
| Publisher | Vysoké učení technické v Brně. Fakulta chemická |
| Source Sets | Czech ETDs |
| Language | Czech |
| Detected Language | English |
| Type | info:eu-repo/semantics/masterThesis |
| Rights | info:eu-repo/semantics/restrictedAccess |
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