Primjena punog faktorskog plana i metode odzivnih površina pri ispitivanju biorazgradnje poli(vinil-klorida) bakterijskom kulturom Bacillus cereus

master's thesis

• Title (english): Application of the Full Factorial Plan and Response Surface Methodology in the study of biodegradation of polyvinyl chloride by bacterial culture Bacillus cereus
• Author: Lucija Anzulović
• Mentor: Dajana Kučić Grgić (mentor)
• Committee member: Dajana Kučić Grgić (predsjednik povjerenstva)
• Committee member: Šime Ukić (član povjerenstva)
• Committee member: Lidija Furač (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2022-07-11, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

Plastika je sveprisutna u našem svakodnevnom životu zbog široke upotrebe u uobičajenim rutinskim predmetima. Njezino kontinuirano korištenje, nakupljanje i neadekvatno odlaganje plastičnog otpada predstavlja ozbiljnu prijetnju biotičkim i abiotičkim sastavnicama okoliša. Mikroplastika (MP) su čestice sintetskih organskih polimera veličine manje od 5 mm, uključujući one koje nisu vidljive golim okom. MP-e je postala jedna od vodećih prijetnji okolišu zbog svoje postojanosti, sveprisutnosti i intrinzičnog toksičnog potencijala. Biološka razgradivost polimera ovisi o fizikalnim i kemijskim svojstvima polimera, abiotičkim svojstvima, ali i o svojstvima samih mikroorganizama. Biorazgradnja je jedna od najčešće primjenjivanih metoda za uklanjanje MP-a iz okoliša, a da bi bila visoko učinkovita potrebno je optimirati značajne procesne čimbenike. U ovom radu ispitivana je biorazgradnja čestica poli(vinil-klorida) (PVC) primjenom bakterije Bacillus cereus. Cilj ovoga istraživanja bio je prvo odrediti značajne čimbenike za proces biorazgradnje MP PVC primjenom Bacillus cereus te su se potom ispitali optimalni uvjeti za proces biorazgradnje MP-a primjenom navedene bakterijske kulture. Eksperiment se provodio prema dizajnu punog faktorskog plana (FF) u kombinaciji za tri ispitivana čimbenika – veličina MP-a, koncentracija MP-a, i optička gustoća (OG) priređene suspenzije bakterije – na tri razine (minimalna, srednja i maksimalna vrijednost). Tijekom 30 dana provedbe pokusa biorazgradnje, praćena je promjena OG-a te ukupni broj izraslih kolonija bakterija (CFU). U vodenoj fazi određivane su vrijednosti ukupnog (TC), organskog (TOC) i anorganskog (TIC) ugljika. LC/MS analizom praćeni su otpušteni aditivi s čestica MP-a te potencijalno nastali razgradni produkti prilikom biorazgradnje MP-a. Strukturne promjene PVC-a određene su FTIR-ATR spektroskopijom. Na kraju procesa biorazgradnje ispitana je i ekotoksičnost filtrata primjenom bakterije Vibrio fischeri. Eksperimentalni rezultati obrađeni su korištenjem statističke analize varijance (ANOVA). Rezultati pokusa ukazuju da je bolji rast bakterije Bacillus cereus uočen pri srednjoj koncentraciji PVC-a od 500 mg/L, srednjoj veličini čestice od 300-500 μm i najvećoj OG u iznosu od 0,5. S obzirom na navedeno, ispitivana bakterijska kultura ima sposobnost biorazgradnje MP-a.

Abstract (english)

Due to its widespread use in common routine items, plastic is ubiquitous in our daily lives. Its continuous use, accumulation and inadequate disposal of plastic waste pose a serious threat to the biotic and abiotic components of the environment. Microplastics (MPs) are particles of synthetic organic polymers less than 5 mm in size, including those not visible to the naked eye. MPs have become one of the leading threats to the environment due to their persistence, ubiquity and intrinsic toxic potential. The biodegradability of polymers depends on the physical and chemical properties of the polymer, abiotic properties, as well as on the properties of the microorganisms themselves. Biodegradation is one of the most commonly used methods for removing MPs from the environment, but in order to be highly effective, it is necessary to optimize significant process factors. In this paper, the biodegradation of polyvinyl chloride (PVC) particles was researched using the Bacillus cereus bacteria. The aim of this study was to firstly determine the significant factors for the process of biodegradation of MP PVC using Bacillus cereus and then examine the optimal conditions for the process of biodegradation of MP using the mentioned bacterial culture. The experiment was performed according to Full factorial (FF) design in combination for three examined factors - MP size, MP concentration, and optical density (OD) of the prepared bacterial suspension - at three levels (minimum, mean and maximum). During the 30 days of the biodegradation experiment, the change in OD and the total number of grown bacterial colonies (Colony Forming Unit, CFU) were monitored. In the aqueous phase, the values of total (TC), organic (TOC) and inorganic (TIC) carbon were determined. LC/MS analysis monitored the release of additives from MP particles and potentially formed degradation products which formed during the biodegradation of MP. Structural changes in PVC were determined by ATR-FTIR spectroscopy. At the end of the biodegradation process, the ecotoxicity of the filtrate was examined using the Vibrio fischeri bacteria. The experimental results were processed using statistical analysis of variance (ANOVA). The results of the experiment indicate that better growth of the Bacillus cereus bacteria was observed at a mean PVC concentration of 500 mg/L, a mean particle size of 300-500 μm and a maximum OD of 0,5. In view of the above, the tested bacterial culture has the ability to biodegrade MPs.

• Keywords: mikroplastika; poli(vinil-klorid); biorazgradnja; Bacillus cereus; puni faktorski plan; optimalni uvjeti
• Keywords (english): microplastics; polyvinyl chloride; biodegradation; Bacillus cereus; Full factorial design; optimal conditions
• Language: croatian
• URN:NBN: urn:nbn:hr:149:250709
• 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: Closed access
• Created on: 2023-02-26 16:49:13