Title Utjecaj fizikalno-kemijskih parametara na biorazgradnju mikroplastike Title (english) Influence of physico-chemical parameters on biodegradation of microplastics Author Antonija Kovačević Mentor Dajana Kučić Grgić (mentor)Committee member Dajana Kučić Grgić (predsjednik povjerenstva)Committee member Šime Ukić (član povjerenstva)Committee member Matija Cvetnić (član povjerenstva)Granter University of Zagreb Defense date and country 2020-07-02, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Stalno povećanje proizvodnje plastike i loše gospodarenje plastičnim otpadom doveli su do ogromnog porasta odlaganja otpada u okoliš. Razgradnjom makroplastike ili ciljanom proizvodnjom čestica mikro veličina nastaju čestice mikroplastike (MP). Sve plastične čestice manje od 5 mm smatraju se mikroplastikom. Mikroplastika sadrži različite aditive i često je prijenosnik različitih onečišćujućih tvari što doprinosi njenom štetnom djelovanju na biocenozu. Zbog štetnog učinka, MP-u je potrebno ukloniti iz okoliša. U posljednje vrijeme istražuju se mogućnosti biorazgradnje MP-e mikroorganizmima izoliranih iz okoliša. U ovom radu ispitala se učinkovitost biorazgradnje dviju vrsta mikroplastike, polistirena (PS) i polietilena niske gustoće (LDPE), primjenom bakterija Bacillus cereus, Bacillus subtilis i mješovitom kulturom Pseudomonas alcaligenes i Bacillus sp.. Istraživanja su se provodila 22 dana pri 160 o/min, T = ± 25 °C, veličini čestica PS-a i LDPE-a 300 – 500 μm i koncentraciji od 100 mg/L. Tijekom 22 dana pratila se promjena optičke gustoće (OG), broja izraslih kolonija bakterija (CFU), koncentracije kisika, temperature, pH-vrijednosti, ukupnog organskog ugljika (TOC), anorganskog ugljika (IC) i ukupnog ugljika (TC) te koncentracije aniona i kationa. Na početku i na kraju procesa LDPE i PS su se okarakterizirali infracrvenom spektroskopijom s Fourierovim transformacijama (FTIR-ATR). Dobiveni rezultati ukazuju da se tijekom procesa biorazgradnje pH – vrijednost, temperatura i provodnost nisu mijenjale. Ispitane bakterijske kulture učinkovito su razgradile PS i LDPE tijekom 22 dana, što je dokazano smanjenjem koncentracije otopljenog kisika u uzorcima s MP-om, povećanjem CFU te nastajanjem anorganskog ugljika (CO2). Nadalje, spektri dobiveni FTIR-ATR analizom prije i nakon biorazgradnje ukazuju na nastajanje novih skupina, smanjenje intenziteta pikova te pomicanja pikova prema manjim valnim duljinama. B. cereus je bolje razgradio PS od LDPE, B. subtilis LDPE, a Ps. alcaligenes i Bacillus sp. PS. Rezultati provedenih analiza ukazuju da je mješovita bakterijska kultura Ps. alcaligenes i Bacillus sp. najbolje razgradila obje vrste mikroplastike.
Abstract (english) The continuous increase of plastic production and mismanagement of the plastic waste have led to a tremendous increase of plastic in the environment. Both, decomposition of larger plastic waste and targeted production of micro-sized particles generates microplastic particles (MP). Microplastics are plastic particles whose size is smaller than 5 mm. Microplastics can be a carrier of various toxins such as additives from industrial manufacturing processes or heavy metals. These toxins can affect entire ecosystem. Due to the harmful effect, MP needs to be removed from the environment. The possibilities of microplastics degradation using bacteria from the environment, that have properties which could degradate microplastics, are being explored. In this paper, biodegradation of two types of the microplastics was conducted, polystyrene (PS) and low density polyethylene (LDPE), with Bacillus cereus, Bacillus subtilis and mixed bacterial culture Pseudomonas alcaligenes and Bacillus sp.. Duration of the experiment was 22 days at 160 rpm, T = ±25 °C, particle size of 300 - 500 μm and concentration of 100 mg/L. Changes in optical density (OD), bacterial colony forming unit (CFU), oxygen concetration, temperature, pH – value, electrical conductivity, total organic carbon (TOC), inorganic carbon (IC) and total carbon (TC) were monitored for 22 days. Variations in anion and cation concentrations were monitored as well. At the beginning and the end of the experiment, LDPE and PS were characterized by infrared spectroscopy with Fourier transformations (FTIR-ATR). According to the results, temperature, pH – value and electrical conductivity have not alternated during the experiment. Bacterial cultures that were used have effectively degraded PS and LDPE over 22 days. Biodegradation is proven by higher decrease of dissolved oxygen concentration in samples with MP, higher bacterial CFU number and formation of inorganic carbon (CO2). FTIR spectrums before and after biodegradation were compared and they show the formation of new groups, reduction of peak intensities and shift of peaks towards the smaller wavelengths. Furthermore, B. cereus and Ps. alcaligenes + Bacillus sp. are better at degradation of PS whilst B. subtilis is better at degradation of LDPE. The results of the performed analysis show that the mixed bacterial culture of Ps. alcaligenes and Bacillus sp. is the best for degradation of both types of microplastics.
Keywords
mikroplastika
biorazgradnja
Bacillus cereus
Bacillus subtilis
Pseudomonas alcaligenes
Keywords (english)
microplastics
biodegradation
Bacillus cereus
Baccilus subtilis
Pseudomonas alcaligenes
Language croatian URN:NBN urn:nbn:hr:149:931493 Project Number: IP-2019-04-9661 Study programme Title: Materials Science and Engineering - Graduate study Type of resource Text File origin Born digital Access conditions Access restricted to students and staff of home institution Terms of use Created on 2022-03-05 10:17:21
