Određivanje optimalnih uvjeta biorazgradnje polistirena primjenom bakterije Bacillus subtilis

master's thesis

• Title (english): Determination of the optimal conditions for the biodegradation of polystyrene using the bacterium Bacillus subtilis
• Author: Mirela Kovačević
• Mentor: Dajana Kučić Grgić (mentor)
• Committee member: Dajana Kučić Grgić (predsjednik povjerenstva)
• Committee member: Vesna Ocelić Bulatović (član povjerenstva)
• Committee member: Lidija Furač (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2023-06-30, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

Plastika je materijal koji se često koristi u svakodnevnim predmetima, a njezino nepravilno odlaganje i nakupljanje postali su ozbiljna briga za okoliš. Mikroplastika (MP) male su čestice sintetskih organskih polimera manje od 5 mm i predstavljaju veliku prijetnju okolišu zbog svoje postojanosti i inherentne toksičnosti. Biorazgradnja polimera ovisi o različitim čimbenicima, kao što su fizikalna i kemijska svojstva polimera, uvjeti u okolišu i prisutnost mikroorganizama. Iako je biorazgradnja često korišten proces za uklanjanje MP iz okoliša, njezina učinkovitost ovisi o optimizaciji značajnih čimbenika procesa. Cilj ovog istraživanja bio je istražiti biorazgradnju čestica polistirena (PS) pomoću bakterije Bacillus subtilis, odnosno odrediti značajne čimbenike koji utječu na proces biorazgradnje te optimizirati uvjete biorazgradnje. Eksperiment je osmišljen korištenjem punog faktorskog plana (FFP) za proučavanje učinaka tri čimbenika, odnosno veličine MP, brzine okretaja i optičke gustoće (OG) bakterijske suspenzije, na tri razine. Proces biorazgradnje praćen je 30 dana tijekom kojih se pratio ukupan broj bakterijskih kolonija (eng. Colony Forming Units, CFU) i vrijednosti ukupnog (TC), organskog (TOC) i anorganskog (TIC) ugljika. LC/MS analiza je provedena kako bi se otkrilo otpuštanje aditiva iz PS MP i stvaranje potencijalno toksičnih proizvoda razgradnje. Promjene u strukturi PS-a ispitane su ATR-FTIR spektroskopijom. Ekotoksičnost filtrata procijenjena je pomoću bakterije Vibrio fischeri. Za procjenu eksperimentalnih rezultata korištena je statistička analiza varijance (ANOVA).

Abstract (english)

Plastic is a material commonly used in everyday objects, and its improper disposal and accumulation have become a serious environmental concern. Microplastics (MP) are small particles of synthetic organic polymers measuring less than 5 mm and pose a significant threat to the environment due to their persistence and inherent toxicity. The biodegradation of polymers depends on various factors, such as the physical and chemical properties of the polymer, environmental conditions, and the presence of microorganisms. Although biodegradation is often used as a process to remove MP from the environment, its effectiveness relies on optimizing significant process factors. The aim of this research was to investigate the biodegradation of polystyrene (PS) particles using the bacterium Bacillus subtilis. The objective was to identify significant factors influencing the biodegradation process of PS microplastics (MP) using Bacillus subtilis and to optimize the biodegradation conditions using this bacterial culture. The experiment was designed using a full factorial design (FFD) to study the effects of three factors, namely MP size, rotational speed, and optical density (OD) of the bacterial suspension, at three levels. The biodegradation process was monitored for 30 days, during which the total colony-forming units (CFU) of bacteria and the values of total carbon (TC), organic carbon (TOC), and inorganic carbon (TIC) were measured. LC/MS analysis was conducted to detect the release of additives from PS MP and the formation of potentially toxic degradation products. Changes in the structure of PS were examined using ATR-FTIR spectroscopy. The ecotoxicity of the filtrate was assessed using the bacterium Vibrio fischeri. A statistical analysis of variance (ANOVA) was used to evaluate the experimental results.

• Keywords: mikroplastika; polistiren; biorazgradnja; Bacillus subtilis; puni faktorski plan
• Keywords (english): microplastics; polystyrene; biodegradation; Bacillus subtilis; full factorial plan
• Language: croatian
• URN:NBN: urn:nbn:hr:149:338310
• Project: Number: IP-2019-04-9661; Title: Primjena naprednih tehnologija obrade voda za uklanjanje mikroplastike; Title: Advanced Water Treatment Technologies for Microplastics Removal; Acronym: AdWaTMiR; Leader: Tomislav Bolanča; Jurisdiction: Croatia; Funder: HRZZ; Funding stream: IP
• Study programme: Title: Environmental Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka ekoinženjerstva (magistar/magistra inženjer/inženjerka ekoinženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2024-01-01
• Created on: 2023-07-26 13:08:25